The study of angular correlations of identified hadrons makes it possible to understand the impact of different processes that contribute to the hadronization mechanism in heavy-ion collisions and small collision systems. Depending on the quark composition and the system properties, the angular correlations exhibit different shapes.
The mechanism of hadron production is non-perturbative, and because of that, only phenomenological models can be used. Those models still fail to fully describe hadron production. In particular, angular correlations for like-sign baryons are not reproduced by the models. The upgraded ALICE detector and the new analysis framework allow for precise measurements of baryon angular correlations which provide stronger constraints on the hadronization mechanisms.
The ALICE detector has been commissioned and is ready for taking data at the Large Hadron Collider. The first proton-proton collisions are expected in 2009. This contribution describes the current status of the detector, the results of the commissioning phase and its capabilities to contribute to the understanding of both pp and PbPb collisions
ALICE is the general purpose heavy-ion detector at the CERN LHC. Its goal is to investigate the properties of the strongly interacting matter under the extreme conditions of density and temperature reached in Pb{Pb collisions, with the aim to characterize the Quark-Gluon Plasma (QGP). In this scenario, the upgrade of the ALICE inner tracker targets physics topics in which ALICE can bring a unique contribution to the QGP characterization via the heavy avour probes. We present an overview of the inner tracker upgrade and the expected physics performance for heavy avour measurements.
These proceedings summarise recent measurements of angular correlations between the $Ξ$ baryon and identified hadrons in pp collisions at $\sqrt{s}=13\,\mathrm{TeV}$ using the ALICE detector. The results are compared with both string-based (PYTHIA8 with extensions) and core-corona (EPOS-LHC) models, to improve our understanding of strangeness and baryon production in small systems. The results favour baryon production through string junctions over diquark breaking, but the PYTHIA models fail at describing the relatively wide $Ξ-$strangeness jet peak, indicating stronger diffusion of strange qu…
In this contribution, the latest results for measurements of charm baryons in proton--proton collisions at $\sqrt{s}=5.02$ and $13\,\mathrm{TeV}$ are presented. The production yields of $Λ_\mathrm{c}^{+}$, $Ξ_\mathrm{c}^{0,+}$, $Ω_\mathrm{c}^{0}$, and $Σ_\mathrm{c}^{0,++}$ are shown along with their yield ratios to $\mathrm{D}^{0}$ mesons, and observations about charm hadronisation with respect to previous results from lepton colliders are discussed. Further differential measurements are shown of the $Λ_\mathrm{c}^{+}/\mathrm{D}^{0}$ yield ratio as a function of charged-particle multiplicity. …
Heavy quarks, i.e. charm and beauty, are sensitive probes of the medium produced in high-energy heavy-ion collisions. They are produced in the early stage of the collision, mainly in hard partonic scattering processes, and are expected to experience the whole collision evolution interacting with the medium constituents via both elastic and inelastic processes. The nuclear modification factor ($R_{\rm AA}$) is one of the main experimental observables that allow us to investigate the interaction strength of heavy quarks with the medium. The ALICE collaboration measured the production of open hea…
In these proceedings, measurements of angular correlations between hadron pairs in pp collisions obtained by the ALICE experiment at the LHC are presented and compared with phenomenological predictions. Correlations between particles carrying the same and opposite quantum numbers are studied to understand the hadron production mechanism, and the difference between same-sign and opposite-sign correlations is used to probe charge-dependent effects in particle production. Correlation measurements dominated by minijet fragmentation agree well with the models, but other results, in particular corre…
We present the first fully-corrected semi-inclusive distribution of charged jets recoiling from a trigger hadron in 0-10% Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV as a function of the azimuthal angle between the trigger hadron and jet, $Δφ$. This technique provides a precise data-driven subtraction of the large uncorrelated background contaminating the measurement, and enables the exploration of jet acoplanarity. Results for $R=0.2$ recoil jets in the region $30 < p_{\mathrm{T,jet}}^{\mathrm{ch}} < 40~\mathrm{GeV}/c$ are shown, where a suppression and narrowing of the $Δφ$ distr…
Measurements of the semi-inclusive distribution of charged jets recoiling from a trigger hadron in pp and Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV are presented. This technique provides precise, data-driven subtraction of the large uncorrelated background in jet measurements. It uniquely enables the exploration of medium-induced modification of jet production and acoplanarity over wide phase space, including low transverse momentum ($p_\mathrm{T}$) and large resolution parameter ($R$) jets. This proceeding reports the measurements of medium-induced jet energy redistribution thr…
A review is given on photon-hadron and photon-photon collisions in the ALICE experiment. The physics motivation for studying such reactions is outlined, and the results obtained in proton-lead and lead-lead collisions in Run 1 of the LHC are discussed. The improvement in detector rapidity coverage due to a newly added detector system is presented. The ALICE perspectives for data taking in LHC Run II are summarised.
The production of heavy-flavour hadrons in high-energy hadronic collisions is a unique source of information on various aspects of quantum chromodynamics (QCD). Production of heavy-flavour hadrons in proton--proton collisions allows the test of perturbative QCD models, while the comparison of mesons and baryons with heavy-flavour quarks can differentiate between fragmentation scenarios. Multiplicity-dependent measurements allow for the understanding of semi-hard vacuum QCD effects, as well as to study the coalescence mechanisms of heavy-flavour quarks with light and strange quarks. Recent resu…
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 resonances $\mathrm{K}^{*}(892)^{0}$, $ϕ$(1020) and $Σ(1385)^{\pm}$ have been measured by the ALICE experiment in pp collisions at $\sqrt{s}=7$ TeV and in Pb-Pb collisions at $\sqrt{s_{_\mathrm{NN}}}=2.76$ TeV. Transverse momentum spectra, particle ratios, nuclear modification factor and comparison with model predictions are discussed. In addition, ALICE results are compared with data obtained at RHIC energy.
Among the probes used to investigate the properties of the Quark-Gluon Plasma, the measurement of the energy loss of high-energy partons can be used to put constraints on energy-loss models and to ultimately access medium characteristics, such as the energy density or the temperature. The study of two-particle correlations allows us to obtain very different constraints compared to the nuclear modification factor. In particular, the correlation of charged hadrons with high energy $π^{0}$ or direct photons is believed to give a measurement of the parton energy loss and insights into the medium-i…
Studies of the production of heavy-flavour baryons are of prominent importance to investigate hadronization mechanisms at the LHC, in particular through the study of the evolution of the baryon-over-meson production ratio. Measurements performed in pp and p--Pb collisions at the LHC have revealed unexpected features, qualitatively similar to what was observed in heavy-ion collisions 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 charmed baryon formation might not be universa…
In this work we are studying the relative beauty to charm production in pp collisions at \sqrt{s} = 2.76 TeV, through correlations between electrons from heavy-flavour decay and charged hadrons, with the ALICE detector at the LHC. This study represents a baseline for the analysis in heavy-ion collisions where heavy flavour production is a powerful tool to study the Quark Gluon Plasma (QGP).
The early production of heavy-flavor (HF, charm and beauty) quarks makes them an excellent probe of the dynamical evolution of quantum chromodynamics (QCD) systems. Jets tagged by the presence of a HF hadron give access to the kinematics of the heavy quarks, and along with correlation measurements involving HF hadrons allow for comparisons of their production, propagation and fragmentation across different systems. In this contribution the latest results on HF jets and correlations measured with the ALICE detector in pp, p--Pb and Pb--Pb collisions from the LHC Run 2 data are reported.
At high pT, direct photons produced in Compton and annihilation QCD leading order processes are associated to a jet in the opposite direction. Such processes are tagged experimentally by identifying leading isolated photons and their correlated associated hadrons in the opposite azimuthal direction. The jet fragmentation can be estimated from the hadrons and the photon via the imbalance parameter xE. We present the results extracted from gamma-hadron correlations measured by the ALICE experiment in pp collisions at {\sqrt(s)} = 7 TeV. Direct photons are first identified using isolated criteria…
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.
ALICE measured electrons from inclusive heavy-flavour hadron decays and beauty-hadron decays at mid-rapidity in pp collisions at \sqrt{s} = 7 TeV and 2.76 TeV and p-Pb collisions at \sqrt{s_{NN}} = 5.02 TeV. For both pp collision energies, p_T-differential electron production cross sections are presented and compared to pQCD predictions. For p-Pb collisions, the p_T-dependent nuclear modification factor of electrons from inclusive heavy-flavour hadron decays is presented.
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…
Short lived hadronic resonances are a very important tool for the study of the dynamics of the matter produced in heavy-ion collisions since they should be sensitive to the medium properties such as temperature, density and expansion velocity. In particular they are sensitive to the time span between chemical and kinetic freeze-out of the hadronic phase of the fireball. The study of resonances in 7 TeV pp collisions is useful both in order to constrain QCD inspired models and to form a baseline for the production in heavy-ion collisions. The resonances $\mathrm{K}^{*0}$(892), $\phiup$(1020), $…
The ALICE detector has excellent Particle IDentification (PID) capabilities in the central barrel ($\lvert η\rvert <$ 0.9). This allows identified hadron production to be measured over a wide transverse momentum ($p_{\rm{T}}$) range, using different sub-detectors and techniques: their specific energy loss (d$E$/d$x$), the velocity determination via time-of-flight measurement, the Cherenkov angle or their characteristic weak decay topology. Results on identified light flavour hadron production at mid-rapidity measured by ALICE in proton-proton collisions at $\sqrt{s}$ = 13 TeV are presented and…
In relativistic heavy-ion physics two-particle correlations provide a very useful tool to investigate the Quark-Gluon Plasma (QGP). This observable is sensitive to several of the properties of the QGP such as resonances, interaction of partons with the medium and collective effects (e. g. elliptic flow). In the present work, the correlation function between electrons from heavy-flavour hadron decays and light hadrons was measured in pp and Pb-Pb collisions (central and semi-central). Furthermore, in pp collisions the relative beauty contribution to the total cross section of electrons from hea…
We report measurement of the semi-inclusive distribution of charged-particle jets recoiling from a high transverse momentum ($p_{\rm T}$) hadron trigger, for p-Pb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV, in p-Pb events classified by event activity. This observable has been measured in pp and Pb-Pb collisions at the LHC, providing a new probe to measure quenching. Jets are reconstructed from charged particle tracks using anti-$k_{\rm t}$ with $R = 0.4$ and low IR cutoff of jet constituents ($p_{\rm T,track} > 0.15$ GeV/$c$). The complex uncorrelated jet background is corrected by a data-dr…
In ultra-relativistic heavy-ion collisions heavy quarks (charm and beauty) are produced in hard scattering processes and thus carry relevant information on the properties of the created hot and dense medium. Heavy-flavour hadrons can be measured using electrons from their semileptonic decay channels. The relative contribution of charm and beauty hadrons can be estimated from the study of the near side azimuthal angular correlations between these electrons and charged hadrons. We present the measurement of azimuthal angular correlations between electrons and charged hadrons in pp collisions at …
Untriggered di-hadron correlations studies are shown which provide a map of the bulk correlation structures in Pb-Pb collisions. Long-range correlations are further studied by triggered correlations which address the dependence on trigger and associated pT. Measured correlation functions are decomposed with a multi-parameter fit and into Fourier coefficients. The jet-yield modification factor I_AA is presented.
Studies of light hadron and nuclei production are fundamental to characterize the hot and dense fireball created in ultra-relativistic heavy ion collisions and to investigate hadronisation mechanisms at the LHC. Observables investigated as a function of the charged particle multiplicity in proton-proton and proton-lead collisions have shown features not expected and qualitatively similar to what has been observed in larger size colliding systems. The ALICE experiment, exploiting its excellent tracking and PID capabilities, has performed an extensive and systematic study of strange and non-stra…
Heavy-flavour hadrons, i. e. hadrons carrying charm or beauty quarks, are a well-suited probe to study the Quark-Gluon Plasma (QGP) in relativistic heavy-ion collisions. For this reason, measurements of electrons from heavy-flavour hadron decays have been performed in pp, p-Pb and Pb-Pb collisions at the LHC with the ALICE detector. Results for the nuclear modification factors ($R_{\rm{pA}}$ and $R_{\rm{AA}}$) support a final-state energy loss of heavy quarks in central Pb-Pb collisions and, in semi-central collisions a positive elliptic flow coefficient $v_{2}$ of electrons from heavy-flavour…
A selection of recent ALICE results from pp, p--Pb, Pb--Pb and Xe--Xe collisions taken during the Run 1 and Run 2 phases are summarized in this contribution, and the prospects for the upcoming Run 3 phase are outlined.
Hadronic resonances are a valuable tool to study the properties of the medium formed in heavy-ion collisions. In particular, they can provide information on particle-formation mechanisms and on the properties of the medium at chemical freeze-out. Furthermore they contribute to the systematic study of parton energy loss and quark recombination. Measurements of resonances in pp and in p-Pb collisions provide a necessary baseline for heavy-ion data and help to disentangle initial-state effects from medium-induced effects. In this paper the latest ALICE results on mid-rapidity K*(892)^0 and ϕ(1020…
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…
We report the first measurement of charged pion, kaon and (anti-)proton production in jets from hadron colliders. The measurement was carried out with the ALICE detector using $2\times10^8$ minimum bias pp collisions at a centre-of-mass energy of $\sqrt{s}=7$ TeV at the LHC. We present the $π$, K and p transverse momentum ($p_\textrm{T}$) spectra, as well as the spectra of the reduced momentum (${z^\textrm{ch}\equiv p_\textrm{T}^\textrm{track}/p_\textrm{T, jet}^\textrm{ch}}$), in charged jets of $p_\textrm{T}$ between 5--20 $\textrm{GeV}/c$. The measurement is compared to Monte Carlo calculati…
Open heavy flavour and J/psi production are powerful tools to test pQCD calculations in proton-proton collisions in the new LHC energy regime. In addition, they provide the necessary reference for the ALICE heavy-ion program. The ALICE experiment at the LHC collected proton-proton collisions at sqrt{s} = 7 and 2.76 TeV in 2010 and 2011. We report here the latest results of open heavy flavour and J/psi production at both mid- and forward-rapidity via their various hadronic and leptonic decay channels. These include, among other topics, the first LHC result on J/psi polarization, multiplicity de…
The ALICE experiment has measured the production of a rich set of hadronic resonances, such as $ρ(770)^{0}$, ${\rm K}^{\ast}(892)^{0}$, $ϕ$(1020), $Σ^{\pm}$(1385), $Λ(1520)$ and $Ξ^{\ast 0}$ in pp, p-Pb and Pb-Pb collisions at various energies at the LHC. A comprehensive overview and the latest results are presented in this paper. Special focus is given to the role of hadronic resonances for the study of final-state effects in high-energy collisions. In particular, the measurement of resonance production in heavy-ion collisions has the capability to provide insight into the existence of a prol…
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…
Lattice Quantum Chromodynamics (QCD) calculation predicts that a colour-deconfined QCD matter, Quark-Gluon Plasma (QGP), is formed at high temperature and energy density reached in ultra-relativistic heavy-ion collisions. Heavy quarks (charm and beauty) are mostly produced by initial hard scatterings before the formation of the QGP. Therefore heavy-flavour hadrons are ideal probes to investigate the properties of the hot and dense QCD matter. In Pb-Pb collisions, a strong suppression of the production of heavy-flavour hadrons with high transverse momentum has been observed. A deeper understand…
We report on the first measurement of the charged hadron composition in charged jets from pp collisions. The ALICE detector at the LHC was used to study charged pion, kaon and (anti-)proton production in jets. The results were extracted from $2 \times 10^8$ minimum bias events at a centre-of-mass energy of $\sqrt{s} = 7$ TeV. We present the transverse momentum ($p_{\mathrm{T}}$) spectra and reduced momentum spectra ($z^{\mathrm{ch}} \equiv p_{\mathrm{T}}^{\mathrm{track}} / p_{\mathrm{T, jet}}^{\mathrm{ch}}$) of $π$, K and p in charged jets with $p_{\mathrm{T, jet}}^{\mathrm{ch}}$ between 5 and…
Measurements of the heavy-flavour hadron production are a powerful tool to study the nature of strong interaction and to understand the properties of nuclear matter that is created in ultra-relativistic hadron-hadron collisions. The excellent tracking and vertexing capabilities of the ALICE experiment, together with its particle identification systems, allow for an efficient identification and reconstruction of decays of hadrons that contain heavy quarks. A selection of recent measurements on open heavy-flavour production from pp collisions at $\sqrt{s}=7$ TeV and p--Pb collisions at $\sqrt{s_…
Heavy quarks produced in pp and heavy ion collisions are studied using heavy-flavour decay electrons and heavy-flavour mesons. Detailed understanding of the production processes and fragmentation of heavy quarks can be obtained by studying the azimuthal angular correlation of heavy-flavour hadrons. The azimuthal angular correlations of heavy-flavour mesons and charged hadrons can be used to disentangle charm and beauty-hadrons in pp collisions. In this contribution the fraction of electrons from beauty-hadron decays in the heavy-flavour decay electron yield is shown as well as the beauty produ…
We report recent results from the ALICE experiment the Large Hadron Collider on open charmed hadron production in pp collisions at $\sqrt{s} = 2.76$ and 7 TeV, and Pb-Pb collisions at $\sqrt{\mathrm{s}_{_{\mathrm{NN}}}} = 2.76$ TeV. Open charmed hadrons are kinematically fully reconstructed in the hadronic decay channels \DtoKpi, \DtoKpipi, and \DstartoDpi %$D^0\rightarrow K^-π^+$, $D^+\rightarrow K^-π^+ π^+$, and $D^{*+} \rightarrow D^0 (K^-π^+) + π^+$ and identified through their invariant mass. Combinatorial background is minimized by selecting a displaced vertex topology. Inclusive charm a…
The production of resonances in heavy-ion collisions is expected to be sensitive to the properties of strongly interacting matter created in such collisions. We report on the measurements of $ϕ$ and $K^{*0}$ resonances in Pb-Pb collisions at $\sqrt{s_{NN}} $ = 2.76 TeV. The masses, widths and yields in Pb-Pb collisions as a function of centrality are compared to that in pp collisions to understand the role of re-scattering and regeneration. The resonance to non-resonance particle ratios are shown as a function of collision centrality and compared with the results at lower energies.
Azimuthal correlation studies of heavy-flavour particles with charged particles in p--Pb collisions can give an insight into the cold nuclear matter effects \cite{Andronic:2015wma} on heavy-quark production and hadronization into heavy-flavour jets. Multiplicity-dependent measurements of angular correlations of heavy-flavour particles with charged hadrons allow us to investigate the collective behavior of the system and the initial state effects on heavy flavour hadron production. In addition, they can reveal possible modifications of the heavy-quark fragmentation and hadronization at differen…
The measurement of the identified charged hadron p_t spectra using the ITS energy loss signal in the p-p data at sqrt{s}=900 GeV collected by the ALICE experiment at LHC will be discussed. It is performed using the Inner Tracking System (ITS) in stand-alone mode, both for track reconstruction and particle identification, allowing one to detect low momentum particles with p_t below 200 MeV/c. A second method using the tracks reconstructed by both the ITS and the Time Projection Chamber (TPC) has also been developed. The obtained results will be compared with the ones obtained from the TPC and f…
Comprehensive results on transverse momentum distributions and their ratios for identified light flavor hadrons ($π$, K, p) at low $p_{T}$ and mid-rapidity as a function of charged particle multiplicity are reported for pp collisions at 7 TeV. Particle mass dependent hardening of the spectral shapes in Pb-Pb collisions at 2.76 TeV were attributed to hydrodynamical flow and quantitatively parameterized with Boltzmann-Gibbs Blast Wave fits. In this contribution, we investigate the existence of collective phenomena in small systems: pp, p-Pb and peripheral Pb-Pb where similar patterns are observe…
