The transverse momentum ($p_{\rm T}$) dependence of the nuclear modification factor $R_{\rm AA}$ and the centrality dependence of the average transverse momentum $\langle p_{\rm T}\rangle$ for inclusive J/$ψ$ have been measured with ALICE for Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV in the e$^+$e$^-$ decay channel at mid-rapidity ($|y|<0.8$). The $\langle p_{\rm T}\rangle$ is significantly smaller than the one observed for pp collisions at the same centre-of-mass energy. Consistently, an increase of $R_{\rm AA}$ is observed towards low $p_{\rm T}$. These observations might be indicative of a sizable contribution of charm quark coalescence to the J/$ψ$ production. Additionally, the fraction of non-prompt J/$ψ$ from beauty hadron decays, $f_{\rm B}$, has been determined in the region $1.5 < p_{\rm T} < 10$ GeV/c in three centrality intervals. No significant centrality dependence of $f_{\rm B}$ is observed. Finally, the $R_{\rm AA}$ of non-prompt J/$ψ$ is discussed and compared with model predictions. The nuclear modification in the region $4.5 < p_{\rm T} < 10$ GeV/c is found to be stronger than predicted by most models.
We have studied the transverse-momentum ($p_{\rm T}$) dependence of the inclusive J/$ψ$ production in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, in three center-of-mass rapidity ($y_{\rm cms}$) regions, down to zero $p_{\rm T}$. Results in the forward and backward rapidity ranges ($2.03 < y_{\rm cms} < 3.53$ and $-4.46 <y_{\rm cms}< -2.96$) are obtained by studying the J/$ψ$ decay to $μ^+μ^-$, while the mid-rapidity region ($-1.37 < y_{\rm cms} < 0.43$) is investigated by measuring the ${\rm e}^+{\rm e}^-$ decay channel. The $p_{\rm T}$ dependence of the J/$ψ$ production cross section …
We report on the inclusive J/psi nuclear modification factor in p-Pb collisions at sqrt(s_NN) = 5.02 TeV as a function of rapidity y and transverse momentum p_T. The experimental coverage extends down to p_T = 0 GeV/c in the three rapidity ranges accessible by ALICE (-4.46 < y_cms < -2.96, -1.37 < y_cms < 0.46, 2.03 < y_cms < 3.53). The obtained results as a function of rapidity are in agreement with theory predictions based only on shadowing or on coherent energy loss. At forward and backward rapidity, the psi(2S) measurement complements the J/psi results. The ratio between the psi(2S) and J/…
The production of J/$ψ$ and $ψ(2S)$ was measured with the ALICE detector in Pb-Pb collisions at the LHC. The measurement was performed at forward rapidity ($2.5 < y < 4 $) down to zero transverse momentum ($p_{\rm T}$) in the dimuon decay channel. Inclusive J/$ψ$ yields were extracted in different centrality classes and the centrality dependence of the average $p_{\rm T}$ is presented. The J/$ψ$ suppression, quantified with the nuclear modification factor ($R_{\rm AA}$), was studied as a function of centrality, transverse momentum and rapidity. Comparisons with similar measurements at lower co…
Inclusive J/$ψ$ production is studied in minimum-bias proton-proton collisions at a centre-of-mass energy of $\sqrt{s}$ = 5.02 TeV by ALICE at the CERN LHC. The measurement is performed at mid-rapidity ($|y| < 0.9$) in the dielectron decay channel down to zero transverse momentum $p_{\rm T}$, using a data sample corresponding to an integrated luminosity of $L_{\rm int} = 19.4 \pm$ 0.4 nb$^{-1}$. The measured $p_{\rm T}$-integrated inclusive J/$ψ$ production cross section is d$σ$/d$y$ = 5.64 $\pm$ 0.22 (stat.) $\pm 0.33$ (syst.) $\pm 0.12$ (lumi.) $μ$b. The $p_{\rm T}$-differential cross sectio…
We report on the measurement of the inclusive J/$ψ$ polarization parameters in pp collisions at a center of mass energy $\sqrt{s} = 8$ TeV with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.23 pb$^{-1}$. J/$ψ$ resonances are reconstructed in their di-muon decay channel in the rapidity interval $2.5 < y < 4.0$ and over the transverse-momentum interval $2 < p_{\rm T} < 15$ GeV/$c$. The three polarization parameters ($λ_θ$, $λ_φ$, $λ_{θφ}$) are measured as a function of $p_{\rm T}$ both in the helicity and Collins-Soper refere…
Inclusive J/$ψ$ production is studied in p-Pb interactions at a centre-of-mass energy per nucleon-nucleon collision $\sqrt{s_{\rm NN}}=8.16$ TeV, using the ALICE detector at the CERN LHC. The J/$ψ$ meson is reconstructed, via its decay to a muon pair, in the centre-of-mass rapidity intervals $2.03<y_{\rm {cms}}<3.53$ and $-4.46<y_{\rm {cms}}<-2.96$, where positive and negative $y_{\rm {cms}}$ refer to the p-going and Pb-going direction, respectively. The transverse momentum coverage is $p_{\rm T}<20$ GeV/$c$. In this paper, $y_{\rm cms}$- and $p_{\rm T}$-differential cross sections for inclusi…
We report on the inclusive production cross sections of J/$ψ$, $ψ$(2S), $Υ$(1S), $Υ$(2S) and $Υ$(3S), measured at forward rapidity with the ALICE detector in pp collisions at a center-of-mass energy $\sqrt{s}=8$ TeV. The analysis is based on data collected at the LHC and corresponds to an integrated luminosity of 1.28 pb$^{-1}$. Quarkonia are reconstructed in the dimuon-decay channel. The differential production cross sections are measured as a function of the transverse momentum $p_{\rm T}$ and rapidity $y$, over the $p_{\rm T}$ ranges $0<p_{\rm T}<20$ GeV/$c$ for J/$ψ$, $0<p_{\rm T}<12$ GeV/…
We present a measurement of inclusive J/$ψ$ production in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, $p_{\rm T}$, in the backward ($-4.46 < y_{\rm cms} < -2.96$) and forward ($2.03 < y_{\rm cms} < 3.53$) rapidity intervals in the dimuon decay channel and in the mid-rapidity region ($-1.37 < y_{\rm cms} < 0.43$) in the dielectron decay channel. The backward and forward rapidity inte…
Quarkonia states are expected to provide essential information on the properties of the high-density strongly-interacting system formed in the early stages of high-energy heavy-ion collisions. ALICE is the LHC experiment dedicated to the study of nucleus-nucleus collisions and can study charmonia at forward rapidity (2.5 < y < 4) via the mu+ mu- decay channel and at mid rapidity (|y| < 0.9) via the e+ e- decay channel. In both cases charmonia are measured down to zero transverse momentum. The inclusive J/psi production as a function of transverse momentum and rapidity in pp collisions at sqrt{…
Semi-inclusive charged jet spectra per trigger at STAR are presented binned by event activity (EA) as determined by the Beam Beam Counter (BBC) signal in the Au-going direction. The selected EA determination is motivated by correlations between the number of charged tracks in the Time Projection Chamber (TPC) ($|η|<1$) and EA ($η_\mathrm{EA}\in[-5,-2]$) which are also presented. The jet spectra per trigger at high EA are suppressed relative to the spectra at low EA. A PYTHIA investigation refutes that the suppression results from a trivial autocorrelation between jet kinematics and the accepta…
We have measured the ratios of antiparticles to particles for charged pions, kaons and protons near mid-rapidity in central Au+Au collisions at sqrt(s_NN) = 130 GeV. For protons, we observe pbar/p = 0.60 +/- 0.04 (stat.) +/- 0.06 (syst.) in the transverse momentum range 0.15 < p_T < 1.0 GeV/c. This leads to an estimate of the baryo-chemical potential mu_B of 45 MeV, a factor of 5-6 smaller than in central Pb+Pb collisions at sqrt(s_NN) = 17.2 GeV.
We present an overview of the ALICE measurements on the production of $\mathrm{J/}ψ$ in Pb-Pb collisions at a centre-of-mass energy per nucleon pair of $\sqrt{s_\mathrm{NN}} = 2.76\,\mathrm{TeV}$ and p-Pb collisions at $\sqrt{s_\mathrm{NN}}= 5.02\,\mathrm{TeV}$ at mid-rapidity ($|y_\mathrm{lab} | < 0.8$) down to zero transverse momentum. The cold nuclear matter effects estimated from the p-Pb measurements and their impact on the interpretation of Pb-Pb results are discussed, based on comparison of data to model calculations.
We present the recent results for D-meson production measured by the ALICE collaboration in pp collisions at $\sqrt{s}=7$ TeV, Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV and p-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV.
We study the recent PHOBOS data on the pseudorapidity density of inclusive charged particles in centrality-binned d+Au collisions at sqrt(s_NN) = 200 GeV. It appears that one can understand the increasing forward-backward asymmetry in the data by assuming that the entire distribution "shifts" backwards in rapidity according to the initial-state kinematics, while the total multiplicity scales linearly with Npart/2. Two models are explored, both of which achieve a reasonable description of the available data for rapidities sufficiently far from the pro jectiles (|eta|< 3 at the top RHIC energy).…
We present the first measurement of pseudorapidity densities of primary charged particles near mid-rapidity in Au+Au collisions at $\sqrt{s} =$ 56 and 130 AGeV. For the most central collisions, we find the charged particle pseudorapidity density to be $dN/dη|_{|η|<1} = 408 \pm 12 {(stat)} \pm 30 {(syst)}$ at 56 AGeV and $555 \pm 12 {(stat)} \pm 35 {(syst)}$ at 130 AGeV, values that are higher than any previously observed in nuclear collisions. Compared to proton-antiproton collisions, our data show an increase in the pseudorapidity density per participant by more than 40% at the higher energy.
Measurements of the centrality and rapidity dependence of inclusive jet production in $\sqrt{s_\mathrm{NN}} = 5.02$ TeV proton--lead ($p$+Pb) collisions and the jet cross-section in $\sqrt{s} = 2.76$ TeV proton--proton collisions are presented. These quantities are measured in datasets corresponding to an integrated luminosity of 27.8 nb$^{-1}$ and 4.0 pb$^{-1}$, respectively, recorded with the ATLAS detector at the Large Hadron Collider in 2013. The $p$+Pb collision centrality was characterised using the total transverse energy measured in the pseudorapidity interval $-4.9 < η< -3.2$ in the d…
The pseudorapidity densities of charged particles and inclusive photons produced in high energy nuclear collisions are essential observables to characterise the global properties of the collisions, such as the achieved energy density, and to provide important constraints for Monte Carlo model calculations. In the LHC Run 1 and Run 2 configurations, ALICE had large coverage to measure charged particles over a pseudorapidity range ($-3.4~<~η~<~5.0$), combining the data from the Silicon Pixel Detector (SPD) and the Forward Multiplicity Detector (FMD). The inclusive photons are measured at forward…
Measurements of the production of high energy pi0 mesons at large pseudorapidity, coincident with charged hadrons at mid-rapidity, for proton+proton and deuteron+gold collisions at sqrt(s)_NN=200 GeV are reported. The p+p cross section for inclusive pi0 production follows expectations from next-to-leading order perturbative QCD. Both the inclusive cross section and the di-hadron azimuthal correlations are consistent with a model where parton showers supplement leading-order pQCD. A suppression of the back-to-back azimuthal correlations was observed in d+Au, qualitatively consistent with the gl…
The invariant differential cross section for inclusive neutral pion production in p+p collisions at sqrt(s_NN) = 200 GeV has been measured at mid-rapidity |eta| < 0.35 over the range 1 < p_T <~ 14 GeV/c by the PHENIX experiment at RHIC. Predictions of next-to-leading order perturbative QCD calculations are consistent with these measurements. The precision of our result is sufficient to differentiate between prevailing gluon-to-pion fragmentation functions.
The first measurement of energy produced transverse to the beam direction at RHIC is presented. The mid-rapidity transverse energy density per participating nucleon rises steadily with the number of participants, closely paralleling the rise in charged-particle density, such that E_T / N_ch remains relatively constant as a function of centrality. The energy density calculated via Bjorken's prescription for the 2% most central Au+Au collisions at sqrt(s_NN)=130 GeV is at least epsilon_Bj = 4.6 GeV/fm^3 which is a factor of 1.6 larger than found at sqrt(s_NN)=17.2 GeV (Pb+Pb at CERN).
Measurements of the per-event charged-particle yield as a function of the charged-particle transverse momentum and rapidity are performed using $p+$Pb collision data collected by the ATLAS experiment at the LHC at a centre-of-mass energy of $\sqrt{s_{NN}}=5.02$ TeV. Charged particles are reconstructed over pseudorapidity $|η|<2.3$ and transverse momentum between $0.1$ GeV and $22$ GeV in a dataset corresponding to an integrated luminosity of $1$ $μb^{-1}$. The results are presented in the form of charged-particle nuclear modification factors, where the $p+$Pb charged-particle multiplicities ar…
The multiplicity dependence of the pseudorapidity density of charged particles in proton-proton (pp) collisions at centre-of-mass energies $\sqrt{s}$ = 5.02, 7 and 13 TeV measured by ALICE is reported. The analysis relies on track segments measured in the midrapidity range ($|η| < 1.5$). Results are presented for inelastic events having at least one charged particle produced in the pseudorapidity interval $|η|<1$ ($\mathrm{INEL}_{>0}$). The multiplicity dependence of the pseudorapidy density of charged particles is measured with mid and forward rapidity multiplicity estimators, the latter bein…
The ALICE collaboration has studied inclusive J/$ψ$ and $ψ$(2S) production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV with the ALICE Muon Spectrometer. The analysis has been carried out on a data sample corresponding to an integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35 pb$^{-1}$. The production cross-sections of J/$ψ$ and $ψ$(2S), integrated over \pt\ (0 $<$ \pt\ $<$ 20 GeV/$c$) and \y\ (2.5 $<$ \y\ $<$ 4), have been measured. The J/$ψ$ and $ψ$(2S) differential cross-sections, in transverse momentum and rapidity, have also been measured. The results have been compared w…
We report STAR results on the azimuthal anisotropy parameter v2 for strange particles K0S, L and Lbar at midrapidity in Au+Au collisions at sNN = 130 GeV at RHIC. The value of v2 as a function of transverse momentum of the produced particles pt and collision centrality is presented for both particles up to pt 3.0 GeV/c. A strong pt dependence in v2 is observed up to 2.0 GeV/c. The v2 measurement is compared with hydrodynamic model calculations. The physics implications of the pt integrated v2 magnitude as a function of particle mass are also discussed.
A measurement of beauty hadron production at mid-rapidity in proton-lead collisions at a nucleon-nucleon centre-of-mass energy $\sqrt{s_{\rm NN}}=5.02$ TeV is presented. The semi-inclusive decay channel of beauty hadrons into J/$ψ$ is considered, where the J/$ψ$ mesons are reconstructed in the dielectron decay channel at mid-rapidity down to transverse momenta of 1.3 GeV/$c$. The ${\rm {b\overline{b}}}$ production cross section at mid-rapidity, ${\rm d}σ_{\rm {b\overline{b}}}/{\rm d} y$, and the total cross section extrapolated over full phase space, $σ_{\rm {b\overline{b}}}$, are obtained. Th…
The ALICE Collaboration has measured the inclusive production of muons from heavy flavour decays at forward rapidity, 2.5 < y < 4, in pp and Pb-Pb collisions at $\sqrt {s_{NN}}$ = 2.76 TeV. The $p_{\rm T}$-differential inclusive cross section of muons from heavy flavour decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of pt 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 < $p_{\rm T}$ < 10 GeV/$c…
We report on the J$ψ$ nuclear modification factor $R_{\rm AA}$ at mid-rapidity ($|y|<0.9$) in Pb-Pb collisions at $\sqrt{s_{NN}}=$2.76 TeV measured by ALICE. J$ψ$ candidates are reconstructed using their $e^+e^-$ decay channel. The kinematical coverage extends to zero transverse momentum allowing the measurement of integrated cross sections. We show the centrality dependence of the J$ψ$ $R_{\rm AA}$ at mid-rapidity compared to the results from PHENIX at mid-rapidity and ALICE results at forward-rapidity. We also discuss comparisons to calculations from theoretical models.
The production at central rapidity of K0s, Lambda, Xi and Omega particles in Pb-Pb collisions at 158 A GeV/c has been measured by the NA57 experiment over a centrality range corresponding to the most central 53% of the inelastic Pb-Pb cross section. In this paper we present the rapidity distribution of each particle in the central rapidity unit as a function of the event centrality. The distributions are analyzed based on hydrodynamical models of the collisions.
We report the first measurement of inclusive antiproton production at mid-rapidity in Au+Au collisions at 130 GeV by the STAR experiment at RHIC. The antiproton transverse mass distributions in the measured transverse momentum range of 0.25 < pT < 0.95 GeV/c are found to fall less steeply for more central collisions. The extrapolated antiproton rapidity density is found to scale approximately with the negative hadron multiplicity density.
Charmonium production is highly sensitive to the hot and dense medium created in (ultra)-relativistic heavy-ion collisions, known as the Quark-Gluon Plasma (QGP). Measurements of the J/$ψ$ production serve as important tools for studying the properties of this medium. In addition to QGP effects, the J/$ψ$ production is modified by the presence of cold nuclear matter (CNM) effects such as shadowing or parton energy loss. These effects are studied in proton-nucleus collisions where no QGP formation is expected. In order to quantify how the J/$ψ$ production is modified by the medium, the vacuum p…
Event-by-event fluctuations in the net charge and <pT> at mid-rapidity have been studied in Au+Au collisions using the central tracking arms in the PHENIX experiment at RHIC.
The ALICE Collaboration has studied inclusive $ψ$(2S) production in pp, p-Pb and Pb-Pb collisions with the ALICE Muon Spectrometer which covers the rapidity range 2.5 $<$ $y_{\rm lab}$ $<$ 4. The $ψ$(2S) measurement was performed in the dimuon decay channel. The $ψ$(2S) production cross-section and $ψ$(2S) to J/$ψ$ cross-section ratio in pp collisions will be presented, both integrated and differential in rapidity and in transverse momentum. In p-Pb collisions, $ψ$(2S) results will be compared to the J/$ψ$ ones by means of the production cross-section ratio and the double ratio [$ψ$(2S)/J/$ψ$]…
We present new results for the nuclear modification factor \RAA of \jpsi mesons as a function of centrality and transverse momentum at mid-rapidity. The measurement is carried out with the ALICE central barrel detectors in the acceptance range $|y|$ < 0.9 and \pt > 0 in the dielectron decay channel.
The ALICE experiment has measured the inclusive J/$ψ$ production in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}} } = 2.76$ TeV down to zero transverse momentum in the rapidity range $2.5 < y < 4$. A suppression of the inclusive J/$ψ$ 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 $0.545 \pm 0.032 \rm{(stat.)} \pm 0.083 \rm{(syst.)}$ and does not exhibit a significant dependence on the collision centrality. These features a…
Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations at forward rapidity with a mid-rapidity high-pt hadron, on the other hand, are sensitive primarily to quark-gluon hard-scattering and may probe quark-jet modification in nuclear medium. They may be also sensitive to the Color Glass Condensate by separating d-side and Au-side in d+Au collisions. We present the first results on correlations of charged hadrons …
Measurements of the yield and nuclear modification factor, $R_\mathrm{ AA}$, for inclusive jet production are performed using 0.49 nb$^{-1}$ of Pb+Pb data at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV and 25 pb$^{-1}$ of $pp$ data at $\sqrt{s}=5.02$ TeV with the ATLAS detector at the LHC. Jets are reconstructed with the anti-$k_t$ algorithm with radius parameter $R=0.4$ and are measured over the transverse momentum range of 40-1000 GeV in six rapidity intervals covering $|y|<2.8$. The magnitude of $R_\mathrm{ AA}$ increases with increasing jet transverse momentum, reaching a value of approximately 0.6 …
In this proceedings we present STAR measurements of two particle azimuthal correlations between trigger particles at mid-rapidity ($|η|<$ 1) and associated particles at forward rapidities (2.7 $<|η|<$ 3.9) in p+p, d+Au and Au+Au collisions at $\sqrt{s_{NN}} $= 200 GeV. Two particle azimuthal correlations between a mid-rapidity trigger particle and forward-rapidity associated particles preferably probe large-x quarks scattered off small-x gluons in RHIC collisions. Comparison of the separate d- and Au-side measurements in d+Au collisions may potentially probe gluon saturation and the presence o…
The ratios of charged antiparticles to particles have been obtained for pions, kaons and protons near midrapidity in central Au+Au collisions at sqrt(s_NN) = 200 GeV. Ratios of <pi->/<pi+> = 1.025 +/- 0.006 (stat.) +/- 0.018 (syst.), <K->/<K+> = 0.95 +/- 0.03 (stat.) +/- 0.03 (syst.) and <pbar>/<p> = 0.73 +/- 0.02 (stat.) +/- 0.03 (syst.) have been observed. The <K->/<K+> and <pbar>/<p> ratios are consistent with a baryochemical potential mu_B of 27 MeV, roughly a factor of 2 smaller than in sqrt(s_NN) = 130 GeV collisions. The data are compared to results from lower energies and model calcula…
We present a study of the inclusive J/psi cross section at 2.76 TeV and 5.5 TeV. The energy dependence of the cross section, rapidity and transverse momentum distributions are evaluated phenomenologically. Their knowledge is crucial as a reference for the interpretation of A-A and p-A J/psi results at the LHC. Our approach is the following: first, we estimate the energy evolution of the pt-integrated J/psi cross section at mid-rapidity; then, we evaluate the rapidity dependence; finally, we study the transverse momentum distribution trend. Whenever possible, both theory driven (based on pQCD p…
The production of ${\rmΞ}^-$ and ${\rmΩ}^-$ baryons and their anti-particles in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV has been measured using the ALICE detector. The transverse momentum spectra at mid-rapidity ($|y| < 0.5$) for charged $\rmΞ$ and $\rmΩ$ hyperons have been studied in the range $0.6 < p_{\rm T} < 8.0$ GeV/$c$ and $1.2 < p_{\rm T} < 7.0$ GeV/$c$, respectively, and in several centrality intervals (from the most central 0-10% to the most peripheral 60-80% collisions). These spectra have been compared with the predictions of recent hydrodynamic models. In particular, th…
We present a measurement of the pseudorapidity density of primary charged particles near mid-rapidity in Au+Au collisions at sqrt(s_NN) = 130 GeV as a function of the number of participating nucleons. These results are compared to models in an attempt to discriminate between competing scenarios of particle production in heavy ion collisions.
The ALICE collaboration has studied inclusive J/$ψ$ and $ψ$(2S) production at forward rapidities in pp collisions at $\sqrt{s} = 7$ TeV with the ALICE Muon Spectrometer. The analysis has been carried out on a data sample corresponding to an integrated luminosity $\mathcal{L}_{\rm int}$ = 1.35 pb$^{-1}$. The production cross-sections of J/$ψ$ and $ψ$(2S), integrated over the transverse momentum (0 $<$ $p_{\mathrm T}$ $<$ 20 GeV/$c$) and rapidity (2.5 $<$ $y$ $<$ 4), have been measured. The J/$ψ$ and $ψ$(2S) differential cross-sections, in transverse momentum and rapidity, have also been measure…
We report results on the ratio of mid-rapidity anti-proton to proton yields in Au+Au collisions at $\rts = 130$ GeV per nucleon pair as measured by the STAR experiment at RHIC. Within the rapidity and transverse momentum range of $|y|<0.5$ and 0.4 $<p_t<$ 1.0 GeV/$c$, the ratio is essentially independent of either transverse momentum or rapidity, with an average of $0.65\pm 0.01_{\rm (stat.)} \pm 0.07_{\rm (syst.)}$ for minimum bias collisions. Within errors, no strong centrality dependence is observed. The results indicate that at this RHIC energy, although the $p$-$\pb$ pair production becom…
The first measurements of the production of muons and electrons from heavy-flavour hadron decays in Xe-Xe collisions at $\sqrt{s_{\rm NN}}$ = 5.44 TeV, using the ALICE detector at the LHC, are reported. The measurement of the nuclear modification factor $R_{\rm AA}$ is performed as a function of transverse momentum $p_{\rm T}$ in several centrality classes at forward rapidity ($2.5 < y <4$) and midrapidity ($\vert y \vert < 0.8$) 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 observ…
Mid-rapidity azimuthal correlations probe di-jets originating mainly from gluon-gluon hard-scattering. Measurements of such correlations have revealed significant (gluon-)jet modification in central Au+Au collisions. Azimuthal correlations of hadrons at forward rapidity with a mid-rapidity high-$\pt$ hadron, on the other hand, probe asymmetric partonic scatterings involving large-x quarks and small-x gluons. We present preliminary results from STAR on correlations of charged hadrons at forward rapidity in the forward TPCs ($2.7<|η|<3.9$, $\pt<2$ GeV/$c$) with high-$\pt$ charged hadrons at mid-…
Results are presented on $π^\pm$, $K^\pm$, and $\bar{p}$ transverse mass spectra and particle multiplicity ratios at mid-rapidity in Au+Au collisions at $\sqrt{s_{_{\rm NN}}}$=130 and 200 GeV and in p+p collisions at $\sqrt{s}$=200 GeV. Comparisons are made to results from lower energies. The bulk properties of the collision inferred from these results are discussed.
We report the first measurement of strange ($Λ$) and anti-strange ($\barΛ$) baryon production from $\sqrt{s_{_{NN}}}=130$ GeV Au+Au collisions at the Relativistic Heavy Ion Collider (RHIC). Rapidity density and transverse mass distributions at mid-rapidity are presented as a function of centrality. The yield of $Λ$ and $\barΛ$ hyperons is found to be approximately proportional to the number of negative hadrons. The production of $\barΛ$ hyperons relative to negative hadrons increases very rapidly with transverse momentum. The magnitude of the increase cannot be described by existing hadronic s…
Inclusive $Υ$(1S) and $Υ$(2S) production have been measured in Pb-Pb collisions at the centre-of-mass energy per nucleon-nucleon pair $\sqrt{s_{_{\rm NN}}}=5.02$ 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 transverse-momentum range $p_{\rm T}<15$ GeV/$c$, via their decays to muon pairs. In this Letter, we present results on the inclusive $Υ$(1S) nuclear modification factor $R_{\rm AA}$ as a function of collision centrality, transverse momentum and rapidity. The $Υ$(1S) and $Υ$(2S) $R_{\rm AA}$, int…
The elliptic flow of electrons from heavy-flavour hadron decays at mid-rapidity ($|y|$ $<$ 0.7) is measured in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ TeV with ALICE at the LHC. The particle azimuthal distribution with respect to the reaction plane can be parametrized with a Fourier expansion, where the second coefficient ($v_{\rm 2}$) represents the elliptic flow. The $v_{\rm 2}$ coefficient of inclusive electrons is measured in three centrality classes (0-10%, 10-20% and 20-40%) with the event plane and the scalar product methods in the transverse momentum ($p_{\rm T}$) intervals 0.5-…
The ALICE Collaboration at the LHC has measured the J/$ψ$ and $ψ^{'}$ photoproduction at mid-rapidity in ultra-peripheral Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV. The charmonium is identified via its leptonic decay for events where the hadronic activity is required to be minimal. The analysis is based on an event sample corresponding to an integrated luminosity of about 23 $μ\rm{b}^{-1}$. The cross section for coherent and incoherent J/$ψ$ production in the rapidity interval $-0.9<y<0.9$, are $\mathrm{d}σ_{{\rm J}/ψ}^{\rm coh}/\mathrm{d}y = 2.38^{+0.34}_{-0.24}\big(\mathrm{sta+sys}\bi…
We present results on transverse momentum ($p_{\rm T}$) and rapidity ($y$) differential production cross sections, mean transverse momentum and mean transverse momentum square of inclusive J/$ψ$ and $ψ(2S)$ at forward rapidity ($2.5<y<4$) as well as $ψ(2S)$-to-J/$ψ$ cross section ratios. These quantities are measured in pp collisions at center of mass energies $\sqrt{s}=5.02$ and 13 TeV with the ALICE detector. Both charmonium states are reconstructed in the dimuon decay channel, using the muon spectrometer. A comprehensive comparison to inclusive charmonium cross sections measured at $\sqrt{s…
The ratios of the yields of charged antiparticles to particles have been obtained for pions, kaons, and protons near mid-rapidity for d+Au collisions at sqrt(s_NN) = 200 GeV as a function of centrality. The reported values represent the ratio of the yields averaged over the rapidity range of 0.1<y_pi<1.3 and 0<y_(K,p)<0.8, where positive rapidity is in the deuteron direction, and for transverse momenta 0.1<p_(T)^(pi,K)<1.0 GeV/c and 0.3<p_(T)^(p)<1.0 GeV/c. Within the uncertainties, a lack of centrality dependence is observed in all three ratios. The data are compared to results from other sys…
The first measurement of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at a centre-of-mass energy per nucleon pair $\sqrt{s_{\rm NN}}$ = 2.76 TeV is presented. For an event sample corresponding to the most central 5% of the hadronic cross section the pseudo-rapidity density of primary charged particles at mid-rapidity is 1584 $\pm$ 4 (stat) $\pm$ 76 (sys.), which corresponds to 8.3 $\pm$ 0.4 (sys.) 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 c…
We report on the production of inclusive $Υ$(1S) and $Υ$(2S) in p-Pb collisions at $\sqrt{s_{\rm NN}}=5.02$ TeV at the LHC. The measurement is performed with the ALICE detector at backward ($-4.46< y_{\rm cms}<-2.96$) and forward ($2.03< y_{\rm cms}<3.53$) rapidity down to zero transverse momentum. The production cross sections of the $Υ$(1S) and $Υ$(2S) are presented, as well as the nuclear modification factor and the ratio of the forward to backward yields of $Υ$(1S). A suppression of the inclusive $Υ$(1S) yield in p-Pb collisions with respect to the yield from pp collisions scaled by the nu…
The inclusive J/$ψ$ production in Pb-Pb collisions at the center-of-mass energy per nucleon pair $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV, measured with the ALICE detector at the CERN LHC, is reported. The J/$ψ$ meson is reconstructed via the dimuon decay channel at forward rapidity ($2.5<y<4$) down to zero transverse momentum. The suppression of the J/$ψ$ yield in Pb-Pb collisions with respect to binary-scaled pp collisions is quantified by the nuclear modification factor ($R_{\rm{AA}}$). The $R_{\rm{AA}}$ at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV is presented and compared with previous measurements at $\sqr…
We present multiplicity and pseudorapidity distributions of inclusive photons at forward rapidity in proton-lead (p-Pb) collisions at $\sqrt{s\rm_{NN}}$ = 5.02 TeV using the data obtained from Photon Multiplicity Detector (PMD) of ALICE. The centrality dependence of pseudorapidity distributions of inclusive photons is also studied. Results are compared with the previous ALICE measurements of charged-particle production and with theoretical predictions from Monte Carlo models, DPMJET and HIJING.
The centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor 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.
