Search results for "hiukkasfysiikka"
showing 10 items of 536 documents
Production of light-flavor hadrons in pp collisions at √s = 7 and √s = 13 TeV
2021
The production of π±, K±, K0S, K∗(892)0, p, ϕ(1020), Λ, Ξ−, Ω−, and their antiparticles was measured in inelastic proton–proton (pp) collisions at a center-of-mass energy of √s = 13 TeV at midrapidity (|y|<0.5) as a function of transverse momentum (pT) using the ALICE detector at the CERN LHC. Furthermore, the single-particle pT distributions of K0S, Λ, and Λ¯ in inelastic pp collisions at √s = 7 TeV are reported here for the first time. The pT distributions are studied at midrapidity within the transverse momentum range 0≤pT≤20 GeV/c, depending on the particle species. The pT spectra, integrated yields, and particle yield ratios are discussed as a function of collision energy and compared …
Global polarization of ΛΛ¯ hyperons in Pb-Pb collisions at √sNN = 2.76 and 5.02 TeV
2020
The global polarization of the Λ and Λ¯ hyperons is measured for Pb-Pb collisions at √sNN=2.76 and 5.02 TeV recorded with the ALICE at the Large Hadron Collider (LHC). The results are reported differentially as a function of collision centrality and hyperon's transverse momentum (pT) for the range of centrality 5–50%, 0.5<5 GeV/c, and rapidity |y|<0.5. The hyperon global polarization averaged for Pb-Pb collisions at √sNN=2.76 and 5.02 TeV is found to be consistent with zero, ⟨PH⟩(%)≈0.01±0.06(stat.)±0.03(syst.) in the collision centrality range 15–50%, where the largest signal is expected. The results are compatible with expectations based on an extrapolation from measurements at lower coll…
ϒ production in p–Pb collisions at √sNN = 8.16 TeV
2020
ϒ production in p–Pb interactions is studied at the centre-of-mass energy per nucleon–nucleon collision √sNN=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<3.53 and −4.46<−2.96, down to zero transverse momentum. In this work, results on the ϒ(1S) production cross section as a function of rapidity and transverse momentum are presented. The corresponding nuclear modification factor shows a suppression of the ϒ(1S) yields with respect to pp collisions, both at forward and backward rapidity. This suppression is stronger in the low transverse momentu…
J/ψ and ψ(2S) production at forward rapidity in p+p collisions at √s = 510 GeV
2020
The PHENIX experiment at the Relativistic Heavy Ion Collider has measured the differential cross section, mean transverse momentum, mean transverse momentum squared of inclusive J/ψ, and cross section ratio of ψ(2S) to J/ψ at forward rapidity in p+p collisions at √s=510 GeV via the dimuon decay channel. Comparison is made to inclusive J/ψ cross sections measured at √s=200 GeV and 2.76–13 TeV. The result is also compared to leading-order nonrelativistic QCD calculations coupled to a color-glass-condensate description of the low-x gluons in the proton at low transverse momentum (pT) and to next-to-leading order nonrelativistic QCD calculations for the rest of the pT range. These calculation…
Measurement of electrons from beauty-hadron decays in p-Pb collisions at √sNN = 5.02 TeV and Pb-Pb collisions at √sNN = 2.76 TeV
2017
The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1<pT< 8 GeV/c in minimum-bias p-Pb collisions at √sNN=5.02 TeV and in 1.3 < pT< 8 GeV/c in the 20% most central Pb-Pb collisions at √sNN=2.76 TeV. The pp reference spectra at √sNN=5.02 TeV and √s=2.76 TeV, needed for the calculation of the nuclear modification factors RpPb and RPbPb, were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at √s=7 TeV. In the pT interval 3 < pT< 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to …
Measurement of prompt D0, D+, D*+, and D+S production in p–Pb collisions at √sNN = 5.02 TeV
2019
The measurement of the production of prompt D0, D+, D*+, and D+S mesons in proton–lead (p–Pb) collisions at the centre-of-mass energy per nucleon pair of √sNN = 5.02 TeV, with an integrated luminosity of 292 ± 11 μb−1, are reported. Differential production cross sections are measured at mid-rapidity (−0.96 < ycms< 0.04) as a function of transverse momentum (pT) in the intervals 0 < pT< 36 GeV/c for D0, 1 < pT< 36 GeV/c for D+ and D*+, and 2 < pT< 24 GeV/c for D+ mesons. For each species, the nuclear modification factor RpPb is calculated as a function of pT using a proton-proton (pp) reference measured at the same collision energy. The results are compatible with unity in the whole pT range…
Low-momentum direct-photon measurement in Cu + Cu collisions at √sNN = 200 GeV
2018
We measured direct photons for pT < 5 GeV/c in minimum bias and 0%–40% most-central events at midrapidity for Cu+Cu collisions at √sNN = 200 GeV. The e+e− contribution from quasireal direct virtual photons has been determined as an excess over the known hadronic contributions in the e+e− mass distribution. A clear enhancement of photons over the binary scaled p+p fit is observed for pT < 4 GeV/c in Cu+Cu data. The pT spectra are consistent with the Au+Au data covering a similar number of participants. The inverse slopes of the exponential fits to the excess after subtraction of the p+p baseline are 285 ± 53(stat) ± 57(syst) MeV/c and 333 ± 72(stat) ± 45(syst) MeV/c for minimum bias and 0%–4…
High-precision Q-value measurement and nuclear matrix element calculations for the double-β decay of 98Mo
2022
The 98Mo double-beta decay Q-value has been measured, and the corresponding nuclear matrix elements of neutrinoless double-beta (0νββ) decay and the standard two-neutrino double-beta (2νββ) decay have been provided by nuclear theory. The double-beta decay Q-value has been determined as Qββ=113.668(68) keV using the JYFLTRAP Penning trap mass spectrometer. It is in agreement with the literature value, Qββ=109(6) keV, but almost 90 times more precise. Based on the measured Q-value, precise phase-space factors for 2νββ decay and 0νββ decay, needed in the half-life predictions, have been calculated. Furthermore, the involved nuclear matrix elements have been computed in the proton–neutron quasi…
Soft-Dielectron Excess in Proton-Proton Collisions at √s = 13 TeV
2021
A measurement of dielectron production in proton-proton (pp) collisions at √s=13 TeV, recorded with the ALICE detector at the CERN LHC, is presented in this Letter. The data set was recorded with a reduced magnetic solenoid field. This enables the investigation of a kinematic domain at low dielectron (ee) invariant mass mee and pair transverse momentum pT,ee that was previously inaccessible at the LHC. The cross section for dielectron production is studied as a function of mee, pT,ee, and event multiplicity dNch/dη. The expected dielectron rate from hadron decays, called hadronic cocktail, utilizes a parametrization of the measured η/π0 ratio in pp and proton-nucleus collisions, assuming th…
p−p, p−Λ, and Λ−Λ correlations studied via femtoscopy in pp reactions at √s = 7 TeV
2019
We report on the first femtoscopic measurement of baryon pairs, such as p−p, p−Λ, and Λ−Λ, measured by ALICE at the Large Hadron Collider (LHC) in proton-proton collisions at √s=7 TeV. This study demonstrates the feasibility of such measurements in pp collisions at ultrarelativistic energies. The femtoscopy method is employed to constrain the hyperon-nucleon and hyperon-hyperon interactions, which are still rather poorly understood. A new method to evaluate the influence of residual correlations induced by the decays of resonances and experimental impurities is hereby presented. The p−p, p−Λ, and Λ−Λ correlation functions were fitted simultaneously with the help of a new tool developed spec…