showing 81 related works from this author
Search for contact interactions and large extra dimensions in dilepton events fromppcollisions ats=7 TeVwith the ATLAS detector
2013
A search for nonresonant new phenomena, originating from either contact interactions or large extra spatial dimensions, has been carried out using events with two isolated electrons or muons. These events, produced at the LHC in proton-proton collisions at root s = 7 TeV, were recorded by the ATLAS detector. The data sample, collected throughout 2011, corresponds to an integrated luminosity of 4.9 and 5.0 fb(-1) in the e(+)e(-) and mu(+)mu(-) channels, respectively. No significant deviations from the Standard Model expectation are observed. Using a Bayesian approach, 95% confidence level lower limits ranging from 9.0 to 13.9 TeV are placed on the energy scale of llqq contact interactions in…
Measurement of the top pair production cross section in 8 TeV proton-proton collisions using kinematic information in thelepton+jetsfinal state with …
2015
A measurement is presented of the (tt) over bar inclusive production cross section in pp collisions at a center-ofmass energy of pffisffiffi root s = 8 TeV using data collected by the ATLAS detector at the CERN Large Hadron Collider. The measurement was performed in the lepton + jets final state using a data set corresponding to an integrated luminosity of 20.3 fb(-1). The cross section was obtained using a likelihood discriminant fit and b-jet identification was used to improve the signal-to-background ratio. The inclusive (tt) over bar production cross section was measured to be 260 +/- 1(stat)(-23)(+22)(stat) +/- 8(lumi) +/- 4(beam) pb assuming a top-quark mass of 172.5 GeV, in good agre…
Search for New Phenomena intt¯Events with Large Missing Transverse Momentum in Proton-Proton Collisions ats=7 TeVwith the ATLAS Detector
2012
A search for new phenomena in tt events with large missing transverse momentum in proton-proton collisions at a center-of-mass energy of 7 TeV is presented. The measurement is based on 1.04 fb-1 of data collected with the ATLAS detector at the LHC. Contributions to this final state may arise from a number of standard model extensions. The results are interpreted in terms of a model where new top-quark partners are pair produced and each decay to an on-shell top (or antitop) quark and a long-lived undetected neutral particle. The data are found to be consistent with standard model expectations. A limit at 95% confidence level is set excluding a cross section times branching ratio of 1.1 pb …
Measurement of the azimuthal anisotropy for charged particle production insNN=2.76TeV lead-lead collisions with the ATLAS detector
2012
Differential measurements of charged particle azimuthal anisotropy are presented for lead-lead collisions at root sNN = 2.76 TeV with the ATLAS detector at the LHC, based on an integrated luminosity of approximately 8 mu b(-1). This anisotropy is characterized via a Fourier expansion of the distribution of charged particles in azimuthal angle relative to the reaction plane, with the coefficients v(n) denoting the magnitude of the anisotropy. Significant v(2)-v(6) values are obtained as a function of transverse momentum (0.5 = 3 are found to vary weakly with both eta and centrality, and their p(T) dependencies are found to follow an approximate scaling relation, v(n)(1/n)(p(T)) proportional …
Evidence ofWγγProduction inppCollisions ats=8 TeVand Limits on Anomalous Quartic Gauge Couplings with the ATLAS Detector
2015
This Letter reports evidence of triple gauge boson production pp -> W(l nu)gamma gamma + X, which is accessible for the first time with the 8 TeV LHC data set. The fiducial cross section for this process is measured in a data sample corresponding to an integrated luminosity of 20.3 fb(-1), collected by the ATLAS detector in 2012. Events are selected using the W boson decay to e nu or mu nu as well as requiring two isolated photons. The measured cross section is used to set limits on anomalous quartic gauge couplings in the high diphoton mass region.
Measurement of charged-particle event shape variables in inclusive(s)=7 TeVproton-proton interactions with the ATLAS detector
2013
The measurement of charged-particle event shape variables is presented in inclusive inelastic pp collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the LHC. The observables studied are the transverse thrust, thrust minor, and transverse sphericity, each defined using the final-state charged particles' momentum components perpendicular to the beam direction. Events with at least six charged particles are selected by a minimum-bias trigger. In addition to the differential distributions, the evolution of each event shape variable as a function of the leading charged-particle transverse momentum, charged-particle multiplicity, and summed transverse momentum is presented.…
Measurements of four-lepton production in pp collisions at s=8 TeV with the ATLAS detector
2016
A search is presented for a high-mass Higgs boson in the , , , and decay modes using the ATLAS detector at the CERN Large Hadron Collider. The search uses proton-proton collision data at a centre-o ...
Measurement of the cross section of high transverse momentumZ→bb¯production in proton–proton collisions ats=8 TeVwith the ATLAS detector
2014
This Letter reports the observation of a high transverse momentum Z -> b (b) over bar signal in proton-proton collisions at root s = 8TeVand the measurement of its production cross section. The data analysed were collected in 2012 with the ATLAS detector at the LHC and correspond to an integrated luminosity of 19.5 fb(-1). The Z -> b (b) over bar decay is reconstructed from a pair of b-tagged jets, clustered with the anti- k(t) jet algorithm with R = 0.4, that have low angular separation and form a dijet with p(T) > 200 GeV. The signal yield is extracted from a fit to the dijet invariant mass distribution, with the dominant, multi-jet background mass shape estimated by employing a fully dat…
Search for anomalous electroweak production of WW/WZ in association with a high-mass dijet system in pp collisions at s=8 TeV with the ATLAS detector
2017
A search is presented for anomalous quartic gauge boson couplings in vector-boson scattering. The data for the analysis correspond to $20.2$ fb$^{-1}$ of $\sqrt{s}=8$ TeV $pp$ collisions, and were collected in 2012 by the ATLAS experiment at the Large Hadron Collider. The search looks for the production of $WW$ or $WZ$ boson pairs accompanied by a high-mass dijet system, with one $W$ decaying leptonically, and a $W$ or $Z$ decaying hadronically. The hadronically decaying $W/Z$ is reconstructed as either two small-radius jets or one large-radius jet using jet substructure techniques. Constraints on the anomalous quartic gauge boson coupling parameters $\alpha_4$ and $\alpha_5$ are set by fit…
Measurement of inclusive jet charged-particle fragmentation functions in Pb+Pb collisions at sNN=2.76 TeV with the ATLAS detector
2014
Measurements of charged-particle fragmentation functions of jets produced in ultra-relativistic nuclear collisions can provide insight into the modification of parton showers in the hot, dense medi ...
Search for Higgs bosons decaying toaain theμμττfinal state inppcollisions ats=8 TeVwith the ATLAS experiment
2015
A search for the decay to a pair of new particles of either the 125 GeV Higgs boson (h) or a second charge parity (CP)-even Higgs boson (H) is presented. The data set corresponds to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded by the ATLAS experiment at the LHC in 2012. The search was done in the context of the next-to-minimal supersymmetric standard model, in which the new particles are the lightest neutral pseudoscalar Higgs bosons (a). One of the two a bosons is required to decay to two muons while the other is required to decay to two tau leptons. No significant excess is observed above the expected backgrounds in the dimuon invariant mass range fr…
Search for new phenomena in events with a photon and missing transverse momentum inppcollisions ats=8 TeVwith the ATLAS detector
2015
© 2015 CERN. © 2015 CERN, for the ATLAS Collaboration. Published by the American Physical Society under the terms of the »http://creativecommons.org/licenses/by/3.0/» Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Results of a search for new phenomena in events with an energetic photon and large missing transverse momentum with the ATLAS experiment at the LHC are reported. Data were collected in proton-proton collisions at a center-of-mass energy of 8 TeV and correspond to an integrated luminosity of 20.3 fb-1. The observed data are well described by the expe…
Search for an excess of events with an identical flavour lepton pair and significant missing transverse momentum in root s=7 TeV proton-proton collis…
2011
Results are presented of a search for supersymmetric particles decaying into final states with significant missing transverse momentum and exactly two identical flavour leptons (e or mu) of opposite charge in sqrt{s}=7 TeV collisions at the Large Hadron Collider. This channel is particularly sensitive to supersymmetric particle cascade decays producing flavour correlated lepton pairs. Flavour uncorrelated backgrounds are subtracted using a sample of opposite flavour lepton pair events. Observation of an excess beyond Standard Model expectations following this subtraction procedure would offer one of the best routes to measuring the masses of supersymmetric particles. In a data sample corres…
Measurement of the transverse momentum distribution ofWbosons inppcollisions ats=7 TeVwith the ATLAS detector
2012
This paper describes a measurement of the W boson transverse momentum distribution using ATLAS pp collision data from the 2010 run of the LHC at root s = 7 TeV, corresponding to an integrated lumin ...
Search for the neutral Higgs bosons of the Minimal Supersymmetric Standard Model in $pp$ collisions at $\sqrt{s}=7$ TeV with the ATLAS detector
2013
A search for neutral Higgs bosons of the Minimal Supersymmetric Standard Model (MSSM) is reported. The analysis is based on a sample of proton-proton collisions at a centre-of-mass energy of 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. The data were recorded in 2011 and correspond to an integrated luminosity of 4.7 fb[superscript −1] to 4.8 fb[superscript −1]. Higgs boson decays into oppositely-charged muon or τ lepton pairs are considered for final states requiring either the presence or absence of b-jets. No statistically significant excess over the expected background is observed and exclusion limits at the 95% confidence level are derived. The exclusion limits ar…
Measurements ofWγandZγproduction inppcollisions ats=7 TeVwith the ATLAS detector at the LHC
2013
The integrated and differential fiducial cross sections for the production of a W or Z boson in association with a high-energy photon are measured using pp collisions at root s = 7 TeV. The analyse ...
Measurements of the Total and Differential Higgs Boson Production Cross Sections Combining theH→γγandH→ZZ*→4ℓDecay Channels ats=8 TeVwith the ATLAS …
2015
Measurements of the total and differential cross sections of Higgs boson production are performed using 20.3 fb(-1) of pp collisions produced by the Large Hadron Collider at a center-of-mass energy of root s = 8 TeV and recorded by the ATLAS detector. Cross sections are obtained from measured H -> gamma gamma and H -> ZZ*. 4l event yields, which are combined accounting for detector efficiencies, fiducial acceptances, and branching fractions. Differential cross sections are reported as a function of Higgs boson transverse momentum, Higgs boson rapidity, number of jets in the event, and transverse momentum of the leading jet. The total production cross section is determined to be sigma(pp -> …
Search for Dilepton Resonances inppCollisions ats=7 TeVwith the ATLAS Detector
2011
This Letter reports on a search for narrow high-mass resonances decaying into dilepton final states. The data were recorded by the ATLAS experiment in pp collisions at root s = 7 TeV at the Large Hadron Collider and correspond to a total integrated luminosity of 1.08 (1.21) fb(-1) in the e(+)e(-) (mu(+)mu(-)) channel. No statistically significant excess above the standard model expectation is observed and upper limits are set at the 95% C. L. on the cross section times branching fraction of Z' resonances and Randall-Sundrum gravitons decaying into dileptons as a function of the resonance mass. A lower mass limit of 1.83 TeV on the sequential standard model Z' boson is set. A Randall-Sundrum…
Measurement of the transverse polarization ofΛandΛ¯hyperons produced in proton-proton collisions ats=7 TeVusing the ATLAS detector
2015
The transverse polarization of Λ and Λ¯ hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760 μb−1 of minimum bias data collected by the ATLAS detector at the LHC in the year 2010. The measured transverse polarization averaged over Feynman xF from 5×10−5 to 0.01 and transverse momentum pT from 0.8 to 15 GeV is −0.010±0.005(stat)±0.004(syst) for Λ and 0.002±0.006(stat)±0.004(syst) for Λ¯. It is also measured as a function of xF and pT, but no significant dependence on these variables is observed. Prior to this measurement, the polarization was measured at fixed-target experiments with center-of-mass energies up to about 40 GeV. …
Measurement of jet charge in dijet events froms=8 TeVppcollisions with the ATLAS detector
2016
The momentum-weighted sum of the charges of tracks associated to a jet is sensitive to the charge of the initiating quark or gluon. This paper presents a measurement of the distribution of momentum ...
Search for Scalar Charm Quark Pair Production inppCollisions ats=8 TeVwith the ATLAS Detector
2015
The results of a dedicated search for pair production of scalar partners of charm quarks are reported. The search is based on an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV recorded with the ATLAS detector at the LHC. The search is performed using events with large missing transverse momentum and at least two jets, where the two leading jets are each tagged as originating from c quarks. Events containing isolated electrons or muons are vetoed. In an R-parity-conserving minimal super-symmetric scenario in which a single scalar-charm state is kinematically accessible, and where it decays exclusively into a charm quark and a neutralino, 95% confidence-level upper li…
Search for dark matter candidates and large extra dimensions in events with a jet and missing transverse momentum with the ATLAS detector
2013
A search for new phenomena in events with a high-energy jet and large missing transverse momentum is performed using data from proton-proton collisions at √s = 7 TeV with the ATLAS experiment at the Large Hadron Collider. Four kinematic regions are explored using a dataset corresponding to an integrated luminosity of 4.7 fb[superscript −1]. No excess of events beyond expectations from Standard Model processes is observed, and limits are set on large extra dimensions and the pair production of dark matter particles.
Measurement of the differential cross-section of highly boosted top quarks as a function of their transverse momentum ins=8 TeVproton-proton collisi…
2016
The differential cross-section for pair production of top quarks with high transverse momentum is measured in 20.3 fb(-1) of proton-proton collisions at a center-of-mass energy of 8 TeV. The measur ...
Measurement of the Inelastic Proton-Proton Cross Section at s=13 TeV with the ATLAS Detector at the LHC
2016
This Letter presents a measurement of the inelastic proton-proton cross section using 60 μb^{-1} of pp collisions at a center-of-mass energy sqrt[s] of 13 TeV with the ATLAS detector at the LHC. Inelastic interactions are selected using rings of plastic scintillators in the forward region (2.07 10^{-6}, where M_{X} is the larger invariant mass of the two hadronic systems separated by the largest rapidity gap in the event. In this ξ range the scintillators are highly efficient. For diffractive events this corresponds to cases where at least one proton dissociates to a system with M_{X}>13 GeV. The measured cross section is compared with a range of theoretical predictions. When extrapolated…
Determination of the Ratio ofb-Quark Fragmentation Fractionsfs/fdinppCollisions ats=7 TeVwith the ATLAS Detector
2015
With an integrated luminosity of 2.47 fb^{-1} recorded by the ATLAS experiment at the LHC, the exclusive decays B_{s}^{0}→J/ψϕ and B_{d}^{0}→J/ψK^{*0} of B mesons produced in pp collisions at sqrt[s]=7 TeV are used to determine the ratio of fragmentation fractions f_{s}/f_{d}. From the observed B_{s}^{0}→J/ψϕ and B_{d}^{0}→J/ψK^{*0} yields, the quantity (f_{s}/f_{d})[B(B_{s}^{0}→J/ψϕ)/B(B_{d}^{0}→J/ψK^{*0})] is measured to be 0.199±0.004(stat)±0.008(syst). Using a recent theory prediction for [B(B_{s}^{0}→J/ψϕ)/B(B_{d}^{0}→J/ψK^{*0})] yields (f_{s}/f_{d})=0.240±0.004(stat)±0.010(syst)±0.017(th). This result is based on a new approach that provides a significant improvement of the world aver…
Measurement of theZZProduction Cross Section and Limits on Anomalous Neutral Triple Gauge Couplings in Proton-Proton Collisions ats=7 TeVwith the AT…
2012
A measurement of the ZZ production cross section in proton-proton collisions at root s = 7 TeV using data corresponding to an integrated luminosity of 1.02 fb(-1) recorded by the ATLAS experiment a ...
Search for dark matter produced in association with a Higgs boson decaying to two bottom quarks inppcollisions ats=8 TeVwith the ATLAS detector
2016
This article reports on a search for dark matter pair production in association with a Higgs boson decaying to a pair of bottom quarks, using data from 20.3 fb(-1) of pp collisions at a center-of-m ...
Measurement of the correlation between flow harmonics of different order in lead-lead collisions at sNN=2.76 TeV with the ATLAS detector
2015
Correlations between the elliptic or triangular flow coefficients v(m) (m = 2 or 3) and other flow harmonics v(n) (n = 2 to 5) are measured using root S-NN = 2.76 TeV Pb + Pb collision data collected in 2010 by the ATLAS experiment at the LHC, corresponding to an integrated luminosity of 7 mu b(-1). The v(m)-v(n) correlations aremeasured in midrapidity as a function of centrality, and, for events within the same centrality interval, as a function of event ellipticity or triangularity defined in a forward rapidity region. For events within the same centrality interval, v(3) is found to be anticorrelated with v(2) and this anticorrelation is consistent with similar anticorrelations between th…
Search for extra dimensions in diphoton events from proton-proton collisions at root s=7 TeV in the ATLAS detector at the LHC
2013
The large difference between the Planck scale and the electroweak scale, known as the hierarchy problem, is addressed in certain models through the postulate of extra spatial dimensions. A search for evidence of extra spatial dimensions in the diphoton channel has been performed using the full set of proton–proton collisions at √s = 7 TeV recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. This dataset corresponds to an integrated luminosity of 4.9fb[superscript −1]. The diphoton invariant mass spectrum is observed to be in good agreement with the Standard Model expectation. In the context of the model proposed by Arkani–Hamed, Dimopoulos and Dvali, 95% confidence le…
Search for Dark Matter in Events with Missing Transverse Momentum and a Higgs Boson Decaying to Two Photons inppCollisions ats=8 TeVwith the ATLAS D…
2015
Results of a search for new phenomena in events with large missing transverse momentum and a Higgs boson decaying to two photons are reported. Data from proton-proton collisions at a center-of-mass energy of 8 TeV and corresponding to an integrated luminosity of 20.3 fb−1 have been collected with the ATLAS detector at the LHC. The observed data are well described by the expected standard model backgrounds. Upper limits on the cross section of events with large missing transverse momentum and a Higgs boson candidate are also placed. Exclusion limits are presented for models of physics beyond the standard model featuring dark-matter candidates.
Search for new phenomena in final states with large jet multiplicities and missing transverse momentum using root s=7 TeV pp collisions with the ATLA…
2011
Results are presented of a search for any particle(s) decaying to six or more jets in association with missing transverse momentum. The search is performed using 1.34fb−1 of s √ s = 7 TeV proton-proton collisions recorded by the ATLAS detector during 2011. Data-driven techniques are used to determine the backgrounds in kinematic regions that require at least six, seven or eight jets, well beyond the multiplicities required in previous analyses. No evidence is found for physics beyond the Standard Model. The results are interpreted in the context of a supersymmetry model (MSUGRA/CMSSM) where they extend previous constraints.
Search for WH production with a light Higgs boson decaying to prompt electron-jets in proton–proton collisions at \(\sqrt {s}=7\) TeV with the ATLAS…
2013
A search is performed for WH production with a light Higgs boson decaying to hidden-sector particles resulting in clusters of collimated electrons, known as electron-jets. The search is performed with 2.04 fb[superscript −1] of data collected in 2011 with the ATLAS detector at the Large Hadron Collider in proton–proton collisions at √s=7 TeV . One event satisfying the signal selection criteria is observed, which is consistent with the expected background rate. Limits on the product of the WH production cross section and the branching ratio of a Higgs boson decaying to prompt electron-jets are calculated as a function of a Higgs boson mass in the range from 100 to 140 GeV.
Measurements of Higgs boson production and couplings in the four-lepton channel inppcollisions at center-of-mass energies of 7 and 8 TeV with the ATL…
2015
The final ATLAS Run 1 measurements of Higgs boson production and couplings in the decay channel H -> ZZ* -> l(+)l(-)l(+)l'(-), where l, l' = e or mu, are presented. These measurements were performed using pp collision data corresponding to integrated luminosities of 4.5 and 20.3 fb(-1) at center-of-mass energies of 7 and 8 TeV, respectively, recorded with the ATLAS detector at the LHC. The H -> ZZ* -> 4l signal is observed with a significance of 8.1 standard deviations, with an expectation of 6.2 standard deviations, at m(H) = 125.36 GeV, the combined ATLAS measurement of the Higgs boson mass from the H -> gamma gamma and H -> ZZ* -> 4l channels. The production rate relative to the Standard…
Measurement of the high-mass Drell–Yan differential cross-section in pp collisions at s=7 TeV with the ATLAS detector
2013
This Letter reports a measurement of the high-mass Drell–Yan differential cross-section in proton–proton collisions at a centre-of-mass energy of 7 TeV at the LHC. Based on an integrated luminosity ...
Search for Higgs andZBoson Decays toJ/ψγandϒ(nS)γwith the ATLAS Detector
2015
A search for the decays of the Higgs and Z bosons to J/psi gamma and Upsilon(nS)gamma (n = 1,2,3) is performed with pp collision data samples corresponding to integrated luminosities of up to 20.3 fb(-1) collected at root s = 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. No significant excess of events is observed above expected backgrounds and 95% C.L. upper limits are placed on the branching fractions. In the J/psi gamma final state the limits are 1.5 x 10(-3) and 2.6 x 10(-6) for the Higgs and Z boson decays, respectively, while in the Upsilon(1S, 2S, 3S)gamma. final states the limits are (1.3, 1.9, 1.3) x 10(-3) and (3.4, 6.5, 5.4) x 10(-6), respectively.
Measurement of Spin Correlation in Top-Antitop Quark Events and Search for Top Squark Pair Production inppCollisions ats=8 TeVUsing the ATLAS Detect…
2015
A measurement of spin correlation in t (t) over bar production is presented using data collected with the ATLAS detector at the Large Hadron Collider in proton-proton collisions at a center-of-mass ...
Measurement ofW+W−production inppcollisions ats=7 TeVwith the ATLAS detector and limits on anomalousWWZandWWγcouplings
2013
This paper presents a measurement of the W+W- production cross section in pp collisions at root s = 7 TeV. The leptonic decay channels are analyzed using data corresponding to an integrated luminosity of 4: 6 fb(-1) collected with the ATLAS detector at the Large Hadron Collider. The W+W- production cross section sigma(pp -> W+W- + X) is measured to be 51.9 +/- 2.0(stat) +/- 3.9(syst) +/- 2.0(lumi) pb, compatible with the Standard Model prediction of 44.7(-1.9)(+2.1) pb. A measurement of the normalized fiducial cross section as a function of the leading lepton transverse momentum is also presented. The reconstructed transverse momentum distribution of the leading lepton is used to extract li…
Measurement of hard double-parton interactions inW(???) + 2-jet events at $\sqrt{s}\,=7$ TeV with the ATLAS detector
2013
The production of W bosons in association with two jets in proton–proton collisions at a centre-of-mass energy of √s=7 TeV has been analysed for the presence of double-parton interactions using data corresponding to an integrated luminosity of 36 pb[superscript −1], collected with the ATLAS detector at the Large Hadron Collider. The fraction of events arising from double-parton interactions, f[superscript (D) over subscript DP], has been measured through the p[subscript T] balance between the two jets and amounts to f[superscript (D) over subscript DP] = 0.08 ± 0.01 (stat.) ± 0.02 (sys.) for jets with transverse momentum p[subscript T] > 20 GeV and rapidity |y| < 2.8. This corresponds to a …
Comprehensive measurements oft-channel single top-quark production cross sections ats=7 TeVwith the ATLAS detector
2014
This article presents measurements of the t-channel single top-quark ((t) over bart) and top-antiquark (_ t) total production cross sections sdtq_ and sd _ tq_, their ratio Rt sdtq_= sd _ tq_, and a measurement of the inclusive production cross section sdtq _ _ tq_ in proton-proton collisions at ffiffiffi ps = 7 TeV at the LHC. Differential cross sections for the tq and _ tq processes are measured as a function of the transverse momentum and the absolute value of the rapidity of t and _ t, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb-1. Selected events contain one charged lepton, large missing transverse mome…
Measurements of spin correlation in top-antitop quark events from proton-proton collisions ats=7 TeVusing the ATLAS detector
2014
Measurements of spin correlation in top quark pair production are presented using data collected with the ATLAS detector at the LHC with proton-proton collisions at a center-of-mass energy of 7 TeV, corresponding to an integrated luminosity of 4.6 fb(-1). Events are selected in final states with two charged leptons and at least two jets and in final states with one charged lepton and at least four jets. Four different observables sensitive to different properties of the top quark pair production mechanism are used to extract the correlation between the top and antitop quark spins. Some of these observables are measured for the first time. The measurements are in good agreement with the Stan…
Search for heavy vector-like quarks coupling to light quarks in proton–proton collisions at s=7 TeV with the ATLAS detector
2012
This letter presents a search for singly produced vector-like quarks, Q, coupling to light quarks, q. The search is sensitive to both charged current (CC) and neutral current (NC) processes, p p --> Q q --> W q q' and p p --> Q q --> Z q q' with a leptonic decay of the vector gauge boson. In 1.04/fb of data taken in 2011 by the ATLAS experiment at a center-of-mass energy sqrt(s) = 7 TeV, no evidence of such heavy vector-like quarks is observed above the expected Standard Model background. Limits on the heavy vector-like quark production cross section times branching ratio as a function of mass m_Q are obtained. For a coupling kappa_(qQ) = v/m_Q, where v is the Higgs vacuum expectation value…
Search for a Heavy Neutral Particle Decaying toeμ,eτ, orμτinppCollisions ats=8 TeVwith the ATLAS Detector
2015
This Letter presents a search for a heavy neutral particle decaying into an opposite-sign different-flavor dilepton pair, e(+/-) mu(-/+), e(+/-) tau(-/+), or mu(+/-) tau(-/+) using 20.3 fb(-1) of pp collision data at root s = 8 TeV collected by the ATLAS detector at the LHC. The numbers of observed candidate events are compatible with the standard model expectations. Limits are set on the cross section of new phenomena in two scenarios: the production of (nu) over tilde (tau) in R-parity-violating supersymmetric models and the production of a lepton-flavor-violating Z' vector boson.
Search for Higgs andZBoson Decays toϕγwith the ATLAS Detector
2016
A search for the decays of the Higgs and Z bosons to a ϕ meson and a photon is performed with a pp collision data sample corresponding to an integrated luminosity of 2.7 fb^{-1} collected at sqrt[s]=13 TeV with the ATLAS detector at the LHC. No significant excess of events is observed above the background, and 95% confidence level upper limits on the branching fractions of the Higgs and Z boson decays to ϕγ of 1.4×10^{-3} and 8.3×10^{-6}, respectively, are obtained.
Measurement of the correlation between the polar angles of leptons from top quark decays in the helicity basis ats=7 TeVusing the ATLAS detector
2016
A measurement of the correlations between the polar angles of leptons from the decay of pair-produced t and (t) over bar quarks in the helicity basis is reported, using proton-proton collision data collected by the ATLAS detector at the LHC. The dataset corresponds to an integrated luminosity of 4.6 fb(-1) at a center-of-mass energy of root s = 7 TeV collected during 2011. Candidate events are selected in the dilepton topology with large missing transverse momentum and at least two jets. The angles theta(1) and theta(2) between the charged leptons and the direction of motion of the parent quarks in the t (t) over bar rest frame are sensitive to the spin information, and the distribution of …
Combined performance studies for electrons at the 2004 ATLAS combined test-beam
2010
In 2004 at the ATLAS (A Toroidal LHC ApparatuS) combined test beam, one slice of the ATLAS barrel detector (including an Inner Detector set-up and the Liquid Argon calorimeter) was exposed to particles from the H8 SPS beam line at CERN. It was the first occasion to test the combined electron performance of ATLAS. This paper presents results obtained for the momentum measurement p with the Inner Detector and for the performance of the electron measurement with the LAr calorimeter (energy E linearity and resolution) in the presence of a magnetic field in the Inner Detector for momenta ranging from 20 GeV/c to 100 GeV/c. Furthermore the particle identification capabilities of the Transition Ra…
Search for type-III seesaw heavy leptons inppcollisions ats=8 TeVwith the ATLAS detector
2015
A search for the pair production of heavy leptons (N-0, L-+/-) predicted by the type-III seesaw theory formulated to explain the origin of small neutrino masses is presented. The decay channels N-0 -> W(+/-)l(+/-) (l = e, mu, tau) and L-+/- -> W(+/-)v (v = v(e), v(mu), v(tau)) are considered. The analysis is performed using the final state that contains two leptons (electrons or muons), two jets from a hadronically decaying W boson and large missing transverse momentum. The data used in the measurement correspond to an integrated luminosity of 20.3 fb(-1) of pp collisions at root s = 8 TeV collected by the ATLAS detector at the LHC. No evidence of heavy lepton pair production is observed. H…
Search for scalar leptoquarks in pp collisions at $\sqrt{s}$=13 TeV with the ATLAS experiment
2016
An inclusive search for a new-physics signature of lepton-jet resonances has been performed by the ATLAS experiment. Scalar leptoquarks, pair-produced in pp collisions at s √s = 13 TeV at the large hadron collider, have been considered. An integrated luminosity of 3.2 fb-1, corresponding to the full 2015 dataset was used. First (second) generation leptoquarks were sought in events with two electrons (muons) and two or more jets. The observed event yield in each channel is consistent with Standard Model background expectations. The observed (expected) lower limits on the leptoquark mass at 95% confidence level are 1100 and 1050 GeV (1160 and 1040 GeV) for first and second generation leptoqua…
Search for massive, long-lived particles using multitrack displaced vertices or displaced lepton pairs inppcollisions ats=8 TeVwith the ATLAS detect…
2015
Many extensions of the Standard Model posit the existence of heavy particles with long lifetimes. This article presents the results of a search for events containing at least one long-lived particle that decays at a significant distance from its production point into two leptons or into five or more charged particles. This analysis uses a data sample of proton-proton collisions at root s = 8 TeV corresponding to an integrated luminosity of 20.3 fb(-1) collected in 2012 by the ATLAS detector operating at the Large Hadron Collider. No events are observed in any of the signal regions, and limits are set on model parameters within supersymmetric scenarios involving R-parity violation, split sup…
Search for displaced muonic lepton jets from light Higgs boson decay in proton–proton collisions at s=7 TeV with the ATLAS detector
2013
A search is performed for collimated muon pairs displaced from the primary vertex produced in the decay of long-lived neutral particles in proton-proton collisions at root s = 7 TeV centre-of-mass ...
Search for a Charged Higgs Boson Produced in the Vector-Boson Fusion Mode with DecayH±→W±ZusingppCollisions ats=8 TeVwith the ATLAS Experiment
2015
A search for a charged Higgs boson, H-+/-, decaying to a W-+/- boson and a Z boson is presented. The search is based on 20.3 fb(-1) of proton-proton collision data at a center-of-mass energy of 8 TeV recorded with the ATLAS detector at the LHC. The H-+/- boson is assumed to be produced via vector-boson fusion and the decays W-+/- -> q (q') over bar and Z -> e(+)e(-)/mu(+)mu(-) are considered. The search is performed in a range of charged Higgs boson masses from 200 to 1000 GeV. No evidence for the production of an H+ boson is observed. Upper limits of 31-1020 fb at 95% C.L. are placed on the cross section for vector-boson fusion production of an H-+/- boson times its branching fraction to W…
Measurement of the b-hadron production cross section using decays to D⁎+μ−X final states in pp collisions at s=7 TeV with the ATLAS detector
2012
The b-hadron production cross section is measured with the ATLAS detector in pp collisions at root s = 7 TeV, using 3.3 pb(-1) of integrated luminosity, collected during the 2010 LHC run. The b-had ...
Search for nonpointing photons in the diphoton andETmissfinal state ins=7 TeVproton-proton collisions using the ATLAS detector
2013
A search has been performed for photons originating in the decay of a neutral long-lived particle, exploiting the capabilities of the ATLAS electromagnetic calorimeter to make precise measurements of the flight direction of photons, as well as the calorimeter's excellent time resolution. The search has been made in the diphoton plus missing transverse energy final state, using the full data sample of 4.8 fb(-1) of 7 TeV proton-proton collisions collected in 2011 with the ATLAS detector at the LHC. No excess is observed above the background expected from Standard Model processes. The results are used to set exclusion limits in the context of gauge mediated supersymmetry breaking models, with…
Measurements of the Nuclear Modification Factor for Jets inPb+PbCollisions atsNN=2.76 TeVwith the ATLAS Detector
2015
Measurements of inclusive jet production are performed in pp and Pb+Pb collisions at √sNN = 2.76 TeV with the ATLAS detector at the LHC, corresponding to integrated luminosities of 4.0 pb−1 and 0.14 nb−1, respectively. The jets are identified with the anti-kt algorithm with R = 0.4, and the spectra are measured over the kinematic range of jet transverse momentum 32 < pT < 500 GeV, and absolute rapidity |y| < 2.1 and as a function of collision centrality. The nuclear modification factor, RAA, is evaluated and jets are found to be suppressed by approximately a factor of two in central collisions compared to pp collisions. The RAA shows a slight increase with pT and no significant variation wi…
Measurements of normalized differential cross sections fortt¯production inppcollisions at(s)=7 TeVusing the ATLAS detector
2014
Measurements of normalized differential cross sections for top-quark pair production are presented as a function of the top-quark transverse momentum, and of the mass, transverse momentum, and rapidity of the t (t) over bar system, in proton proton collisions at a center-of-mass energy of root s = 7 TeV. The data set corresponds to an integrated luminosity of 4.6 fb(-1), recorded in 2011 with the ATLAS detector at the CERN Large Hadron Collider. Events are selected in the lepton jets channel, requiring exactly one lepton and at least four jets with at least one of the jets tagged as originating from a b-quark. The measured spectra are corrected for detector efficiency and resolution effects…
Search for Magnetic Monopoles ins=7 TeVppCollisions with the ATLAS Detector
2012
This Letter presents a search for magnetic monopoles with the ATLAS detector at the CERN Large Hadron Collider using an integrated luminosity of 2.0 fb(-1) of pp collisions recorded at a center-of- ...
Measurement of the cross-section for W boson production in association with b-jets in pp collisions at root s=7 TeV with the ATLAS detector
2013
This paper reports a measurement of the W +b-jets (W +b+ X and W + b[¯ over b] +X) production cross-section in proton-proton collisions at a centre-of-mass energy of 7 TeV at the LHC. These results are based on data corresponding to an integrated luminosity of 4.6 fb[superscript −1], collected with the ATLAS detector. Cross-sections are presented as a function of jet multiplicity and of the transverse momentum of the leading b-jet for both the muon and electron decay modes of the W boson. The W +b-jets cross-section, corrected for all known detector effects, is quoted in a limited kinematic range. Combining the muon and electron channels, the fiducial cross-section for W +b-jets is measured…
Measurement of top quark pair differential cross sections in the dilepton channel in pp collisions at s=7 and 8 TeV with ATLAS
2016
Measurements of normalized differential cross-sections of top quark pair ($t\bar t$) production are presented as a function of the mass, the transverse momentum and the rapidity of the $t\bar t$ system in proton-proton collisions at center-of-mass energies of $\sqrt{s}$ = 7 TeV and 8 TeV. The dataset corresponds to an integrated luminosity of 4.6 fb$^{-1}$ at 7 TeV and 20.2 fb$^{-1}$ at 8 TeV, recorded with the ATLAS detector at the Large Hadron Collider. Events with top quark pair signatures are selected in the dilepton final state, requiring exactly two charged leptons and at least two jets with at least one of the jets identified as likely to contain a $b$-hadron. The measured distributi…
Search for squarks and gluinos with the ATLAS detector in final states with jets and missing transverse momentum using4.7 fb−1ofs=7 TeVproton-proto…
2013
A search for squarks and gluinos in final states containing jets, missing transverse momentum and no high-p(T) electrons or muons is presented. The data represent the complete sample recorded in 2011 by the ATLAS experiment in 7 TeV proton-proton collisions at the Large Hadron Collider, with a total integrated luminosity of 4.7 fb(-1). No excess above the Standard Model background expectation is observed. Gluino masses below 860 GeV and squark masses below 1320 GeV are excluded at the 95% confidence level in simplified models containing only squarks of the first two generations, a gluino octet and a massless neutralino, for squark or gluino masses below 2 TeV, respectively. Squarks and glui…
Measurement of upsilon production in 7 TeV pp collisions at ATLAS
2013
Artículo escrito por un elevado número de autores, solo se referencian el que aparece en primer lugar, el nombre del grupo de colaboración, si le hubiere, y los autores pertenecientes a la UAM
Search for pair production of gluinos decaying via stop and sbottom in events withb-jets and large missing transverse momentum inppcollisions ats=13 …
2016
A search for supersymmetry involving the pair production of gluinos decaying via third-generation squarks to the lightest neutralino (chi) over tilde (0)(1) is reported. It uses an LHC proton-proto ...
Simultaneous measurements of thett¯,W+W−, andZ/γ*→ττproduction cross-sections inppcollisions ats=7 TeVwith the ATLAS detector
2015
Simultaneous measurements of the t (t) over bar, W+W-, and Z/gamma* -> tau tau production cross-sections using an integrated luminosity of 4.6 fb(-1) of pp collisions at root s = 7 TeV collected ...
Photon reconstruction in the ATLAS Inner Detector and Liquid Argon Barrel Calorimeter at the 2004 Combined Test Beam
2011
The reconstruction of photons in the ATLAS detector is studied with data taken during the 2004 Combined Test Beam, where a full slice of the ATLAS detector was exposed to beams of particles of known energy at the CERN SPS. The results presented show significant differences in the longitudinal development of the electromagnetic shower between converted and unconverted photons as well as in the total measured energy. The potential to use the reconstructed converted photons as a means to precisely map the material of the tracker in front of the electromagnetic calorimeter is also considered. All results obtained are compared with a detailed Monte-Carlo simulation of the test-beam setup which i…
Measurements of the charge asymmetry in top-quark pair production in the dilepton final state ats=8 TeVwith the ATLAS detector
2016
Measurements of the top--antitop quark pair production charge asymmetry in the dilepton channel are presented using data corresponding to an integrated luminosity of 20.3 fb−1 from pp collisions at a center-of-mass energy of s√=8 TeV collected with the ATLAS detector at the Large Hadron Collider at CERN. Inclusive and differential measurements as a function of the invariant mass, transverse momentum, and longitudinal boost of the tt¯ system are performed both in the full phase space and in a fiducial phase space closely matching the detector acceptance. Two observables are studied: AllC based on the selected leptons and Att¯C based on the reconstructed tt¯ final state. The inclusive asymmet…
Measurement of exclusiveγγ→W+W−production and search for exclusive Higgs boson production inppcollisions ats=8 TeVusing the ATLAS detector
2016
Searches for exclusively produced $W$ boson pairs in the process $pp(\gamma\gamma) \rightarrow pW^+W^-p$ and exclusively produced Higgs boson in the process $pp(gg) \rightarrow pHp$ have been performed using $e^{\pm}\mu^{\mp}$ final states. These measurements use 20.2 fb$^{-1}$ of $pp$ collisions collected by the ATLAS experiment at a center-of-mass energy $\sqrt{s}=8$ TeV at the LHC. Exclusive production of $W^+W^-$ consistent with the Standard Model prediction is found with 3.0$\sigma$ significance. The exclusive $W^+W^-$ production cross-section is determined to be $\sigma (\gamma\gamma\rightarrow W^{+}W^{-}\rightarrow e^{\pm}\mu^{\mp} X) = 6.9 \pm 2.2 (\mathrm{stat.}) \pm 1.4 (\mathrm{s…
Search for the Higgs Boson in theH→WW→lνjjDecay Channel inppCollisions ats=7 TeVwith the ATLAS Detector
2011
A search for a Higgs boson has been performed in the H -> WW -> l nu jj channel in 1.04 fb(-1) of pp collision data at root s = 7 TeV recorded with the ATLAS detector at the Large Hadron Collider. No significant excess of events is observed over the expected background and limits on the Higgs boson production cross section are derived for a Higgs boson mass in the range 240 GeV WW production is 3.1 pb, or 2.7 times the standard model prediction.
Search for the Standard Model Higgs boson in the decay channel H→ZZ(⁎)→4ℓ with 4.8 fb−1 of pp collision data at s=7 TeV with ATLAS
2012
This Letter presents a search for the Standard Model Higgs boson in the decay channel H -> ZZ((*)) -> l(+)l(-)l(-)+l(')-, where l,l' = e or mu, using proton-proton collisions at root s = 7 TeV recorded with the ATLAS detector and corresponding to an integrated luminosity of 4.8 fb(-1). The four-lepton invariant mass distribution is compared with Standard Model background expectations to derive upper limits on the cross section of a Standard Model Higgs boson with a mass between 110 GeV and 600 GeV. The mass ranges 134-156 GeV, 182-233 GeV, 256-265 GeV and 268-415 GeV are excluded at the 95% confidence level. The largest upward deviations from the background-only hypothesis are observed for …
Search for high-mass diphoton resonances inppcollisions ats=8 TeVwith the ATLAS detector
2015
Search for high-mass diphoton resonances in pp collisions at pffisffi root s=8 TeV with the ATLAS detector
Search for new phenomena in final states with an energetic jet and large missing transverse momentum inppcollisions ats=13 TeVusing the ATLAS detect…
2016
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses proton-proton collision data corresponding to an inte ...
Search for quark contact interactions in dijet angular distributions in pp collisions at s=7 TeV measured with the ATLAS detector
2011
Dijet angular distributions from the first LHC pp collisions at center-of-mass energy sqrt(s) = 7 TeV have been measured with the ATLAS detector. The dataset used for this analysis represents an integrated luminosity of 3.1 pb-1. Dijet $\chi$ distributions and centrality ratios have been measured up to dijet masses of 2.8 TeV, and found to be in good agreement with Standard Model predictions. Analysis of the $\chi$ distributions excludes quark contact interactions with a compositeness scale $\Lambda$ below 3.4 TeV, at 95% confidence level, significantly exceeding previous limits.
Search for TeV-scale gravity signatures in final states with leptons and jets with the ATLAS detector at s=7 TeV
2012
A search for physics beyond the Standard Model, in final states with at least one high transverse momentum charged lepton (electron or muon) and two additional high transverse momentum leptons or jets, is performed using 3.2 fb−1 of proton–proton collision data recorded by the ATLAS detector at the Large Hadron Collider in 2015 at √s = 13 TeV. The upper end of the distribution of the scalar sum of the transverse momenta of leptons and jets is sensitive to the production of high-mass objects. No excess of events beyond Standard Model predictions is observed. Exclusion limits are set for models of microscopic black holes with two to six extra dimensions.
Measurement of theZZproduction cross section inpp¯collisions ats=1.96 TeV
2016
The ZZ production cross section in proton-proton collisions at 13 TeV center-of-mass energy is measured using 3.2 fb⁻¹ of data recorded with the ATLAS detector at the Large Hadron Collider. The considered Z boson candidates decay to an electron or muon pair of mass 66-116 GeV. The cross section is measured in a fiducial phase space reflecting the detector acceptance. It is also extrapolated to a total phase space for Z bosons in the same mass range and of all decay modes, giving 16.7 +2.2 −2.0 (stat.) +0.9 −0.7 (syst.) +1.0 −0.7 (lumi.) pb. The results agree with standard model predictions.
Dynamics of isolated-photon plus jet production in pp collisions at s=7 TeV with the ATLAS detector
2013
The dynamics of isolated-photon plus jet production in pp collisions at a centre-of-mass energy of 7 TeV has been studied with the ATLAS detector at the LHC using an integrated luminosity of 37 pb( ...
Search for charged Higgs bosons through the violation of lepton universality in t(t)over-bar events using pp collision data at root s=7 TeV with the …
2013
In several extensions of the Standard Model, the top quark can decay into a bottom quark and a light charged Higgs boson H [superscript +], t → bH [superscript +], in addition to the Standard Model decay t → bW. Since W bosons decay to the three lepton generations equally, while H [superscript +] may predominantly decay into τν, charged Higgs bosons can be searched for using the violation of lepton universality in top quark decays. The analysis in this paper is based on 4.6 fb[superscript −1] of proton-proton collision data at √s = 7 TeV collected by the ATLAS experiment at the Large Hadron Collider. Signatures containing leptons (e or μ) and/or a hadronically decaying τ (τ [subscript had])…
Measurement of the inclusiveW±andZ/γ*cross sections in theeandμdecay channels inppcollisions ats=7 TeVwith the ATLAS detector
2012
The production cross sections of the inclusive Drell-Yan processes W-+/- -> l nu and Z/gamma* -> ll (l = e, mu) are measured in proton-proton collisions at root s = 7 TeV with the ATLAS detector. The cross sections are reported integrated over a fiducial kinematic range, extrapolated to the full range, and also evaluated differentially as a function of the W decay lepton pseudorapidity and the Z boson rapidity, respectively. Based on an integrated luminosity of about 35 pb(-1) collected in 2010, the precision of these measurements reaches a few percent. The integrated and the differential W-+/- and Z/gamma* cross sections in the e and mu channels are combined, and compared with perturbative…
Observation of Long-Range Elliptic Azimuthal Anisotropies ins=13and 2.76 TeVppCollisions with the ATLAS Detector
2016
ATLAS has measured two-particle correlations as a function of relative azimuthal-angle, $\Delta \phi$, and pseudorapidity, $\Delta \eta$, in $\sqrt{s}$=13 and 2.76 TeV $pp$ collisions at the LHC using charged particles measured in the pseudorapidity interval $|\eta|$<2.5. The correlation functions evaluated in different intervals of measured charged-particle multiplicity show a multiplicity-dependent enhancement at $\Delta \phi \sim 0$ that extends over a wide range of $\Delta\eta$, which has been referred to as the "ridge". Per-trigger-particle yields, $Y(\Delta \phi)$, are measured over 2<$|\Delta\eta|$<5. For both collision energies, the $Y(\Delta \phi)$ distribution in all multiplicity …
Centrality, rapidity, and transverse momentum dependence of isolated prompt photon production in lead-lead collisions atsNN=2.76TeV measured with the…
2016
Prompt photon production in root S-NN = 2.76-TeV Pb + Pb collisions has been measured by the ATLAS experiment at the Large Hadron Collider using data collected in 2011 with an integrated luminosity ...
Beam-induced and cosmic-ray backgrounds observed in the ATLAS detector during the LHC 2012 proton-proton running period
2016
This paper discusses various observations on beam-induced and cosmic-ray backgrounds in the ATLAS detector during the LHC 2012 proton-proton run. Building on published results based on 2011 data, the correlations between background and residual pressure of the beam vacuum are revisited. Ghost charge evolution over 2012 and its role for backgrounds are evaluated. New methods to monitor ghost charge with beam-gas rates are presented and observations of LHC abort gap population by ghost charge are discussed in detail. Fake jets from colliding bunches and from ghost charge are analysed with improved methods, showing that ghost charge in individual radio-frequency buckets of the LHC can be resol…
Search for stable hadronising squarks and gluinos with the ATLAS experiment at the LHC
2011
Hitherto unobserved long-lived massive particles with electric and/or colour charge are predicted by a range of theories which extend the Standard Model. In this Letter a search is performed at the ATLAS experiment for slow-moving charged particles produced in proton–proton collisions at 7 TeV centre-of-mass energy at the LHC, using a data-set corresponding to an integrated luminosity of 34 pb[superscript −1]. No deviations from Standard Model expectations are found. This result is interpreted in a framework of supersymmetry models in which coloured sparticles can hadronise into long-lived bound hadronic states, termed R-hadrons, and 95% CL limits are set on the production cross-sections of…
Observation of top-quark pair production in association with a photon and measurement of thett¯γproduction cross section inppcollisions ats=7TeV usin…
2015
A search is performed for top-quark pairs (t (t) over bar) produced together with a photon (gamma) with transverse energy greater than 20 GeV using a sample of t (t) over bar candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The data set used corresponds to an integrated luminosity of 4.59 fb(-1) of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total, 140 and 222 t (t) over bar gamma candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 +/- 26 and 120 +/- 39 non-t (t) over bar gamma background events,…
Observation of an Excited $B^{\pm}_c$ Meson State with the ATLAS Detector
2014
A search for excited states of the B±c meson is performed using 4.9 fb-1 of 7 TeV and 19.2 fb-1 of 8 TeV pp collision data collected by the ATLAS experiment at the LHC. A new state is observed through its hadronic transition to the ground state, with the latter detected in the decay B±c→J/ψπ±. The state appears in the m(Bc±π+π-)-m(Bc±)-2m(π±) mass difference distribution with a significance of 5.2 standard deviations. The mass of the observed state is 6842±4±5 MeV, where the first error is statistical and the second is systematic. The mass and decay of this state are consistent with expectations for the second S-wave state of the B±c meson, B±c(2S).
Femtoscopy with identified charged pions in proton-lead collisions at sNN=5.02 TeV with ATLAS
2017
Bose-Einstein correlations between identified charged pions are measured for $p$+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV using data recorded by the ATLAS detector at the LHC corresponding to a total integrated luminosity of $28$ $\mathrm{nb}^{-1}$. Pions are identified using ionization energy loss measured in the pixel detector. Two-particle correlation functions and the extracted source radii are presented as a function of collision centrality as well as the average transverse momentum ($k_{\mathrm{T}}$) and rapidity ($y^{\star}_{\pi\pi}$) of the pair. Pairs are selected with a rapidity $-2 < y^{\star}_{\pi\pi} < 1$ and with an average transverse momentum $0.1 < k_{\mathrm{T}} <…