Bottomonium production is a powerful tool to investigate hadron collisions and the properties of the medium created in heavy-ion collisions. According to the color-screening model, these mesons give important information about the deconfined medium called Quark-Gluon Plasma (QGP) produced in ultrarelativistic heavy-ion collisions. Cold nuclear matter (CNM) effects can modify the bottomonium production even in absence of deconfined matter: the study of proton-nucleus collisions is therefore essential to disentangle these effects from the hot ones. Last but not least, measurement in pp collisions serve as crucial test of different QCD models of quarkonium hadroproduction and provide the reference for the study in nucleus-nucleus collisions.
In ALICE, bottomonium is measured at forward rapidity ($2.5 < y < 4$) down to zero transverse momentum, exploiting the dimuon decay channel. The latest results in pp, Pb-Pb and p-Pb collisions are discussed and compared to theoretical calculations.
In ultrarelativistic nucleus-nucleus collisions, a deconfined state of strongly interacting matter is thought to be produced, commonly known as the quark--gluon plasma (QGP). Quarkonia, bound states of a heavy quark and antiquark, are an important probe to study the properties of the QGP. At the LHC, bottomonium (b$\rm\overline{b}$) is of particular interest to study the QGP complementarily to the lighter charmonium (c$\rm\overline{c}$) system. In addition to the measurements in nucleus-nucleus collisions, reference measurements in proton-proton and proton-nucleus collisions have been also car…
An overview of recent ${\rm D^+}$, ${\rm D^0}$, ${\rm D^{*+}}$ and ${\rm D_s^+}$ measurements performed by ALICE at central rapidity in proton-proton collisions at $\sqrt{s}=7$ and 8 TeV, as well as lead-lead collisions at $\sqrt{s_\mathrm{NN}}=2.76$ TeV, is presented. An emphasis is put on the discussion of theoretical predictions with respect to the LHC Run I data.
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.
In the ALICE experiment, at forward rapidity (2.5 < y < 4), the production of heavy quarkonium states is measured via their mu+ mu- decay channels. We present the first measurement of inclusive J/Psi production, down to pT = 0, from Pb-Pb data collected at the LHC at sqrt(s_NN) = 2.76 TeV. Preliminary results on the nuclear modification factor (R_AA) and the central to peripheral nuclear modification factor (R_CP) show J/Psi suppression with no significant centrality dependence and an integrated R_AA(0-80%) = 0.49 \pm 0.03(stat.) \pm 0.11(syst.).
The ALICE experiment studies nucleus-nucleus collisions at the LHC in order to investigate the properties of QCD matter at extreme energy densities. The measurement of open charm and open beauty production allows to investigate the interaction of heavy quarks with the hot and dense medium formed in high-energy nucleus-nucleus collisions. In particular, in-medium energy loss is predicted to be different for gluons, light quarks and heavy quarks and to depend on the medium energy density and size. ALICE has measured open heavy-flavour particle production at central rapidity in several decay chan…
The ALICE experiment measured the heavy-flavour production in the semi-muonic decay channel at forward rapidities ($2.5<y<4$) in pp and Pb--Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV. We report on the first results on the $p_{\rm T}$-differential cross-sections in pp collisions as well as on the nuclear modification factors as a function of the transverse momentum and centrality.
The production of muons from heavy flavour decays is measured at forward rapidity (2.5 < y < 4) with the muon spectrometer of the ALICE experiment at the LHC. In pp collisions at \sqrt{s} = 7 TeV, the measurement of the transverse momentum and rapidity differential production cross section of muons from heavy flavour decays is carried out from a data sample corresponding to an integrated luminosity of Lint = 16.5 nb^-1 and results are compared to predictions based on perturbative QCD calculations. In Pb-Pb collisions at \sqrt{s_{NN}}= 2.76 TeV, the analysis of a data sample corresponding to an…
The production of open heavy-flavour particles was studied in p-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV using the ALICE detector. Three separate observables were used: the hadronic decays of D mesons at mid-rapidity, and semileptonic decays of heavy-flavour hadrons to electrons and muons at mid-rapidity and forward rapidity, respectively. The most recent ALICE measurements of the nuclear modification factor, $R_\mathrm{pPb}$, of open charm and beauty are reported, along with the centrality and multiplicity dependence of D-meson production in p-Pb collisions.
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…
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…
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 measurements of open heavy-flavours, i.e. D mesons at central rapidity and leptons from charm and beauty decays at central and forward rapidity was studied in p-Pb collisions at $\sqrt{s_{\rm{NN}}}$ = 5.02 TeV using the ALICE detector. The results are presented and compared to model predictions including cold nuclear matter effects.
J/psi suppression induced by color screening of its constituent quarks was proposed 26 years ago as a signature of the formation of a quark gluon plasma in heavy-ion collisions. Recent results from ALICE in Pb-Pb collisions exhibit a smaller suppression with respect to previous measurements at the SPS and RHIC. The study of azimuthal anisotropy in particle production gives information on the collective hydrodynamic expansion at the early stage of the fireball, where the matter created in high-energy nuclear collisions is expected to be in a deconfined state. In particular, J/psi elliptic flow …
We present the preliminary pt differential cross section in pp collisions of the D+s meson measured in the mid-rapidity region of ALICE with an integrated luminosity of 4.8 nb^-1. The ratios between all the D meson preliminary pt differential cross sections measured in the ALICE experiment (D+s,D0,D+,D*+) are also presented and compared with the results of other experiments.
The study of formation of heavy quarkonia in relativistic heavy ion collisions provides important insight into the properties of the produced high density QCD medium. Lattice QCD studies show sequential suppression of quarkonia states with increasing temperature; which affirms that a full spectroscopy, can provide us a thermometer for the matter produced under extreme conditions in relativistic heavy ion collisions and one of the most direct probes of de-confinement. Muons from the decay of charmonium resonances are detected in ALICE Experiment in p+p and Pb+Pb collisions with a muon spectrome…
The ratios of yields of anti-baryons to baryons probes the mechanisms of baryon-number transport. Results for $\bar{\rm p}/{\rm p}$, $\bar{\rm Λ}/{\rm Λ}$, $\rm\barΞ$$^{+}/{\rm Ξ}^{-}$ and $\rm\barΩ$$^{+}/{\rm Ω}^{-}$ in pp collisions at $\sqrt{s} = 0.9$, 2.76 and 7 TeV, measured with the ALICE detector at the LHC, are reported. Within the experimental uncertainties and ranges covered by our measurement, these ratios are independent of rapidity, transverse momentum and multiplicity for all measured energies. The results are compared to expectations from event generators, such as PYTHIA and HIJ…
Heavy quarks are produced at the first instant of a nucleus--nucleus collision and therefore are an important tool to study the subsequent high energy-density medium formed in ultra-relativistic heavy-ion collisions. A series of experimental efforts for understanding the properties of the Quark--Gluon Plasma (QGP), a medium consisting of a deconfined state of quarks and gluons, are based on measuring the bound states of heavy quark--anti-quark pairs known as quarkonia. However, the medium modification of heavy-flavour hadron production includes also the contribution of Cold Nuclear Matter (CNM…
The ALICE apparatus at the LHC was designed and built to perform dedicated studies of the Quark-Gluon Plasma (QGP), a strongly interacting phase of QCD matter, expected to be created in heavy-ion collisions, where quarks and gluons are deconfined. In such collisions heavy flavours are produced at the very early stage of the interaction by the initial hard scattering processes and hence can be used to characterize the hot and dense medium. In particular the sequential suppression of quarkonia (charmonia and bottomonia) was proposed as a thermometer of the deconfined medium. The inclusive $Υ(1S)…
The relative J/$ψ$ yields as a function of relative charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 5.02 TeV, measured at forward rapidity, are investigated for the first time. A linear increase of the relative J/$ψ$ yield with respect to multiplicity is observed. A comparison of the findings of the present work with the available ALICE measurements obtained in pp collisions at $\sqrt{s}$ = 13 TeV at forward and mid-rapidity indicates that the increase of J/$ψ$ with multiplicity is independent of energy but exhibits a strong dependence on the rapidity gap between the J/$ψ$ and m…
Hadronic resonances are unique tools to investigate the interplay of re-scattering and regeneration effects during the hadronization phase in heavy-ion collisions. Measurements in small collision systems provide a necessary baseline for heavy-ion data, help to tune pQCD inspired event generators and give insight into the search for the onset of collective effects. As the $ϕ$ meson has a longer lifetime compared to other resonances, it is expected that its production would be much less affected by regeneration and re-scattering processes. We report on measurements of $ϕ$ meson production in min…
We report on the pseudo-rapidity dependence of the charged particle anisotropic flow in Pb-Pb collisions at 2.76 TeV. The measurement is done over a wide range of pseudo-rapidity, |η|<5 using the forward detectors of ALICE at the LHC. Results are obtained from two- and multi-particle correlation techniques with the latter being less sensitive to non-flow effects. Elliptic flow longitudinal scaling, comparison with RHIC data and AMPT model calculations for the LHC are discussed.
The ALICE experiment has measured charm and beauty production in pp and Pb-Pb collisions at sqrt(s) = 2.76 and 7 TeV and sqrt(sNN) = 2.76 TeV, respectively, via the exclusive reconstruction of hadronic D meson decays and semi-leptonic D and B meson decays. In this contribution, recent results on the nuclear modification factor for open charmed mesons and heavy-flavour decay electrons at central rapidity and muons at forward rapidity are presented and discussed.
ALICE is the dedicated heavy-ion experiment at the LHC. Its main physics goal is to study the properties of the strongly-interacting matter in the conditions of high energy density (>10 GeV/fm3) and high temperature (> 0.3 GeV) expected to be reached in central PbâPb collisions. Charm and beauty quarks are a powerful tool to investigate this high density and strongly interacting state of matter as they are produced in initial hard scatterings, and due to their long life time, they probe all the stages of the system evolution. The detector design was optimized for heavy ions but is also well su…
We report the recent measurements of the inclusive J/ψ production in pp collisions at \sqrt{s} = 2.76 TeV, in pp collisions at \sqrt{s} = 7 TeV and in Pb-Pb collisions at \sqrt{s_{NN}} = 2.76 TeV with the ALICE detector at the LHC. The J/ψ mesons are detected down to pT = 0 GeV/c via their di-muon decay channel at forward rapidity (2.5 < y < 4) and via their di-electron decay channel at mid-rapidity (|y| < 0.9). A special emphasis is put on the nuclear modification factor which is compared to the predictions of current J/ψ production models.
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{…
We present the first preliminary results on photon multiplicity measurements at LHC at forward pseudorapidity (2.3 $\textless$ $η$ $\textless$ 3.9) in proton-proton ($pp$) collisions at $\sqrt{s}$ = 7 TeV. The multiplicity distribution is found to be reasonably well explained by a double Negative Binomial Distribution (NBD). The average photon multiplicity increases logarithmically with $\sqrt{s}$. It is found that none of the models we used (PYTHIA6D6T, PHOJET, and HERWIG) could explain the data.
The heavy-flavour nuclear modification factor $R_{\rm pPb}$ has been measured with the ALICE detector in p--Pb collisions at the nucleon--nucleon center of mass energy $\sqrt{s_{\rm NN}}$ = 5.02 TeV at the CERN LHC in a wide rapidity and transverse momentum range, as well as in several decay channels. $R_{\rm pPb}$ is consistent with unity within uncertainties at mid-rapidity and forward rapidity. In the backward region a slight enhancement of the yield of heavy-flavour decay muons is found in the region $2<p_{\rm T}<4$ GeV/$c$. The results are described within uncertainties by theoretical cal…
ALICE measures the J/psi production at mid-rapidity (|y| < 0.9) in the di-electron decay channel as well as at forward rapidity (2.5 < y < 4.0) in the di-muon decay channel. In both channels the acceptance goes down to zero transverse momentum. We present the rapidity dependence of the inclusive J/psi production cross-section and transverse momentum spectra.
By studying the balance functions of several hadronic species, one can gain insight into the chem-ical evolution of the Quark \textendash Gluon Plasma and radial flow. In a picture of early hadronisation,pairs of particles and anti-particles (created at the same space \textendash time point) are separated furtherin rapidity due to the higher initial temperature and diffusive interactions with other particles.Therefore delayed hadronisation will lead to strong correlations in rapidity in the final state. In this work, balance functions for identified charged-pion pairs measured by the ALICE det…
We report on the first measurement of J/Psi production as a function of charged particle pseudo-rapidity density dN_ch/d_eta in pp collisions at sqrt{s} = 7 TeV with the ALICE experiment at the LHC. J/Psi mesons are detected down to p_T = 0 via their decays into e+e- pairs at mid-rapidity (|y| < 0.9) and into mu+mu- pairs at forward rapidity (2.5<y<4). dN_ch/d_eta is measured within |eta| < 1. We compare results in the two different J/Psi rapidity ranges. Preliminary PYTHIA simulations are also presented.
ALICE is the LHC experiment devoted to the study of the Quark-Gluon Plasma (QGP). To probe this high energy density state of strongly interacting matter expected to be produced in heavy-ion collisions at high energies, measurements performed in various systems (pp, p-Pb and Pb-Pb) are compared to each other. Heavy quarks are produced in initial hard partonic scatterings on a short time scale and participate in the subsequent evolution of the medium. This makes them sensitive probes of the QGP. With ALICE, open heavy flavours are studied using D mesons (D$^0$, D$^+$, D$^{*+}$) reconstructed via…
Thanks to its excellent tracking and particle identification performance, the ALICE detector is capable of measuring D mesons at central rapidity via their hadronic decay channels down to very low transverse momentum. We show an extension of the prompt ${\rm D}^0$ $p_{\rm T}$-differential cross section measurement down to zero transverse momentum, which allows us to determine the $p_{\rm T}$-integrated charm production cross section at central rapidity in pp collisions at $\sqrt{s}$ = 7 TeV. We also present measurements of azimuthal correlations of prompt ${\rm D}^0$, ${\rm D}^+$ and ${\rm D}^…
Hadrons containing heavy quarks, i.e. charm or beauty, are unique probes of the properties of the hot and dense QCD medium produced in heavy-ion collisions. Due to their large masses, heavy quarks are produced at the initial stage of the collision, almost exclusively via hard partonic scattering processes. Therefore, they are expected to experience the full collision history propagating through the QCD medium losing energy via elastic and inelastic collisions with the medium constituents. The ALICE collaboration has measured the production of open heavy-flavour hadrons via their hadronic and s…
Quarkonia and open heavy flavour production are crucial to study the properties of the nuclear matter at high energy densities and of the Quark Gluon Plasma (QGP). In proton-proton collisions at LHC, the measurement of their production cross-section will allow to test perturbative QCD calculations in a new energy regime and provide the baseline for measurements in heavy ion collisions. In the latter, as they experience the full evolution of the collision, heavy quarks are ideal probes to study the property of the system. During the 2010 campaign of the LHC, ALICE took proton-proton data at $\s…
We have studied the azimuthal correlations between $\rm D^0$, $\rm D^+$ and $\rm D^{*+}$ mesons and charged particles in pp collisions at $\sqrt{s}=7~\mathrm{TeV}$ and p-Pb collisions at ${\sqrt{s_{\scriptscriptstyle \rm NN}}}=5.02~\mathrm{TeV}$ at the Large Hadron Collider. D mesons were reconstructed from their hadronic decays in the central rapidity region and in the transverse-momentum range 3 $\le p_{T} \le$ 16 $\mathrm{GeV}/c$, and they were correlated to charged particles reconstructed in the pseudo-rapidity range $|η| < 0.8$. A comparative study of the pp results with Monte Carlo Pythi…
Heavy quarks are produced in the early stages of ultra-relativistic hadron collisions via hard scatterings and are an important tool for studying different aspects of Quantum Chromodynamics (QCD) in hadronic collisions. Charged-particle multiplicity gives information on the global characteristics of the event and could be used to characterize particle production mechanisms. In hadronic collisions at Large Hadron Collider (LHC) energies, there is a significant contribution of multi-parton interactions. The measurement of heavy-flavour yields as a function of charged-particle multiplicity gives …
A review is given on photon-hadron and photon-photon collisions in the ALICE experiment. The physics motivation for studying such reactions is outlined, and the results obtained in proton-lead and lead-lead collisions in Run 1 of the LHC are discussed. The improvement in detector rapidity coverage due to a newly added detector system is presented. The ALICE perspectives for data taking in LHC Run II are summarised.
Heavy quarks, i.e. charm and beauty, are sensitive probes of the medium produced in high-energy heavy-ion collisions. They are produced in the early stage of the collisions and are expected to experience the whole collision evolution interacting with the medium constituents via both elastic and inelastic processes. The nuclear modification factor ($R_{\rm AA}$) and the elliptic flow ($v_{2}$) are two of the main experimental observables that allow us to investigate the interaction strength of heavy quarks with the medium. The ALICE collaboration measured the production and elliptic flow of ope…
Heavy-flavour production measurements in pp collisions are important tools to test theoretical models based on perturbative quantum chromodymanics (pQCD) and to investigate the heavy-quark hadronization mechanisms. In ALICE, heavy quarks are measured via the hadronic and electronic decay channels at central rapidity (-0.9 $<$ $\textit{y}$ $<$ 0.9) and via the muon decay channels at forward rapidity (-4 $<$ $\textit{y}$ $<$ -2.5). In this contribution, the production cross-section measurements via the leptonic decay of heavy-flavour hadrons are presented and compared to pQCD theoretical calcula…
Charm and beauty quark production measurement represents a fundamental means to access the initial stage of hadronic collisions. Being produced almost exclusively in initial hard partonic scatterings due to their large masses, $m_{\text{c}}=$ 1.3 $ \text{GeV}/c^2$ and $m_{\text{b}} =$ 4.1 $ \text{GeV}/c^2$, charm and beauty quarks are ideal tools to investigate various QCD aspects. In addition, the corresponding measurements in pp collisions represent a baseline for cold nuclear matter studies in p--A collisions as well as for the characterization of the hot and dense interacting nuclear matte…
ALICE (A Large Ion Collider Experiment) is devoted to the study of heavy-ion collisions at LHC energies. In such collisions a deconfined state of nuclear matter, the Quark-Gluon Plasma (QGP), is formed. Due to their early production, quarkonium states are good probes to study the QGP evolution. Such states are affected by suppression mechanisms which lead to reduced yields with respect to pp and p-Pb collisions, while regeneration phenomena might lead to an enhancement of their production. The latter effects are expected to be negligible at LHC for bottomonium states. The recent ALICE results …
Charge fluctuations provide a possible signature for the existence of the de-confined Quark Gluon Plasma phase (QGP). Being sensitive to the square of the charges, fluctuations in QGP, with fractionally charged partons, are significantly different from those of a hadron gas with unit charged particles. Studies of charge fluctuations have been carried out using the variable, $ν_{(+-,dyn)}$ which, by its construction, is free from collisional bias (impact parameter fluctuations and fluctuations from the finite number of charged particles within the detector acceptance). The dependence of charge …
ALICE is the dedicated heavy-ion experiment at the Large Hadron Collider (LHC). It is designed to provide excellent capabilities to study the quark-gluon plasma (QGP) in the highest energy density regime opened up by the LHC. Quarkonia are crucial probes of the QGP. High-precision data from pp collisions are an essential baseline, and serve as a crucial test for competing models of quarkonium hadroproduction. ALICE measures quarkonia down to pt=0 via their decay channels into e+e- at central (|y|<0.9) and into mu+mu- at forward rapidity (-4.0<y<-2.5). We present first results on the transverse…
In ALICE, open heavy-flavour production is studied through the measurements of the leptons (electrons and muons) from heavy-flavour hadron decays at central and forward rapidity and via the reconstruction of D-meson hadronic decays at mid-rapidity. An overview of the open heavy-flavour production with ALICE in pp ($\sqrt{s}$ = 2.76 TeV and 7 TeV), p--Pb ($\sqrt {s_{\rm NN}}$ = 5.02 TeV) and Pb--Pb ($\sqrt {s_{\rm NN}}$ = 2.76 TeV) collisions will be presented. We will discuss the production cross sections, modifications of the transverse momentum distributions, azimuthal anisotropic emissions …
The measurement of the heavy-flavour production cross sections in pp collisions at the LHC will allow to test perturbative QCD calculations in a new energy domain. Moreover, within the physics program of the ALICE experiment, it will provide the reference for the study of medium effects in Pb-Pb collisions, where heavy quarks are regarded as sensitive probes of parton-medium interaction dynamics. We present the status and first preliminary results of charm and beauty production measurements with the ALICE experiment, using hadronic D meson decays and semi-leptonic D and B meson decays, includi…
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 ALICE Collaboration studies the production of J/psi meson in pp collisions at the center-of-mass energies of 2.76 and 7 TeV at mid- and forward-rapidity. Inclusive production cross-sections are presented as a function of the collision energy, rapidity and transverse-momentum. The J/psi polarization measurements in the helicity and Collins-Soper frames are discussed. A novel result on the correlation between the collision charged particle multiplicity and J/psi yield is also shown.
The production of $ϕ$ mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region $2.5 < y < 4$. Measurements of the differential cross section ${\rm d}^2σ/{\rm d}y {\rm d}p_{\rm T}$ are presented as a function of the transverse momentum ($p_{\rm T}$) at the center-of-mass energies $\sqrt{s}=5.02$, 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at $\sqrt{s}=5.02$ and 13 TeV are also studied in several rapidity intervals as a function of $p_{\rm T}$, and as a function of ra…
The ALICE experiment at the CERN LHC has conducted first systematic studies of heavy-flavour hadron production in pp collisions at sqrt(s) = 7 TeV and in Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV. In pp collisions the differential production cross sections of D mesons at mid-rapidity, as well as the cross sections for electrons and muons from semileptonic heavy-flavour hadron decays at mid- and forward-rapidity, respectively, have been measured. These data provide a crucial testing ground for perturbative QCD calculations in the new LHC energy regime. In Pb-Pb collisions, the nuclear modificat…
The photoproduction of heavy vector mesons in the electromagnetic interactions of ultra-relativistic nuclei is sensitive to the gluon distribution in the nucleus and thus to cold nuclear matter effects like shadowing or parton saturation. Besides the well known observations of vector meson production in ultra-peripheral collisions, first observations of an excess over the expected hadronic J/$ψ$ production at very low transverse momentum ($p_T < $~0.3 GeV/$c$) in peripheral and semi-central nucleus-nucleus collisions both at LHC and RHIC energies were interpreted as the first sign of coherent …
Heavy-flavour (HF) quarks, i.e. charm and beauty, are produced in the early stages of ultra-relativistic collisions via hard scattering processes. The measurement of heavy flavour as a function of charged-particle multiplicity not only provides information on how the production mechanisms are influenced by the event activity, but can also be considered as a tool to test the role of multiple parton interactions. Furthermore, charged-particle multiplicity studies are essential for reference measurements, to tune theoretical models and to provide information on the global characteristics of event…
The production of strange and multi-strange hadrons in proton-proton (pp) and lead-lead (Pb-Pb) collisions is studied with the ALICE experiment at the CERN LHC. These particles are reconstructed via their weak decay topologies, exploiting the tracking and particle identification capabilities of ALICE. Measurements of central rapidity yields of $Λ$, $Ξ^{-}$ and $Ω^{-}$ baryons, their antiparticles and ${\mathrm K}^{0}_{S}$ mesons are presented as a function of transverse momentum for Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. They are compared to those observed in pp collisions as well as to…
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 present the elliptic flow $v_{2}$ of electrons from the semi-leptonic decays of heavy-flavour hadrons at mid-rapidity for semi-central ($20-40%$ centrality) Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 2.76 TeV measured with the ALICE detector. A positive $v_{2}$ is observed at low $p_\mathrm{T}$ in semi-central collisions. Comparisons with previous measurements obtained at lower collision energy at RHIC in Au-Au collisions at $\sqrt{s_\mathrm{NN}}$ = 0.2 TeV and with theoretical models are also presented.
ALICE at the LHC has a unique potential to study proton-proton collisions with the goal to probe Quantum ChromoDynamics (QCD). The apparatus was designed to reconstruct particles over a large range in transverse momentum and rapidity. In particular, quarkonia are very interesting probes of QCD, because their production mechanisms are governed by both perturbative and non-perturbative QCD processes. In ALICE, quarkonia are reconstructed via their dilepton decay channel down to zero transverse momentum. This contribution gives a short overview of quarkonium production results in proton-proton co…
Probes for the small-x parton densities and predicted effects of gluon saturation are discussed. At very low x and intermediate Q, only results on hadronic observables at the LHC are available, which do not provide unambiguous information. It is shown that the measurement of direct photons at forward rapidity at the LHC is particularly promising to provide a unique signal. We further discuss the possibilities to perform such measurements with a detector upgrade in the ALICE experiment and present the R&D activities ongoing.
Quarkonia represent excellent tools for understanding the role of multiparton interactions (MPI) in small systems, i.e., pp and p-A collisions. Probing MPI with quarkonia can be done directly by looking at quarkonium associated production, or indirectly by studying the multiplicity dependence of quarkonium production. In these proceedings, the results from the ALICE experiment on direct and indirect MPI probes are discussed. The self-normalized yields of charmonium production as a function of the charged-particle multiplicity in pp and p--Pb collisions at \sqrt{s} = 13 TeV and \sqrt{s_{NN} = 8…
The ratio of the yields of antiprotons to protons in pp collisions has been measured by the ALICE experiment at $\sqrt{s} = 0.9$ and $7$ TeV during the initial running periods of the Large Hadron Collider(LHC). The measurement covers the transverse momentum interval $0.45 < p_{\rm{t}} < 1.05$ GeV/$c$ and rapidity $|y| < 0.5$. The ratio is measured to be $R_{|y| < 0.5} = 0.957 \pm 0.006 (stat.) \pm 0.014 (syst.)$ at $0.9$ TeV and $R_{|y| < 0.5} = 0.991 \pm 0.005 (stat.) \pm 0.014 (syst.)$ at $7$ TeV and it is independent of both rapidity and transverse momentum. The results are consistent with …
ALICE is the dedicated heavy-ion experiment at the LHC. Due to the unique particle identification capabilities of the central barrel detectors (|eta|<0.9), J/psi can be measured in the di-electron channel in the very demanding environment of central Pb-Pb collisions at the LHC. In addition J/psi are measured at forward rapidity (2.5<y<4) with a dedicated muon spectrometer. ALICE is the only LHC experiment with an acceptance for J/psi that reaches down to p_T=0 at both, mid- and forward rapidity. Preliminary results on the nuclear modification factor of the inclusive J/psi production at mid- an…
