0000000001140249
AUTHOR
Borge Svane Nielsen
showing 182 related works from this author
Experimental Evidence for an Attractive p-φ Interaction
2021
Physical review letters 127(17), 172301 (2021). doi:10.1103/PhysRevLett.127.172301
Measurement of electrons from semileptonic heavy-flavour hadron decays at midrapidity in pp and Pb–Pb collisions at sNN=5.02 TeV
2020
The differential invariant yield as a function of transverse momentum (pT) of electrons from semileptonic heavy-flavour hadron decays was measured at midrapidity in central (0–10%), semi-central (30–50%) and peripheral (60–80%) lead–lead (Pb–Pb) collisions at sNN=5.02 TeV in the pT intervals 0.5–26 GeV/c (0–10% and 30–50%) and 0.5–10 GeV/c (60–80%). The production cross section in proton–proton (pp) collisions at s=5.02 TeV was measured as well in 0.5<pT<10 GeV/c and it lies close to the upper band of perturbative QCD calculation uncertainties up to pT=5 GeV/c and close to the mean value for larger pT. The modification of the electron yield with respect to what is expected for an inco…
Identified particles in quark and gluon jets
1997
A sample of about 1.4 million hadronic Z decays, selected among the data recorded by the DELPHI detector at LEP during 1994, was used to measure for the first time the momentum spectra of K+, K-0, p, Lambda and their antiparticles in gluon and quark jets. As observed for inclusive charged particles, the production spectra of identified particles were found to be softer in gluon jets than in quark jets, with a higher total multiplicity. (C) 1997 Published by Elsevier Science B.V.
ϒ production in p–Pb collisions at sNN=8.16 TeV
2020
$\Upsilon$ production in p-Pb interactions is studied at the centre-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV with the ALICE detector at the CERN LHC. The measurement is performed reconstructing bottomonium resonances via their dimuon decay channel, in the centre-of-mass rapidity intervals $2.03 < y_{\rm{cms}} < 3.53$ and $-4.46 < y_{\rm{cms}} < -2.96$, down to zero transverse momentum. In this work, results on the inclusive $\Upsilon(1\rm{S})$ production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the $\Upsilon(1\rm{S})$ yields with respect to pp collis…
Measurement of charged jet production cross sections and nuclear modification in p–Pb collisions at sNN=5.02 TeV
2015
Charged jet production cross sections in p–Pb collisions at √sNN = 5.02 TeV measured with the ALICE detector at the LHC are presented. Using the anti-kT algorithm, jets have been reconstructed in the central rapidity region from charged particles with resolution parameters R = 0.2 and R = 0.4. The reconstructed jets have been corrected for detector effects and the underlying event background. To calculate the nuclear modification factor, RpPb, of charged jets in p–Pb collisions, a pp reference was constructed by scaling previously measured charged jet spectra at √s = 7 TeV. In the transverse momentum range 20 ≤ pT, ch jet ≤ 120 GeV/c, RpPb is found to be consistent with unity, indicating th…
Soft-dielectron excess in proton-proton collisions at $\sqrt{s}$ = 13 TeV
2021
Physical review letters 127(4), 042302 (2021). doi:10.1103/PhysRevLett.127.042302
D -Meson Azimuthal Anisotropy in Midcentral Pb-Pb Collisions at sNN=5.02 TeV
2018
A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung fur Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep), and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Brazil; Ministry of Science and Technology of China (MSTC), National Natural Science Foundation of …
Measurement of PromptD-Meson Production inp−PbCollisions atsNN=5.02 TeV
2014
The p_{T}-differential production cross sections of the prompt charmed mesons D^{0}, D^{+}, D^{*+}, and D_{s}^{+} and their charge conjugate in the rapidity interval -0.96<y_{cms}<0.04 were measured in p-Pb collisions at a center-of-mass energy sqrt[s_{NN}]=5.02 TeV with the ALICE detector at the LHC. The nuclear modification factor R_{pPb}, quantifying the D-meson yield in p-Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%-20% uncertainties with unity in the transverse momentum interval 1<p_{T}<24 GeV/c. No significant difference among the R_{pPb} of the four D-meson species is observed. The results…
Search for neutral heavy leptons produced in Z decays
1997
Weak isosinglet Neutral Heavy Leptons ($\nu_m$) have been searched for using data collected by the DELPHI detector corresponding to $3.3\times 10^{6}$ hadronic~Z$^{0}$ decays at LEP1. Four separate searches have been performed, for short-lived $\nu_m$ production giving monojet or acollinear jet topologies, and for long-lived $\nu_m$ giving detectable secondary vertices or calorimeter clusters. No indication of the existence of these particles has been found, leading to an upper limit for the branching ratio $BR($Z$^0\rightarrow \nu_m \overline{\nu})$ of about $1.3\times10^{-6}$ at 95\% confidence level for $\nu_m$ masses between 3.5 and 50 GeV/$c^2$. Outside this range the limit weakens rap…
Measurement of the forward-backward asymmetry of e(+)e(-)-]z-]b(b)over-bar using prompt leptons and a lifetime tag
1995
The forward-backward asymmetry of the process e+e-→Z→b {Mathematical expression} has been measured using events collected by the DELPHI experiment during the 1991 and 1992 LEP runs. This data sample corresponded to 884 000 hadronic Z decays at a centre-of-mass energy {Mathematical expression}. The tagging of b-quark events was performed using two approaches; the first was based on the semileptonic decay channels b→X+μ and b→X+e, the second used a lifetime tag with jet-charge reconstruction. The results of these two methods were combined to give {Mathematical expression} With the semileptonic sample, the forward-backward asymmetry of the process e+e-→Z→ {Mathematical expression} was also mea…
Suppression of Λ(1520) resonance production in central Pb-Pb collisions at sNN=2.76 TeV
2019
The production yield of the Λ(1520) baryon resonance is measured at midrapidity in Pb-Pb collisions at sNN = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is performed in the Λ(1520)→pK− (and charge conjugate) hadronic decay channel as a function of the transverse momentum (pT) and collision centrality. The ratio of the pT-integrated production of Λ(1520) baryons relative to Λ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first 3σ evidence of Λ(1520) suppression within a single collision system. The mea…
Measurement of the lifetime of tau-lepton
1996
The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in tau_tau = 293.2 +/- 2.0 (stat) +/- 1.5 (syst) fs. The comparison of this result with the muon lifetime supports lepton universality of the weak charged current at the level of six per mille. Assuming lepton universality, the value of the strong coupling constant, alpha_s is found to be alpha_s(m_tau^2) = 0.319 +/- 0.015(exp.) +/- 0.014 (theory). The tau lepton lifetime is measured with the L3 detector at LEP using the complete data taken at centre-of-mass energies around the Z pole resulting in τ τ =293.2 ± 2.0 (stat) ± 1.5 (syst) fs . The c…
J/ψ suppression at forward rapidity in Pb–Pb collisions at sNN=5.02 TeV
2017
The inclusive J/$\psi$ production has been studied in Pn-Pb and pp collisions at the centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV, using the ALICE detector at the CERN LHC. The J/$\psi$ meson is reconstructed, in the centre-of-mass rapidity interval $2.5<y<4$ and in the transverse-momentum range $p_{\rm T}<12$ GeV/$c$, via its decay to a muon pair. In this Letter, we present results on the inclusive J/$\psi$ cross section in pp collisions at $\sqrt{s}=5.02$ TeV and on the nuclear modification factor $R_{\rm AA}$. The latter is presented as a function of the centrality of the collision and, for central collisions, as a function of the transverse momentum $p_{\rm T}$ of…
Rapidity correlations in Lambda baryon and proton production in hadronic Z0 decays
1998
In an analysis of multihadronic events recorded at LEP by DELPHI in the years 1992 through 1994, charged hadrons are identified using the measurement of their energy loss and their Cherenkov angle. Rapidity correlations of \La-\La, proton-proton, and \La-proton pairs are compared. The agreement with the string and cluster fragmentation models is tested. For those pairs that frame a meson in terms of rapidity the compensation of strangeness is studied. For \La{}$\overline{\mathrm{p}}$ pairs the additional correlation with respect to charged kaons is analysed.
Measurement of the (anti-)3He elliptic flow in Pb–Pb collisions at sNN=5.02TeV
2020
The elliptic flow ( v 2 ) of (anti-) 3He is measured in Pb–Pb collisions at s NN = 5.02 TeV in the transverse-momentum ( p T ) range of 2–6 GeV/c for the centrality classes 0–20%, 20–40%, and 40–60% using the event-plane method. This measurement is compared to that of pions, kaons, and protons at the same center-of-mass energy. A clear mass ordering is observed at low p T , as expected from relativistic hydrodynamics. The violation of the scaling of v 2 with the number of constituent quarks at low p T , already observed for identified hadrons and deuterons at LHC energies, is confirmed also for (anti-) 3He. The elliptic flow of (anti-) 3He is underestimated by the Blast-Wave model and overe…
Production of Muons from Heavy Flavor Decays at Forward Rapidity inppand Pb-Pb Collisions atsNN=2.76 TeV
2012
The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at root s(NN) = 2.76 TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6 < p(t) < 10 GeV/c. The suppression shows no significant p(t) dependence.
J/ψElliptic Flow in Pb-Pb Collisions atsNN=2.76 TeV
2013
We report on the first measurement of inclusive J/psi elliptic flow v(2) in heavy-ion collisions at the LHC. The measurement is performed with the ALICE detector in Pb-Pb collisions at root s(NN) = 2.76 TeV in the rapidity range 2.5 < y < 4.0. The dependence of the J/psi v(2) on the collision centrality and on the J/psi transverse momentum is studied in the range 0 <= p(T) < 10 GeV/c. For semicentral Pb-Pb collisions at root s(NN) = 2.76 TeV, an indication of nonzero v(2) is observed with a largest measured value of v(2) = 0.116 +/-0.046(stat) +/- 0.029(syst) for J/psi in the transverse momentum range 2 <= p(T) < 4 GeV/c. The elliptic flow measurement complements the previously reported ALI…
Measurement of trilinear gauge couplings in e(+)e(-) collisions at 161 GeV and 172 GeV
1998
Trilinear gauge boson couplings are measured using data taken by DELPHI at 161 GeV and 172 GeV, Values for WWV couplings (V = Z,gamma) are determined from a study of the reactions e(+)e(-) --> W+W- and e(+)e(-) --> We nu, using differential distributions from the WW final state in which one W decays hadronically and the other leptonically, and total cross,section data from other channels, Limits are also derived on neutral ZV gamma couplings from an analysis of the reaction e(+)e(-) --> gamma + invisible particles. (C) 1998 Elsevier Science B.V.
A search for neutral higgs particles in Z$^0$ decays
1992
Abstract The search in DELPHI data for neutral Higgs bosons is described. No candidate for the Standard Model Higgs is seen in Z0 decays to H 0 ν ν , H 0 μ + μ − or H0τ+τ− after selections that proved efficient for finding simulated H0. One remaining candidate for Z0 → H0e+e− is consistent with background. Together with our earlier studies, these results restrict the H0 mass to be above 38 GeV/c2 at the 95% confidence level. No signal is found for decays of Minimal Supersymmetric Standard Model neutral Higgs bosons to τ+τ−. Limits are obtained for their decays to produce four jets.
Elliptic Flow of Electrons from Beauty-Hadron Decays in Pb-Pb Collisions at sNN=5.02 TeV
2021
The elliptic flow of electrons from beauty hadron decays at midrapidity ($|y|$ $<$ 0.8) is measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV with the ALICE detector at the LHC. The azimuthal distribution of the particles produced in the collisions can be parameterized with a Fourier expansion, in which the second harmonic coefficient represents the elliptic flow, $v_{\rm 2}$. The $v_{\rm 2}$ coefficient is measured for the first time in transverse momentum ($p_{\rm{T}}$) range 1.3-6 GeV/$c$ in the centrality class 30-50%. The measurement of electrons from beauty-hadron decays exploits their larger mean proper decay length $c\tau \approx$ 500 $\mu$m compared to that of charm had…
Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb–Pb collisions at sNN=2.76 TeV
2016
The elliptic flow, $v_{2}$, of muons from heavy-flavour hadron decays at forward rapidity ($2.5 < y < 4$) is measured in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$~=~2.76 TeV with the ALICE detector at the LHC. The scalar product, two- and four-particle $Q$ cumulants and Lee-Yang zeros methods are used. The dependence of the $v_2$ of muons from heavy-flavour hadron decays on the collision centrality, in the range 0--40\%, and on transverse momentum, $p_{\rm T}$, is studied in the interval $3 < p_{\rm T} < 10$~GeV/$c$. A positive $v_2$ is observed with the scalar product and two-particle $Q$ cumulants in semi-central collisions (10--20\% and 20--40\% centrality classes) for the $p_{\rm T}$ int…
PRODUCTION CHARACTERISTICS OF K-0 AND LIGHT MESON RESONANCES IN HADRONIC DECAYS OF THE Z(0)
1995
An analysis of inclusive production of K0and the meson resonances K*±(892), Ï0(770), f0(975) and f2(1270) in hadronic decays of the Z0is presented, based on about 973,000 multihadronic events collected by the DELPHI detector at LEP during 1991 and 1992. Overall multiplicities have been determined as 1.962±0.060 K0mesons, 0.712±0.067 K*±(892) and 1.21±0.15Ï0(770) per hadronic Z0decay. The average multiplicities of f0(975) for scaled momentum, xp, in the range 0.05â¤xpâ¤0.6 and of f2(1270) for 0.05â¤xpâ¤1.0 are 0.098±0.016 and 0.170±0.043 respectively. The f0(975) and Ï0(770)xp-spectra have similar shapes. The f2(1270)/Ï0(770) ratio increases with xp. The average multiplicities…
Kaon-proton strong interaction at low relative momentum via femtoscopy in Pb-Pb collisions at the LHC
2021
Physics letters / B 822, 136708 (2021). doi:10.1016/j.physletb.2021.136708
Pseudorapidity Density of Charged Particles inp+PbCollisions atsNN=5.02 TeV
2013
The charged-particle pseudorapidity density measured over four units of pseudorapidity in nonsingle-diffractive p + Pb collisions at a center-of-mass energy per nucleon pair root s(NN) = 5.02 TeV is presented. The average value at midrapidity is measured to be 16.81 +/- 0.71 (syst), which corresponds to 2.14 +/- 0.17 (syst) per participating nucleon, calculated with the Glauber model. This is 16% lower than in nonsingle-diffractive pp collisions interpolated to the same collision energy and 84% higher than in d + Au collisions at root s(NN) = 0.2 TeV. The measured pseudorapidity density in p + Pb collisions is compared to model predictions and provides new constraints on the description of …
Performance of the DELPHI detector
1996
DELPHI (DEtector with Lepton, Photon and Hadron Identification) is a detector for e(+)e(-) physics, designed to provide high granularity over a 4 pi solid angle, allowing an effective particle identification, It has been operating at the LEP (Large Electron-Positron) collider at CERN since 1989. This article reviews its performance.
Measurement of ϒ(1S) Elliptic Flow at Forward Rapidity in Pb-Pb Collisions at sNN=5.02 TeV
2019
The first measurement of the Υ(1S) elliptic flow coefficient (v2) is performed at forward rapidity (2.5 < y < 4) in Pb–Pb collisions at √sNN=5.02 TeV with the ALICE detector at the LHC. The results are obtained with the scalar product method and are reported as a function of transverse momentum (pT) up to 15 GeV/c in the 5%–60% centrality interval. The measured Υ(1S)v2 is consistent with 0 and with the small positive values predicted by transport models within uncertainties. The v2 coefficient in 2 < pT < 15 GeV/c is lower than that of inclusive J/ψ mesons in the same pT interval by 2.6 standard deviations. These results, combined with earlier suppression measurements, are in agreement with…
Observation of orbitally excited B mesons
1995
Experimental evidence for the existence of orbitally excited B meson states is presented in an analysis of the BÏ and B*Ï distribution of Q = m(B**) - m(B(*)) - m(Ï) using Z0decay data taken with the DELPHI detector at LEP. The mean Q-value of the decays B**â B(*)Ï is measured to be 284 ± 5 (stat.) ± 15 (syst.) MeV/c2, and the Gaussian width of the signal is 79 ± 5 (stat.) ± 8 (syst.) MeV/c2. This signal can be described as a single resonance of mass m = 5732 ± 5 (stat.) ± 20 (syst.) MeV/c2and full width Î = 145 ± 28 MeV/c2. The observed shape is also consistent with the production of several broad and narrow states as predicted by the quark model and partly observed in the D-…
A Search for Sleptons and Gauginos in Z0 Decays
1990
Using a data sample corresponding to 10 000 hadronic Z0 decays, we have searched for the production of sleptons and gauginos in the two-prong decays of Z0. No candidate remains after straightforward selections. For neutralinos, we use selection methods developed in our previous search for neutral Higgs particles. The negative results are translated into improved mass limits and parameter constraints on the minimal supersymmetric extension of the standard model.
Jet-hadron correlations measured relative to the second order event plane in Pb-Pb collisions at sNN=2.76TeV
2020
The quark gluon plasma produced in ultrarelativistic heavy-ion collisions at the Large Hadron Collider (LHC) can be studied by measuring the modifications of jets formed by hard scattered partons which interact with the medium. We studied these modifications via angular correlations of jets with charged hadrons for jets with momenta 20
FIRST MEASUREMENT OF THE STRANGE QUARK ASYMMETRY AT THE Z(0) PEAK
1995
A measurement of the strange quark forward-backward asymmetry at the Z0 peak was performed using 718,000 multihadronic Z0 decays collected by the DELPHI detector at LEP in 1992. The s-quark was tagged by the presence of high momentum charged kaons identified by the Ring Imaging Cherenkov detector and by Λ0;s decaying into pπ-. The s-quark purity obtained was estimated for the two hadrons to be 43%. The average s-quark asymmetry was found to be 0.131±0.035 (stat.) ±0.013 (syst.). The forward-backward asymmetry was measured for unresolved d-and s-quarks, tagged by the detection of a high energy neutron or neutral kaon in the Hadron Calorimeter. The combined d-and s-quark purity was 69% and th…
Tuning and test of fragmentation models based on identified particles and precision event shape data
1996
Event shape and charged particle inclusive distributions are measured using 750000 decays of the $Z$ to hadrons from the DELPHI detector at LEP. These precise data allow a decisive confrontation with models of the hadronization process. Improved tunings of the JETSET ARIADNE and HERWIG parton shower models and the JETSET matrix element model are obtained by fitting the models to these DELPHI data as well as to identified particle distributions from all LEP experiments. The description of the data distributions by the models is critically reviewed with special importance attributed to identified particles.
Measurement and interpretation of the $W$-pair cross-section in $e^+e^-$ interactions at 161 GeV
1997
In 1996 LEP ran at a centre-of-mass energy of 161~GeV, just above the threshold of W-pair production. DELPHI accumulated data corresponding to an integrated luminosity of $9.93 {\mathrm{~pb^{-1}}}$, and observed 29 events that are considered as candidates for W-pair production. From these, a cross-section for the doubly resonant $e^+e^-\to\mathrm{WW}$ process of $3.67~^{+0.97}_{-0.85} \pm 0.19{\mathrm{~pb}}$ has been measured. Within the Standard Model, this cross-section corresponds to a mass of the W-boson of ${\mathrm{80.40~\pm~0.44~(stat.)~\pm~0.09~(syst.) ~\pm 0.03~(LEP)~GeV}}/c^2$. Alternatively, if $m_{\mathrm{W}}$ is held fixed at its current value determined by other experiments, t…
KS0andΛProduction in Pb-Pb Collisions atsNN=2.76 TeV
2013
The ALICE measurement of K^0_S and {\Lambda} production at mid-rapidity in Pb-Pb collisions at sqrt(sNN) = 2.76 TeV is presented. The transverse momentum (pT) spectra are shown for several collision centrality intervals and in the pT range from 0.4 GeV/c (0.6 GeV/c for {\Lambda}) to 12 GeV/c. The pT dependence of the {\Lambda}/K^0_S ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher pT with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb-Pb collisions. This baryon excess at intermediate pT is not observed in pp interactions at sqrt(s) = 0.9 Te…
Search for heavy charged scalars in Z$^0$ Decays
1990
Using a sample of Z0's corresponding to about 12 000 events, we have searched for the production of charged scalars, primarily charged Higgs particles, decaying into c̄scs̄, τν+jets, and τντν. The average detection efficiency is 20%. No candidate was found in the leptonic modes. Masses in the range up to 30-36 GeV/c2 are excluded, extending the mass domain covered by previous e+e- machines.
Flow dominance and factorization of transverse momentum correlations in Pb-Pb collisions at the LHC
2017
Physical review letters 118(16), 162302 (2017). doi:10.1103/PhysRevLett.118.162302
Measurements of the tau polarisation in Z0 decays
1995
A sample of Z0→τ+τ- events observed in the DELPHI detector at LEP in 1991 and 1992 is analysed to measure the τ polarisation in the exclusive decay channels {Mathematical expression}, {Mathematical expression}, πν, ρν and a1ν. The τ polarisation is also measured with an inclusive hadronic analysis which benefits from a higher efficiency and a better systematic precision than the use of the exclusive decay modes. The results have been combined with those published on the 1990 data. A measurement of the τ polarisation as a function of production angle yields the values for the mean τ polarisation 〈P〉τ=-0.148±0.022 and for the Z0 polarisation PZ=-0.136±0.027. These results are used to determin…
J / psi production in the hadronic decays of the Z.
1994
Abstract: J/psi mesons have been reconstructed from their decay to mu(+)mu(-) and e(+)e(-), using the data collected by the DELPHI experiment during 1991 and 1992 at the LEP collider. From about 1 million hadronic Z decays 153 +/- 17 J/psi were found, 5.4 +/- 2.3 psi' were obtained in the channel J/psi(--> mu(+)mu(-))pi(+)pi(-) and 6.4 +/- 2.7 chi(c) in the channel J/psi(--> mu(+)mu(-))gamma. As the dominant source of J/psi mesons is from b quarks, the following branching ratios: Br(b-->J/psi X) = (1.12 +/- 0.12 (stat.) +/- 0.10 (syst.))%, Br(b --> psi' X) = (0.48 +/- 0.22 (stat.) +/- 0.10 (syst.))%, Br(b-->chi(cl) X) = (1.4 +/- 0.6 (stat.)(-0.2)(+0.4) (syst.))% were measured. From the prop…
K*(892)0 and ϕ(1020) production at midrapidity in pp collisions at s=8 TeV
2020
The production of K∗(892)0 and φ(1020) in pp collisions at s=8 TeV was measured by using Run 1 data collected by the ALICE collaboration at the CERN Large Hadron Collider (LHC). The pT-differential yields d2N/dydpT in the range 0
Production of charged pions, kaons, and (anti-)protons in Pb-Pb and inelastic pp collisions at sNN=5.02 TeV
2020
Mid-rapidity production of $\pi^{\pm}$, $\rm{K}^{\pm}$ and ($\bar{\rm{p}}$)p measured by the ALICE experiment at the LHC, in Pb-Pb and inelastic pp collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, is presented. The invariant yields are measured over a wide transverse momentum ($p_{\rm{T}}$) range from hundreds of MeV/$c$ up to 20 GeV/$c$. The results in Pb-Pb collisions are presented as a function of the collision centrality, in the range 0$-$90%. The comparison of the $p_{\rm{T}}$-integrated particle ratios, i.e. proton-to-pion (p/$\pi$) and kaon-to-pion (K/$\pi$) ratios, with similar measurements in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV show no significant energy dependence. B…
Search for exclusive charmless b meson decays with the Delphi detector at Lep
1995
Charmless hadronic decays of beauty mesons have been searched for using the data collected with the DELPHI detector at the LEP collider. Several two, three and four-body decay modes have been investigated. Particle identification was used to distinguish the final states with protons, kaons and pions. Three candidate events selected in two-body decay modes are interpreted as evidence for charmless B decays. No excess has been found in higher multiplicity modes and improved upper limits for some of the branching ratios are given. © 1995.
Pseudorapidity dependence of the anisotropic flow of charged particles in Pb–Pb collisions at sNN=2.76 TeV
2016
We present measurements of the elliptic ($\mathrm{v}_2$), triangular ($\mathrm{v}_3$) and quadrangular ($\mathrm{v}_4$) anisotropic azimuthal flow over a wide range of pseudorapidities ($-3.5< \eta < 5$). The measurements are performed with Pb-Pb collisions at $\sqrt{s_{\text{NN}}} = 2.76$ TeV using the ALICE detector at the Large Hadron Collider (LHC). The flow harmonics are obtained using two- and four-particle correlations from nine different centrality intervals covering central to peripheral collisions. We find that the shape of $\mathrm{v}_n(\eta)$ is largely independent of centrality for the flow harmonics $n=2-4$, however the higher harmonics fall off more steeply with increasing $|…
Measurement of inclusive production of light meson resonances in hadronic decays of the Z0
1993
A study of inclusive production of the meson resonances ρ0, K*0 (892), f{hook}0 (975) and f{hook}2 (1270) in hadronic decays of the Z0 is presented. The measured mean meson multiplicity per hadronic event is 0.83 ± 0.14 for the ρ0 0.64 ± 0.24 for the K*0 (892), 0.10 ± 0.04 for the f{hook}0 (975) in the momentum range p > 0.05pbeam (xp > 0.05) and 0.11 ± 0.05 for the f{hook}2 (1270) for xp > 0.1. These values and the corresponding differential cross sections ( 1 σhadr) dσ dxp for the vector mesons are in good agreement with the predictions of the JETSET 7.3 PS and HERWIG 5.4 models. The f{hook}2 (1270) production is overestimated by HERWIG but its xp-shape is correctly reproduced. T…
Measurement of spin-orbital angular momentum interactions in relativistic heavy-ion collisions
2020
The first evidence of spin alignment of vector mesons ($K^{*0}$ and $\phi$) in heavy-ion collisions at the Large Hadron Collider (LHC) is reported. The spin density matrix element $\rho_{00}$ is measured at midrapidity ($|y| <$ 0.5) in Pb-Pb collisions at a center-of-mass energy ($\sqrt{s_{\rm NN}}$) of 2.76 TeV with the ALICE detector. $\rho_{00}$ values are found to be less than 1/3 (1/3 implies no spin alignment) at low transverse momentum ($p_{\rm T} <$ 2 GeV/$c$) for $K^{*0}$ and $\phi$ at a level of 3$\sigma$ and 2$\sigma$, respectively. No significant spin alignment is observed for the $K^0_S$ meson (spin = 0) in Pb-Pb collisions and for the vector mesons in $pp$ collisions. The meas…
First measurement of coherent ρ0 photoproduction in ultra-peripheral Xe–Xe collisions at sNN=5.44 TeV
2021
Abstract The first measurement of the coherent photoproduction of ρ 0 vector mesons in ultra-peripheral Xe–Xe collisions at s NN = 5.44 TeV is presented. This result, together with previous HERA γp data and γ–Pb measurements from ALICE, describes the atomic number (A) dependence of this process, which is particularly sensitive to nuclear shadowing effects and to the approach to the black-disc limit of QCD at a semi-hard scale. The cross section of the Xe + Xe → ρ 0 + Xe + Xe process, measured at midrapidity through the decay channel ρ 0 → π + π − , is found to be d σ / d y = 131.5 ± 5.6 ( stat . ) − 16.9 + 17.5 ( syst . ) mb. The ratio of the continuum to resonant contributions for the prod…
Measurement of the inclusive charmless and double-charm B branching ratios
1998
The DELPHI experiment at LEP has measured the inclusive charmless B hadron decay branching ratio, the B branching ratio into two charmed particles, and the total number of charmed particles per B decay, using the hadronic Z data taken between 1992 and 1995. The results are extracted from a fit to the b-tagging probability distribution based on the precise impact parameter measurements made using the microvertex detector. The inclusive charmless B branching ratio, including B decays into hidden charm (c (c) over bar), is measured to be 0.033 +/- 0.021. The B branching ratio into two open charmed particles is 0.136 +/- 0.042. The mean number of charmed particles per B decay (including hidden …
Azimuthal anisotropy ofD-meson production in Pb-Pb collisions atsNN=2.76TeV
2014
The production of the prompt charmed mesons D0, D+, and D*+ relative to the reaction plane was measured in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon collision of √sNN=2.76TeV with the ALICE detector at the CERN Large Hadron Collider. D mesons were reconstructed via their hadronic decays at central rapidity in the transverse-momentum (p_T) interval 2–16 GeV/c. The azimuthal anisotropy is quantified in terms of the second coefficient v2 in a Fourier expansion of the D-meson azimuthal distribution and in terms of the nuclear modification factor R_AA, measured in the direction of the reaction plane and orthogonal to it. The v2 coefficient was measured with three different …
Charge separation relative to the reaction plane in Pb-Pb collisions atsNN=2.76 TeV
2013
Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at root s(NN) = 2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range vertical bar eta vertical bar < 0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal co…
First evidence for a charm radial excitation, D
1998
Using D*+ mesons exclusively reconstructed in the DELPHI detector at LEP, an excess of 66 +/- 14(stat.) events is observed in the D(*+)pi(+)pi(-) final state with a mass of 2637 +/- 2(stat.) +/- 6(syst.) MeV/c(2) and a full width smaller than 15 MeV/c(2) (95% C.L.). This signal is compatible with the expected decay of a radially excited D*' (J(P) = 1(-))meson. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
Multiplicity dependence of inclusive J/ψ production at midrapidity in pp collisions at s=13 TeV
2020
Measurements of the inclusive J/ψ yield as a function of charged-particle pseudorapidity density dNch/dη in pp collisions at √s = 13 TeV with ALICE at the LHC are reported. The J/ψ meson yield is measured at midrapidity (|y| < 0.9) in the dielectron channel, for events selected based on the charged-particle multiplicity at midrapidity (|η| < 1) and at forward rapidity (−3.7 < η < −1.7 and 2.8 < η < 5.1); both observables are normalized to their corresponding averages in minimum bias events. The increase of the normalized J/ψ yield with normalized dNch/dη is significantly stronger than linear and dependent on the transverse momentum. The data are compared to theoretical predictions, which de…
A comparison of jet production rates on the Z0 resonance to perturbative QCD
1990
The production rates for 2-, 3-, 4- and 5-jet hadronic final states have been measured with the DELPHI detector at the e+e- storage ring LEP at centre of mass energies around 91.5 GeV. Fully corrected data are compared to O(αs 2) QCD matrix element calculations and the QCD scale parameter ΛMS is determined for different parametrizations of the renormalization scale μ2. Including all uncertainties our result is αs(MZ 2)=0.114±0.003[stat.]±0.004[syst.]±0.012[theor.] .
Measurement of the low-energy antideuteron inelastic cross section
2020
In this Letter, we report the first measurement of the inelastic cross section for antideuteron-nucleus interactions at low particle momenta, covering a range of $0.3 \leq p < 4$ GeV/$c$. The measurement is carried out using p-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, recorded with the ALICE detector at the CERN LHC and utilizing the detector material as an absorber for antideuterons and antiprotons. The extracted raw primary antiparticle-to-particle ratios are compared to the results from detailed ALICE simulations based on the GEANT4 toolkit for the propagation of antiparticles through the detector material. The analysis of th…
Long-range angular correlations of π, K and p in p–Pb collisions at sNN=5.02 TeV
2013
Angular correlations between unidentified charged trigger particles and various species of charged associated particles (unidentified particles, pions, kaons, protons and antiprotons) are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV in the transverse-momentum range 0.3 < p(T) < 4 GeV/c. The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range vertical bar n(lab)vertical bar < 0.8. Fourier coefficients are extracted from the long-range correlations projected onto the azimuthal angle difference and studied as a function of p(T) and in intervals of event multiplicity. In high-multipl…
Scattering Studies with Low-Energy Kaon-Proton Femtoscopy in Proton-Proton Collisions at the LHC
2020
The study of the strength and behaviour of the antikaon-nucleon ($\mathrm{\overline{K}N}$) interaction constitutes one of the key focuses of the strangeness sector in low-energy Quantum Chromodynamics (QCD). In this letter a unique high-precision measurement of the strong interaction between kaons and protons, close and above the kinematic threshold, is presented. The femtoscopic measurements of the correlation function at low pair-frame relative momentum of (K$^+$ p $\oplus$ K$^-$ $\overline{\mathrm{p}}$) and (K$^-$ p $\oplus$ K$^+$ $\overline{\mathrm{p}}$) pairs measured in pp collisions at $\sqrt{s}$ = 5, 7 and 13 TeV are reported. A structure observed around a relative momentum of 58 Me…
Study of very forward energy and its correlation with particle production at midrapidity in pp and p-Pb collisions at the LHC
2022
Journal of high energy physics 08(8), 86 (2022). doi:10.1007/JHEP08(2022)086
ϕ-Meson production at forward rapidity in p–Pb collisions at sNN=5.02 TeV and in pp collisions at s=2.76 TeV
2017
The first study of $\phi$-meson production in p–Pb collisions at forward and backward rapidity, at a nucleon– nucleon centre-of-mass energy $\sqrt{S_{NN}}$= 5.02 TeV, has been performed with the ALICE apparatus at the LHC. The $\phi$-mesons have been identified in the dimuon decay channel in the transverse momentum ($p_T$) range 1 < $p_T$ < 7 GeV/c, both in the p-going (2.03 < y < 3.53) and the Pb-going (−4.46 < y < −2.96) directions — where $y$ stands for the rapidity in the nucleon–nucleon centre-of-mass — the integrated luminosity amounting to 5.01 ± 0.19 nb$^{−1}$ and 5.81 ± 0.20 nb$^{−1}$ , respectively, for the two data samples. Differential cross sections as a function of transverse …
J/ψSuppression at Forward Rapidity in Pb-Pb Collisions atsNN=2.76 TeV
2012
The ALICE experiment has measured the inclusive J/psi production in Pb-Pb collisions at root s(NN) = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4. A suppression of the inclusive J/psi yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%-80% most central collisions, is 0.545 +/- 0.032(stat) +/- 0.083dsyst_ and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/psi production from charm quarks in…
First Observation of an Attractive Interaction between a Proton and a Cascade Baryon
2019
Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. This Letter presents the first experimental observation of the attractive strong interaction between a proton and a multistrange baryon (hyperon) Ξ−. The result is extracted from two-particle correlations of combined p−Ξ−⊕¯p−¯Ξ+ pairs measured in p−Pb collisions at √sNN=5.02 TeV at the LHC with ALICE. The measured correlation function is compared with the prediction obtained assuming only an attractive Coulomb interaction and a stand…
First measurement of f′2 (1525) production in Z0 hadronic decays
1996
The inclusive production of the f(2)'(1525) in hadronic Z(0) decays has been studied in data collected by the DELPHI detector at LEP. The Ring Imaging Cherenkov detectors were important tools in the identification of the decay f(2)'(1525) --> K+K-. The average number of f(2)(')(1525) produced per hadronic Z decay, [f(2)'] = 0.020 +/- 0.005 (stat) +/- 0.006 (syst), and the momentum distribution of the f(2)'(1525) have both been measured. The mass and width of the f(2)'(1525) are found to be [M(f2)'] = 1535 +/- 5 (stat) +/- 4 (syst) MeV/c(2). [Gamma(f2)'] = 60 +/- 20 (stat) +/- 19 (syst) MeV/c(2)
Energy dependence of inclusive spectra in e+ e- annihilation
1999
Inclusive charged hadron distributions as obtained from the DELPHI measurements at 130, 136, 161, 172 and 183 GeV are presented as a function of the variables rapidity, xi(p), p and transversal momenta. Data are compared with event generators and with MLLA calculations, in order to examine the hypothesis of local parton hadron duality. The differential momentum spectra show an indication for coherence effects in the production of soft particles. The relation between the energy dependence of the charged multiplicity and the rapidity distribution is examined. (C) 1999 Elsevier Science B.V. All rights reserved.
ϒ production and nuclear modification at forward rapidity in Pb–Pb collisions at sNN=5.02TeV
2021
Abstract The production of ϒ mesons in Pb–Pb collisions at a centre-of-mass energy per nucleon pair s NN = 5.02 TeV is measured with the muon spectrometer of the ALICE detector at the LHC. The yields as well as the nuclear modification factors are determined in the forward rapidity region 2.5 y 4.0 , as a function of rapidity, transverse momentum and collision centrality. The results show that the production of the ϒ ( 1S ) meson is suppressed by a factor of about three with respect to the production in proton–proton collisions. For the first time, a significant signal for the ϒ ( 2S ) meson is observed at forward rapidity, indicating a suppression stronger by about a factor 2–3 with respec…
Measurement of transverse energy at midrapidity in Pb-Pb collisions atsNN=2.76TeV
2016
We report the transverse energy ($E_{\mathrm T}$) measured with ALICE at midrapidity in Pb-Pb collisions at ${\sqrt{s_{\mathrm {NN}}}}$ = 2.76 TeV as a function of centrality. The transverse energy was measured using identified single particle tracks. The measurement was cross checked using the electromagnetic calorimeters and the transverse momentum distributions of identified particles previously reported by ALICE. The results are compared to theoretical models as well as to results from other experiments. The mean $E_{\mathrm T}$ per unit pseudorapidity ($\eta$), $\langle $d$E_{\mathrm T}/$d$\eta \rangle$, in 0-5% central collisions is 1737 $\pm$ 6(stat.) $\pm$ 97(sys.) GeV. We find a si…
Anisotropic Flow of Charged Particles in Pb-Pb Collisions atsNN=5.02 TeV
2016
We report the first results of elliptic (v2), triangular (v3), and quadrangular (v4) flow of charged particles in Pb-Pb collisions at a center-of-mass energy per nucleon pair of √sNN=5.02 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurements are performed in the central pseudorapidity region |η|<0.8 and for the transverse momentum range 0.2<pT<5 GeV/c. The anisotropic flow is measured using two-particle correlations with a pseudorapidity gap greater than one unit and with the multiparticle cumulant method. Compared to results from Pb-Pb collisions at √sNN=2.76 TeV, the anisotropic flow coefficients v2, v3, and v4 are found to increase by (3.0±0.6)%, (4.3±1.4)%, …
Measuring KS0K± interactions using Pb–Pb collisions at sNN=2.76 TeV
2019
We present the first measurements of femtoscopic correlations between the KS0 and K± particles in pp collisions at s=7 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding solely via the a0(980) resonance. The extracted kaon source radius and correlation strength parameters for KS0K− are found to be equal within the experimental uncertainties to those for KS0K+ . Results of the present study are compared with those from identical-kaon femtoscopic studies also performed with pp collisions at s=7 TeV by ALICE and with a KS0K± measurement in Pb–Pb collisions at sNN=2.76 TeV. Combined with the Pb–Pb results, our pp a…
Search for weakly decaying Λn‾ and ΛΛ exotic bound states in central Pb–Pb collisions at sNN=2.76 TeV
2016
We present results of a search for two hypothetical strange dibaryon states, i.e. the H-dibaryon and the possible (Lambda n) over bar bound state. The search is performed with the ALICE detector in central (0-10%) Pb-Pb collisions at root S-NN = 2.76 TeV, by invariant mass analysis in the decay modes (Lambda n) over bar (d) over bar pi(+) and H-dibaryon -> Lambda p pi(-). No evidence for these bound states is observed. Upper limits are determined at 99% confidence level for a wide range of lifetimes and for the full range of branching ratios. The results are compared to thermal, coalescence and hybrid UrQMD model expectations, which describe correctly the production of other loosely bound s…
Pseudorapidity and transverse-momentum distributions of charged particles in proton–proton collisions at s=13 TeV
2016
The pseudorapidity (η) and transverse-momentum (pT) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy s√ = 13 TeV. The pseudorapidity distribution in |η|< 1.8 is reported for inelastic events and for events with at least one charged particle in | η|< 1. The pseudorapidity density of charged particles produced in the pseudorapidity region |η|< 0.5 is 5.31 ± 0.18 and 6.46 ± 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 < pT < 20 GeV/c and |η|< 0.8 for events with at least one charged particle in |η|< 1. The correlation between transverse momen…
Search for promptly produced heavy quarkonium states in hadronic Z decays
1996
A search has been made for direct production of heavy quarkonium states in more than 3 million hadronic Z^{0} decays in the 1991-1994 DELPHI data. Prompt J/\psi, \psi(2S) and \Upsilon candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay vertex positions. New upper limits are set at the 90 \% confidence level for {Br( Z^0 \rightarrow \left( Q \bar{Q} \right) X ) / Br( Z^0 \rightarrow \mbox{hadrons})} for various strong production mechanisms of J/\psi and \Upsilon; these range down to 0.9 \times 10^{-4}. The limits are set in the presence of a small excess (\sim 1 \% statistical probability of a background fluctuation) in the su…
Measurement of electrons from semileptonic heavy-flavor hadron decays inppcollisions ats=2.76 TeV
2015
The pT-differential production cross section of electrons from semileptonic decays of heavy-flavor hadrons has been measured at midrapidity in proton-proton collisions at s=2.76TeV in the transverse momentum range 0.5<pT<12GeV/c with the ALICE detector at the LHC. The analysis was performed using minimum bias events and events triggered by the electromagnetic calorimeter. Predictions from perturbative QCD calculations agree with the data within the theoretical and experimental uncertainties.
Production of charged pions, kaons and protons at large transverse momenta in pp and Pb–Pb collisions at sNN=2.76 TeV
2014
Transverse momentum spectra of pi(+/-), K-+/- and p((p) over bar) up to p(T) = 20 GeV/c at mid-rapidity in pp, peripheral (60-80%) and central (0-5%) Pb-Pb collisions at v root s(NN) = 2.76 TeV have been measured using the ALICE detector at the Large Hadron Collider. The proton-to-pion and the kaon-to-pionratios both show a distinct peak at p(T) approximate to 3 GeV/c in central Pb-Pb collisions. Below the peak, p(T) 10 GeV/c particle ratios in pp and Pb-Pb collisions are in agreement and the nuclear modification factors for pi(+/-), K-+/- and p((p) over bar) indicate that, within the systematic and statistical uncertainties, the suppression is the same. This suggests that the chemical comp…
Investigation of the p–Σ0 interaction via femtoscopy in pp collisions
2020
This Letter presents the first direct investigation of the p-$\Sigma^{0}$ interaction, using the femtoscopy technique in high-multiplicity pp collisions at $\sqrt{s}$ = 13 TeV measured by the ALICE detector. The $\Sigma^{0}$ is reconstructed via the decay channel to $\Lambda \gamma$, and the subsequent decay of $\Lambda$ to p$\pi^-$. The photon is detected via the conversion in material to e$^{+}$e$^{-}$ pairs exploiting the unique capability of the ALICE detector to measure electrons at low transverse momenta. The measured p-$\Sigma^{0}$ correlation indicates a shallow strong interaction. The comparison of the data to several theoretical predictions obtained employing the $Correlation~Anal…
Jet-associated deuteron production in pp collisions at s=13 TeV
2021
Author(s): Acharya, S; Adamova, D; Adler, A; Adolfsson, J; Aglieri Rinella, G; Agnello, M; Agrawal, N; Ahammed, Z; Ahmad, S; Ahn, SU; Akbar, Z; Akindinov, A; Al-Turany, M; Albuquerque, DSD; Aleksandrov, D; Alessandro, B; Alfanda, HM; Alfaro Molina, R; Ali, B; Ali, Y; Alici, A; Alizadehvandchali, N; Alkin, A; Alme, J; Alt, T; Altenkamper, L; Altsybeev, I; Anaam, MN; Andrei, C; Andreou, D; Andronic, A; Angeletti, M; Anguelov, V; Anticic, T; Antinori, F; Antonioli, P; Apadula, N; Aphecetche, L; Appelshauser, H; Arcelli, S; Arnaldi, R; Arratia, M; Arsene, IC; Arslandok, M; Augustinus, A; Averbeck, R; Aziz, S; Azmi, MD; Badala, A; Baek, YW; Bai, X; Bailhache, R; Bala, R; Balbino, A; Baldisseri, …
A Precise Measurement of the Tau Lepton Lifetime
1996
The tau lepton lifetime has been measured using three different methods with the DELPHI detector. Two measurements of one-prong decays are combined, accounting for correlations, giving a result of \tau_\tau = 291.8 \pm 3.3 \mbox{ (stat.)} \pm 2.0 \mbox{(sys.) fs} while the decay length distribution of three-prong decays gives the result \tau_{\tau} = 286.7 \pm 4.9 \mbox{ (stat.)} \pm 3.3 \mbox{ (sys.) fs}. Combining the results presented here with previous DELPHI measurements, we get \tau_{\tau} = 291.4 \pm 3.0 fs and find that the ratio of the coupling constant for tau decay relative to that for muon decay is 0.990 \pm 0.009, compatible with lepton universality.
A search for invisible Higgs bosons produced in e+e- interactions at LEP 2 energies
1999
Searches for HZ production with the Higgs boson decaying into an invisible final state have been performed with the data collected by the DELPHI experiment up to the centre-of-mass energy of 183 GeV. The hadronic and muon pair final states of the Z boson were analysed. From the absence of signal, upper limits on the cross-section and the corresponding Higgs boson mass limits were set at 95% confidence level. The results are interpreted as excluded parameter regions in the framework of the minimal supersymmetric standard model and in the simplest Majoron model with one Higgs doublet and one Higgs singlet field. (C) 1999 Elsevier Science B.V. All rights reserved.
Strange baryon production in Z hadronic decays
1995
A study of the production of strange octet and decuplet baryons in hadronic decays of the Z recorded by the DELPHI detector at LEP is presented. This includes the first measurement of the ∑± average multiplicity. The total and differential cross sections, the event topology and the baryon-antibaryon correlations are compared with current hadronization models. © 1995 Springer-Verlag.
Search for chargino pair production in scenarios with gravitino LSP and stau NLSP at GeV at LEP
1999
Promptly decaying lightest charginos were searched for in the context of scenarios with gravitino LSP. It was assumed that the stau is the next to lightest supersymmetric particle (NLSP). Data collected with the DELPHI detector at a centre-of-mass energy near 183~{~mbox{${mathrm{GeV}}$}}\nwere analysed combining the methods developed in previous searches. No evidence for the production of these particles was found. Hence, limits were derived at 95% confidence level. The mass of charginos was found to be greater than 85.5~GeV/$c^2$ for $m_{ ilde{chi}^+_1}-m_{ ilde{ au}_1}geq 0.3 {mathrm{GeV}}/c^2$, independently of the mass of the gravitino.
J/ψ production as a function of charged particle multiplicity in pp collisions at s =7 TeV
2012
The ALICE Collaboration reports the measurement of the relative J/psi yield as a function of charged particle pseudorapidity density dN(ch)/d eta in pp collisions at root s = 7 TeV at the LHC. J/psi particles are detected for p(t) > 0, in the rapidity interval vertical bar y vertical bar 0. In the highest multiplicity interval with (dN(ch)/d eta)(bin)) = 24.1, corresponding to four times the minimum bias multiplicity density, an enhancement relative to the minimum bias J/psi yield by a factor of about 5 at 2.5 < y <4 (8 at vertical bar y vertical bar < 0.9) is observed. (C) 2012 CERN. Published by Elsevier B.V. All rights reserved.
Alignment of the ALICE Inner Tracking System with cosmic-ray tracks
2010
ALICE (A Large Ion Collider Experiment) is the LHC (Large Hadron Collider) experiment devoted to investigating the strongly interacting matter created in nucleus-nucleus collisions at the LHC energies. The ALICE ITS, Inner Tracking System, consists of six cylindrical layers of silicon detectors with three different technologies; in the outward direction: two layers of pixel detectors, two layers each of drift, and strip detectors. The number of parameters to be determined in the spatial alignment of the 2198 sensor modules of the ITS is about 13,000. The target alignment precision is well below 10 micron in some cases (pixels). The sources of alignment information include survey measurement…
Light vector meson production in pp collisions at s=7 TeV
2012
The ALICE experiment has measured low-mass dimuon production in pp collisions at root s = 7 TeV in the dimuon rapidity region 2.5 < y < 4. The observed dimuon mass spectrum is described as a superposition of resonance decays (eta, rho, omega, eta', phi) into muons and semi-leptonic decays of charmed mesons. The measured production cross sections for omega and phi are sigma(omega)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 5.28 +/- 0.54(stat) +/- 0.49(syst) mb and sigma(phi)(1 < p(t) < 5 GeV/c. 2.5 < y < 4) = 0.940 +/- 0.084(stat) +/- 0.076(syst) mb. The differential cross sections d(2)sigma/dy dp(t) are extracted as a function of p(t) for omega and phi. The ratio between the rho and omega cross sec…
Probing the Effects of Strong Electromagnetic Fields with Charge-Dependent Directed Flow in Pb-Pb Collisions at the LHC
2020
The first measurement at the LHC of charge-dependent directed flow ($v_{1}$) relative to the spectator plane is presented for Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV. Results are reported for charged hadrons and $\rm D^{0}$ mesons for the transverse momentum intervals $p_{\rm T}>0.2$ GeV/$c$ and $3<p_{\rm T}<$ 6 GeV/$c$ in the 5-40% and 10-40% centrality classes, respectively. The difference between the positively and negatively charged hadron $v_{1}$ has a positive slope as a function of pseudorapidity $\eta$, ${\rm d}\Delta{v_1}/{\rm d}\eta=$[1.68 $\pm$ 0.49 (stat.) $\pm$ 0.41 (syst.)] $\times 10^{-4}$. The same measurement for $\rm D^{0}$ and $\rm\bar{D}{}^0$ mesons yields a p…
Multi-particle azimuthal correlations in p-Pb and Pb-Pb collisions at the CERN Large Hadron Collider
2014
Measurements of multi-particle azimuthal correlations (cumulants) for charged particles in p-Pb and Pb-Pb collisions are presented. They help address the question of whether there is evidence for global, flow-like, azimuthal correlations in the p-Pb system. Comparisons are made to measurements from the larger Pb-Pb system, where such evidence is established. In particular, the second harmonic two-particle cumulants are found to decrease with multiplicity, characteristic of a dominance of few-particle correlations in p-Pb collisions. However, when a $|\Delta \eta|$ gap is placed to suppress such correlations, the two-particle cumulants begin to rise at high-multiplicity, indicating the prese…
Investigations of Anisotropic Flow Using Multiparticle Azimuthal Correlations in pp , p−Pb , Xe-Xe, and Pb-Pb Collisions at the LHC
2019
Measurements of anisotropic flow coefficients (vn) and their cross-correlations using two- and multiparticle cumulant methods are reported in collisions of pp at √s=13 TeV, p−Pb at a center-of-mass energy per nucleon pair √sNN=5.02 TeV, Xe-Xe at √sNN=5.44 TeV, and Pb-Pb at √sNN=5.02 TeV recorded with the ALICE detector. The multiplicity dependence of vn is studied in a very wide range from 20 to 3000 particles produced in the midrapidity region |η| v3>v4 is found in pp and p−Pb collisions, similar to that seen in large collision systems, while a weak v2 multiplicity dependence is observed relative to nucleus-nucleus collisions in the same multiplicity range. Using a novel subevent method, v…
Net-charge fluctuations in Pb-Pb collisions at sqrt[sNN]=2.76TeV.
2013
We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudo-rapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the ALICE data points are between the theoretically predicted values for a hadron gas and a Quark-Gluon Plasma.…
Neutral pion and η meson production at midrapidity in Pb-Pb collisions at sNN=2.76 TeV
2018
Neutral pion and η meson production in the transverse momentum range 1 <pT< 20 GeV/c have been measured at midrapidity by the ALICE experiment at the Large Hadron Collider (LHC) in central and semicentral Pb-Pb collisions at sNN = 2.76 TeV. These results were obtained using the photon conversion method as well as the Photon Spectrometer (PHOS) and Electromagnetic Calorimeter detectors. The results extend the upper pT reach of the previous ALICE π0 measurements from 12 to 20 GeV/c and present the first measurement of η meson production in heavy-ion collisions at the LHC. The η/π0 ratio is similar for the two centralities and reaches at high pT a plateau value of 0.457 ± 0.013stat ± 0.018sys…
Constraints on jet quenching in p–Pb collisions at sNN=5.02 TeV measured by the event-activity dependence of semi-inclusive hadron-jet distributions
2018
The ALICE Collaboration reports the measurement of semi-inclusive distributions of charged-particle jets recoiling from a high-transverse momentum trigger hadron in p–Pb collisions at √sNN = 5.02 TeV. Jets are reconstructed from charged-particle tracks using the anti-kT algorithm with resolution parameter R = 0.2 and 0.4. A data-driven statistical approach is used to correct the uncorrelated background jet yield. Recoil jet distributions are reported for jet transverse momentum 15 < pch T,jet < 50 GeV/c and are compared in various intervals of p–Pb event activity, based on charged-particle multiplicity and zero-degree neutral energy in the forward (Pb-going) direction. The semi-inclusive ob…
Anisotropic flow of charged hadrons, pions and (anti-)protons measured at high transverse momentum in Pb–Pb collisions at sNN=2.76 TeV
2013
The elliptic, v(2), triangular, v(3), and quadrangular, v(4), azimuthal anisotropic flow coefficients are measured for unidentified charged particles, pions, and (anti-)protons in Pb-Pb collisions at root S-NN = 2.76 TeV with the ALICE detector at the Large Hadron Collider. Results obtained with the event plane and four-particle cumulant methods are reported for the pseudo-rapidity range vertical bar eta vertical bar 8 GeV/c. The small p(T) dependence of the difference between elliptic flow results obtained from the event plane and four-particle cumulant methods suggests a common origin of flow fluctuations up to p(T) = 8 GeV/c. The magnitude of the (anti-)proton elliptic and triangular flo…
Unveiling the strong interaction among hadrons at the LHC
2020
One of the key challenges for nuclear physics today is to understand from first principles the effective interaction between hadrons with different quark content. First successes have been achieved using techniques that solve the dynamics of quarks and gluons on discrete space-time lattices1,2. Experimentally, the dynamics of the strong interaction have been studied by scattering hadrons off each other. Such scattering experiments are difficult or impossible for unstable hadrons3–6 and so high-quality measurements exist only for hadrons containing up and down quarks7. Here we demonstrate that measuring correlations in the momentum space between hadron pairs8–12 produced in ultrarelativistic…
Searches for heavy neutrinos from Z decays
1992
We have searched for possible fourth family heavy neutrinos, pair produced in Z0 decays, in a sample of about 112 000 hadronic Z0 final states collected with the DELPHI detector. For all mixing matrix elements we exclude a new Dirac neutrino lighter than 44.5 GeV at a 95% confidence level, if the neutrino couples to the electron or muon family, and lighter than 44.0 GeV, if the neutrino couples to the tau family. Depending on the values of the mixing element and to which lepton family the neutrino couples, we obtain mass limits up to 46.2 GeV. For all mixing matrix elements we exclude a new Majorana neutrino lighter than 39.0 GeV, if it couples to the electron or the muon family, and lighte…
Two-pion Bose-Einstein correlations inppcollisions ats=900 GeV
2010
We report on the measurement of two-pion correlation functions from pp collisions at root s = 900 GeV performed by the ALICE experiment at the Large Hadron Collider. Our analysis shows an increase of the Hanbury Brown-Twiss radius with increasing event multiplicity, in line with other measurements done in particle- and nuclear collisions. Conversely, the strong decrease of the radius with increasing transverse momentum, as observed at the Relativistic Heavy Ion Collider and at Tevatron, is not manifest in our data.
Search For Light Neutral Higgs Particles Produced In Z0-decays
1990
A search for the neutral Higgs boson in Z0-decays has been performed using the DELPHI detector at the Large Electron Positron collider (LEP) at CERN. We looked for the decay of Z0 into a neutral Higgs particle and a pair of fermions. No events fulfilled the criteria for H0-production. Our results, which are based on an integrated luminosity of 530 nb-1, exclude a minimal Standard Model Higgs boson with a mass in the range 210 MeV/c2 to 14 GeV/c2 at 95% confidence level.
Charged kaon femtoscopic correlations inppcollisions ats=7 TeV
2013
Correlations of two charged identical kaons (KchKch) are measured in pp collisions at root s = 7 TeV by the ALICE experiment at the Large Hadron Collider (LHC). One-dimensional (KKch)-K-ch correlation functions are constructed in three multiplicity and four transverse momentum ranges. The (KKch)-K-ch femtoscopic source parameters R and lambda are extracted. The (KKch)-K-ch correlations show a slight increase of femtoscopic radii with increasing multiplicity and a slight decrease of radii with increasing transverse momentum. These trends are similar to the ones observed for pi pi and K-s(0) K-s(0) correlations in pp and heavy-ion collisions. However at high multiplicities, there is an indica…
Forward-central two-particle correlations in p–Pb collisions at sNN=5.02 TeV
2016
Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 < |η| < 4.0) and associated particles in the cen
A measurement of the \(\tau\) leptonic branching fractions
1995
Abstract: A sample of 25000 Z(0) --> tau(-)tau(+) events collected by the DELPHI experiment at LEP in 1991 and 1992 is used to measure the leptonic branching fractions of the tau lepton. The results are B(tau --> e nu) = (17.51+/-0.39)% and B(tau --> mu nu) = (17.02+/-0.31)%. The ratio of the muon and electron couplings to the weak charged current is measured to be g(mu)/g(e) = 1.000+/-0.013, satisfying e-mu universality. The average leptonic branching fraction corrected to the value for a massless lepton, assuming e-mu universality, is found to be B(tau --> l nu) = (17.50+/-0.25)%.
Search for collectivity with azimuthal J/ψ-hadron correlations in high multiplicity p–Pb collisions at sNN=5.02 and 8.16 TeV
2018
A.I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences and Nationalstiftung fur Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Universidade Federal do Rio Grande do Sul (UFRGS), Financiadora de Estudos e Projetos (Finep) and Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Brazil; Ministry of Science & Technology of China (MSTC), National Natural Science Foundation of Chi…
Ds+ meson production at central rapidity in proton–proton collisions at s=7 TeV
2012
The pt-differential inclusive production cross section of the prompt charm-strange meson D_s in the rapidity range |y| phi pi, with phi -> KK, and its charge conjugate, about 480 D_s mesons were counted, after selection cuts, in the transverse momentum range 2
Charged-Particle Multiplicity Density at Midrapidity in Central Pb-Pb Collisions atsNN=2.76 TeV
2010
The first measurement of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair root s(NN) = 2.76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section, the pseudorapidity density of primary charged particles at midrapidity is 1584 +/- 4(stat) +/- 76(syst), which corresponds to 8.3 +/- 0.4(syst) per participating nucleon pair. This represents an increase of about a factor 1.9 relative to pp collisions at similar collision energies, and about a factor 2.2 to central Au-Au collisions at root s(NN) = 0.2 TeV. This measurement provides the first experimental constraint for models…
Linear and non-linear flow mode in Pb–Pb collisions at sNN=2.76 TeV
2017
The second and the third order anisotropic flow, V2 and V3, are mostly determined by the corresponding initial spatial anisotropy coefficients, e2 and e3, in the initial density distribution. In addition to their dependence on the same order initial anisotropy coefficient, higher order anisotropic flow, Vn (n > 3), can also have a significant contribution from lower order initial anisotropy coefficients, which leads to mode-coupling effects. In this Letter we investigate the linear and non-linear modes in higher order anisotropic flow Vn for n = 4, 5, 6 with the ALICE detector at the Large Hadron Collider. The measurements are done for particles in the pseudorapidity range |η| < 0.8 and the…
PRODUCTION-RATE AND DECAY LIFETIME MEASUREMENTS OF B(S)0 MESONS AT LEP USING D(S) AND PHI MESONS
1994
The study of the properties of inclusive production of Ds mesons and of events in which a φ{symbol} and a muon are present in the same jet provides two independent measurements of the probability, fs w, for a heavy quark to hadronize into a strange B or D meson. The data sample analysed corresponds to 243,000 hadronic Z0 decays. The combined value of these measurements is fs w=0.19±0.06±0.08. From the flight distance distributions of Ds and of (φ{symbol}-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for the Bs 0 meson lifetime. Combining these measurements with a previous result based on the study of Ds-μ ev…
A measurement of αs from the scaling violation in e+e- annihilation
1997
The hadronic fragmentation functions of the various quark flavours and of gluons are measured in a study of the inclusive hadron production from $\zz$ decays with the DELPHI detector and are compared with the fragmentation functions measured elsewhere at energies between 14 GeV and 91 GeV. A large scaling violation is observed, which is used to extract the strong coupling constant from a fit using a numerical integration of the second order DGLAP evolution equations. The result is \begin{displaymath} \alpha_s(M_Z) = 0.124^{+0.006}_{-0.007}(exp)\pm 0.009 (theory) \end{displaymath} where the first error represents the experimental uncertainty and the second error is due to the factorization a…
Energy dependence of event shapes and of $\alpha_s$ at LEP 2
1999
Infrared and collinear safe event shape distributions and their mean values are determined using the data taken at five different centre of mass energies above M-Z with the DELPHI detector at LEP. From the event shapes, the strong coupling alpha(s) is extracted in O(alpha(s)(2)), NLLA and a combined scheme using hadronisation corrections evaluated with fragmentation model generators as well as using an analytical power ansatz. Comparing these measurements to those obtained at M-Z, the energy dependence (running) of alpha(s) is accessible. The logarithmic energy slope of the inverse strong coupling is measured to be d alpha(s)(-1)/d log(E-cm) = 1.39 +/- 0.34 (stat) +/- 0.17(syst), in good ag…
Azimuthally Differential Pion Femtoscopy in Pb-Pb Collisions at sNN=2.76 TeV
2017
We present the first azimuthally differential measurements of the pion source size relative to the second harmonic event plane in Pb-Pb collisions at a center-of-mass energy per nucleon-nucleon pair of √sNN = 2.76 TeV. The measurements have been performed in the centrality range 0%-50% and for pion pair transverse momenta 0.2 < kT < 0.7 GeV/c. We find that the Rside and Rout radii, which characterize the pion source size in the directions perpendicular and parallel to the pion transverse momentum, oscillate out of phase, similar to what was observed at the Relativistic Heavy Ion Collider. The final-state source eccentricity, estimated via Rside oscillations, is found to be significantly sma…
One-dimensional charged kaon femtoscopy in p -Pb collisions at sNN = 5.02 TeV
2019
The correlations of identical charged kaons were measured in p-Pb collisions at √sNN=5.02 TeV by the ALICE experiment at the LHC. The femtoscopic invariant radii and correlation strengths were extracted from one-dimensional kaon correlation functions and were compared with those obtained in pp and Pb-Pb collisions at √s=7 TeV and √sNN=2.76 TeV, respectively. The presented results also complement the identical-pion femtoscopic data published by the ALICE collaboration. The extracted radii increase with increasing charged-particle multiplicity and decrease with increasing pair transverse momentum. At comparable multiplicities, the radii measured in p-Pb collisions are found to be close to tho…
Midrapidity Antiproton-to-Proton Ratio inppCollisons ats=0.9and 7 TeV Measured by the ALICE Experiment
2010
The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at root s = 0.9 and 7 TeV during the initial running periods of the Large Hadron Collider. The measurement covers the transverse momentum interval 0.45 < p(t) < 1.05 GeV/c and rapidity vertical bar y vertical bar < 0.5. The ratio is measured to be R-vertical bar y vertical bar<0.5 = 0.957 +/- 0.006(stat) +/- 0.0014(syst) at 0.9 Tev and R-vertical bar y vertical bar<0.5 = 0.991 +/- 0.005 +/- 0.014(syst) at 7 TeV and it is independent of both rapidity and transverse momentum. The results are consistent with the conventional model of baryon-number transport and set stringent limits on a…
Charged particle multiplicity in e^{+}e_{-}$ → q[L:q] events at 161 and 172 GeV and from the decay of the W boson
1998
The data collected by DELPHI in 1996 have been used to measure the average charged particle multiplicities and dispersions in $q\bar{q}$ events at centre-of-mass energies of $\sqrt{s}=161$~GeV and $\sqrt{s}=172$~GeV, and the average charge multiplicity in WW events at $\sqrt{s}=172$~GeV. The multiplicities in $q\bar{q}$ events are consistent with the evolution predicted by QCD. The dispersions in the multiplicity distributions are consistent with Koba-Nielsen-Olesen (KNO) scaling. The average multiplicity of charged particles in hadronic W decays has been measured for the first time; its value, $19.23 \pm 0.74 (stat+syst)$, is consistent with that expected for an $e^+e^-$ interaction at a c…
Elliptic Flow of Charged Particles in Pb-Pb Collisions atsNN=2.76 TeV
2010
We report the first measurement of charged particle elliptic flow in Pb-Pb collisions at root s(NN) p = 2.76 TeV with the ALICE detector at the CERN Large Hadron Collider. The measurement is performed in the central pseudorapidity region (vertical bar eta vertical bar < 0.8) and transverse momentum range 0.2 < p(t) < 5.0 GeV/c. The elliptic flow signal v(2), measured using the 4-particle correlation method, averaged over transverse momentum and pseudorapidity is 0.087 +/- 0.002(stat) +/- 0.003(syst) in the 40%-50% centrality class. The differential elliptic flow v(2)(p(t)) reaches a maximum of 0.2 near p(t) = 3 GeV/c. Compared to RHIC Au-Au collisions at root s(NN) = 200 GeV, the elliptic f…
Jet-like correlations with neutral pion triggers in pp and central Pb–Pb collisions at 2.76 TeV
2016
Physics letters / B B763, 238 - 250 (2016). doi:10.1016/j.physletb.2016.10.048
Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV
2020
The measurement of the deuteron and anti- deuteron production in the rapidity range −1 < y < 0 as a function of transverse momentum and event multiplicity in p–Pb collisions at √sNN= 5.02 TeV is presented. (Anti-)deuterons are identified via their specific energy loss dE/dxand via their time-of-flight. Their production in p–Pb collisions is compared to pp and Pb–Pb collisions and is discussed within the context of thermal and coalescence models. The ratio of integrated yields of deuterons to protons (d/p) shows a significant increase as a function of the charged-particle multiplicity of the event starting from values similar to those observed in pp collisions at low multiplicities and appro…
Production of 4He and 4He‾ in Pb–Pb collisions at sNN=2.76TeV at the LHC
2018
Results on the production of 4 He and He‾4 nuclei in Pb–Pb collisions at sNN=2.76TeV in the rapidity range |y|<1 , using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0–10% central events are found to be dN/dyHe4=(0.8±0.4(stat)±0.3(syst))×10−6 and dN/dyHe‾4=(1.1±0.4(stat)±0.2(syst))×10−6 , respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature ( Tchem=156MeV ) as for light hadrons. The measured ratio of He‾4/4He is 1.4±0.8(stat)±0.5(syst) .
Λc+ Production and Baryon-to-Meson Ratios in pp and p -Pb Collisions at sNN=5.02 TeV at the LHC
2021
The prompt production of the charm baryon Λ c + and the Λ c + / D 0 production ratios were measured at midrapidity with the ALICE detector in p p and p -Pb collisions at s NN = 5.02 TeV . These new measurements show a clear decrease of the Λ c + / D 0 ratio with increasing transverse momentum ( p T ) in both collision systems in the range 2 p T 12 GeV / c , exhibiting similarities with the light-flavor baryon-to-meson ratios p / π and Λ / K S 0 . At low p T , predictions that include additional color-reconnection mechanisms beyond the leading-color approximation, assume the existence of additional higher-mass charm-baryon states, or include hadronization via coalescence can describe the dat…
Production of muons from heavy-flavour hadron decays in p–Pb collisions at sNN=5.02 TeV
2017
Abstract The production of muons from heavy-flavour hadron decays in p–Pb collisions at s NN = 5.02 TeV was studied for 2 p T 16 GeV/c with the ALICE detector at the CERN LHC. The measurement was performed at forward (p-going direction) and backward (Pb-going direction) rapidity, in the ranges of rapidity in the centre-of-mass system (cms) 2.03 y cms 3.53 and − 4.46 y cms − 2.96 , respectively. The production cross sections and nuclear modification factors are presented as a function of transverse momentum ( p T ). At forward rapidity, the nuclear modification factor is compatible with unity while at backward rapidity, in the interval 2.5 p T 3.5 GeV/c, it is above unity by more than 2σ. Th…
Search for pair production of neutral Higgs bosons in Z$^0$ decays
1990
The pair production of the lightest scalar Higgs boson, h, and a pseudoscalar Higgs boson, A, was searched for in a data sample containing 10 000 hadronic Z0 decays. The search involved both leptonic and purely hadronic decay channels of each Higgs boson. No signal was found, and limits on the Higgs boson masses, in the framework of the minimal supersymmetric extension of the standard model, ar reported up to 35 GeV/c2 at 95% CL, for both tan β > 1 and tan β < 1, where tan β is the ratio of the vacuum expectation values of the two Higgs doublets.
A study of intermittency in Hadronic Z$^0$ Decays
1990
The correlations in rapidity in hadron production from e+e- annihilation near the Z0 resonance were studied by means of the method of factorial moments, using data taken with the DELPHI detector at LEP. The parton shower hadronization model was found to be in quantitative agreement with the data, in contrast with previous results at lower energies. © 1990.
Exploration of jet substructure using iterative declustering in pp and Pb–Pb collisions at LHC energies
2020
The ALICE collaboration at the CERN LHC reports novel measurements of jet substructure in pp collisions at $\sqrt{s}$= 7 TeV and central Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 TeV. Jet substructure of track-based jets is explored via iterative declustering and grooming techniques. We present the measurement of the momentum sharing of two-prong substructure exposed via grooming, the $z_{\rm{g}}$, and its dependence on the opening angle, in both pp and Pb-Pb collisions. We also present the first measurement of the distribution of the number of branches obtained in the iterative declustering of the jet, which is interpreted as the number of its hard splittings. In Pb-Pb collisions, we…
Neutron emission from electromagnetic dissociation of Pb nuclei at $\sqrt {s_{NN}} = 2.76$ TeV measured with the ALICE ZDC
2014
The ALICE Zero Degree Calorimeter system (ZDC) is composed of two identical sets of calorimeters, placed at opposite sides with respect to the interaction point, 114 meters away from it, complemented by two small forward electromagnetic calorimeters (ZEM). Each set of detectors consists of a neutron (ZN) and a proton (ZP) ZDC. They are placed at zero degrees with respect to the LHC axis and allow to detect particles emitted close to beam direction, in particular neutrons and protons emerging from hadronic heavy-ion collisions (spectator nucleons) and those emitted from electromagnetic processes. For neutrons emitted by these two processes, the ZN calorimeters have nearly 100% acceptance. Du…
Measurement of the spin density matrix for the rho(0), K*(0)(892) and phi produced in Z(0) decays
1997
The spin density matrix elements for the rho(0), K-*0(892) and phi produced in hadronic Z(0) decays are measured in the DELPHI detector. There is no evidence for spin alignment of the K-*0(892) and phi, in the region x(p) less than or equal to 0.3 (x(p) = p/p(beam)), where rho(00) = 0.33 +/- 0.05 and rho(00) = 0.30 +/- 0.04, respectively. In the fragmentation region, x(p) greater than or equal to 0.4, there is some indication for spin alignment of the rho(0) and K-*0(892), since rho(00) = 0.43 +/- 0.05 and rho(00) = 0.46 +/- 0.08, respectively. These values are compared with those found in meson-induced hadronic reactions. For the phi, rho(00) = 0.30 +/- 0.04 for x(p) greater than or equal …
Centrality dependence of the pseudorapidity density distribution for charged particles in Pb–Pb collisions at sNN=2.76 TeV
2017
We present the charged-particle pseudorapidity density in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02\,\mathrm{Te\kern-.25exV}$ in centrality classes measured by ALICE. The measurement covers a wide pseudorapidity range from $-3.5$ to $5$, which is sufficient for reliable estimates of the total number of charged particles produced in the collisions. For the most central (0-5%) collisions we find $21\,400\pm 1\,300$ while for the most peripheral (80-90%) we find $230\pm 38$. This corresponds to an increase of $(27\pm4)\%$ over the results at $\sqrt{s_{\mathrm{NN}}}=2.76\,\mathrm{Te\kern-.25exV}$ previously reported by ALICE. The energy dependence of the total number of charged particles…
Multiplicity dependence of jet-like two-particle correlation structures in p–Pb collisions at sNN=5.02 TeV
2015
Two-particle angular correlations between unidentified charged trigger and associated particles are measured by the ALICE detector in p-Pb collisions at a nucleon-nucleon centre-of-mass energy of 5.02 TeV. The transverse-momentum range 0.7<pT,assoc<pT,trig<5.0 GeV/c is examined, to include correlations induced by jets originating from low momentum-transfer scatterings (minijets). The correlations expressed as associated yield per trigger particle are obtained in the pseudorapidity range |η|<0.9. The near-side long-range pseudorapidity correlations observed in high-multiplicity p-Pb collisions are subtracted from both near-side short-range and away-side correlations in order to remove the no…
Multiharmonic Correlations of Different Flow Amplitudes in Pb-Pb Collisions at ...
2021
The event-by-event correlations between three flow amplitudes are measured for the first time in Pb-Pb collisions, using higher-order symmetric cumulants. We find that different three-harmonic correlations develop during the collective evolution of the medium when compared to correlations that exist in the initial state. These new results cannot be interpreted in terms of previous lower-order flow measurements since contributions from two-harmonic correlations are explicitly removed in the new observables. A comparison to Monte Carlo simulations provides new and independent constraints for the initial conditions and system properties of nuclear matter created in heavy-ion collisions. © 2021…
Measurement of $\Delta^{++}$(1232) production in hadronic Z decays
1995
A measurement of the \Delta^{++}(1232) inclusive production in hadronic decays of the Z at LEP is presented, based on 1.3 million hadronic events collected~ by the DELPHI~ detector in the 1994 LEP running~ period. The DELPHI ring imaging Cherenkov counters are used for identifying hadrons. The average \Delta^{++}(1232) multiplicity per hadronic event is 0.079 \pm 0.015 which is more than a factor of two below the JETSET, HERWIG and UCLA model predictions. It agrees with a recently proposed universal mass dependence of particle production rates in e^{+}e^- annihilations.
Measurement of correlations between pions from different W's in e+e- → W+W- events
1997
Correlations between pions from different W's in e(+)e(-) --> W+W- events are studied using data collected by the DELPHI detector at LEP running at a centre-of-mass energy of 172 GeV in 1996. At the present level of statistics, no enhancement of the correlation function above that expected from a pair of uncorrelated W's is observed at small values of the four-momentum difference of the pions. (C) 1997 Published by Elsevier Science B.V.
Two-particle angular correlations in e(+)e(-) interactions compared with QCD predictions
1998
Two-particle angular correlations in jet cones have been measured in e(+)e(-) annihilation into hadrons at LEP energies (root s = 91 and 183 GeV) and are compared with QCD predictions using the LPHD hypothesis. Two different functions have been tested. While the differentially normalized correlation function shows substantial deviations from the predictions, a globally normalized correlation function agrees well. The size of alpha(s)(eff) land other QCD parameters) and its running with the relevant angular scale, the validity of LPHD, and problems due to non-perturbative effects are discussed critically. (C) 1998 Elsevier Science B.V. All rights reserved.
First measurement of quarkonium polarization in nuclear collisions at the LHC
2021
The polarization of inclusive J/$\psi$ and $\Upsilon(1{\rm S})$ produced in Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}=5.02$ TeV at the LHC is measured with the ALICE detector. The study is carried out by reconstructing the quarkonium through its decay to muon pairs in the rapidity region $2.5<y<4$ and measuring the polar and azimuthal angular distributions of the muons. The polarization parameters $\lambda_{\theta}$, $\lambda_{\phi}$ and $\lambda_{\theta\phi}$ are measured in the helicity and Collins-Soper reference frames, in the transverse momentum interval $2<p_{\rm T}<10$ GeV/$c$ and $p_{\rm T}<15$ GeV/$c$ for the J/$\psi$ and $\Upsilon(1{\rm S})$, respectively. The polarization parameter…
A precise measurement of the Z resonance parameters through its hadronic decays
1990
A measurement of the cross section for e+e-→ hadrons using 11 000 hadronic decays of the Z boson at ten different center-of-mass energies is presented. A three-parameter fit gives the following values for the Z mass MZ, the total width ΓZ, the product of the electronic and hadronic partial widths ΓeΓh, and the unfolded pole cross section σ0: MZ = 91.171 ± 0.030 (stat.) ± 0.030 (beam) GeV, ΓZ = 2.511 ± 0.065 GeV, ΓeΓh = 0.148 ± 0.006 (stat.) ± 0.004 (syst.) GeV2, σ0 = 41.6 ± 0.7 (stat.) ± 1.1 (syst.) nb, Good agreement with the predictions of the standard model is observed. From a two-parameter fit the number of massless neutrino generations is found to be Nv = 2.91 ± 0.26. Thus the hypothes…
Energy dependence of the differences between the quark and gluon jet fragmentation
1996
Three jet events arising from decays of the Z beson, collected by the DELPHI detector, were used to measure differences in quark and gluon fragmentation. Gluon jets were anti-tagged by identifying b quark jets. Unbiased quark jets came from events with two jets plus one photon. Quark and gluon jet properties in different energy ranges were compared for the first time within the same detector. Quark and gluon jets of nearly the same energy in symmetric three jet event topologies were also compared. Using three independent methods, the average value of the ratio of the mean charged multiplicities of gluon and quark jets is [ r ] = 1.241 +/- 0.015 (stat.) +/- 0.025 (syst.). Gluon jets are broa…
Multi-strange baryon production in p Pb collisions at sNN=5.02 TeV
2016
The multi-strange baryon yields in Pb--Pb collisions have been shown to exhibit an enhancement relative to pp reactions. In this work, $\Xi$ and $\Omega$ production rates have been measured with the ALICE experiment as a function of transverse momentum, ${p_{\rm T}}$, in p-Pb collisions at a centre-of-mass energy of ${\sqrt{s_{\rm NN}}}$ = 5.02 TeV. The results cover the kinematic ranges 0.6 GeV/$c<{p_{\rm T}} <$7.2 GeV/$c$ and 0.8 GeV/$c<{p_{\rm T}}<$ 5 GeV/$c$, for $\Xi$ and $\Omega$ respectively, in the common rapidity interval -0.5 $<{y_{\rm CMS}}<$ 0. Multi-strange baryons have been identified by reconstructing their weak decays into charged particles. The ${p_{\rm T}}$ spectra are ana…
Production of (anti-)He3 and (anti-)H3 in p-Pb collisions at sNN=5.02 TeV
2020
The transverse momentum (pT) differential yields of (anti-)3He and (anti-)3H measured in p-Pb collisions at √sNN = 5.02 TeV with ALICE at the Large Hadron Collider (LHC) are presented. The ratios of the pTintegrated yields of (anti-)3He and (anti-)3H to the proton yields are reported, as well as the pT dependence of the coalescence parameters B3 for (anti-)3 He and (anti-)3H. For (anti-)3He, the results obtained in four classes of the mean charged-particle multiplicity density are also discussed. These results are compared to predictions from a canonical statistical hadronization model and coalescence approaches. An upper limit on the total yield of 4He is determined.
First study of the two-body scattering involving charm hadrons
2022
Physical review / D 106(5), 052010 (2022). doi:10.1103/PhysRevD.106.052010
Neutral pion and η meson production in proton–proton collisions at s=0.9 TeV and s=7 TeV
2012
The first measurements of the invariant differential cross sections of inclusive pi(0) and eta meson production at mid-rapidity in proton-proton collisions root s = 0.9 TeV and root s = 7 TeV are reported. The pi(0) measurement covers the ranges 0.4 < p(T) < 7 GeV/c and 0.3 < p(T) < 25 GeV/c for these two energies, respectively. The production of eta mesons was measured at root s = 7 TeV in the range 0.4 < p(T) < 15 GeV/c. Next-to-Leading Order perturbative QCD calculations, which are consistent with the pi(0) spectrum at root s = 0.9 TeV, overestimate those of pi(0) and eta mesons at root s = 7 TeV, but agree with the measured eta/pi(0) ratio at root s = 7 TeV. (C) 2012 CERN. Published by …
Transverse Momentum Distribution and Nuclear Modification Factor of Charged Particles inp+PbCollisions atsNN=5.02 TeV
2013
The transverse momentum (pT) distribution of primary charged particles is measured in minimum bias (non-single-diffractive) p + Pb collisions at root(NN)-N-s = 5.02 TeV with the ALICE detector at the LHC. The pT spectra measured near central rapidity in the range 0.5< p(T) < 20 GeV/c exhibit a weak pseudorapidity dependence. The nuclear modification factor R-pPb is consistent with unity for p(T) above 2 GeV/c. This measurement indicates that the strong suppression of hadron production at high p(T) observed in Pb + Pb collisions at the LHC is not due to an initial-state effect. The measurement is compared to theoretical calculations. DOI: 10.1103/PhysRevLett.110.082302
Study of the leptonic decays of the Z0 boson
1990
Measurements are presented of the cross section ratios Rℓ = σℓ(e+e-→ℓ+ℓ -)/σhh(e+e-→hadrons) for ℓ = e, μ and τ using data taken from a scan around the Z0. The results are Re = (5.09±0.32±0.18)%, Rμ = (4.96±0.35±0.17)% and Rτ,=(4.72±0.38± 0.29)% where, for the ratio Re, the t-channel contribution has been subtracted. These results are consistent with the hypothesis of lepton universality and test this hypothesis at the energy scale s ∼ 8300 GeV2. The absolute cross sections σℓ(e+e-→ℓ +ℓ-) have also been measured. From the cross sections the leptonic partial widths Γe = (83.2±3.0±2.4) MeV, (ΓeΓμ) 1/2=(84.6±3.0±2.4) MeV and (ΓeΓτ) 1/2=(82.6±3.3±3.2) MeV have been extracted. Assuming lepton un…
Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions atsNN=5.02 TeV
2016
The pseudorapidity density of charged particles, dNch/dη, at midrapidity in Pb-Pb collisions has been measured at a center-of-mass energy per nucleon pair of √sNN=5.02 TeV. For the 5% most central collisions, we measure a value of 1943 ± 54. The rise in dNch/dη as a function of √sNN p is steeper than that observed in proton-proton collisions and follows the trend established by measurements at lower energy. The increase of dNch/dη as a function of the average number of participant nucleons, ⟨Npart⟩, calculated in a Glauber model, is compared with the previous measurement at √sNN=2.76 TeV. A constant factor of about 1.2 describes the increase in dNch/dη from √sNN=2.76 to 5.02 TeV for all cen…
Azimuthal anisotropy of charged jet production in sNN=2.76 TeV Pb–Pb collisions
2016
We present measurements of the azimuthal dependence of charged jet production in central and semicentral √sNN = 2.76 TeV Pb–Pb collisions with respect to the second harmonic event plane, quantified as vch jet 2 . Jet finding is performed employing the anti-kT algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero vch jet 2 is observed in semi-central …
Determination of the event collision time with the ALICE detector at the LHC
2017
The European physical journal / Plus 132(2), 99 (2017). doi:10.1140/epjp/i2017-11279-1
Inclusive J/ψ production in pp collisions at s=2.76 TeV
2012
The ALICE Collaboration has measured inclusive J/psi production in pp collisions at a center of mass energy sqrt(s)=2.76 TeV at the LHC. The results presented in this Letter refer to the rapidity ranges |y|<0.9 and 2.5
Performance of the ALICE VZERO system
2013
ALICE is an LHC experiment devoted to the study of strongly interacting matter in proton-proton, proton--nucleus and nucleus-nucleus collisions at ultra-relativistic energies. The ALICE VZERO system, made of two scintillator arrays at asymmetric positions, one on each side of the interaction point, plays a central role in ALICE. In addition to its core function as a trigger, the VZERO system is used to monitor LHC beam conditions, to reject beam-induced backgrounds and to measure basic physics quantities such as luminosity, particle multiplicity, centrality and event plane direction in nucleus-nucleus collisions. After describing the VZERO system, this publication presents its performance o…
Two-particle differential transverse momentum and number density correlations in p−Pb collisions at 5.02 TeV and Pb-Pb collisions at 2.76 TeV at the …
2019
The production cross section and the transverse momentum distribution of charged particles is measured in pp collisions at √s = 2.76 TeV, 5.02 TeV, 7 TeV and 13 TeV, as well as for Pb-Pb collision at √s_NN = 5.02 TeV and Xe-Xe at √s_NN = 5.44 TeV in ALICE at the LHC. The measurement is performed in the transverse momentum region of 0.15 results show a faster-than-linear increase with the center-of-mass energy and follow a similar trend with respect to previous measurements. The analysis of the p_T spectra in multiplicity intervals show a weak center-of-mass energy dependence when they are compared to their respective inelastic (INEL) pp measurement. The average multiplicity as a function of…
Production of muons from heavy-flavour hadron decays at high transverse momentum in Pb–Pb collisions atsNN=5.02and 2.76 TeV
2021
Abstract Measurements of the production of muons from heavy-flavour hadron decays in Pb–Pb collisions at s NN = 5.02 and 2.76 TeV using the ALICE detector at the LHC are reported. The nuclear modification factor R AA at s NN = 5.02 TeV is measured at forward rapidity ( 2.5 y 4 ) as a function of transverse momentum p T in central, semi-central, and peripheral collisions over a wide p T interval, 3 p T 20 GeV/c, in which muons from beauty-hadron decays are expected to take over from charm as the dominant source at high p T ( p T > 7 GeV/c). The R AA shows an increase of the suppression of the yields of muons from heavy-flavour hadron decays with increasing centrality. A suppression by a fact…
Study of the four-jet anomaly observed at LEP centre-of-mass energies of 130 and 136 GeV
1999
The four-jet events collected by DELPHI during the special LEP run at centre-of-mass energies of 130 and 136 GeV in 1997 with an integrated luminosity of 5.9 pb(-1) are analysed. Their rate and the distributions of their di-jet masses, their smallest jet charges, and their di-jet charge separations all agree well with Standard Model predictions. Thus the hypothesis of pair production of a new particle with a sum of di-jet masses around 105 GeV/c(2) is not supported. The combined result of the four LEP collaborations refuting this hypothesis at over 99% confidence level is also given. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
Measurement of the Cross Section for Electromagnetic Dissociation with Neutron Emission in Pb-Pb Collisions atsNN=2.76 TeV
2012
The first measurement of neutron emission in electromagnetic dissociation of Pb-208 nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at root s(NN) = 2.76 TeV with neutron emission are sigma(singleEMD) = 187.4 +/- 0.2(stat)(-11.2)(+13.2) (syst) b and sigma(mutualEMD) = 5. 7 +/- 0.1(stat) +/- 0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model. DOI: 10.1103/PhysRevLett.109.252302
Inclusive heavy-flavour production at central and forward rapidity in Xe–Xe collisions at TeV
2021
The first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe–Xe collisions at sNN=5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor RAA is performed as a function of transverse momentum pT in several centrality classes at forward rapidity (2.5<y<4) and midrapidity (|y|<0.8) for muons and electrons from heavy-flavour hadron decays, respectively. A suppression by a factor up to about 2.5 compared to the binary-scaled pp reference is observed in central collisions at both central and forward rapidities. The RAA of muons from heavy-flavour hadron decays is compared to previous measur…
Coherent ψ(2S) photo-production in ultra-peripheral Pb Pb collisions at sNN=2.76 TeV
2015
We have performed the first measurement of the coherent ψ(2S) photo-production cross section in ultraperipheral Pb–Pb collisions at the LHC. This charmonium excited state is reconstructed via the ψ(2S) → l +l − and ψ(2S) → J/ψπ+π− decays, where the J/ψ decays into two leptons. The analysis is based on an event sample corresponding to an integrated luminosity of about 22 μb−1. The cross section for coherent ψ(2S) production in the rapidity interval −0.9 < y < 0.9 is dσcoh ψ(2S)/dy = 0.83±0.19 stat+syst mb. The ψ(2S) to J/ψ coherent cross section ratio is 0.34+0.08 −0.07(stat + syst). The obtained results are compared to predictions from theoretical models.
Suppression of ϒ(1S) at forward rapidity in Pb–Pb collisions at sNN=2.76 TeV
2014
We report on the measurement of the inclusive Υ (1S) production in Pb–Pb collisions at √sNN = 2.76 TeV carried out at forward rapidity (2.5 < y < 4) and down to zero transverse momentum using its μ+μ− decay channel with the ALICE detector at the Large Hadron Collider. A strong suppression of the inclusive Υ (1S) yield is observed with respect to pp collisions scaled by the number of independent nucleon– nucleon collisions. The nuclear modification factor, for events in the 0–90% centrality range, amounts to 0.30 ± 0.05(stat) ± 0.04(syst). The observed Υ (1S) suppression tends to increase with the centrality of the collision and seems more pronounced than in corresponding mid-rapidity measur…
Higher Harmonic Anisotropic Flow Measurements of Charged Particles in Pb-Pb Collisions atsNN=2.76 TeV
2011
We report on the first measurement of the triangular nu(3), quadrangular nu(4), and pentagonal nu(5) charged particle flow in Pb-Pb collisions at root s(NN) = 2.76 TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow nu(2) and nu(3) have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained fr…
Centrality determination of Pb-Pb collisions atsNN=2.76TeV with ALICE
2013
This publication describes the methods used to measure the centrality of inelastic Pb-Pb collisions at a center-of-mass energy of 2.76 TeV per colliding nucleon pair with ALICE. The centrality is a key parameter in the study of the properties of QCD matter at extreme temperature and energy density, because it is directly related to the initial overlap region of the colliding nuclei. Geometrical properties of the collision, such as the number of participating nucleons and the number of binary nucleon-nucleon collisions, are deduced from a Glauber model with a sharp impact parameter selection and shown to be consistent with those extracted from the data. The centrality determination provides …
Measurement of jet suppression in central Pb–Pb collisions at sNN=2.76 TeV
2015
The transverse momentum(p(T)) spectrum and nuclear modification factor (R-AA) of reconstructed jets in 0-10% and 10-30% central Pb-Pb collisions at root s(NN) = 2.76 TeV were measured. Jets were reconstructed using the anti-k(T) jet algorithm with a resolution parameter of R = 0.2 from charged and neutral particles, utilizing the ALICE tracking detectors and Electromagnetic Calorimeter (EMCal). The jet p(T) spectra are reported in the pseudorapidity interval of \eta(jet)\ 5 GeV/c to suppress jets constructed from the combinatorial background in Pb-Pb collisions. The leading charged particle requirement applied to jet spectra both in pp and Pb-Pb collisions had a negligible effect on the R-A…
Multiplicity dependence of charged pion, kaon, and (anti)proton production at large transverse momentum in p–Pb collisions at sNN=5.02 TeV
2016
The production of charged pions, kaons and (anti)protons has been measured at mid-rapidity ($-0.5 10$ GeV/$c$), the particle ratios are consistent with those reported for pp and Pb-Pb collisions at the LHC energies. At intermediate $p_{\rm T}$ the (anti)proton $R_{\rm pPb}$ shows a Cronin-like enhancement, while pions and kaons show little or no nuclear modification. At high $p_{\rm T}$ the charged pion, kaon and (anti)proton $R_{\rm pPb}$ are consistent with unity within statistical and systematic uncertainties.
Longitudinal and azimuthal evolution of two-particle transverse momentum correlations in Pb–Pb collisions at sNN=2.76TeV
2020
This paper presents the first measurements of the charge independent (CI) and charge dependent (CD) two-particle transverse momentum correlators G2CI and G2CD in Pb–Pb collisions at sNN=2.76TeV by the ALICE collaboration. The two-particle transverse momentum correlator G2 was introduced as a measure of the momentum current transfer between neighboring system cells. The correlators are measured as a function of pair separation in pseudorapidity (Δη) and azimuth (Δφ) and as a function of collision centrality. From peripheral to central collisions, the correlator G2CI exhibits a longitudinal broadening while undergoing a monotonic azimuthal narrowing. By contrast, G2CD exhibits a narrowing alo…
Investigations of Anisotropic Flow Using Multiparticle Azimuthal Correlations in pp, p-Pb, Xe-Xe, and Pb-Pb Collisions at the LHC
2019
Measurements of anisotropic flow coefficients ($v_n$) and their cross-correlations using two- and multi-particle cumulant methods are reported in collisions of pp at $\sqrt{s} = 13$ TeV, p-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV, Xe-Xe at $\sqrt{s_{_{\rm NN}}} = 5.44$ TeV, and Pb-Pb at $\sqrt{s_{_{\rm NN}}} = 5.02$ TeV recorded with the ALICE detector. The multiplicity dependence of $v_n$ is studied in a very wide range from 20 to 3000 particles produced in the mid-rapidity region $|��|<0.8$ for the transverse momentum range $0.2 < p_{\rm T} < 3.0$ GeV/$c$. An ordering of the coefficients $v_2 > v_3 > v_4$ is found in pp and p-Pb collisions, similar to that seen in large coll…
Femtoscopy ofppcollisions ats=0.9and 7 TeV at the LHC with two-pion Bose-Einstein correlations
2011
We report on the high statistics two-pion correlation functions from pp collisions at root s = 0.9 TeV and root s = 7 TeV, measured by the ALICE experiment at the Large Hadron Collider. The correlation functions as well as the extracted source radii scale with event multiplicity and pair momentum. When analyzed in the same multiplicity and pair transverse momentum range, the correlation is similar at the two collision energies. A three-dimensional femtoscopic analysis shows an increase of the emission zone with increasing event multiplicity as well as decreasing homogeneity lengths with increasing transverse momentum. The latter trend gets more pronounced as multiplicity increases. This sug…
Global polarization of Λ and Λ¯ hyperons in Pb-Pb collisions at sNN= 2.76 and 5.02 TeV
2020
The global polarization of the $\Lambda$ and $\overline\Lambda$ hyperons is measured for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV recorded with the ALICE at the LHC. The results are reported differentially as a function of collision centrality and hyperon's transverse momentum ($p_{\rm{T}}$) for the range of centrality 5-50%, $0.5 < p_{\rm{T}} <5$ GeV/$c$, and rapidity $|y|<0.5$. The hyperon global polarization averaged for Pb-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 2.76 and 5.02 TeV is found to be consistent with zero, $\langle P_{\rm{H}}\rangle$ (%) $\approx$ 0.01 $\pm$ 0.06 (stat.) $\pm$ 0.03 (syst.) in the collision centrality range 15-50%, where the largest signal i…
Pion–kaon femtoscopy and the lifetime of the hadronic phase in Pb−Pb collisions at sNN=2.76 TeV
2021
Abstract In this paper, the first femtoscopic analysis of pion–kaon correlations at the LHC is reported. The analysis was performed on the Pb–Pb collision data at s NN = 2.76 TeV recorded with the ALICE detector. The non-identical particle correlations probe the spatio-temporal separation between sources of different particle species as well as the average source size of the emitting system. The sizes of the pion and kaon sources increase with centrality, and pions are emitted closer to the centre of the system and/or later than kaons. This is naturally expected in a system with strong radial flow and is qualitatively reproduced by hydrodynamic models. ALICE data on pion–kaon emission asymm…
Search for scalar quarks in Z0 decays
1990
A search has been made for pairs of scalar quarks (squarks) produced in e+e- annihilations at LEP (√s≃MZ0), and decaying into a standard quark and a neutral, non-interacting, stable, massive particle (the lightest supersymmetric particle, LSP). The search has been conducted for differences in the mass of the squark and LSP of 2 GeV/c2 and above. Up squarks with masses below 42 GeV/c2 and down squarks below 43 GeV/c2 were excluded. Six squark flavours degenerate in mass were excluded below 45 GeV/c2.
Multiplicity dependence of mean transverse momentum in $e^+e^-$ annihilations at LEP energies
1992
A strong increase of the mean transverse momentum [p(t)] with the number of charged particles n(ch) is observed in e+e- annihilations into hadrons at LEP energies, The effect resembles correlations observed in hadron-hadron interactions. In e+e- annihilations the [p(t)] and n(ch) correlations can be accounted for by gluon radiation.
Charged particle multiplicity distributions in restricted rapidity intervals in Z0 hadronic decays.
1991
The multiplicity distributions of charged particles in restricted rapidity intervals in Z0 hadronic decays measured by the DELPHI detector are presented. The data reveal a shoulder structure, best visible for intervals of intermediate size, i.e. for rapidity limits around ±1.5. The whole set of distributions including the shoulder structure is reproduced by the Lund Parton Shower model. The structure is found to be due to important contributions from 3-and 4-jet events with a hard gluon jet. A different model, based on the concept of independently produced groups of particles, "clans", fluctuating both in number per event and particle content per clan, has also been used to analyse the pres…
Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb–Pb collisions at sNN=2.76 TeV
2016
State Committee of Science, World Federation of Scientists (WFS) and Swiss Fonds Kidagan, Armenia; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP); National Natural Science Foundation of China (NSFC), the Chinese Ministry of Education (CMOE) and the Ministry of Science and Technology of China (MSTC); Ministry of Education and Youth of the Czech Republic; Danish Natural Science Research Council, the Carlsberg Foundation and the Danish National Research Foundation; The European Research Council under the European Community's Seventh Framework Programme; Helsinki Inst…
Measurement of an Excess in the Yield ofJ/ψat Very LowpTin Pb–Pb Collisions atsNN=2.76 TeV
2016
We report on the first measurement of an excess in the yield of J/ψ at very low transverse momentum (pT< 0.3 GeV/c) in peripheral hadronic Pb-Pb collisions at √sNN = 2.76 TeV, performed by ALICE at the CERN LHC. Remarkably, the measured nuclear modification factor of J/ψ in the rapidity range 2.5< y< 4 reaches about 7 (2) in the pT range 0- 0.3 GeV/c in the 70-90% (50-70%) centrality class. The J/ψ production cross section associated with the observed excess is obtained under the hypothesis that coherent photoproduction of J/ψ is the underlying physics mechanism. If confirmed, the observation of J/ψ coherent photoproduction in Pb-Pb collisions at impact parameters smaller than twice the nuc…
Measurements of inclusive jet spectra in pp and central Pb-Pb collisions at sNN=5.02TeV
2020
This article reports measurements of the pT- differential inclusive jet cross section in pp collisions at √s=5 .02TeV and the pT- differential inclusive jet yield in Pb-Pb 0–10% central collisions at√sNN =5.02TeV. Jets were reconstructed at midrapidity with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm. For ppcollisions, we report jet cross sections for jet resolution parameters R =0.1–0.6 over the range 20 < pT, jet < 140 GeV/c, as well as the jet cross-section ratios of different R and comparisons to two next-to-leading-order (NLO)– based theoretical predictions. For Pb-Pb collisions, we report the R=0.2 and R=0.4 jet spectra for 40 < pT, jet < 1…
Transverse-momentum and event-shape dependence of D-meson flow harmonics in Pb–Pb collisions at
2021
A. I. Alikhanyan National Science Laboratory (Yerevan Physics Institute) Foundation (ANSL), State Committee of Science and World Federation of Scientists (WFS), Armenia; Austrian Academy of Sciences, Austrian Science Fund (FWF): [M 2467-N36] and Nationalstiftung fur Forschung, Technologie und Entwicklung, Austria; Ministry of Communications and High Technologies, National Nuclear Research Center, Azerbaijan; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Financiadora de Estudos e Projetos (Finep), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) and Universidade Federal do Rio Grande do Sul (UFRGS), Brazil; Ministry of Education of China (MOEC), Ministry …
Charm-quark fragmentation fractions and production cross section at midrapidity in pp collisions at the LHC
2022
Physical review / D 105(1), L011103 (2022). doi:10.1103/PhysRevD.105.L011103
Determination of 55-155-155-1in second order QCD from hadronic Z decays
1992
Distributions of event shape variables obtained from 120600 hadronic Z decays measured with the DELPHI detector are compared to the predictions of QCD based event generators. Values of the strong coupling constant αs are derived as a function of the renormalization scale from a quantitative analysis of eight hadronic distributions. The final result, αs(MZ), is based on second order perturbation theory and uses two hadronization corrections, one computed with a parton shower model and the other with a QCD matrix element model. © 1992 Springer-Verlag.
Centrality dependence ofπ,K, andpproduction in Pb-Pb collisions atsNN=2.76TeV
2013
In this paper measurements are presented of pi(+/-), K-+/-, p, and (p) over bar production at midrapidity (vertical bar y vertical bar < 0.5), in Pb-Pb collisions at root s(NN) = 2.76 TeV as a function of centrality. The measurement covers the transverse-momentum (p(T)) range from 100, 200, and 300 MeV/c up to 3, 3, and 4.6 GeV/c for pi, K, and p, respectively. The measured p(T) distributions and yields are compared to expectations based on hydrodynamic, thermal and recombination models. The spectral shapes of central collisions show a stronger radial flow than measured at lower energies, which can be described in hydrodynamic models. In peripheral collisions, the p(T) distributions are not…
Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions atsNN=2.76TeV
2016
We report on results obtained with the event-shape engineering technique applied to Pb-Pb collisions at √sNN=2.76 TeV. By selecting events in the same centrality interval, but with very different average flow, different initial-state conditions can be studied. We find the effect of the event-shape selection on the elliptic flow coefficient v2 to be almost independent of transverse momentum pT, which is as expected if this effect is attributable to fluctuations in the initial geometry of the system. Charged-hadron, -pion, -kaon, and -proton transverse momentum distributions are found to be harder in events with higher-than-average elliptic flow, indicating an interplay between radial and ell…
Measurement of inclusive ρ0, f0(980), f2(1270), K and f′2(1525) production in Z0 decays
1999
DELPHI results are presented on the inclusive production of the neutral mesons ρ0, f0(980), f2(1270), KView the MathML source and f′2(1525) in hadronic Z0 decays. They are based on about 2 million multihadronic events collected in 1994 and 1995, using the particle identification capabilities of the DELPHI Ring Imaging Cherenkov detectors and measured ionization losses in the Time Projection Chamber. The total production rates per hadronic Z0 decay have been determined to be: 1.19±0.10 for ρ0; 0.164±0.021 for f0(980); 0.214±0.038 for f2(1270); 0.073±0.023 for KView the MathML source; and 0.012±0.006 for f′2(1525). The total production rates for all mesons and differential cross-sections for …
Production of inclusive ϒ(1S) and ϒ(2S) in p–Pb collisions at sNN=5.02 TeV
2015
We report on the production of inclusive Y{hooktop}(1S) and Y{hooktop}(2S) in p-Pb collisions at √sNN=5.02 TeV at the LHC. The measurement is performed with the ALICE detector at backward (-4.46<ycms<-2.96) and forward (2.03<ycms<3.53) rapidity down to zero transverse momentum. The production cross sections of the Y{hooktop}(1S) and Y{hooktop}(2S) are presented, as well as the nuclear modification factor and the ratio of the forward to backward yields of Y{hooktop}(1S). A suppression of the inclusive Y{hooktop}(1S) yield in p-Pb collisions with respect to the yield from pp collisions scaled by the number of binary nucleon-nucleon collisions is observed at forward rapidity but not at backwar…
Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions atsNN=2.76 TeV
2011
The centrality dependence of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at root s(NN) = 2: 76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor of 2 from peripheral (70%-80%) to central (0%-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.
Lifetime and production rate of beauty baryons from Z decays
1995
The production and decay of beauty baryons (b-baryons) have been studied using 1.7 \times 10^6 Z hadronic decays collected by the DELPHI detector at LEP. Three different techniques were used to identify the b-baryons. The first method used pairs of a \Lambda and a lepton to tag the b-baryon decay. The second method associated fully reconstructed \Lambda_c baryons with leptons. The third analysis reconstructed the b-baryon decay points by forming secondary vertices from identified protons and muons of opposite sign. Using these methods the following production rates were measured: \begin{eqnarray*} f(\qb \ra \Bb) \times \BR(\Bb \ra \mLs \ell\bar{\nu}_{\ell}\X) & = & (0.30 \pm 0.06 \pm0.04)\%…
K*(892)0 and ϕ(1020) meson production at high transverse momentum in pp and Pb-Pb collisions at sNN=2.76 TeV
2017
The yields of the K*(892)(0) and phi(1020) resonances are measured in Pb-Pb collisions at root s(NN) = 2.76 TeV through their hadronic decays using the ALICE detector. The measurements are performed in multiple centrality intervals at mid-rapidity (vertical bar y vertical bar <0.5) in the transverse-momentum ranges 0.3 <p(T) <5 GeV/c for the K*(892)(0) and 0.5 <p(T) <5 GeV/c for the phi(1020). The yields of K*(892)(0) are suppressed in central Pb-Pb collisions with respect to pp and peripheral Pb-Pb collisions (perhaps due to rescattering of its decay products in the hadronic medium), while the longer-lived phi(1020) meson is not suppressed. These particles are also used as probes to study …
Correlated Event-by-Event Fluctuations of Flow Harmonics in Pb-Pb Collisions at sNN=2.76 TeV
2016
We report the measurements of correlations between event-by-event fluctuations of amplitudes of anisotropic flow harmonics in nucleus-nucleus collisions, obtained for the first time using a new analysis method based on multiparticle cumulants in mixed harmonics. This novel method is robust against systematic biases originating from non-flow effects and by construction any dependence on symmetry planes is eliminated. We demonstrate that correlations of flow harmonics exhibit a better sensitivity to medium properties than the individual flow harmonics. The new measurements are performed in Pb-Pb collisions at the centre-of-mass energy per nucleon pair of $\sqrt{s_{_{\rm NN}}}=2.76$ TeV by the…
Multiplicity dependence of K*(892)0 and ϕ(1020) production in pp collisions at s=13 TeV
2020
The striking similarities that have been observed between high-multiplicity proton-proton (pp) collisions and heavy-ion collisions can be explored through multiplicity-differential measurements of identified hadrons in pp collisions. With these measurements, it is possible to study mechanisms such as collective flow that determine the shapes of hadron transverse momentum ( pT ) spectra, to search for possible modifications of the yields of short-lived hadronic resonances due to scattering effects in an extended hadron-gas phase, and to investigate different explanations provided by phenomenological models for enhancement of strangeness production with increasing multiplicity. In this paper,…
Particle identification in ALICE: a Bayesian approach
2016
We present a Bayesian approach to particle identification (PID) within the ALICE experiment. The aim is to more effectively combine the particle identification capabilities of its various detectors. After a brief explanation of the adopted methodology and formalism, the performance of the Bayesian PID approach for charged pions, kaons and protons in the central barrel of ALICE is studied. PID is performed via measurements of specific energy loss ($\mathrm{d}E/\mathrm{d}x$) and time-of-flight. PID efficiencies and misidentification probabilities are extracted and compared with Monte Carlo simulations using high-purity samples of identified particles in the decay channels ${\rm K}^0_S \righta…
Search for charged Higgs bosons in e^{+}e^{-}$ collisions at √s=172 GeV
1998
This paper presents results on charged Higgs boson production, based on LEP data collected at √s = 172 GeV, that complement the previous DELPHI results obtained at centre of mass energies up to 161 GeV. The charged Higgs bosons are assumed to be pair produced and to decay either into a quark pair or into τVτ. The three different possible final states are included in the analysis. Data from ring imaging Cherenkov and microvertex detectors are used to identify the quarks as a cs pair. The number of candidates found is compatible with the background expected from standard processes. Combining the results of the present analysis with those of the previous analysis at lower energies, a new lower…
Measurement of the partial width of the decay of the Z0 into charm quark pairs
1990
A determination of the partial width Γc̄ of the Z0 boson into charm quark pairs is presented, based on a total sample of 36 900 Z0 hadronic decays measured with the DELPHI detector at the LEP collider. The production rate of cc events is derived from the inclusive analysis of charged pions coming from the decay of charmed meson D*+-→D0π+ and D*-→D̄0π- where the π± is constrained by kinematics to have a low pT with respect to the jet axis. The probability to procedure these π± from D*± decay in cc events is taken to be 0.31±0.05 as measured at √S = 10.55 GeV. The measured relative partial width Γ∞/Γh = 0.162± 0.030(stat.) ± 0.050(syst.) is in good agreement with the standard model value of 0…
Calibration of the photon spectrometer PHOS of the ALICE experiment
2019
Journal of Instrumentation 14(05), P05025 - P05025 (2019). doi:10.1088/1748-0221/14/05/P05025
Centrality dependence of particle production inp−Pbcollisions atsNN=5.02TeV
2015
We report measurements of the primary charged-particle pseudorapidity density and transverse momentum distributions in p-Pb collisions at root s(NN) = 5.02 TeV and investigate their correlation with experimental observables sensitive to the centrality of the collision. Centrality classes are defined by using different event-activity estimators, i.e., charged-particle multiplicities measured in three different pseudorapidity regions as well as the energy measured at beam rapidity (zero degree). The procedures to determine the centrality, quantified by the number of participants (N-part) or the number of nucleon-nucleon binary collisions (N-coll) are described. We show that, in contrast to Pb…
MEASUREMENT OF THE FORWARD-BACKWARD ASYMMETRY OF CHARM AND BOTTOM QUARKS AT THE Z-POLE USING D-ASTERISK(+/-)-MESONS
1995
The forward-backward asymmetries for the processes $$e^ + e^ - \to c\bar c$$ and $$e^ + e^ - \to b\bar b$$ at theZ resonance are measured using identifiedD *± mesons. In 905,000 selected hadronic events, taken in 1991 and 1992 with the DEL-PHI detector at LEP, 4757D *+→D 0π+ decays are reconstructed. Thec andb quark forward-backward asymmetries are determined to be: $$\begin{gathered} A_{FB}^{c\bar c} = 0.077 \pm 0.029(stat) \pm 0.012(sys), \hfill \\ A_{FB}^{b\bar b} = 0.059 \pm 0.062(stat) \pm 0.024(sys). \hfill \\ \end{gathered} $$ Constraining theb asymmetry to the value measured by DELPHI using independent analyses, the charm asymmetry is determined to be: $$A_{FB}^{c,const} = 0.068 \pm…
Centrality dependence of the nuclear modification factor of charged pions, kaons, and protons in Pb-Pb collisions atsNN=2.76TeV
2016
Transverse momentum (pT) spectra of pions, kaons, and protons up to pT=20GeV/c have been measured in Pb-Pb collisions at √sNN=2.76TeV using the ALICE detector for six different centrality classes covering 0%–80%. The proton-to-pion and the kaon-to-pion ratios both show a distinct peak at pT≈3GeV/c in central Pb-Pb collisions that decreases for more peripheral collisions. For pT>10GeV/c, the nuclear modification factor is found to be the same for all three particle species in each centrality interval within systematic uncertainties of 10%–20%. This suggests there is no direct interplay between the energy loss in the medium and the particle species composition in the hard core of the quenched…
J/ψPolarization inppCollisions ats=7 TeV
2012
The ALICE Collaboration has studied J/psi production in pp collisions at root s = 7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/psi polarization parameters lambda(theta) and lambda(phi) were obtained. The study was performed in the kinematic region 2: 5 < y < 4, 2 < p(t) < 8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.
Characterizing the initial conditions of heavy-ion collisions at the LHC with mean transverse momentum and anisotropic flow correlations
2022
Physics letters / B 834, 137393 (2022). doi:10.1016/j.physletb.2022.137393
mb at MZ
1998
Abstract The value of the b quark mass at the M Z scale defined in the MS renormalization scheme, m b ( M Z ), was determined using 2.8 million hadronic Z decays collected during 1992-1994 by the DELPHI detector to be m b (M Z )=2.67±0.25 ( stat. )±0.34 ( frag. )±0.27 ( theo. ) GeV/c 2 . The analysis considers NLO corrections to the three-jet production rate including mass effects, and the result obtained agrees with the QCD prediction of having a running b quark mass at an energy scale equal to M Z . This is the first time that such a measurement is performed far above the b b production threshold. The study also verifies the flavour independence of the strong coupling constant for b and l…
A measurement of the photon structure function F-2(gamma) at an average Q(2) of 12 GeV2/c(4)
1995
The hadronic photon structure function F_{2}^{gamma} has been measured in the Q^{2} range from 4 to 30~GeV^2/c^{4} and down to x values of order 0.001, using data taken with the DELPHI detector at LEP between 1991 and 1993. A comparison is made with several F_{2}^{gamma} parameterizations with special emphasis on their low x behaviour. A result on the Q^{2} evolution of F_{2}^{gamma} is presented.
Search for scalar leptoquarks from Z$^0$ decays
1992
We have searched for pair produced scalar leptoquarks each decaying to a quark and a charged lepton in a sample of 116 000 hadronic Z0 events produced at LEP. No candidate was detected and cross section and branching ratio limits are set for the above process at 95% CL. Mass limits are found to be about 42 GeV/c2 depending only slightly on the models used and a coupling times branching ratio exclusion line is drawn for a scalar leptoquark with a free coupling. We have also probed the mass region above 45 GeV/c2 for a singly produced scalar leptoquark and set limits on the cross section and the coupling lambda(2)/4-pi up to 60 GeV.
MEASUREMENT OF THE GAMMA(B-B-OVER-BAR)/GAMMA(HAD) BRANCHING RATIO OF THE Z BY DOUBLE HEMISPHERE TAGGING
1995
Two measurements of {Mathematical expression} are presented. Both measurements use 250000 Z decays taken with the DELPHI detector in 1991 and rely mainly on the precision of the microvertex detector. One tagging method is as simple as possible so that background rates can be reliably predicted by simulation. The other one uses a more involved tagging technique and reduces the dependence on simulation as much as possible. Combining both results, {Mathematical expression} is found to be 0.2209±0.0041(stat.)±0.0042(syst.)±0.0018 {Mathematical expression}. © 1995 Springer-Verlag.
J/ production as a function of charged-particle pseudorapidity density in p–Pb collisions at
2017
We report measurements of the inclusive J/ψ yield and average transverse momentum as a function of charged-particle pseudorapidity density dNch/dη in p–Pb collisions at sNN=5.02TeV with ALICE at the LHC. The observables are normalised to their corresponding averages in non-single diffractive events. An increase of the normalised J/ψ yield with normalised dNch/dη, measured at mid-rapidity, is observed at mid-rapidity and backward rapidity. At forward rapidity, a saturation of the relative yield is observed for high charged-particle multiplicities. The normalised average transverse momentum at forward and backward rapidities increases with multiplicity at low multiplicities and saturates beyo…
Global baryon number conservation encoded in net-proton fluctuations measured in Pb–Pb collisions at sNN=2.76 TeV
2020
Experimental results are presented on event-by-event net-proton fluctuation measurements in Pb–Pb collisions at sNN=2.76 TeV, recorded by the ALICE detector at the CERN LHC. These measurements have as their ultimate goal an experimental test of Lattice QCD (LQCD) predictions on second and higher order cumulants of net-baryon distributions to search for critical behavior near the QCD phase boundary. Before confronting them with LQCD predictions, account has to be taken of correlations stemming from baryon number conservation as well as fluctuations of participating nucleons. Both effects influence the experimental measurements and are usually not considered in theoretical calculations. For t…