In this paper selected results obtained by the ALICE experiment at the LHC will be presented. Data collected during the pp runs taken at sqrt(s)=0.9, 2.76 and 7 TeV and Pb-Pb runs at sqrt(s_NN)=2.76 TeV allowed interesting studies on the properties of the hadronic and nuclear matter: proton runs gave us the possibility to explore the ordinary matter at very high energy and up to very low pt, while Pb-Pb runs provided spectacular events where several thousands of particles produced in the interaction revealed how a very dense medium behaves, providing a deeper picture on the quark gluon plasma(QGP) chemical composition and dynamics.
Highly energetic jets and photons are complementary probes for the kinematics and the topology of nuclear collisions. Jets are collimated sprays of charged and neutral particles, which are produced in the fragmentation of hard scattered partons in an early stage of the collision. While traversing the medium formed in nuclear collisions, they lose energy and therefore carry information about the interaction of partons with the medium. The jet substructure is particularly interesting to learn about in-medium modification of the jets and several observables exists to probe it. In contrast to jets…
We overview recent jet measurements in pp and Pb-Pb collisions with the ALICE detector. ALICE reconstructs jets at midrapidity using the anti-$k_{\mathrm{T}}$ algorithm, including both charged particle jets from the ALICE tracking detectors, and full jets from the combination of the ALICE electromagnetic calorimeter with the tracking system. We focus on inclusive and semi-inclusive jet measurements as well as jet substructure measurements, including a variety of groomed and ungroomed observables. In pp collisions, these results test pQCD techniques at $p_{\mathrm{T,\;jet}}<140$ GeV$/c$ in a lo…
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…
Measurement of short-lived hadronic resonances are used to study different aspects of particle production and collision dynamics in pp, p-A and relativistic heavy-ion collisions. The yields of resonances are sensitive to the competing processes of hadron rescattering and regeneration, thus making these particles unique probes of the properties of the late hadronic phase. Measurements of resonances with different masses and quantum numbers also provide insight into strangeness production and processes that determine the shapes of particle momentum spectra at intermediate transverse momenta, as …
Recent results on the production of light nuclei, including deuterons, tritons, $^3$He, $^4$He and the corresponding antinuclei in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are presented and compared with theoretical predictions to provide insight into their production mechanisms in heavy-ion collisions. The large variety of measurements performed with the ALICE apparatus at different energies and collision systems allows us to constrain the models of the production mechanisms of light flavour baryon clusters, in particular those based on the coalescence and statistical hadronisa…
In this contribution the latest measurements of real and virtual photons in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV from the ALICE Collaboration are presented. The extracted photon spectra are compared to predictions from state-of-the-art models that explicitly include the whole evolution of the heavy-ion collision as well as measurements at lower energies. Experimental developments that in the future will help to extend the range and procession of the measurements are introduced before concluding with an outlook to possible future measurements at the LHC.
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。
Full Jet Reconstruction in 2.76 TeV pp and Pb-Pb collisions in the ALICE experiment
在RHIC上对重离子碰撞产生的高pT粒子和远离侧喷流的测量表明，介质引起的能量损失影响了重离子碰撞早期产生的部分子。在大型强子对撞机的能量下，初始产生的截面要高得多，这使得喷流可以在很宽的运动学范围内重建。利用ALICE电磁量热计测量完全重构的喷流，可以对部分子能量损失进行更多的微分研究。部分子能量损失将使我们能够获得在重离子碰撞中产生的热的、致密的物质的关键观测值。所呈现的数据是在2.76 TeV Pb-Pb运行期间收集的，以及来自2.76 TeV pp运行的基线测量。将讨论用于重建射流并从波动背景中提取它们的程序。还将讨论在有限接受度下对背景进行定量的程序。这些结果进行了比较，PP的测量和模拟。
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 …
The event-by-event fluctuations of identified particles in ultrarelativistic nucleus-nucleus collisions give information about the state of matter created in these collisions as well as the phase diagram of nuclear matter. In this proceedings, we present the latest results from ALICE on the centrality and pseudorapidity dependence of net-proton fluctuations, which are closely related to net-baryon fluctuations, as well as net-kaon and net-pion fluctuations. The effects of volume fluctuations and global baryon conservation on these observables are discussed. Furthermore, the correlated fluctuat…
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…
The open heavy-flavour hadron measurements in proton--proton and proton--lead collisions give insight into the charm production and hadronization mechanisms. In this contribution, the latest measurements of the production cross section of prompt $Λ^+_{\rm c}$ and its charge conjugate performed with the ALICE detector at midrapidity in pp, and the new measurement of $Λ_\mathrm{c}^+ \to \mathrm{p} \mathrm{K}_\mathrm{S}^0$ performed down to $p_{\rm T}=0$ in p--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV are presented. We also present the first ALICE measurement of the baryon-to-meson ratio $Λ…
In pp collisions at LHC energies, heavy quarks are produced in initial hard scatterings and then these quarks hadronize in either open heavy-flavor hadrons or quarkonia (e.g. J/$ψ$, $ψ(2S)$, $Υ$). The study of quarkonium production as a function of charged-particle multiplicity links soft and hard processes and allows one to study their interplay. While a linear increase of quarkonium production as a function of charged-particle multiplicity can be reasonably well understood in the context of multi-parton interactions, the observation of deviations with respect to a linear increase requires a …
ALICE is designated to study the quark-gluon plasma (QGP), a state of matter where, due to high temperature and density, quarks and gluons are deconfined. One of the probes used to investigate this state of matter is quarkonium states, bound states of either a charm and anti-charm quark pair (charmonia) or a bottom and anti-bottom quark pair (bottomonia). The presence of the QGP is expected to modify the quarkonium production yields in a very specific way due to a balance between medium-induced suppression, and a recombination mechanism or a hadronization mechanism. To understand the the prope…
One of the key results of the LHC Run 1 was the observation of an enhanced production of strange particles in high multiplicity pp and p--Pb collisions at $\sqrt{s_\mathrm{NN}}$ = 7 and 5.02 TeV, respectively. The strangeness enhancement is investigated by measuring the evolution with multiplicity of single-strange and multi-strange baryon production relative to non-strange particles. A smooth increase of strange particle yields relative to the non-strange ones with event multiplicity has been observed in such systems. We report the latest results on multiplicity dependence of strange and mult…
The PHENIX and STAR Collaborations at the Relativistic Heavy-Ion Collider and ALICE, CMS, ATLAS and LHCb Collaborations at the Large Hadron Collider have measured the production of charmonium and bottonium states as well as open heavy flavor hadrons via their hadronic and semi-leptonic decays at mid-rapidity and in the semi-muonic decay channel at forward rapidity in pp, p--A and A--A collisions in an energy domain that ranges from $\sqrt{s}$ = 0.2 TeV to $\sqrt{s}$ = 13 TeV in pp collisions and from $\sqrt{s_{\rm NN}}$ = 0.2 TeV to $\sqrt{s_{\rm NN}}$ = 5.02 TeV in A--A collisions. In this co…
In these proceedings we present the latest results from ALICE on direct photon and light neutral meson production in p$-$Pb and Pb$-$Pb collisions. The direct photon excess ratio $R_γ$ in different charged particle multiplicity classes of p$-$Pb collisions at $\sqrt{s_{\tiny{NN}}}=5.02\,\mathrm{TeV}$ is shown. In addition, we present the direct photon elliptic flow coefficient $v_2$ in central and semicentral events of Pb$-$Pb collisions at $\sqrt{s_{\tiny{NN}}}=2.76\,\mathrm{TeV}$. An outlook on ongoing and future measurements is given.
The study of identified particle production in proton-proton (pp) collisions as a function of center-of-mass energy ($\sqrt{s}$) and event charged-particle multiplicity is a key tool for understanding similarities and differences between small and large collision systems. We report on new measurements of the production of identified particles and their dependence on multiplicity and $\sqrt{s}$. Latest results for light flavor hadrons, comprising $π^{\pm}$, $\mathrm{K}^{\pm}$, ${\rm p}(\rm \bar{p})$, single-strange ($\mathrm{K_{S}^{0}}$, $\barΛ$, and $Λ$), multi-strange ($Ξ^{-}$, $\overlineΞ^{+…
