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/$ψ$]$_{\mathrm {pPb}}$/[$ψ$(2S)/J/$ψ$]$_{\mathrm {pp}}$ studied as a function of the resonance transverse momentum and event activity of the collision. The $ψ$(2S) nuclear modification factor, $R_{\mathrm {pPb}}$, will also be presented. Theoretical models based on nuclear shadowing, coherent energy loss or both cannot describe our results. Therefore other mechanisms must be invoked in order to describe the $ψ$(2S) production. Finally, results on $ψ$(2S) production in Pb-Pb collisions will be shown in two transverse momentum ranges as a function of centrality.
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.
This contribution focuses on latest ALICE results on charmonium forward production in proton-proton (pp), proton-lead (p-Pb) and lead-lead (Pb-Pb) collisions at the TeV scale. In p-Pb and Pb-Pb collisions, measurements are presented in the form of the charmonium nuclear modification factor (the properly normalized ratio of its production cross section in heavy ion collisions to its pp counterpart) as a function of the charmonium rapidity and transverse momentum. These measurements are compared to available theoretical calculations. Possible interpretations of these results in terms of gluon sa…
Measurement of the nuclear modification factor of electrons from heavy-flavour decays at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV with ALICE
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…
The ALICE Collaboration has measured heavy-flavour production through the reconstruction of hadronic decays of D mesons at mid-rapidity and via semi-electronic (at mid-rapidity) and semi-muonic (at forward rapidity) decays of charm and beauty hadrons in pp, p-Pb and Pb-Pb collisions. A summary of the most recent results from p-Pb collisions at $\sqrt{s_{NN}}=5.02$ TeV and Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV is presented in this paper.
The ALICE Collaboration has studied the inclusive $ψ(\mathrm{2S})$ meson production in pp, p-Pb and Pb-Pb collisions at the CERN LHC. The $ψ(\mathrm{2S})$ is detected through its decay to a muon pair, using the forward Muon Spectrometer, which covers the pseudo-rapidity range $-4<η<-2.5$. The $ψ(\mathrm{2S})$ production cross sections in pp collisions are presented as a function of rapidity (y) and transverse momentum ($p_{\mathrm{T}}$). In p-Pb collisions, $ψ(\mathrm{2S})$ results are compared to the J/$ψ$ ones by the ratio of their production cross sections as a function of rapidity, transve…
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…
One of the key signatures of the Quark-Gluon Plasma (QGP), is the modification of hadron transverse momentum differential cross-sections in heavy-ion collisions (HIC) as compared to proton-proton (pp) collisions. Suppression of hadron production at high transverse momenta (\pt)~in HIC has been explained by the energy loss of the partons produced in the hard scattering processes which traverse the deconfined quantum chromodynamic (QCD) matter. The dependence of the observed suppression on the \pt~ of the measured hadron towards higher \pt~ is an important input for the theoretical understanding…
ALICE is a general purpose experiment designed to investigate nucleus-nucleus collisions at the Large Hadron Collider (LHC), located at CERN. The ALICE detector is optimized for the reconstruction of quarkonia through the dimuon decay channel at foward rapidity as well as the dielectron decay channel at midrapidity. In this contribution, quarkonium measurements performed by the ALICE collaboration at both midrapidity and forward rapidity for various energies and colliding systems (pp, p-Pb and Pb-Pb), will be discussed and compared to theory.
We report on forward-rapidity charmonium production in pp collisions at a center of mass energy $\sqrt{s} = 13$ TeV, as measured by ALICE at the LHC. Differential cross sections for both J/ψ and ψ(2S) are presented as a function of the charmonium transverse momentum and rapidity. Results are compared to similar measurements performed by LHCb, to lower energy measurements and to state of the art model calculations.
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 the ALICE results on the nuclear modification factor and elliptic flow of electrons and muons from open heavy-flavour hadron decays at mid-rapidity and forward rapidity in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV for different centrality intervals. The results are compared to model calculations that include interactions of heavy quarks with the medium.
Muons from the decay of charmonium resonances are detected in the ALICE Experiment at the Large Hadron Collider(LHC) for pp and Pb-Pb collisions with a muon spectrometer, covering the forward rapidity region 2.5$<$ $y$ $<$4.0. Analysis of the nuclear modification factor ($R_{\rm AA}$) at forward rapidity are presented and compared with mid-rapidity results from electrons in the central barrel covering $|y|<$0.9. The roles of suppression and regeneration mechanisms are discussed, as well as the importance of the results of the forthcoming p-Pb data taking for the estimate of cold nuclear matter…
These proceedings report on measurements of the jet spectrum and nuclear modification factor for inclusive full jets (containing both charged and neutral constituents) in Pb-Pb and pp collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV recorded with the ALICE detector. These measurements use a machine learning based background correction, which reduces residual fluctuations. This method allows for measurements to lower transverse momenta and larger jet resolution parameter (R) than previously possible in ALICE. In this method, machine learning techniques are used to correct the jet transverse momentu…
Inclusive jet spectra in 2.76 TeV collisions from ALICE
在RHIC上对重离子碰撞中高pT粒子产生的测量表明，介质引起的能量损失影响重离子碰撞早期产生的部分子。在LHC能量下，部分子初始产生截面的增加使得完全重构的喷流在很宽的运动学范围内可用，这允许对部分子能量损失进行更多的差分研究。部分子能量损失使我们能够获得在重离子碰撞中产生的热的非限定核物质的关键观测值。利用ALICE跟踪探测器和电磁量能器重建的喷流的包含截面是从2.76 TeV pp运行期间收集的数据中给出的。用于重建喷流和提取它们从铅铅碰撞的波动背景的程序进行了讨论。
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.
Measurements of jet yields in heavy-ion collisions can be used to constrain jet energy loss models, and in turn provide information about the physical properties of deconfined QCD matter. ALICE reconstructs charged particle jets ($\textit{charged jets}$) with high-precision tracking of charged particles down to $p_{\mathrm{T}}^{\mathrm{track}} = 150$ MeV/$c$, and jets ($\textit{full jets}$) with the addition of particle information from the electromagnetic calorimeter down to $E_{\mathrm{cluster}} = 300$ MeV. By including low momentum jet constituents, ALICE is uniquely positioned at the LHC t…
Jet suppression has been observed in central heavy ion collisions. This suppression is attributed to partonic energy loss in the Quark Gluon Plasma (QGP) formed in such collisions. However, this measurement is influenced by all stages of the collision. It is expected that in p-Pb collisions similar initial conditions occur as in Pb-Pb collisions without creating a QGP, allowing modification to the jet spectra due to cold nuclear matter effects to be quantified. Inclusive jet spectra in p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV measured by ALICE are presented. Jets are reconstructed via…
Heavy Flavour decay muon production at forward rapidity in pp collisions at \sqrt{s}= 7 TeV and in Pb-Pb collisions at \sqrt{s_{NN}}=2.76 TeV with the ALICE experiment
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 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.
Jets in relativistic heavy-ion collisions (HICs) interact with the quark-gluon plasma (QGP), leading to effects such as a suppression of jet yields and a modification of internal jet structure that are used to measure the properties of the QGP. These proceedings show the inclusive jet nuclear modification factors in Pb--Pb collisions in various centrality classes at $\sqrt{s_{\rm NN}}$ = 5.02 TeV recorded with the ALICE detector for resolution parameters up to $R$ = 0.6 for momenta down to 40 GeV/$c$. The analysis utilizes machine learning techniques to correct the large background in HICs, ex…
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…
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 collision…
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…
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.
We present the centrality dependence of particle production in p-A collisions at sqrt(s_NN) = 5.02 TeV measured by the ALICE experiment, including the pseudo-rapidity and transverse momentum spectra, with a special emphasis on the event classification in centrality classes and its implications for the interpretation of the nuclear effects.
We present the centrality dependence of particle production in p-Pb collisions at sqrt(s_NN)= 5.02 TeV measured by the ALICE experiment, including the pseudo-rapidity and transverse momentum spectra, with a special emphasis on the event classification in centrality classes and its implications for the interpretation of the nuclear effects.
The production of charmonium states, J/$ψ$ and $ψ$(2S), in heavy-ion collisions, is an important probe to investigate the formation of a plasma of quarks and gluons (QGP). In a hot and deconfined medium, quarkonium production is, indeed, expected to be significantly modified, with respect to the pp yields, due to a balance of color screening and charm-quark recombination mechanisms. The ALICE Collaboration at the LHC has measured charmonium production in Pb-Pb collisions at $\sqrt{s}_{\rm NN} =$ 2.76 and 5.02 TeV. The nuclear modification factor of inclusive J/$ψ$, evaluated at forward ($-4<η<…
We report on the performance studies of two correction methods, namely the efficiency-purity method and the Bayesian unfolding method applied to the pseudorapidity distribution of photons. The pseudorapidity distribution of inclusive photons at forward rapidities in the range \mbox{\small $(2.3<η<3.9)$} in p\textendash Pb collisions at $\sqrt{\it{s}_{\rm{NN}}} = 8.16$ TeV is obtained with the HIJING Monte Carlo event generator. The simulated data samples were obtained from the Photon Multiplicity Detector (PMD) in ALICE.
Studying p-Pb collisions at LHC energies allows a quantitative evaluation of the cold nuclear matter (CNM) effects. Event activity dependence of the J/ψ production is under intense studies both theoretically and experimentally and is expected to provide important insights on the influence of CNM. This paper presents the first results on event activity dependence of the inclusive J/ψ production at backward (-4.46 < $y_{cms}$ < -2.96) and forward (2.03 < $y_{cms}$ < 3.53) rapidity in ALICE for p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV.
Studies of longitudinal correlations of the charged-particle multiplicity in heavy-ion collisions have provided insights into the asymmetry and fluctuations of the initial-state collision geometry. In addition to the expansion of the medium in the transverse direction, commonly quantified using Fourier coefficients ($v_{n}$), the initial geometry and resulting longitudinal expansion as a function of azimuthal angle enable us to better understand the full 3-dimensional picture of heavy-ion collisions. In these proceedings, azimuthal correlations of the longitudinal structure of charged-particle…
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…
Highly energetic jets are sensitive probes for the kinematic properties and the topology of high energy hadron collisions. Jets are collimated sprays of charged and neutral particles, which are produced in fragmentation of hard scattered partons from an early stage of the collision. In ALICE, jets have been measured in pp, p-Pb, and Pb-Pb collisions at several collision energies. While analyses of Pb-Pb events unveil properties of the hot and dense medium formed in heavy-ion collisions, pp and p-Pb collisions can shed light on hadronization and cold nuclear matter effects in jet production. Ad…
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…
Measurements of open heavy flavour production in p--A collisions allow the investigation of Cold Nuclear Matter effects. In addition, they are an important tool for a complementary investigation of the long-range correlations found in small systems in the light flavour sector. In this work, production measurements of D mesons at mid-rapidity in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are reported. Production yields are also reported for the heavy-flavour hadron decay electrons at central rapidity at $\sqrt{s_{\rm NN}}$ = 5.02 and 8.16 TeV. The elliptic flow ($v_{\rm 2}$) of heavy-fl…
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…
The measurement of jets recoiling from a trigger hadron in heavy-ion collisions can be used to understand the properties of the Quark Gluon Plasma. Jet-medium interactions cause jets to lose energy in the medium and may modify the jet structure. Jet deflection towards large angles due to scattering off of quasi-particles in the Quark-Gluon Plasma may also occur, which can be studied through a measurement of the hadron-jet acoplanarity. These phenomena can be studied through the semi-inclusive distribution of track-based jets recoiling from a trigger hadron. This contribution presents the lates…
Quarkonium production is an excellent probe to investigate the properties of the hot and dense medium, which can be created in heavy-ion collisions. The production and hadronisation of heavy quarks are well separated in the space-time evolution of a collision and provide a wealth of information of the underlying QCD dynamics from the dense to the eventually dilute system. We report on the latest results from ALICE at the LHC on quarkonium production in heavy-ion collisions at mid- and forward rapidity. The nuclear modification factor as a function of centrality, transverse momentum, and rapidi…
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…
