Angular correlations between unidentified hadron trigger and associated particles are measured by the ALICE experiment for $0.5 < p_T^{t,a} < 15$ GeV, where $\ptt \geq \pta$. The pair correlation shapes are examined in a variety of centrality categories for pairs in $|η| < 1.0$ where $|η^t - η^a| > 0.8$. A series of two-particle Fourier components $V_{nΔ} \equiv <\cos(nΔϕ)>$ are extracted from the long-range azimuthal correlation functions. The sum of $n<6$ terms match the data. For each $n$, a fit is applied over all $p_{T}$ bins simultaneously to test the collectivity hypothesis $V_{nΔ} \simeq v_n^t \, v_n^a$. The factorization holds at $p_{T}^{t,a}$ below approximately 4 GeV but breaks progressively at higher momenta. The divergence between the data and the global fit quantifies the onset of nonflow dominance in long-range correlations due to the away side jet. The $v_n$ values from the global fit are in close agreement with results from more established methods. At higher \pt where jet correlations dominate, the modification of conditional yields in central Pb--Pb collisions is measured with respect to $pp$ ($I_{AA}$) and with respect to peripheral events ($I_{CP}$). Significant suppression is observed on the side opposing the trigger, while a moderate enhancement is measured on the near side.
Measurements of the nuclear modification factor and elliptic flow of leptons from heavy-flavour hadron decays in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 2.76 and 5.02 TeV with ALICE
Measurements of the production of muons from heavy-flavour hadron decays at forward rapidity ($2.5 < y < 4.0$) in Pb--Pb collisions at $\sqrt{s_{\rm NN}} = 2.76$ and 5.02 TeV with the ALICE detector are presented along with the $R_{\rm AA}$ measurements in different centrality intervals as a function of transverse momentum, $p_{\rm T}$. Results of the measured $R_{\rm AA}$ at both energies are shown and are compared to the different model predictions.
The study of the J/$ψ$ production in pp collisions provides important information on perturbative and non-perturbative quantum chromodynamics. Using high multiplicity pp events, we can study how charmonium production depends on the event activity. These measurements are used to investigate the possible influence of multiple partonic interactions to the J/$ψ$ production and the interplay between soft and hard processes.In this work we report on studies of J/$ψ$ production as a function of event multiplicity in pp collisions at $\sqrt{s}$ = 13 TeV at mid-rapidity with ALICE. The J/$ψ$ are recons…
Measurement of the nuclear modification factor of electrons from heavy-flavour hadron decays in Pb-Pb collisions at {\surd}sNN = 2.76 TeV with ALICE at the LHC
In order to understand strangeness production mechanisms, one can study the correlations of hadrons with hidden strangeness (e.g. the $ϕ$ meson) and open strangeness ($\mathrm{K}^{0}_{\mathrm{S}}$, $Λ$ and $\barΛ$) in hard (jet) processes and in soft (bulk) processes. Two-particle angular correlations with $\mathrm{K}^{0}_{\mathrm{S}}$ triggers allow for the study of fragmentation in pp collisions as a function of multiplicity. Similarly, correlations with associated $ϕ$ mesons in p-Pb collisions allow both the jet and the underlying event components of strange particle production to be probed…
Studies on the production of open charm hadrons are of paramount importance to investigate the charm-quark hadronisation mechanisms at the LHC, particularly through the evolution of the production ratio between different charm-hadron species. Measurements performed in pp and p--Pb collisions at the LHC have revealed unexpected features, qualitatively similar to what observed in larger systems and, in the charm sector, not in line with the expectations based on previous measurements from $\rm e^{+}e^{-}$ colliders and in ep collisions. These results suggest that charm fragmentation fractions mi…
Heavy quarks are effective probes of the hot and dense nuclear matter, the quark-gluon plasma, produced in ultra-relativistic heavy-ion collisions. Due to the short time scale characterising their production, heavy quarks experience the whole evolution of the system. In particular, measurements of heavy-flavour hadron production in Pb-Pb collisions at LHC energies give insight into the mechanisms of heavy-quark transport in the deconfined matter. In small hadronic systems, pp and p-Pb collisions, heavy-flavour measurements provide the baseline for observations of hot-medium effects in heavy-io…
Recent multiplicity-dependent analyses of pp and p--Pb collision data have revealed that particle production shares similar features with that in heavy-ion collisions. Studies using resonances could help to understand the possible onset of collective-like phenomena and the presence of a hadronic phase in small collision systems. Measurements of the differential yields of resonances with different lifetime, mass, quark content, and quantum numbers could enable understanding the mechanisms that influence the shape of particle momentum spectra, lifetime of the hadronic phase, strangeness producti…
Jets of high energy collimated particles provide a rich phenomenology to study quantum chromodynamics, from first-principles tests of perturbative calculations to investigations of the emergent properties of the strongly-coupled quark-gluon plasma. In these proceedings, we highlight several recent jet measurements by the ALICE Collaboration, with a focus on jet substructure observables.
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。
In ultra-relativistic heavy-ion collisions a great variety of (anti-)(hyper-)nuclei are produced, namely deuteron, triton, $^3$He, $^4$He, hypertriton ($^3_Λ$H) and their antiparticles. The ALICE experiment is the most suited to investigate the production of (hyper-)nuclei at the LHC, thanks to an excellent particle identification and low-material budget detectors. Recent results on (hyper-)nuclei production as a function of transverse momentum ($p_{\rm{T}}$) and charged particle multiplicity (d$N_{\rm{ch}}$/d$η$) in Pb-Pb collisions are presented. The evolution of the production yields with t…
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.
Recent observations of long-range multi-particle azimuthal correlations in p--Pb and high multiplicity pp collisions provided new insights into collision dynamics and opened a possibility to study collective effects in these small systems. New measurement of $p_\mathrm{T}$-differential elliptic flow ($v_{2}$) coefficient for inclusive charged hadrons as well as a variety of identified particle species in p--Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV recorded by ALICE during the LHC Run 2 data taking are presented. Besides high precision measurements of $v_2(p_\mathrm{T})$ for $\mathrm{π^…
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…
This contribution summarizes a selection of recent results from the ALICE experiment. We show the cross-section of beauty jets in pp collisions, as well as the charmed baryon-to-meson production ratios, down to unprecedentedly low momenta, at $\sqrt{s_{\rm NN}} = 5.02$ and 13 TeV collision energies. We present the nuclear modification of ${\rm D}^0$-jets and the $v_2$ of non-prompt ${\rm D}^0$ in Pb-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV. We also discuss the implications and constraints from comparing these data to some of the most recent theoretical models.
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…
The study of hadronic resonances plays an important role both in pp and in heavy-ion collisions. Since the lifetimes of short-lived resonances are comparable with the lifetime of the fireball formed in heavy-ion collisions, regeneration and re-scattering effects can modify the measured yields, especially at low transverse momentum. Measurements in pp collisions at different energies constitute a baseline for studies in heavy-ion collisions and provide constraints for tuning QCD-inspired event generators. Furthermore, high multiplicity pp collisions, where the density and the volume of the syst…
