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 momentum on a jet-by-jet basis using jet parameters such as information about the constituents of the jet. Studies that investigate the effect of the potential fragmentation bias introduced by learning from constituents will also be discussed. With these studies in mind, the results are compared to theoretical predictions.
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。
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…
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.
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…
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.
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/$ψ$]…
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.
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.
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 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…
Jets correlated with isolated photons are a promising channel to study jet quenching in heavy-ion collisions, as photons do not interact strongly and therefore constrain the $Q^2$ of the initial hard scattering. We present the isolated photon-jet correlations measured in Pb--Pb collisions at $\sqrt{s_{\text{NN}}}$ = 5.02 TeV by the ALICE collaboration. We study correlations of isolated photons above 20 GeV/$c$ with charged-particle jets above 10 GeV/$c$, reconstructed with the anti-$k_\text{T}$ algorithm. The correlations probe the lowest jet $p_\text{T}$ range ever measured at LHC energies, a…
We present the current status of the measurement of jets that contain a D meson (D-tagged jets) with ALICE. D-meson candidates, identified via their hadronic decay channels, were combined with the other charged tracks reconstructed with the central tracking system, using the anti-$k_{\rm T}$ jet-finding algorithm. The yield of D-tagged jets was extracted through an invariant mass analysis of the D-meson candidates. A Monte Carlo simulation was used to determine the detector performance and validate the signal extraction techniques.
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
We present the analysis of the semi-inclusive distribution of reconstructed charged particle jets recoiling from a high pT hadron trigger in central Pb Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV. We measure, subtract and unfold the large underlying event background in such collisions, utilizing a novel technique that does not impose fragmentation bias on the measured jet population. The Pb Pb measurements are compared to a pp PYTHIA reference distribution generated at the same $\sqrt{s}$. Modification of jet structure due to quenching is explored by varying the cone radius $R$ (0.2, 0.4) and th…
The ALICE Collaboration measured dielectron production as a function of the invariant mass ($m_{\rm ee}$), the pair transverse momentum ($p_{\rm T,ee}$) and the pair distance of closest approach ($\rm DCA_{ee}$) in pp collisions at $\sqrt{s} = 7$ TeV. Prompt and non-prompt dielectron sources can be separated with the $\rm DCA_{ee}$, which will give the opportunity in heavy-ion collisions to identify thermal radiation from the medium in the intermediate-mass range dominated by contributions from open-charm and beauty hadron decays. The charm and beauty total cross sections are extracted from th…
The study of inclusive charged-particle production in heavy-ion collisions provides insights into the density of the medium and the energy-loss mechanisms. The observed suppression of high-$\textit{p}_\text{T}$ yield is generally attributed to energy loss of partons as they propagate through a deconfined state of quarks and gluons - Quark-Gluon Plasma (QGP) - predicted by QCD. Such measurements allow the characterization of the QGP by comparison with models. In these proceedings, results on high-$\textit{p}_\text{T}$ particle production measured by ALICE in Pb-Pb collisions at $ \sqrt{\text{s}…
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。
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<…
The D meson yields as a function of charged-particle multiplicity in pp collisions at $\sqrt{s}=7$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are presented. The measurement of the yields of electrons from heavy-flavour hadron decays as a function of charged-particle multiplicity in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are shown as well. The measurement of azimuthal correlations of prompt D mesons and charged hadrons in pp collisions at $\sqrt{s}=7$ TeV and in p-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=5.02$ TeV are also presented. The results are compared w…
We report recent ALICE results on primary charged particle and neutral meson production in pp, p--Pb, Pb--Pb and Xe--Xe collisions at LHC energies. In this article, measurements of the nuclear modification factors $R_{\rm AA}$ of primary charged particles and of light neutral mesons in Pb--Pb, in Xe--Xe and in p--Pb collisions in a wide $p_{\rm T}$ range and different centrality classes are discussed. We compare the nuclear modification factors obtained for different collision systems as a function of transverse momentum, collision centrality as well as charged particle multiplicity (${\rm d}N…
Dielectrons probe a wide range of phenomena in heavy-ion collisions. These include light- and heavy-flavour meson production, thermal radiation and coherent photo-production. The latter process is distinguished by dielectron production at low transverse-pair momentum ($ \it{p}_{\textrm{T,ee}}$). Transverse momentum spectra of dielectrons in central and peripheral Pb-Pb collisions are extracted and compared to the corresponding expectations. In central collisions the data fit the expected spectrum, which is dominated by semi-leptonic decays of correlated heavy-flavour hadrons. In peripheral col…
