Comparing the measurements of the hadronic final state from partonic showers in proton-proton and heavy-ion collisions will reveal the modifications generated by the medium on partons produced in hard scatterings. This can be achieved by selecting the hard processes in which there is a direct photon in the final state. The experimental technique consists in tagging events with a well identified high energy direct photon and in measuring the azimuthal angle correlation with charged hadrons. To establish a reference measurement for heavy-ion collisions, proton-proton collision data collected with ALICE have been analyzed. Preliminary results are presented together with photon and $π^{0}$-charged hadrons correlations showing the characteristic di-jet pattern from where the partonic momentum $k_{T}$ is extracted.
The ALICE experiment at the Large Hadron Collider (LHC) at CERN consists of a central barrel, a muon spectrometer and additional detectors for trigger and event classification purposes. The low transverse momentum threshold of the central barrel gives ALICE a unique opportunity to study the low mass sector of central exclusive production at the LHC.
The measurement of D-meson production in heavy-ion collisions at LHC energy provides insights into the mechanisms of interaction of charm quarks in the hot and dense medium formed in these collisions. ALICE results on the D-meson nuclear modification factor and azimuthal anisotropy in Pb-Pb collisions at $\sqrt{s_{\rm NN}}=2.76$ TeV are presented.
The ALICE detector is well suited to measure heavy-flavour (charm and beauty) production via hadronic and semi-leptonic decay channels of heavy-flavour particles. Here an overview of heavy-flavour measurements made with the ALICE detector during Run 1 in pp and p--Pb collisions is presented and discussed.
We present here recent open heavy-flavour results from the ALICE experiment, including measurements of D-meson, $\mathrm{Λ_{c}^{+}}$ baryon and $\mathrm{Ξ_c^0}$ baryon production in pp collisions at $\sqrt{s} = 7~\mathrm{TeV}$ and p-Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02~\mathrm{TeV}$.
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.
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…
Hadronic resonance production with the ALICE experiment in pp and Pb-Pb collisions at LHC energies
用ALICE实验测量了$\sqrt{s}=7$ TeV pp碰撞和$\sqrt{s_{_\mathrm{NN}}}=2.76$ TeV Pb-Pb碰撞中的强子共振$\mathrm{K}^{*}(892)^{0}$、$ϕ$（1020）和$Σ(1385)^{\pm}$。讨论了横动量谱、粒子比、核修正因子以及与模型预测的比较。此外，ALICE的结果进行了比较，在RHIC能源获得的数据。
ALICE is the heavy-ion experiment at the CERN Large Hadron Collider. The experiment continuously took data during the first physics campaign of the machine from fall 2009 until early 2013, using proton and lead-ion beams. In this paper we describe the running environment and the data handling procedures, and discuss the performance of the ALICE detectors and analysis methods for various physics observables.
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.
We present measurements of charged jet cross sections and jet shape observables in leading jet in proton-proton (pp) collisions at sqrt(s) = 2.76 TeV with the ALICE detector at LHC. Jets are reconstructed at the midrapidity from charged particle using sequential recombination anti-kT jet finding algorithm for various R values. The results are compared to measurements from HERWIG, PHOJET and different tunes of PYTHIA6 and earlier measurements at 7 TeV.
The ALICE experiment is equipped with a wide range of detectors providing excellent tracking and particle identification in the central region, as well as forward detectors with extended pseudorapidity coverage, which are well suited for studying diffractive processes. Cross section measurements of single and double diffractive processes performed by ALICE in pp collisions at $\sqrt{s}=0.9,~2.76,~7$~TeV will be reported. Currently, ALICE is studying double-gap events in pp collisions at $\sqrt{s}=7$~TeV, which give an insight into the central diffraction processes: current status and future pe…
Long-range correlations between particles separated by a pseudorapidity gap are a powerful tool to explore the initial stages and evolution of the medium created in hadron-hadron collisions. An overview of the long-range correlations measured by the ALICE detector in pp, p-Pb and Pb-Pb will be presented. This includes analyses of forward-backward, two- and multi-particle correlations with the use of the central barrel and forward detectors.
Two-particle azimuthal correlations of electrons from heavy-flavour hadron decays with charged particles can give insight into the properties of heavy-quark production and hadronization into heavy-flavour jets.\\ In this contribution, the ALICE results measured in pp collisions at 5.02 TeV, collected in the LHC Run 2, are presented. The yields of charged particles in the near and away-side correlation peaks and the peak width are compared with PYTHIA calculations.
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.
In this paper, an overview of recent $\mathrm D^{0}$, $\mathrm D^{+}$ and $\mathrm D^{*+}$ measurements, performed by ALICE in proton--proton collisions at $\sqrt{s}~=~2.76$, 5, 7, 8 and 13 TeV, is reported. The minimum-bias production cross sections, as well as their energy and species dependences, are compared to perturbative QCD calculations. The evolution of the D-meson yields with the event multiplicity is compared to phenomenological models.
In this manuscript, various beauty production measurements using the ALICE detector will be presented. We will show new measurements of non-prompt D$^0$ mesons in pp collisions at $\sqrt{s} = 5.02$ TeV and beauty-tagged jet production in p--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV. The $R_{\mathrm{AA}}$ of beauty-hadron decay electrons in central Pb--Pb collisions and the $v_{2}$ of beauty-hadron decay electrons in semi-central Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}} = 5.02$ TeV will also be discussed.
The ALICE Collaboration has studied the inclusive J/$ψ$ and $ψ(\mathrm{2S})$ production in p-Pb collisions at $\sqrt{s_{NN}}$ = 5.02 TeV, at the CERN LHC. The J/$ψ$ measurement is performed in the $μ^{+}μ^{-}$ and in the $e^{+}e^{-}$ decay channels, down to zero $p_{\mathrm{T}}$. The results are in fair agreement with theoretical predictions. The $ψ(\mathrm{2S})$ measurement has also been performed. In particular, a smaller $ψ(\mathrm{2S})$ nuclear modification factor, with respect to the J$/ψ$ one, has been observed.
In this work we present a summary of the most relevant results on heavy-ion and astroparticle physics in ALICE. The summary includes a brief overview of the current status on the characterization of the hot and dense QCD medium created in the heavy-ion collisions produced at the LHC, as well as the intriguing finding of collective-like phenomena in small collision systems.
Ultra-peripheral collisions (UPCs), studied using the ALICE detector, allow us to investigate the low-$x$ behavior of the gluon distribution of the colliding particles. Two new measurements of coherent J/$ψ$ photoproduction cross section from Pb-Pb UPCs at $\sqrt{s_{\rm NN}}=5.02$ TeV are presented: the first measurement of the $|t|$-dependence of the cross section providing a new tool to investigate the transverse gluonic structure at low Bjorken-$x$ and a rapidity-differential measurement at midrapidity allowing us to provide stringent constraints on nuclear gluon shadowing and saturation mo…
We present measurements of hadronic resonance, strange and multi-strange particle production in collisions of Xe-Xe and Pb-Pb at the center-of-mass energies of $\sqrt{s_{NN}}=5.44$ and $5.02$ TeV, respectively, by the ALICE collaboration at the LHC. Particle ratios are presented as a function of multiplicity for $K^{0}_{s}$, $Λ$, $Ξ^{-}$, $\barΞ^{+}$, $Ω^{-}$, $\barΩ^{+}$, $ρ(770)^{0}$, $K^{\ast}(892)^{0}$, $ϕ(1020)$ and $Λ(1520)$. Our results are discussed and compared with predictions of QCD-inspired event generators. Additionally, comparisons with lower energy measurements and smaller syste…
Relativistic heavy-ion collisions provide a unique opportunity to search for parity violation in non-central collisions. This could lead to charge separation perpendicular to the reaction plane. An event-by-event measurement of charge separation effect in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV using Sliding Dumbbell Method (SDM) is discussed in this article.
The production mechanism of (anti)nuclei in ultrarelativistic hadronic collisions is under intense debate in the scientific community. The description of the experimental measurements is currently based on two competing phenomenological models: the statistical hadronization model and the coalescence approach. Light (anti)nuclei have been extensively measured in small collision systems, namely pp and p--Pb collisions, with ALICE at the LHC. Recent results on the (anti)deuteron production measured in jets and in the underlying event, and in high-multiplicity pp collisions at a center-of-mass ene…
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 …
We present the results for direct photon and neutral pion production obtained from proton-proton and lead-lead collisions in the ALICE experiment. Measurement of neutral pions in pp collisions allows to test the validity of QCD-inspired models. The study of neutral pion yields in Pb-Pb collisions permits to study the medium-induced suppression relative to the pp case. The yield of direct photons is compared to perturbative QCD calculations. In the case of central Pb-Pb collisions the observed excess of photons below 4 GeV/c is used to find the effective temperature of the matter.
The self-normalised $ψ(2S)$ yields as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV and p--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$= 8.16 TeV, using the ALICE detector at the CERN LHC, are reported in these proceedings. This measurement represents one of the main tools to understand the role of multiparton interactions and their influence on charmonium production in small systems, i.e pp and pA collisions. The ratio of $ψ(2S)$-over-J/$ψ$ as a function of charged-particle multiplicity is also presented for both pp and p--Pb collisions. The comparison to th…
In this contribution, the latest ALICE results on charmed baryon production are presented. In particular the measurements of $Λ_{\rm c}^{+}$-baryon production in pp collisions at ${\sqrt{\rm s}}$ = 5.02 TeV and in p-Pb collisions at $\sqrt{\rm s_{NN}}$ = 5.02 TeV are shown and compared with previous measurements performed using pp and p-Pb data samples collected during LHC Run 1. At mid-rapidity charmed baryons are reconstructed via their hadronic decay and semileptonic decay channels, exploiting the high precision tracking, excellent vertexing and particle identification capabilities offered …
This document describes the plans of the ALICE Collaboration for a major upgrade of its detector, referred to as ALICE 3, which is proposed for physics data-taking in the LHC Run 5 and beyond. ALICE 3 will enable an extensive programme to fully exploit the LHC for the study of the properties of strongly interacting matter with high-energy nuclear collisions. The proposed detector layout, based on advanced silicon sensors, features superb pointing resolution, excellent tracking and particle identification over a large acceptance and high readout-rate capabilities. This document discusses the pr…
The measurement of (anti)nuclei production in pp, p-A and A-A collisions at ultrarelativistic energies is important to understand hadronization. The excellent tracking and particle identification capabilities of ALICE make it the most suited detector at the LHC to study light (anti)nuclei produced in high-energy hadronic collisions. (Anti)nuclei with mass numbers up to 4, such as (anti)deuterons, (anti)tritons, (anti)$^3$He and (anti)$^4$He have been successfully identified in ALICE at midrapidity ($|η|<$0.9). In this contribution, multiplicity dependent results on the yields, nuclei-to-proton…
The main goal of the ALICE experiment is to study the properties of the hot and dense medium created in ultra-relativistic heavy-ion collisions. The measurement of the (multi-)strange particles is an important tool to understand particle production mechanisms and the dynamics of the quark-gluon plasma (QGP). We report on the production of K$^{0}_{S}$, $Λ$($\overlineΛ$), $Ξ^{-}$($\overlineΞ^{+}$) and $Ω^{-}$($\overlineΩ^{+}$) in proton-lead (p-Pb) collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV and lead-lead (Pb-Pb) collisions at $\sqrt{s_{\rm NN}}$ = 2.76 TeV measured by ALICE at the LHC. The com…
Measurements of electroweak-bosons in heavy-ion collisions with ALICE are reported. They are measured at large rapidities, via their (di)muonic decay: Z $\rightarrow μ^+ μ^-$ and W$^\pm \rightarrow μ^\pm ν$. The Z production and nuclear modification factor in Pb--Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 5.02 TeV are presented and compared to theoretical predictions with or without nuclear modifications of the Parton Distribution Functions. Measurements of electroweak-boson production in p--Pb collisions at $\sqrt{s_{_{\rm NN}}}$ = 5.02 and 8.16 TeV are also presented and discussed.
Vector mesons are copiously produced in ultra-peripheral collisions. In these collisions, the impact parameter is larger than the sum of the radii of two projectiles, implying that electromagnetic processes become dominant. The cross section for this process is sensitive to the gluon distribution and can therefore probe nuclear gluon shadowing (Pb-Pb) and the gluon structure function in the nucleon (p-Pb). The ALICE Collaboration has performed the first measurement of the coherent J/$ψ$ and $ψ$(2S) photoproduction cross section in Pb-Pb collisions and that for exclusive J/$ψ$ photoproduction o…
Charmonia, bound states of charm and anti-charm quarks, represent an interesting probe for the study of Quantum Chromodynamics (QCD) since their production involves both hard and soft energy scales. Several effective models are available to describe the production of charmonia, but so far none have been able to describe all experimental observables simultaneously. ALICE has studied the production of charmonia in different collision systems at all available LHC energies at both mid- and forward-rapidity down to zero transverse momentum. In this contribution, different measurements performed in …
