Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Strangeness- and Rapidity-Dependent Studies in Small Systems with ALICE at the LHC

We report about recent studies of strange hadron production in p–Pb at $\sqrt{s_\mathrm{{NN}}}$ = 5.02, 8.16 TeV and in pp collisions at $\sqrt{s}$ = 7, 13 TeV. The transverse momentum ($p_\mathrm{{T}}$) integrated yields and particle ratios as a function of charged-particle multiplicity are reported to study the particle production mechanism and the strangeness enhancement. The rapidity asymmetry ($Y_\mathrm{{asym}}$) for $\phi$ and K*$^{0}$ is measured in p–Pb collisions to explore possible nuclear effects. The $Y_\mathrm{{asym}}$ is measured as a function of transverse momentum ($p_\mathrm{{T}}$) in various multiplicity classes and are compared with EPOS and HIJING model predictions

Identified particle production in p–Pb collisions with ALICE at the LHC

The study of identified particle production in p--Pb and pp collisions provides a baseline measurement to be compared with Pb--Pb results. The excellent tracking and particle identification capabilities of the ALICE detector allow the study of identified particle production up to a very high transverse momentum ($p_{\mathrm{T}}$). We report recent results on $\phi$ and K*$^{0}$ in p--Pb collisions at $\sqrt{s_{NN}}$ = 8.16 TeV along with measurements of $\pi$, K, p, $\Xi$, $\Lambda$ and $\Omega$ in p--Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV. Integrated yields, mean transverse momenta, and particle ratios as a function of the charged particle multiplicity are studied to understand the particle production mechanism. The nuclear modification factor ($R_{\mathrm{pPb}}$) as a function of $p_{\mathrm{T}}$ is studied to understand the parton energy loss mechanism and the Cronin effect

Φ(1020) meson production in p-Pb collisions with ALICE detector at the LHC

Quantum Chromodynamics (QCD) describes quarks and gluons interactions. Due to asymptotic freedom, a sufficiently high energy density can lead matter to transition into the Quark-Gluon Plasma (QGP), a deconfined form of matter. In heavy-ion collisions, a medium governed by strong interactions is formed, and its evolution can be studied by the produced particles. The primary objective of the heavy-ion programme at the Large Hadron Collider (LHC) at CERN in Geneva, Switzerland, is to search for the possible formation of the QGP. The ALICE experiment at the LHC is designed to study the hot and dense medium produced in ultrarelativistic heavy-ion collisions. Hadronic resonances have shorter lifetimes relative to other stable hadrons, which is analogous to the time taken by the dense nuclear matter to reach its final state. This can be used to explore the hadronic phase's characteristics that results from heavy-ion collisions. The yield of resonances might be modified with respect to the expectations due to in-medium effects such as re-scattering and regeneration. The study of resonance production in p-Pb collisions fills the gap between pp and heavy-ion (Pb-Pb, Xe-Xe) collisions and helps us understand initial state effects due to cold nuclear matter. In this thesis, we study the $\phi$ (1020) mesons production using invariant mass reconstruction from their decay daughters (kaons) in p-Pb collisions. The kaon particles are identified by the Time Projection Chamber (TPC) and Time of Flight (TOF) in the ALICE experiment. The details of ALICE detector and its subsystems are described in this thesis. We present the measurement of $\phi$ mesons production in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 8.16 TeV using the ALICE detector. Resonances are reconstructed via their hadronic decay channels in the rapidity interval -0.5 8 GeV/$c$), the $R_{\rm{pPb}}$ values of all hadrons are consistent with unity within uncertainties. The $R_{\rm{pPb}}$ of $\phi$ mesons at $\sqrt{s_{\rm{NN}}}$ = 8.16 and 5.02 TeV show no significant energy dependence. The results are compared with EPOS-LHC, DPMJET and HIJING models predictions. We also present the first measurement of multiplicity and rapidity dependence of $\phi$ mesons production in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV. The transverse-momentum ($p_{\rm{T}}$) spectra of $\phi$ mesons measured with the ALICE detector up to $p_{\rm{T}}$ = 16 GeV/$c$ for various multiplicity classes in five rapidity intervals (-1.2 5 GeV/$c$), the $(Q_{\rm{CP}})$ values are greater than unity and no significant rapidity dependence is observed. The results are compared with EPOS-LHC, DPMJET, Pythia8, EPOS3 and HIJING models predictions

Φ\Phi and K*0^{0} Production in p–Pb and Pb–Pb Collisions with ALICE at the LHC

We report recent measurements of $\phi$ and K*$^{0}$ production in p–Pb and Pb–Pb collisions at $\sqrt{s_\mathrm{{NN}}}$ = 8.16 and 5.02 TeV, respectively. The integrated yield and mean transverse momentum are reported as a function of charged particle multiplicity to explore the particle production mechanism. Particle ratios K*$^{0}$/K and $\phi$/K are studied as a function of charged particle multiplicity to explore rescattering and regeneration effects. The nuclear modification factor ($R_\mathrm{{AA}}$) as a function of $p_\mathrm{{T}}$ is studied to explore parton energy loss

Multiplicity dependence of light (anti-)nuclei production in p–Pb collisions at sNN=5.02 TeV

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/dx and 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 approaching those observed in Pb–Pb collisions at high multiplicities. The mean transverse particle momenta are extracted from the deuteron spectra and the values are similar to those obtained for p and particles. Thus, deuteron spectra do not follow mass ordering. This behaviour is in contrast to the trend observed for non-composite particles in p–Pb collisions. In addition, the production of the rare 3He and 3He nuclei has been studied. The spectrum corresponding to all non-single diffractive p-Pb collisions is obtained in the rapidity window −1 < y < 0 and the pT-integrated yield dN/dy is extracted. It is found that the yields of protons, deuterons, and 3He, normalised by the spin degeneracy factor, follow an exponential decrease with mass number

Pseudorapidity densities of charged particles with transverse momentum thresholds in pp collisions at √ s = 5.02 and 13 TeV

The pseudorapidity density of charged particles with minimum transverse momentum (pT) thresholds of 0.15, 0.5, 1, and 2 GeV/c is measured in pp collisions at the center of mass energies of √s=5.02 and 13 TeV with the ALICE detector. The study is carried out for inelastic collisions with at least one primary charged particle having a pseudorapidity (η) within 0.8pT larger than the corresponding threshold. In addition, measurements without pT-thresholds are performed for inelastic and nonsingle-diffractive events as well as for inelastic events with at least one charged particle having |η|2GeV/c), highlighting the importance of such measurements for tuning event generators. The new measurements agree within uncertainties with results from the ATLAS and CMS experiments obtained at √s=13TeV.

Measurement of inclusive J/ψ\psi pair production cross section in pp collisions at s=13\sqrt{s} = 13 TeV

International audienceThe production cross section of inclusive J/$\psi$ pairs in pp collisions at a centre-of-mass energy $\sqrt{s} = 13$ TeV is measured with ALICE. The measurement is performed for J/$\psi$ in the rapidity interval $2.5 0$. The production cross section of inclusive J/$\psi$ pairs is reported to be $10.3 \pm 2.3 {\rm (stat.)} \pm 1.3 {\rm (syst.)}$ nb in this kinematic interval. The contribution from non-prompt J/$\psi$ (i.e. originated from beauty-hadron decays) to the inclusive sample is evaluated. The results are discussed and compared with data

Inclusive and multiplicity dependent production of electrons from heavy-flavour hadron decays in pp and p−-Pb collisions

International audienceMeasurements of the production of electrons from heavy-flavour hadron decays in pp collisions at $\sqrt{s} = 13$ TeV at midrapidity with the ALICE detector are presented down to a transverse momentum ($p_{\rm T}$) of 0.2 GeV$/c$ and up to $p_{\rm T} = 35$ GeV$/c$, which is the largest momentum range probed for inclusive electron measurements in ALICE. In p$-$Pb collisions, the production cross section and the nuclear modification factor of electrons from heavy-flavour hadron decays are measured in the $p_{\rm T}$ range $0.5 < p_{\rm T} < 26$ GeV$/c$ at $\sqrt{s_{\rm NN}} = 8.16$ TeV. The nuclear modification factor is found to be consistent with unity within the statistical and systematic uncertainties. In both collision systems, first measurements of the yields of electrons from heavy-flavour hadron decays in different multiplicity intervals normalised to the multiplicity-integrated yield (self-normalised yield) at midrapidity are reported as a function of the self-normalised charged-particle multiplicity estimated at midrapidity. The self-normalised yields in pp and p$-$Pb collisions grow faster than linear with the self-normalised multiplicity. A strong $p_{\rm T}$ dependence is observed in pp collisions, where the yield of high-$p_{\rm T}$ electrons increases faster as a function of multiplicity than the one of low-$p_{\rm T}$ electrons. The measurement in p$-$Pb collisions shows no $p_{\rm T}$ dependence within uncertainties. The self-normalised yields in pp and p$-$Pb collisions are compared with measurements of other heavy-flavour, light-flavour, and strange particles, and with Monte Carlo simulations