Search results for "Pb–Pb collisions"
showing 10 items of 18 documents
Multiplicity dependence of the average transverse momentum in pp, p–Pb, and Pb–Pb collisions at the LHC
2013
The average transverse momentum $\langle p_{\rm T}\rangle$ versus the charged-particle multiplicity $N_{\rm ch}$ was measured in p-Pb collisions at a collision energy per nucleon-nucleon pair $\sqrt{s_{\rm NN}}=5.02$ TeV and in pp collisions at collision energies of $\sqrt{s}=0.9$, 2.76, and 7 TeV in the kinematic range $0.15<p_{\rm T}<10.0$ GeV/$c$ and $|\eta|<0.3$ with the ALICE apparatus at the LHC. These data are compared to results in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV at similar charged-particle multiplicities. In pp and p-Pb collisions, a strong increase of $\langle p_{\rm T}\rangle$ with $N_{\rm ch}$ is observed, which is much stronger than that measured in Pb-Pb colli…
Production of 4He and 4He_ in Pb–Pb collisions at √sNN = 2.76 TeV at the LHC
2018
Results on the production of 4He and 4He nuclei in Pb–Pb collisions at √sNN = 2.76 TeV 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/dy4He = (0.8 ± 0.4 (stat) ± 0.3 (syst)) × 10−6 and dN/dy4He = (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 = 156 MeV) as for light hadrons. The measured ratio of 4He/4He is 1.4 ± 0.8 (stat) ± 0.5 (syst). peerReviewed
Measuring K0SK± interactions using Pb–Pb collisions at √sNN=2.76TeV
2017
We present the first ever measurements of femtoscopic correlations between the K0 S and K± particles. The analysis was performed on the data from Pb–Pb collisions at √sNN = 2.76 TeV measured by the ALICE experiment. The observed femtoscopic correlations are consistent with final-state interactions proceeding via the a0(980) resonance. The extracted kaon source radius and correlation strength parameters for K0 SK− are found to be equal within the experimental uncertainties to those for K0 SK+. Comparing the results of the present study with those from published identical-kaon femtoscopic studies by ALICE, mass and coupling parameters for the a0 resonance are tested. Our results are also comp…
J/ψ suppression at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV
2017
The inclusive J/ψ production has been studied in Pb–Pb and pp collisions at the centre-of-mass energy per nucleon pair √sNN = 5.02 TeV, using the ALICE detector at the CERN LHC. The J/ψ meson is reconstructed, in the centre-of-mass rapidity interval 2.5 < y < 4 and in the transverse-momentum range pT < 12 GeV/c, via its decay to a muon pair. In this Letter, we present results on the inclusive J/ψ cross section in pp collisions at √s = 5.02 TeV and on the nuclear modification factor RAA. The latter is presented as a function of the centrality of the collision and, for central collisions, as a function of the transverse momentum pT of the J/ψ. The measured RAA values indicate a suppression of…
Top-quark production in proton–nucleus and nucleus–nucleus collisions at LHC energies and beyond
2015
Single and pair top-quark production in proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the CERN Large Hadron Collider (LHC) and future circular collider (FCC) energies, are studied with next-to-leading-order perturbative QCD calculations including nuclear parton distribution functions. At the LHC, the pair-production cross sections amount to sigma(t-tbar) = 3.4 mub in Pb-Pb at sqrt(s) = 5.5 TeV, and sigma(t-tbar) = 60 nb in p-Pb at sqrt(s) = 8.8 TeV. At the FCC energies of sqrt(s) = 39 and 63 TeV, the same cross sections are factors of 90 and 55 times larger respectively. In the leptonic final-state t-tbar --> W+b W-bbar --> b bbar l+l- nu+nu-, after typical acceptance and eff…
Measurement of jet radial profiles in Pb–Pb collisions at √sNN = 2.76 TeV
2019
The jet radial structure and particle transverse momentum (pT) composition within jets are presented in centrality-selected Pb–Pb collisions at √sNN = 2.76 TeV. Track-based jets, which are also called charged jets, were reconstructed with a resolution parameter of R=0.3 at midrapidity |ηch jet|<0.6 for transverse momenta pT,ch jet=30–120 GeV/c. Jet–hadron correlations in relative azimuth and pseudorapidity space (Δφ,Δη) are measured to study the distribution of the associated particles around the jet axis for different pT,assoc-ranges between 1 and 20 GeV/c. The data in Pb–Pb collisions are compared to reference distributions for pp collisions, obtained using embedded PYTHIA simulations. Th…
ϒ suppression at forward rapidity in Pb–Pb collisions at √sNN = 5.02 TeV
2019
Inclusive ϒ(1S) and ϒ(2S) production have been measured in Pb–Pb collisions at the centre-of-mass energy per nucleon–nucleon pair √sNN = 5.02 TeV, using the ALICE detector at the CERN LHC. The ϒ mesons are reconstructed in the centre-of-mass rapidity interval 2.5 < y < 4 and in the transversemomentum range pT < 15 GeV/c, via their decays to muon pairs. In this Letter, we present results on the inclusive ϒ(1S) nuclear modification factor RAA as a function of collision centrality, transverse momentum and rapidity. The ϒ(1S) and ϒ(2S) RAA, integrated over the centrality range 0–90%, are 0.37± 0.02(stat) ± 0.03(syst) and 0.10 ± 0.04(stat) ± 0.02(syst), respectively, leading to a ratio Rϒ(2S) AA…
3ΛH and 3Λ¯H‾ production in Pb–Pb collisions at √sNN = 2.76 TeV
2016
The production of the hypertriton nuclei 3 H and 3 ¯ H has been measured for the first time in Pb–Pb collisions at √sNN = 2.76 TeV with the ALICE experiment at LHC. The pT-integrated 3 H yield in one unity of rapidity, dN/dy × B.R. 3 H→3He,π− = (3.86 ± 0.77(stat.) ± 0.68(syst.)) × 10−5 in the 0–10% most central collisions, is consistent with the predictions from a statistical thermal model using the same temperature as for the light hadrons. The coalescence parameter B3 shows a dependence on the transverse momentum, similar to the B2 of deuterons and the B3 of 3He nuclei. The ratio of yields S3 = 3 H/(3He×/p) was measured to be S3 = 0.60±0.13(stat.)±0.21(syst.) in 0–10% centrality events; t…
Measurement of jet suppression in central Pb–Pb collisions at √sNN = 2.76 TeV
2015
The transverse momentum (pT) spectrum and nuclear modification factor (RAA) of reconstructed jets in 0–10% and 10–30% central Pb–Pb collisions at √sNN = 2.76 TeV were measured. Jets were reconstructed using the anti-kT 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 pT spectra are reported in the pseudorapidity interval of |ηjet| 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 RAA. The nuclear m…
Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb–Pb collisions at √sNN = 2.76 TeV
2016
The centrality dependence of the charged-particle pseudorapidity density measured with ALICE in Pb–Pb collisions at √sNN = 2.76 TeV over a broad pseudorapidity range is presented. This Letter extends the previous results reported by ALICE to more peripheral collisions. No strong change of the overall shape of charged-particle pseudorapidity density distributions with centrality is observed, and when normalised to the number of participating nucleons in the collisions, the evolution over pseudorapidity with centrality is likewise small. The broad pseudorapidity range (−3.5 < η < 5) allows precise estimates of the total number of produced charged particles which we find to range from 162 ± 22…