Measurements of dijet production in heavy ion collisions can be used to probe the nuclear matter. In proton-lead collisions, the normalized average dijet pseudorapidity distributions can be used as a sensitive tool for constraining the nuclear modifications of parton distribution functions (nPDF) at different $Q^2$ scales and Bjorken-$x$. In such studies, it is possible to investigate, with a...
Measurements of jets that traverse a quark gluon plasma can provide in- sights into the jet energy loss in heavy ion collisions. Furthermore, considering jets of various radii can help elucidate how the parton energy is transferred to the medium as well as the corresponding medium response. This talk presents measurements of the nuclear modification factor and dijet momentum balance for...
Measurements at the LHC have provided evidence for collective behavior in high-multiplicity proton-lead (pPb) collisions through multiparticle correlation techniques. Yet, no conclusive evidence of jet quenching, indicating the energy loss of high-$p_\mathrm{T}$ partons as they traverse the medium, has been detected in pPb. This raises the intriguing question: How can a medium described by...
Recent research suggested that hot nuclear matter phenomena also occur in small systems in the charm sector. To deepen the understanding of the source of such phenomena, we will present the charm hadron production in pPb collisions, focusing on the $\Lambda_{c}$-to-$D^{0}$ ratio in different multiplicities to examine the hadronization mechanisms. The results are also compared to the light and...
This talk presents two recent ATLAS measurements of multi-particle correlations in pp collisions. The first investigates the relationship between the pp “ridge” and hard scattering processes. In particular, it is not known whether jets or their soft fragments are correlated with particles in the underlying event. To study this “soft-hard” correlation, measurements of two-particle correlations...
Measurements of jet substructure in heavy-ion collisions provide critical insights into the mechanisms of jet quenching within the hot and dense QCD medium created during these collisions, spanning a wide range of energy scales. This talk presents new measurements from the ATLAS Collaboration on jet suppression and substructure, employing the Soft-Drop grooming procedure in Pb+Pb and pp...
In hadron-hadron collisions at LHC energies, Multiple Parton Interactions (MPI), where multiple hard-parton scatterings can occur in the same collision, play a significant role. Among MPI scenarios, Double-Parton Scatterings (DPS) represent the simplest case. The DPS contribution to a given process with two final-states A and B can be expressed as the product of the cross-sections of the...
Measurements of top quarks in heavy-ion collisions are expected to provide novel probes of nuclear modifications to parton distribution functions as well as to bring unique information about the evolution of strongly interacting mat- ter. We report the observation of the top-quark pair production in proton-lead collisions at the centre-of-mass energy of 8.16 TeV in the ATLAS experiment at the...
Experiments at RHIC and LHC have found no observable evidence of jet quenching in small systems, with one exception — a recent measurement by PHENIX [2303.12899], which compared the yield of neutral pion and direct photon production in very central d+Au collisions. The argument is that the photon yields can be used to correct out any centrality bias effects, and thus the surprisingly strong...
Jet substructure observables are an effective probe of the QCD matter created in heavy ion collisions, studying various jet and medium interaction scales. Measurements of these observables have been typically limited to single dimensions, leaving unanswered questions about the interplay of momentum and angular components in the evolution of jets. Here we present two new multi-dimensional jet...
Measurements of beauty-hadron production in ultrarelativistic hadronic collisions provide a fundamental tool for testing perturbative QCD calculations. Recent results at the LHC show that the beauty fragmentation function, as well as that of charm, is not universal across different collision systems. An extension of these studies to further energies, rapidities and collision systems has thus...
The novel fixed-target program pioneered by the LHCb experiment during
the LHC Run 2 has been upgraded for Run 3 with a dedicated gas injection system, SMOG2. Featuring an improved gas confinement to increase the fixed-target luminosity and a new system that allows the injection of non-noble gases, SMOG2 enables the collection of large samples of pA and PbA fixed-target collisions, including...
In high-energy collider physics, one of the most important questions is whether quark-gluon plasma (QGP) is formed in pp collisions. Recently, flow-like behaviours have been found in high-multiplicity pp collisions implying collectivity. Stronger evidence for the QGP formation in pp collisions would be signatures of jet quenching, which has not yet been observed. In this contribution, the...
We propose a novel approach to investigate the evolution of jets in heavy-ion collisions by employing a combination of jet substructure measurements. Our method focuses on isolating the perturbative regime of jet evolution. As a proof of concept, we analyze the distribution of the hardest splitting above a transverse momentum scale, $k_{t,{\rm cut}}$ , in high-$p_T$ jets. For a $k_{t,{\rm...
In hadronic collisions, charm and beauty quarks are mainly produced in hard partonic scatterings due to their large masses. Thus, they are ideal tools to investigate various aspects of perturbative QCD. In addition, measurements in pp collisions represent a baseline for cold nuclear matter studies in p-A collisions, and for the characterization of the hot and dense medium, the quark-gluon...
High-multiplicity pp collisions at LHC energies have revealed that small systems can exhibit QGP-like features, suggesting that light-flavor hadron production arises from complex mechanisms whose relative contributions evolve smoothly from low to high multiplicity collisions. Several analyses have recently been performed with event shape classifiers to separate soft and hard components, namely...
Deciphering jet substructure modification patterns in heavy ion collisions holds the key to finding the inner working of the quark-gluon plasma. In the past few years, significant progress was made to studying the modifications of soft-drop jet observables, which were designed to probe the hard jet substructure. Collinear-drop observables were constructed to enhance the sensitivity to soft jet...
Jet energy loss is an important signature of the creation of QGP. High-precision energy-loss model is essential to independently verifying the QGP properties learned from soft particles. In this work, we study the phenomenological influence of the higher order collision kernels --- the up-to-NLO one evaluated by EQCD and the non-perturbative (NP) one computed in lattice QCD --- in the energy...
The JETSCAPE Collaboration presents a new, multi-observable study of jet transport in the QGP using Bayesian Inference, for the first time incorporating all available inclusive hadron and jet suppression data, and jet substructure data. The theoretical description of jet quenching is multi-stage, based on the MATTER and LBT models, with virtuality-dependent jet-medium interaction. Detailed...
With its precise vertex reconstruction and particle identification capabilities,
the LHCb detector is ideally suited to study the production and polarization
of primary and secondary particles. In particular, as the origin of hyperon po-
larization from unpolarized proton-proton and proton-nucleus collisions is not
yet fully understood, measurements in different collision systems and...
Measurements of elliptic flow ($v_2$) of light and heavy flavor particles can provide key insight into the transport properties and collective behavior of QGP. The PHENIX experiment has a unique forward rapidity coverage at RHIC ($1.2\leq|\eta|\leq2.2$), and large muon datasets collected in 2014 and 2016 with Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV, allowing for statistically significant...
Jets are powerful probes used to improve our understanding of the strong force at short distances. The radiation pattern of jets can be visualized via the Lund jet plane, a two-dimensional representation of the phase space of intrajet emissions using the splitting angle $\Delta R$ and the relative transverse momentum of the emission relative to the emitter $k_{\mathrm{T}}$. The Lund jet plane...
The transverse energy in heavy ion collisions is one of the key observables characterizing global properties of the Quark-Gluon Plasma (QGP). The transverse energy per unit pseudorapidity (dE$_T$/d$\eta$) probes the energy carried by the medium along the longitudinal direction, providing essential information related to the initial geometry and subsequent hydrodynamic evolution of the QGP....
The production of a Z boson provides a clean handle to control the population of events to be studied. By selecting muonic decays of Z bosons, we can isolate the effect of the recoiling process without potential bias from requiring isolation, as is the case for photons. Di-hadron correlations can naturally separate effects from different angular scales. Similar to the energy-energy correlator...
Heavy quarks (charm and beauty) are useful probes for investigating the properties of the quark-gluon plasma (QGP) generated in ultrarelativistic heavy-ion collisions. Measurements of the nuclear modification factor $R_{\rm{AA}}$ of charm and beauty hadrons offer a means to characterize the in-medium energy loss of heavy quarks in the QGP. Insights into their participation in the medium...
A search for medium-induced jet transverse momentum broadening is performed with isolated photon-tagged jet events in proton-proton (pp) and lead-lead (PbPb) collisions at nucleon-nucleon center-of-mass energy $5.02$ TeV. The difference between jet axes as determined via energy-weight and winner-take-all clustering schemes, also known as the decorrelation of jet axes and denoted $\Delta j$, is...
This talk presents recent studies of event-wise mean transverse momentum, [pT] that can help differentiate the interplay between the effect of radial collectivity, random thermal motion and deformation in nuclear geometry. In addition, the Pearson Correlation Coefficient (PCC) between flow, vn and [pT] , ρ(vn, [pT]), will be shown. The results bear on aspects of the initial state, such as...
Exploiting the first measurements of the same ion species in O+O collisons at RHIC and LHC, we propose an experimentally acessible observable to distinguish whether collective behavior builds up through a hydrodynamic expansion of a strongly interacting QGP or through few rescatterings in a non-equilibrated dilute medium. Our procedure allows to disentangle the effects of the initial state...
The far-from equilibrium dynamics of the pre-hydrodynamic quark-gluon plasma (QGP) formed in heavy ion collisions can be characterized by distinct stages, during each of which the system loses some memory of its initial condition, until only the hydrodynamic modes remain. This attractor behavior has been characterized previously in both strongly and weakly coupled descriptions. In particular,...
Jets are established tools for studies of the Quark Gluon Plasma (QGP) properties. In this talk, we present a new measurement of the jet substructure modification via the observable ${\Delta R}_{\rm{axis}}$, characterizing the distance between two types of jet axis constructed with the same jet constituents. We use E-scheme and WTA axes with different sensitivity to soft and semi-hard...
Heavy-ion collisions produce a hot, dense medium, and high-momentum par- tons from the collision traverse this medium while losing energy in it. Because of the initial geometry of the QGP, partons produced at different angles, with respect to the impact parameter, traverse different path lengths in the medium leading to azimuthal-angle dependence of the yields of high transverse momen- tum...
The interaction of heavy quarks with the quark-gluon plasma (QGP) affects their azimuthal distribution and transverse momentum ($p_{\mathrm{T}}$) spectrum. Hence, azimuthal anisotropy coefficients ($v_n$) and nuclear modification factors ($R_{AA}$) of heavy flavor hadrons are vital probes to study QGP properties. This talk presents the first measurements of the elliptic ($v_{2}$) and...
This talk presents the first measurements of the groomed jet radius $R_{\rm{g}}$ and the jet girth $g$ in events with an isolated photon recoiling against a jet in PbPb and pp collisions at the LHC at 5.02 TeV. The observables $R_{\rm{g}}$ and $g$ provide a quantitative measure of how narrow or broad a jet is. Events are required to have a photon with transverse momentum $p_{\rm{T}}^{\gamma} >...
Charm and beauty quarks are powerful tools to characterize the quark-gluon plasma (QGP) produced in heavy-ion collisions. Although they are initially produced out of kinetic equilibrium via hard partonic scattering processes, recent measurements of anisotropic flow of charmed hadrons pose the question regarding the degree thermalization of heavy quarks in the medium. Our recent work [1] has...
The study of the initial nonequilibrium stages in heavy-ion collisions is an exciting research frontier. In particular, for jet quenching observables, jet-medium interactions during the initial stages have been argued to be one of the major theoretical uncertainties. To calculate the medium-induced gluon spectrum and jet energy loss, knowledge of the momentum broadening kernel is required,...
Leveraging on the injection of noble gases into the LHC accelerator beam-
pipe, LHCb has been collecting since 2015 proton- and lead-gas collisions, which
give access to the poorly explored high-x and moderate Q2 kinematic region. In
particular, studies of strangeness production provides information on hadroniza-
tion and serve as important inputs to models of particle production in...
Through a comprehensive analysis with Monte Carlo simulations using a multi-stage jet evolution model, we demonstrate that by comparing the jet substructure modifications for inclusive jets and gamma-tagged jets, the virtuality dependence and flavor dependence in jet-medium interactions can be closely examined. Recent findings reveal that a reduction in jet-medium interaction at the early...
Charm-baryon production measurements in proton-proton (pp) collisions at the LHC are fundamental tools to investigate the charm-quark hadronisation and to test pQCD calculations. Recent measurements in pp collisions have shown baryon-to-meson ratios significantly larger than those in $\mathrm{e^+e^-}$ collisions, challenging the validity of theoretical calculations based on the factorisation...
The early glasma stage of heavy-ion collisions is characterized by strong color fields which deflect jet partons, resulting in sizable jet momentum broadening. An outstanding question is how this momentum broadening leads to jet quenching in the glasma and how important this quenching is for jet phenomenology. In this work we aim to answer these questions by performing the first calculation of...
Measurements of the light-by-light scattering (LbL, $\gamma\gamma\to\gamma\gamma$) and the Breit--Wheeler (B--W, $\gamma\gamma\to\mathrm{e}^+\mathrm{e}^-$) processes are reported in ultraperipheral collisions at 5.02 TeV using the 2018 CMS lead-lead data sample of $1.65~\mathrm{nb}^{-1}$. Events with a pair of exclusively produced photons or electrons are selected, each with transverse energy...
In this work, we study the evolution of a jet, modelled as a linear perturbation of the distribution of quarks or gluons, in an out of equilibrium system of quarks and gluons. The hard probe and the bulk QCD matter are described in an unified approaching using QCD kinetic theory. This allows us to investigate the interplay between the hard and soft sectors of jets as well as those in the bulk....
Measurements of the anomalous magnetic moment of leptons are good handles for precision tests of the Standard Model and hints of physics beyond the Standard Model. These measurements for electrons and muons are among the most precisely measured quantities in physics. However, due to the short lifetime of the tau lepton, its anomalous magnetic moment is not as precisely known and needs to be...
The differences in hadron chemistry observed at e+e- machines versus hadron
colliders may indicate that the mechanisms by which partons evolve into visible
matter are not universal. In particular, the presence of many other quarks
produced in the underlying event may affect the hadronization process. With
full particle ID, precision vertexing, and a high rate DAQ, the LHCb detector
is...
Jet substructure is a powerful tool for performing fundamental QCD tests in elementary particle collisions and offers unique insight into the microscopic structure of the QGP in heavy-ion collisions. Defined as the energy-weighted cross section of particle pairs inside jets, the two-point energy-energy correlator (EEC) is a novel jet substructure observable probing the correlation of energy...
Charmonia are a valuable tool to investigate nuclear matter under extreme conditions, and particularly the strongly interacting medium formed in heavy-ion collisions. At the LHC energies, the regeneration process has been found to significantly impact the observed charmonium yields. In particular, the measurement of $\psi(2S)$ production relative to $J/\psi$ in Pb-Pb collisions has a strong...
The idea of using dilepton measurements to construct a phenomenology of the early pre-equilibrium phase of heavy-ion collisions has been recently posed [1,2]. Nevertheless, a full computation of pre-equilibrium radiation yields was still missing. In this work, we use QCD kinetic theory to compute dilepton production coming from the pre equilibrium phase of the Quark-Gluon Plasma created in...
The latest measurement of bottom baryon-to-meson production ratio [1], $\Lambda_b/B$, in proton-proton collisions at the LHC, shows a continuous evolution from the saturation value toward the small value identified in electron-positron collisions as the system size reduces. We address this in a canonical ensemble statistical hadronization model, and demonstrate that the decreasing trend of...
Modifications of quarkonia production in hadronic collisions provide an im-
portant experimental observable to probe the heavy quark interaction with the
nuclear medium. The excited ψ(2S) state, with a relatively low binding en-
ergy, is especially sensitive to these effects. In this contribution, we will present
a new LHCb result on ψ(2s)/J/ψ production in PbPb collisions, along...
Energy-energy correlator has the advantage of isolating physics of different angular scales, which has attracted a lot of interest recently to study it in heavy-ion environments. Any modification from proton-proton reference can reveal hints about the inner workings of the quark-gluon plasma. In this presentation we will present the first measurement of the energy-energy correlator of jets in...
Dileptons are produced throughout the entire evolution history of the medium. Owing to their electromagnetic coupling to strongly interacting matter, dileptons traverse the QGP medium unaltered after their production and carry information about their space-time points of production. The emissivity is correlated with the quark abundance in the collision system as well. Therefore, dileptons...
Energy-energy correlators (EECs) have manifested an important probe to unveil the properties of QCD splitting in vacuum, which should be modified in the nuclear medium such as the quark-gluon plasma. By employing the recently developed multi-stage jet evolution framework JETSCAPE, we have investigated the nuclear modification of EECs of inclusive jets in heavy-ion collisions. We find EECs are...
Charm quarks produced in the initial stages of relativistic heavy-ion collisions serve as crucial probes of the produced medium, including the pre-equilibrium and hydrodynamic stages of the evolution. We simulate relativistic heavy-ion collisions using a hybrid method that integrates a fluctuating IP-Glasma initial state with subsequent viscous hydrodynamics. Utilizing the MARTINI event...
High-energy proton-nucleus (pA) collisions have provided intriguing playgrounds for disentangling various cold nuclear matter effects on hadron production. Multiple rescatterings in the cold nuclear target induce many soft gluons that have a long formation time, resulting in the modification of hadron production rates due to fully coherent energy loss (FCEL). Medium-induced FCEL has proven to...
Quarkonium production in high-energy hadronic collisions is sensitive to both perturbative and non-perturbative aspects of QCD calculations. The charmonium production cross section can be split into prompt and non-prompt components, the first corresponding to a direct production of charm (anticharm) quarks, the second originating from the decay of beauty hadrons. The latter is important to...
Measurements of direct photons can provide valuable information on the properties and evolution of the quark-gluon plasma (QGP); from the initial conditions to the pre-equilibrium, QGP, and the hadronic phase. In the ALICE experiment, photons that convert in the detector material are reconstructed down to low momentum using the excellent tracking capabilities. Furthermore, photons are...
The N-Point Energy correlator (ENC) is a jet substructure observable formed out of the distribution of angular distances between all particle groups of N constituents in a jet weighted by their energy product. This observable approximately separates non-perturbative and perturbative effects into the angular scales at which they dominate, reflecting a uniform distribution of hadrons at small...
Measurements at RHIC and the LHC show strongly enhanced inclusive hadron baryon-to-meson yield ratios at intermediate transverse momenta ($p_{\rm{T}}$) in high-energy nuclear collisions compared to $p$+$p$ baseline. This enhancement is attributed to strong hydrodynamic flow and parton recombination in the Quark-Gluon Plasma (QGP). Jet probes have been used extensively to gain insights into...
The nuclear modification of quarkonium state production is one of the smoking gun evidence of the deconfined QCD medium production in nuclear collisions. However, this modification does not solely originate from the medium dissociation but rather is a collection of effects from initial to final states. To better understand the interplay of these effects nowadays, the production relation of...
Photons, both real and virtual, are one of the cleanest probes of high-density partonic matter produced in relativistic heavy-ion collisions as they carry unmodified information about the evolution of the system.
Leveraging the versatility of RHIC, PHENIX has measured low momentum direct photons across different collision systems ranging from $p$+$p$ to Au+Au. An excess of direct photons,...
Jet substructure measurements in heavy-ion collisions provide constraints on jet quenching and the medium response in the QGP. Though there has been remarkable progress in inclusive-charged-hadron jet substructure measurements, understanding the identified particle composition of jets and their modification in heavy-ion collisions remains elusive. Jet quenching models predict that the jet...
Energy correlators have been proposed as a new approach to jet substructure in proton-proton and heavy-ion collisions. In this work, we extend our previous calculations of the two-point energy correlator of heavy-ion gamma-tagged jets to include several effects essential for understanding the behavior of this observable in inclusive heavy-ion jets measurements. Through a semi-analytic...
Using an open quantum system EFT approach we derive a factorization formula for the cross-section of inclusive jet production in heavy ion collisions as a series with an increasing number of independently radiating subject functions resolved by the Quark Gluon Plasma medium, convolved with perturbative matching coefficients. In a strongly coupled system, each term in this series is a distinct...
Polarization is a key observable to study the quarkonium production mechanism in elementary hadronic collisions. Its very small value measured at the LHC challenges the commonly-used theoretical models and it still represents a major standing issue in the field. In nuclear collisions, heavy quarks are produced at the initial stage collisions, on a time scale shorter than the QGP formation...
Measurements of hard probes in $e^{+}e^{-}$ collision data are essential components of parallel studies of hard probes in proton-proton and heavy-ion collisions as $e^{+}e^{-}$ collisions offer a true reference for such systems free from any hadronic initial state effects. Recently, one class of hard-probe observables that has seen a resurgence of interest for studying vacuum QCD are the...
The production of hadrons containing charm and beauty quarks has been extensively studied in hadronic collisions, improving the understanding of the hadronisation mechanisms. One aspect of the transition of the heavy quark to the final-state hadron not yet settled regards the spin properties of particles produced in the quark hadronisation. In proton–proton (pp) collisions, the observation of...
Electromagnetic probes are a unique tool for studying the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. Dielectron pairs are emitted during the entire evolution of the medium created in such collisions, allowing the extraction of the real direct photon fraction at vanishing mass, providing access to thermal radiation from the early hot...
The projected N-point Energy Correlators (ENCs) are a novel tool to probe jet substructure in hadronic collisions by exploring the energy flow within jets. Defined as the energy-weighted correlations of $N$ tracks as a function of their angular separation, these correlators reveal the multiscale nature of jets. Jet evolution from perturbative, hard-scattered partons to non-perturbative sprays...
Ultrarelativistic heavy-ion collisions generate a powerful electromagnetic field that produces photonuclear reactions. Recently, coherent $J/\psi$ photoproduction has been observed in nucleus–nucleus (A–A) collisions with nuclear overlap, based on the measurement of an excess of $J/\psi$ production with respect to hadron-production expectations at very low $p_{\rm T}$. In this context, a...
A path length asymmetry along impact parameter direction ($x$) exists for hard probes in heavy-ion collisions at finite rapidity, as the Quark Gluon Plasma (QGP) bulk is tilted in reaction plane, while the hard scattering profile is not~\cite{ref1}. Jet $v_1$ and $\langle p_x \rangle$ measurements provide access to path length dependent energy loss of partons in the QGP. Such a measurement has...
High energy partons are known to lose energy when passing through the hot and dense medium produced in heavy ion collisions. This energy loss is expected to depend on the mass of the fragmenting parton. For light partons, energy loss via gluon bremsstrahlung is expected to dominate, while for heavy-quarks, collisional energy loss may play a more important role. Comparisons between the...
A new apparatus, NA60+, is proposed for measuring muon pairs in the center-of-mass region from 5 to 17 GeV at CERN SPS in a variety of collisional systems from Pb+Pb and down to p+Be. The physics scope of the new detector will cover topics from the measurement of thermal radiation coming from the hot and dense medium to chiral symmetry restoration, strangeness, and charm production.
The...
High-energy jets are produced by the fragmentation of partons (quarks and gluons) that underwent hard scattering in the early stages of a collision. For quite a number of years, jets have been successfully used to probe the properties of the special form of matter, the quark gluon plasma (QGP), formed in high-energy heavy ion collisions. One of the most recognized signatures of the QGP, the...
The intriguing phenomena emerging in the high-density quantum chromodynamics (QCD) matter are being widely studied in the heavy ion program at the LHC and will be understood more deeply during the high-luminosity LHC (HL-LHC) era. The CMS experiment is under the Phase 2 upgrade towards the HL-LHC era. Among others, a new timing detector is proposed with its timing resolution for minimum...
Charmonium production in hadronic collisions is an important experimen-
tal observable that sheds light on the heavy quark interaction with the nuclear medium. While the bound quarkonium states undergo dissociation and recombination in PbPb collisions, in pPb collisions they can experience a combination of initial and final state effects such as shadowing and comover breakup. A full...
Owing to its spectrometer acceptance, complementary to the other LHC ex-
periments, and to its excellent tracking and particle identification, LHCb has
been performing since the LHC Run2 a unique heavy-ion programme. By ex-
ploiting instead the injection of gases in the LHC accelerator beam-pipe, LHCb
has been simultaneously acquiring data in fixed-target mode. The sum of the
two...
We study the effect of the early stage of heavy-ion collisions on the transport of heavy quarks, by extracting two-particle correlations and nuclear modification factor [1]. We perform numerical simulations for both the temporal evolution of the initial state Glasma fields and the propagation of classical test particles in these background fields [2].
Firstly, we simulate how...
In the last decade, hadron spectroscopy has unveiled a wealth of states that
do not have the properties expected of particles composed of 2 or 3 valence
quarks. Foremost among these is the X(3872), which is thought to contain
a ccbar pair plus two light quarks. In heavy ion collisions, these multiquark
states are especially sensitive to a range of phenomena that can suppress or
enhance...
To date, holographic calculations have provided separate descriptions for the rates of energy loss either for ultrarelativistic massless quarks and gluons or for infinitely massive quarks in strongly coupled plasma, with the latter calculation valid for $\sqrt{\gamma} < M/( \sqrt{\lambda}T)$, where $\gamma$ is the Lorentz boost factor for a heavy quark with velocity $v$ and mass $M$ moving...
We report new ALICE measurements of inclusive charged-particle jet yield suppression $R_\mathrm{AA}$ and jet azimuthal anisotropy $v_2$ in Pb--Pb collisions. The $R_\mathrm{AA}$ measurement is carried out in central Pb--Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV, with uncorrelated background corrected statistically using an event-mixing approach. The charged-particle jet $R_\mathrm{AA}$...
To compare collider experiments, measured data must be corrected for detector distortions through a process known as unfolding. As measurements become more sophisticated, the need for higher-dimensional unfolding increases, but traditional techniques have limitations. To address this, machine learning-based unfolding methods were recently introduced. In this work, we introduce OmniFoldHI, an...
The ALICE Collaboration has proposed a completely new apparatus, ALICE 3, for the LHC Runs 5 and 6 (LoI, arXiv:2211.02491). The detector consists of a large pixel-based tracking system covering eight units of pseudorapidity, complemented by multiple systems for particle identification, including silicon time-of-flight layers, a ring-imaging Cherenkov detector, a muon identification system, and...
The substantial masses of charm hadrons make them exceptional tools for the study of quantum chromodynamics (QCD), providing quantitative insights into QCD dynamics for systems having high parton densities and/or temperatures. Final-state effects, including interactions with co-moving particles or quark coalescence, may modify the hadronization of heavy quarks. To study these effects, we...
During LHC LS3 (2026-28) ALICE is replacing its innermost three tracking layers by a new detector, "ITS3". It will be based on newly developed wafer-scale monolithic active pixel sensors, which are bent into truly cylindrical layers and held in place by light mechanics made from carbon foam. Unprecedented low values of material budget (0.07% per layer) and closeness to interaction point (19...
Measurements of jets recoiling from a trigger hadron are useful probes of jet quenching, where jets are modified in the presence of a QGP. In particular, the spectrum of jets as a function of the separation angle $\Delta\phi$ is a good indicator of jet quenching effects such as azimuthal broadening. In this talk, we present measurements of this hadron-jet observable in high multiplicity (HM)...
A number of new four-quark states containing from one to four $c$ or $\overline c$ quarks have been observed recently. Many of these new states have been discovered at the LHC. The production of these states via intrinsic charm in the proton is investigated. The tetraquark masses obtained in this approach, agree well with the measured masses. These calculations can provide some insight into...
The FoCal is a high-granularity forward calorimeter to be installed as an ALICE upgrade during the LHC Long Shutdown 3 and take data in Run 4.
It will cover a pseudorapidity interval of $3.2 < \eta < 5.8$, allowing to explore QCD at unprecedented low Bjorken-$x$ of down to $\approx 10^{-6}$ -- a regime where non-linear QCD dynamics are expected to be sizable.
The FoCal consists of a compact...
We investigate $\Lambda_{c}-N$ interaction in the spin singlet channel ($^1S_0$) and the spin triplet coupled channel ($^3S_1-{^3D_1}$) from lattice QCD by using HAL QCD method. We perform the first physical point simulation by employing gauge configurations generated by the HAL Collaboration at $m_{\pi}\simeq137$ MeV, $m_{K}\simeq 502$ MeV, and $a \simeq 0.0844$ fm on $96^4$ lattices...
The recent CMS jet measurement provides new insights into understanding the QCD hard processes in the high-multiplicity limit (with $n>100$ tracks in jet). In this study, we aim to understand the dynamics that gives the broad multiplicity distribution $P(n)$ in the jet and the origin of the high-multiplicity tail. We start with a set of assumptions on the multiplicity distribution coming from...
In recent years, CMOS silicon pixel detectors have seen significant advancements and a widespread usage across various physics fields, allowing for significant improvements of the particle detection technologies. One relevant example is the ALPIDE chip, which is a CMOS Monolithic Active Pixel Sensor developed for the upgrade of the Inner Tracking System of the ALICE experiment at the LHC.
On...
This study focuses on the measurement of b-jet production in pp collisions at 13.6 TeV with the ALICE detector. The accurate identification of b-jets is crucial for understanding heavy-flavour quark production and fragmentation. This analysis concentrates on tagging beauty jets using the secondary-vertex method which excels in identifying long-lived hadrons containing a b quark by analyzing...
Beauty-jets (b-jets) refer to sprays of collimated particles produced from the fragmentation of beauty quarks generated in hard scatterings at collider experiments. Compared to jets produced by the fragmentation of light quarks and gluons, b-jets are characterised by the presence of displaced secondary vertices, due to the decay of beauty hadrons which have a relatively long lifetime ($c\tau...
Modification of jets is a powerful tool to diagnose a quark gluon plasma (QGP) in high-energy heavy-ion collisions. During propagation of partons in a jet through the QGP medium, constituents of the medium acquire high energy and momentum from them and are kicked out to be non-equilibrated partons. These partons are called the recoil partons. Together with how the jet partons radiate energy...
The ITS3 is the future upgrade for the ALICE Inner Tracking System for Run 4 of the LHC. It replaces the three innermost layers with a truly cylindrical design of bent and stitched MAPS sensors, along with material budget as low as 0.07% $X_0$ per layer and less than 40 mW/cm$^2$ power consumption. These improvements increase the pointing resolution by a factor of two, and tracking efficiency...
Bottomonium production is sensitive to both the structure of nucleons and
the interactions of b quarks with the nuclear media produced in heavy-ion colli-
sions. The LHCb detector’s forward geometry allows for studying bottomonium
production in a unique kinematic regime. Recent LHCb studies of bottomonium
production will be presented, including measurements sensitive to final-state...
Heavy-flavour jets, defined as collimated bunches of hadrons originating from the fragmentation of heavy-flavour quarks such as beauty quarks, are produced in high-energy collisions. The cross section of heavy-flavour quark production can be calculated using perturbative quantum chromodynamics (pQCD) due to their generation through high momentum transfer at low $p_{T}$, attributed to their...
Quarkonium production is considered one of the golden probes of quark-gluon plasma (QGP) formation in heavy-ion collisions. Quarkonium production in small collision systems is also important for investigating production mechanisms and providing a reference for heavy-ion collisions. Charmonium, a bound state of charm and anti-charm quark pairs, has its production mechanism described by...
Heavy-ion collisions have been used to study quark-gluon plasma (QGP) and can be used to study strong electromagnetic (EM) fields. Because the EM fields penetrate the QGP medium, their evolutions are coupled together. In turn, probes like the flow of direct photons and charged particles will be modified by the coupling [1, 2]. Usually, the EM field modifications are considered separately from...
Measurements of the relative production of strange hadrons in high-energy hadronic collisions have proven to be an important tool for understanding hadronization. In particular, it has been shown that strangeness is produced more abundantly in high-multiplicity pp and p-Pb collisions at the LHC, a phenomenon known as "strangeness enhancement" that has sparked significant interest in both the...
Electron-positron pairs with low invariant mass are a versatile tool for studying the properties of the quark-gluon plasma created in ultra-relativistic heavy-ion collisions. Due to their electromagnetic nature and the variety of sources that can produce such pairs, they allow to study the whole space-time evolution of the system undistorted by strong final-state interactions. However, a...
In high-energy proton-proton (pp) collisions, the study of dimuon production provides crucial insights into particle production mechanisms and can serve as a baseline for the study of the properties of the quark-gluon plasma (QGP). In particular, the low (below the phi mass) and intermediate (between the phi and the J/psi) invariant mass regions are of interest for measurements of vector...
Nonextensive statistics [1] has attracted attention as a description of an extended range of hadronic particle spectra in nuclear collisions. In this study, we consider a relativistic hydrodynamic model with Tsallis statistics [2] to estimate direct photons, which are a prominent observable for understanding the properties of the QCD matter. Nonextensivity enters the model via the modification...
Recent measurement on nuclear modification of $B_c$ mesons at the LHC serves as a novel probe of heavy quark interaction with the QGP in relativistic heavy-ion collisions. Within a linear Boltzmann transport model that incorporates both Yukawa (perturbative) and string (non-perturbative) interactions between heavy quarks and the QGP, we study dissociation and regeneration of $B_c$ in these...
Energy-energy correlators (EECs) have been proposed to study the structure of energy flow within jets. These functions are defined as the energy-weighted cross-section of particle pairs inside jets. The correlation as a function of pair distance and jet transverse momentum shows a clear separation between the perturbative and non-perturbative regimes, where one can probe the dynamics of the...
High-multiplicity triggered events produced in pp collisions at $\sqrt{s}=13$ TeV collected by ALICE detector are analyzed to study the mean transverse momentum ($p_{\rm T}$) fluctuations. The study is inspired by the idea that non-monotonic changes in $p_{\rm T}$ correlations vary with energy and, if observed, may be taken as an indicator for the {\footnotesize QGP} formation. The finding...
Understanding the nonperturbative process of hadronization is a persistent
goal in experimental studies of QCD. Since heavy quark production is suppressed
at the hadronization scale, heavy-flavor hadrons offer a high-precision probe of
the connection between theoretical calculations and experimental final states.
Jets containing different flavors of these heavy hadrons, reconstructed...
Experimental data on a wide range of jet observables measured in heavy ion collisions provide a rich picture of the modification of jets as perturbative probes and of the properties of the created quark-gluon plasma. However, their interpretation is often limited by the assumptions of specific quenching models, and it remains a challenge to establish model-independent statements about the...
In 2022, the ALICE Collaboration commenced Run 3 with upgrades to the Inner Tracking System (ITS2) and the Time Projection Chamber (TPC), both pivotal for probing rare phenomena with unprecedented precision. The upgrades to ITS2 enable higher tracking resolution, while the improvements to the TPC allow for continuous readout, significantly boosting data acquisition and resolution. Using these...
In high-energy hadronic collisions, heavy flavors are a sensitive tool for studying the physics of strong interactions. In particular, heavy-flavor measurements in proton-proton (pp) collisions are most suitable to test QCD calculations and serve as baseline for studies in heavy-ion collisions. One measurement particularly sensitive to the production mechanism of heavy quarks is the azimuthal...
We use the parametric approach to analyze jet suppression measured using the nuclear modification factor of inclusive jets, b-jets, and jets from gamma-jet events. With minimum model assumptions, we quantify the magnitude of the average energy loss, its pt-dependence, intial parton-mass dependence, and flavor dependence. Further, we quantify the impact of fluctuations in the energy loss and...
Particle correlations are powerful tools for studying quantum chromodynam-
ics in hadron collisions. In heavy-ion collisions, azimuthal angular correlations
probe collective phenomena in hot, dense, nuclear media, such as QGP. Angular
correlations in small collision systems could point to QGP production or poten-
tial initial-state correlations. The LHCb experiment has the unique ability...
We propose a novel approach to probe primordial inhomogeneity in hot and dense matter which could be realized in noncentral heavy-ion collisions. We discuss the possibility of clustered sub-structures along the axis parallel to the magnetic field. Even if the magnetic field is short-lived, the pseudo-one-dimensional nature in the early dynamics can induce the inhomogeneity which could remain...
In this contribution, recent results for helium identification and produc-
tion at LHCb will be discussed. From √sNN = 13 TeV pp collisions, a nearly
background-free sample of more than 105 helium candidates is identified by their
ionisation losses in the silicon detectors, combined with information from the
calorimeter, the muon chambers and the RICH detector. Combined with the...
The Forward Calorimeter (FoCal) detector is scheduled for installing in the ALICE experiment for the LHC-Run4 upgrade (2029-2032).
The FoCal consists of the FoCal-E (Electromagnetic Calorimeter) and the FoCal-H (Hadronic Calorimeter). The FoCal-E is a detector based on a Si sensor and tungsten to measure direct photons at forward rapidity.
For the readout, each Si pad hosts the HGCROC2...
In heavy-ion collisions, jets formed from hard-scattered partons experience an overall energy loss and have a modified internal structure compared to vacuum jets. These modifications are a result of the interactions between the energetic partons in a jet shower and the strongly coupled quark-gluon plasma (QGP). As the jet traverses the QGP, it loses momentum to the medium, which in turn...
The phenomena of Jet Quenching, a key signature of the Quark-Gluon Plasma (QGP) formed in Heavy-Ion (HI) collisions, provides a window of insight into the properties of this primordial liquid. In this study, we rigorously evaluate the discriminating power of Energy Flow Networks (EFNs), enhanced with substructure observables, in distinguishing between jets stemming from proton-proton (pp) and...
A collaboration of scientists from LANL, MIT, FNAL, NJIT, ORNL, and GIT, supported by the DOE Office of Science Nuclear Physics AI Machine Learning initiative, is exploring advanced AI technologies to tackle data processing challenges at RHIC and the future EIC. The main objective is to develop a demonstrator for real-time processing of high-rate data streams from sPHENIX experiment tracking...
The sPHENIX collaboration has been taking data since 2023 at the Relativistic Heavy Ion Collider in BNL to study the Quark-Gluon Plasma and cold-QCD. A detector complex consisting of the solenoid magnet, a hadron calorimeter, an electromagnetic calorimeter, a time projection chamber, a MAPS-based vertex detector, and the intermediate silicon tracker (INTT). A tracking system formed by the...
Hadronisation is the complex process through which hadrons form from partons. Given its non-perturbative nature, an exact theoretical description is unavailable, necessitating phenomenological assumptions.
In the first part of my presentation, I will discuss novel observables that differentiate between models with distinct hadronisation mechanisms and examine current models limitations....
Experimental observations have measured finite azimuthal anisotropies in small systems produced in pp and pA collisions, even at large pT which may imply the formation of a Quark-Gluon Plasma. In heavy-ion collisions, high-pT azimuthal anisotropies are understood to be generated by the path-length dependent energy loss. However, in small systems, even if a QGP is formed, the medium is so small...
Elliptic flow ($v_{2}$) at high transverse momentum ($p_{T}$) serves as an important hard probe to study the properties of quark-gluon plasma (QGP). The non-zero high-$p_{T}$ $v_{2}$ values observed in experiments are often attributed to the path-length dependence of energy loss in the medium due to the asymmetry in the reaction zone. However, recent findings suggest a potential role for...
The virtual prompt photons are produced at the initial stage of heavy-ion collisions and are sensitive to the extremely strong magnetic field produced in non-central heavy-ion collisions. At LHC energies, this magnetic field can reach intensities of $10^{15}$ - $10^{16}$ T. In the presence of this magnetic field, the dilepton decayed from a virtual photon can be polarized in response to the...
Azimuthal anisotropies of energetic particles produced in heavy-ion collisions are understood as an effect of a geometrical selection bias due to energy loss. In the measured ensemble, particles oriented in the direction in which the medium is shorter are over-represented as compared to those oriented in the direction in which the medium is longer. In this work we present the first...
Measurements of jets that traverse the QGP provide insights into the jet energy loss. Considering jets of various radii can help elucidate how the parton energy is transferred to the medium as well as the medium response. Measurements of the dijet momentum balance and pair nuclear modification factor are presented for anti-kt jets reconstructed with radius R = 0.2, 0.3, 0.5, 0.4, and 0.6,...
Jets are produced by highly virtual quarks and gluons that emerge from initial hard scattering processes and are an important probe of the QCD evolution of the collision. Jet measurements in small systems such as pp are important in order to provide constraints on the parton distribution functions (PDFs) of the proton and the strong coupling constant $\alpha_{s}$. They also test pQCD...
Collisions of heavy nuclei at relativistic energies generate a hot and dense medium, whose microscopic properties can be studied with electromagnetic probes.
Dileptons serve as a unique tool because they do not interact strongly with the surrounding matter and carry undisturbed information about the QCD matter produced in the reaction.
By examining low-mass and low-momentum dileptons, we...
The small-system collisions (p/d/He+A) became of great interest since the finding of the flow of the particles which had been considered as a strong signature of the QGP production. On the hard and EM probes side, those that have been measured to characterize the QGP, such as Jets (or high pT hadrons), heavy flavor hadrons, and direct/thermal photons, have also been measured in the small...
Recent measurements of charm baryon-to-meson production-yield ratio at the LHC have shown a substantial enhancement of charm-baryon production in pp collisions as compared to electron-positron and electron-proton collisions. This evidence currently can be interpreted as a modification of the charm hadronization mechanism in hadronic collisions, disproving the assumption of universality of...
Jet substructure measurements, using the distribution of final state hadrons, provide insight into partonic showers and hadronisation. Observables for such measurements include the transverse momentum ($j_\mathrm{T}$) with respect to the jet axis and longitudinal momentum fraction ($z$) of jet constituent particles. ALICE has recently measured the $j_\mathrm{T}$ distributions of the jet...
Quarkonium production in high-energy proton-proton (pp) collisions is an important tool for studying perturbative and non-perturbative aspects of quantum chromodynamics. Charmonia are bound states of charm and anti-charm quarks and their production process can be factorized into two stages: the heavy quark production and the formation of the bound state. The former happens within initial hard...
The high-intensity beams provided by the CERN SPS in a wide energy interval offer a unique opportunity to investigate the QCD phase diagram at high baryochemical potential $\mu_B$. The NA60+ experiment, proposed for taking data with heavy-ion collisions at the SPS in the next years, has a strong potential for investigating the QCD phase diagram via measurements of electromagnetic probes in a...
Due to multiple scattering with the medium, hard partons can be driven slightly off-shell leading to medium-induced radiation. The BMDPS-Z framework [1], developed within the light cone path integral formalism, has been instrumental in obtaining the medium-induced radiation spectra. This framework was reformulated by Caron-Huot and Gale [2] into a radiation rate and solved numerically for...
Jet quenching phenomenon serves as a crucial signature of the Quark-Gluon Plasma, observed when hard-scattered partons interact with the hot, dense QCD medium created in high-energy heavy-ion collisions. In central heavy-ion collisions, however, distinguishing jets produced by hard scattering from those originating from combinatorial background is largely limited, especially for jets with low...
We study the energy deposition and thermalisation of high-momentum on-
shell partons (minijets) travelling through a non-equilibrium Quark-Gluon Plasma using QCD kinetic theory. For thermal backgrounds, we show that the parton energy first flows to the soft sector by collinear cascade and then isotropises via elastic scatterings. In contrast, the momentum deposition from a minijet reaches the...
Energy-energy correlators (EECs) offer a novel way to study the structure of jets. Defined as the energy-weighted cross section of particle pairs inside jets, the correlation strength as a function of the pair opening angle allows a distinct separation of the perturbative and non-perturbative regimes. The evolution of parton dynamics in jets to their confinement into hadrons can be studied. We...
The purpose of this study is to elucidate the parton energy loss mechanism depending on path-length within the quark-gluon plasma (QGP) medium. In relativistic heavy ion collision experiments, it is difficult to directly observe the QGP because of its short life time and small size. Detecting a high momentum parton which passes through the QGP provide information of the QGP properties via the...
In this work, we perform computations of inclusive jet and semi-inclusive jet-hadron cross sections for minimum-bias oxygen-oxygen collisions. We compute the no-quenching baseline for the jet nuclear modification factor $R_{AA}$ and jet-, and hadron-triggered semi-inclusive nuclear modification factors $I_{AA}$. We do this with state-of-the-art nuclear parton distribution functions, NLO matrix...
Due to the longer relaxation time of heavy quarks compared to light quarks in the quark-gluon plasma, the non-equilibrium information is expected to be retained in the final momentum distribution of heavy flavors, making them suitable probes of the strongly interacting system. Using the Gribov-Zwanziger prescription to model the infrared behavior of QCD, we study the momentum diffusion...
Generative AI that is data-driven and self-supervising has shown significant potential to transform both science and industry. In this talk, we present two novel applications of generative AI in heavy ion experiments.
- The first application involves full-detector, whole-event simulation of heavy ion collisions using denoising diffusion probabilistic models (DDPMs). Our studies [in...
The production of spectator neutrons depends sensitively on the distribution of neutrons within a nucleus. In this talk we describe a relatively complete model that takes into account clusters forming among the spectators (charged or uncharged), the decay of such clusters using the Gemini code and lastly secondary neutrons produced by particpant nucleons. With this model we calibrate our...
Top quarks, the heaviest elementary particles carrying colour charges, are considered to be attractive candidates for probing the quark-gluon plasma pro- duced in relativistic lead-lead collisions. In proton-lead collisions, top-quark production is expected to be sensitive to nuclear modifications of parton distri- bution functions at high Bjorken-x values. In Run 2, the ATLAS experiment...
Jets originating from hard-scattered partons in the early stages of heavy-ion collisions travel through the Quark Gluon Plasma (QGP) and are modified or quenched relative to a $p$+$p$ collision baseline. Moments of the jet's transverse momentum ($p_{\rm T}$) profile in the $\eta-\phi$ plane relative to the jet-axis are an important class of jet substructure observables to study in medium...
The NA60+ experiment, proposed for data taking from 2029, aims at studying the high $\mu_{\rm B}$ region of the QCD phase space diagram. It will make use of the high intensity of CERN SPS beams, and detect rare probes via a beam-energy scan with Pb-Pb and p-A collisions in the interval $6.3 <\sqrt{s_{\rm {NN}}} < 17.3$ GeV.
In this talk, we will focus on the prospects for measurements of...
Photons and correlated electron-positron pairs (dielectrons) are the ideal probes to study the properties of the medium created in relativistic heavy-ion collisions. They are produced in all stages of the collision and leave the system with no loss of information as they do not interact strongly with the medium. However, at LHC energies, the thermal dielectrons emitted in the early stages of...
The sPHENIX experiment has been taking data since 2023 at the Relativistic Heavy Ion Collider(RHIC) at Brookhaven National Laboratory, USA. We aim to study the properties of the Quark-Gluon Plasma.
The INTT consists of two cylindrical layers of silicon detectors that can precisely measure the passage positions of charged particles. By using the collision point (vertex) of ions and the...
The measurement of dijets in proton-lead collisions at the LHC provides unique possibilities to investigate both nuclear and nucleon initial state effects as a function of the parton scattering kinematics. In particular, color fluctuations can significantly change the average interaction strength of the proton, biasing both the event activity and the number of wounded nucleons in the Pb...
Comparisons of jet production in Pb--Pb collisions compared to pp collisions at LHC energies provide vital information on both jet quenching in the quark-gluon plasma (QGP) and on the medium response to the jet. Jet quenching models with a hydrodynamic medium response predict an enhancement of soft particle production at large angles from the jet axis. However, the mechanism of soft particle...
$N$-point energy correlators are currently attracting both theoretical and experimental interest, as they can be calculated to high order accuracy in perturbation theory and capture many different features contributing to the substructure of jets. The energy-energy correlator (EEC), or two-point correlator, which emphasise the angular structure of the energy flow within jets, allow for a...
Measurements of neutral meson production cross sections in proton-proton (pp) collisions at LHC energies are important as a reference for heavy-ion studies and to test our understanding of QCD. At high transverse momenta ($p_{\rm T}$) where pQCD is applicable these measurements can be used to constrain model calculations. At low momenta, the production rates of neutral mesons are crucial...
In proton-proton (pp) collisions, beauty quarks are produced in hard scattering processes, and therefore their measurements represent an important test of perturbative QCD calculations. Moreover, measurements in pp collisions are needed to provide a baseline for those performed in p--Pb and Pb--Pb collisions. In addition, the production yields as a function of charged-particle multiplicity can...
Jet measurements have long established that as hard scattered partons traverse the quark gluon plasma (QGP) they lose energy resulting in modified jets in A+A collisions relative to p+p collisions with no QGP. Understanding how the jets, their constituents and substructure are modified is crucial to discriminating between energy loss models and extracting the in-medium transport properties....
Quarkonium production is one of the golden probes to study the quark–gluon plasma (QGP). Among many observables, the measurement of azimuthal anisotropies in their production sheds light on the collective behavior of particles in a strongly interacting medium. In particular, the magnitude of the elliptic flow measured at the LHC is interpreted as a signature of the charm-quark thermalization...
Suppression of open heavy flavor quarks and quarkonia in heavy-ion collisions are among the most informative probes of quark-gluon plasma (QGP). Interpreting the full wealth of data obtained from the collision events requires a precise theoretical understanding of the evolution of heavy quarks and quarkonia as they propagate through strongly coupled plasma.
Such calculations require the...
Open charm production is a sensitive probe of both hot and cold nuclear
matter effects. Charm meson production provides strong constraints on nuclear
parton distributions, while charm baryon and strange charm hadron production
can be used to probe strangeness- and baryon-enhancing hot QCD effects, re-
spectively. The LHCb detector is designed to study heavy flavor hadrons at the
LHC,...
In preparation to the LHC Run3, the LHCb gaseous fixed-target, SMOG,
was upgraded to offer higher instantaneous luminosity by up to two orders of
magnitude with respect to Run2, new gases, including non-noble ones such
as hydrogen, and an increased experimental accuracy. Since 2022, LHCb is
working with two independent collision points and as a collider and a fixed-target
experiment...
Strange hadron production provides information about the hadronization
process in high-energy hadron collisions. Strangeness enhancement has been
interpreted as a signature of quark-gluon plasma formation in heavy-ion col-
lisions, and recent observations of strangeness enhancement in small collisions
systems have challenged conventional hadronization models. With its forward
geometry and...
The LHCb detector’s forward geometry provides unprecedented access to
the very low regions of Bjorken x inside the nucleon. LHCb is able to study
charged and neutral light hadron production, as well as relatively rare probes
such as heavy quark. These data provide unique constraints on nuclear parton
distributions. This contribution will discuss recent LHCb measurements sensi-
tive to the...
In heavy-ion collisions, jets can serve as a probe of the hot QCD medium, since they are produced in hard scatterings early in the collision and traverse and interact with the hot medium. Measuring jets at low transverse momentum and large $R$ in the complex environment of central Pb--Pb collisions is a challenging task, due to the large background for the underlying event. In order to be...
In two-particle angular correlation measurements, jets give rise to a near-side peak formed by particles associated with a higher $p_\mathrm{T}$ trigger particle. Measurements of these correlations as a function of pseudorapidity and azimuthal differences are used to extract the centrality and $p_\mathrm{T}$ dependence of the shape of the near-side peak in the $p_\mathrm{T} $ range $3 <...
Quarks and gluons, normally confined within hadrons by strong interactions, are released from the confinement at high temperatures and densities, which is called Quark-Gluon Plasma (QGP). To understand QGP, high-energy heavy ion collision experiment has been conducted in laboratory and research has been carried out to investigate its property. One unknown about QGP is that it reaches thermal...
Charmonia, such as the J/$\psi$ and $\psi$(2S) mesons, are important probes of the quark-gluon plasma (QGP). The measurement of their nuclear modification factor, elliptic and triangular flow can provide strong constraints for the mechanism of in-medium energy loss. In this talk, results on the relative J/$\psi$ and $\psi$(2S) modification, based on the pp and PbPb data collected at...
We present SUBA-Jet, a newly constructed framework for jet and medium production in heavy-ion collisions at ultra-relativistic energies [1]. The framework is developed in a spirit similar to JETSCAPE, and our aim is to simulate the complete dynamics of heavy-ion collisions, with jet and medium hadron production combined.
The development of a jet starts with a seed parton with high virtuality,...
The parton-flavour-dependent properties of the $1\rightarrow2$ splitting processes underpinning parton showers can be uniquely explored using heavy-flavour jets. In this talk, we report a series of charm-tagged jet substructure measurements, using jets tagged with a reconstructed $\rm{D}^{0}$ meson. Using the newly collected Run 3 data, these measurements span a large range of jet transverse...
There is remarkable spin polarization phenomenon in the quark-gluon plasma produced in relativistic heavy ion collisions. The experimental detectable polarization of the vector mesons and spin polarization of the Λ hyperons provides important evidence for this spin polarization phenomenon. So far, there is still sign problem in theories to interpret the experimental results of local...
The Drell-Soding process, non-resonance pair production through photon-nuclear interaction plays a vital role in the exclusive $\pi^{+}\pi^{-}$ pair mass profile description. Among the products of photon-nuclear interactions, the continuum $\pi^{+}\pi^{-}$ pairs are directly produced in addition to decays of photoproduced $\rho^{0}$. Previous measurements and the widely utilized Monte Carlo...
In the context of study of QCD phase diagram, the possibility of inhomogeneous chiral condensed phase in low-temperature and high-density regions has been discussed using the low-energy effective theory of QCD such as the Ginzburg-Landau theory, the Nambu-Jona-Lasinio model and so forth. In such a phase, the lepton production rates may change compared to those of homogeneous chiral condensed...
The early time dynamic which connects the far-from-equilibrium matter created after the high energy collision toward the hydrodynamic regime is still a poorly understood process. We constructed a parton cascade model based on the hadronic transport model SMASH in order to explore this phase since SMASH has been shown to be able to correctly simulate multiparticle interaction in the hadronic...
sPHENIX is a new experiment at the Relativistic Heavy Ion Collider (RHIC), designed with large-acceptance, hermetic EM and hadronic calorimeters to enable qualitatively new measurements of jet probes of the QGP at RHIC. Since jets in heavy ion collisions sit on top of large fluctuating backgrounds, these must be understood to carry out a precision program of jet physics. This talk reports a...
We have calculated all the T-even photon transverse momentum dependent parton distribution functions (TMDs) using light front wave function. For this work, we have considered photon as a Fock-state of quark antiquark pair. All the $9$ T-even TMDs have been presented in the overlap and explicit form of light front wave function. We have found that our result arecoming similar to basic light...
In this talk we discuss using the X-SCAPE Monte Carlo event generator and Hybrid Hadronization to simulate particle production in a large variety of collision systems. New capabilities have been added to X-SCAPE to calculate deep inelastic scattering in $e+p$ collisions. Hybrid Hadronization combines quark recombination, applicable when distances between partons in phase space are small, and...
Partons traversing the hot and dense medium of deconfined color charges produced in collisions of heavy nuclei are expected to lose their energy primar- ily through medium-induced gluon bremsstrahlung. As a result, the amount of induced energy loss is expected to depend on the QCD color charge carried by the parton, i.e. depend on whether it is a quark- or a gluon-initiated jet. In this talk,...
Ultra-strong electromagnetic field in relativistic heavy-ion collisions could be quantized as a large flux of linearly polarized quasi-real photons. These photons can interact with nuclei or nucleons, leading to vector meson production ($\gamma + A \rightarrow V + A$). Notably, azimuthal asymmetries between the pair momentum and the daughter momentum could arise from the linear polarization...
This talk presents a comprehensive study of isolated prompt photon production in pp, p--Pb and Pb--Pb collisions by ALICE, including new analyses which elucidate the low-$x$ structure of matter and the impact of fragmentation photons on the prompt photon cross section. The first measurement of the prompt photon-nuclear modification factor $R_{\text{pA}}$ in p--Pb collisions at $\sqrt{s_{\rm...
The mass of heavy quarks modifies the radiation pattern of heavy-quark jets in comparison to their light quark counterparts, since the heavy quark mass effectively regularizes the soft and collinear divergences that would normally dominate the partonic cascade formation. This leads to the depletion of collinear gluon emissions relative to the heavy quark, an effect known as the dead cone...
Electroweak W and Z bosons, produced in hard-scattering processes at the early stage of hadronic collisions, are excellent probes of their initial state. The W and Z measurements in pp collisions represent a stringent test of perturbative QCD calculations, and provide important input for the determination of parton distribution functions (PDFs). In p-Pb and Pb-Pb collisions, these measurements...
Hard-scattered partons traversing the medium produced in heavy-ion colli- sions lose energy by interacting with the medium. Simultaneously, the medium is modified in this interaction, exchanging energy and momentum with the parton. A typical modification of the medium in this process includes an enhancement of the medium particles in the direction of the parton (the so-called wake) and a...
Ultra-peripheral collisions provide a unique environment to study pomeron-
and photon-induced reactions with heavy nuclei. These interactions can produce
a wide range of final state particles, from light vector mesons to heavy quarko-
nia, and probe potentially exotic phenomena. LHCb’s particle ID capabilities
provide unique opportunities to study hadronic final states in...
The substructure of bottom quark jets is of substantial interest, both in vacuum and in medium, in terms of understanding radiation emitted from heavy quarks. Unfortunately, the decays of b hadrons, which are typically cascading, obscure the parton level branching, by filling the radiative dead cone. To circumvent this, one may study exclusive b-hadron decays, but one then sacrifices the vast...
The strong electromagnetic fields associated with heavy-ions at the LHC lead to large cross sections for exclusive photoproduction of vector mesons in ultra-peripheral collisions (UPCs). Photoproduction of charmonium probes the distribution of gluons in the target nucleus. Earlier studies of charmonium photoproduction have focussed on measuring the production cross sections and rapidity...
We begin by using Hybrid Model calculations to reproduce experimental results published by ATLAS in 2023 on $R_{AA}$ for $R=1$ jets in Pb+Pb collisions. These jets are identified via first reconstructing anti-$k_t$ $R=0.2$ subjets and then reclustering them. Following ATLAS, we investigate how $R_{AA}$ for these large-radius jets depends on the angle between the two subjets involved in the...
The study of ultra-peripheral collisions (UPCs) has so far mostly focussed on exclusive production of a single vector meson or a dilepton pair, while the nuclei have remained in their ground state or have only been slightly excited. There is, however, also the possibility to study a more general class of UPCs involving a photonuclear interaction where the target nucleus is broken up, gamma+A...
The quenching of light and heavy flavor hadrons in relativistic heavy-ion collisions probes the color and flavor dependences of parton energy loss through a color-deconfined quark-gluon plasma (QGP), and thus offers an important test of QCD-based calculation at extremely high density and temperature. By combining a next-to-leading order perturbative QCD calculation of parton production, a...
Particles associated with the jet will be deflected from their initial direction due to the scatterings with the thermal partons flowing in the QGP fluid. Such deflections depend on the energy of the jet, the local energy gradient, and the local flow velocity. In general, the soft particles will drift towards the direction of the flowing medium, away from the center of the jet cone where the...
Effects such as medium-induced radiation and medium response could contribute to the enhancement of low-$p_\mathrm{T}$ particles. The low $p_\mathrm{T}$ particles are shown to be essential in the energy-momentum balance of dijet and photon/Z-jets. In this presentation, we utilize the Z boson reconstructed within the dimuon channel, which does not interact with the quark-gluon plasma (QGP)...
The evolution of jets showers in high energy nuclear collisions is influenced in various ways by the presence of a surrounding medium. The interaction of jet constituents with the medium can happen during the partonic stage of the jet, during hadronization, and even during its hadronic stage. We will demonstrate how flow of the ambient medium in a direction transverse to the jet can introduce...
The study of heavy-quark photoproduction in ultraperipheral collisions (UPC) of heavy ions provides a new tool to characterize the production mechanisms of heavy-quarks with high experimental and theoretical control, and constrain the properties of nuclear matter in a wide region of the ($x$, $Q^2$) with perturbatively-produced hard probes. In this talk, we will present the first measurement...
Within the framework of leading power factorization formalism of nonrelativistic quantum chromodynamics, we calculate the jet fragmentation function for $J/\psi$ production in proton-proton (pp) collisions ranging from $\sqrt{s}=500$ GeV to $13$ TeV. The reasonable agreements between theory and experimental data indicate that $J/\psi$ production within a jet is mainly dominated by gluon...
Energy correlators inside of high energy jets provide a powerful tool to image the intrinsic and emergent angular scales of QCD. They have the potential to provide unprecedented insight on the interplay between vacuum scales inside of a jet and its medium modification. However, as with traditional jet substructure, experimentally these correlators will mix different angular features associated...
In ultra-relativistic heavy-ion collisions, copious rates of γγ processes are expected through the interaction of the large electromagnetic fields of the nu- clei, which enables the production of particles such as leptons, virtual axion-like particle, magnetic monopoles, or can lead to light-by-light scattering via loop diagrams, and even higher-order processes where additional photons are ex-...
In this talk, we present a novel extension to the theory of jet quenching, incorporating the effect of both the flow and anisotropy of matter undergoing hydrodynamic evolution. The interplay between these two vectorial magnitudes results in a significant rescaling of fundamental objects, like the jet quenching parameter. Depending on the relative direction of the two vectors, the energy loss...
In heavy ion ultraperipheral collisions (UPCs), the production of $\rm{J}/\psi$ through photon-nuclear interactions is of particular interest, as its cross section is highly sensitive to the properties of gluons within heavy nuclei. Photons can interact with the nucleus coherently (involving the entire nucleus) or incoherently (with individual nucleons). While coherent interactions probe the...
We derive the leading modifications of the transverse momentum broadening and medium-induced gluon spectrum in anisotropic flowing matter for the case of a heavy leading quark. We show that the broadening and radiation patterns develop new directional dependence due to an interplay of the quark mass and matter flow, absent in the massless case. In turn, the interplay of the medium anisotropy...
Understanding the hadronization mechanism in Quantum Chromodynamics (QCD) remains a significant challenge due to its non-perturbative nature. Hadronization is typically described via phenomenological models in Monte Carlo event generators (such as PYTHIA and HERWIG), whose parameters need to be tuned to data. This work leverages jet substructure to probe underlying features of these...
Photonuclear interactions in ultraperipheral heavy-ion collisions can be used to improve our understanding of gluonic nuclear structure In particular, coherent photoproduction of vector mesons are processes sensitive to the gluon distribution of the target nucleus, especially at small values of the parton momentum fraction x, where the onset of gluon saturation effects is expected. A...
The states of matter produced in the early stage of heavy ion collisions can be highly anisotropic. If such a feature is sufficiently pronounced, one should expect the final particle distribution inside jets to reflect it in the form of non-trivial angle correlations. In this talk, we discuss a first step in exploring such correlations by studying how a $q\bar q$ state branching from an...
In the last years, several exotic hadrons have been observed in the charm sector; such particles cannot be interpreted as conventional baryons or mesons and are thought to be either quark bags or molecular states. To unveil their nature, it is crucial to experimentally constrain the strong force that governs the interaction between the charm hadrons and other hadrons, for instance, by...
In relativistic heavy ion collisions, the charged ions produce an intense flux of equivalent photons. Thus, photon-induced processes are the dominant inter- action mechanism when the colliding nuclei have a transverse separation larger than the nuclear diameter. In these ultra-peripheral collisions (UPCs), the pho- ton provides a clean, energetic probe of the partonic structure of the nucleus,...
$N$-point energy correlators are currently attracting both theoretical and experimental interest, as they can be calculated to high order accuracy in perturbation theory and capture many different features contributing to the substructure of jets. The energy-energy correlator (EEC), or two-point correlator, which emphasise the angular structure of the energy flow within jets, allow for a...
Suppression of open heavy flavor quarks and quarkonia in heavy-ion collisions are among the most informative probes of quark-gluon plasma (QGP). Interpreting the full wealth of data obtained from the collision events requires a precise theoretical understanding of the evolution of heavy quarks and quarkonia as they propagate through strongly coupled plasma.
Such calculations require the...
As electromagnetic probes, photons have the advantage of escaping unimpeded from their emission source. Consequently, photons can carry valuable information about the properties and dynamics of the hot QCD medium created in heavy-ion collisions. Particularly, the transverse momentum distribution of direct virtual photons emitted from the hot QCD medium exhibits sensitivity to the system...
The present work addresses the puzzle related to the observation of collective flow in collisions of small systems (which indicates the presence of a medium even in such collisions) and the absence of jet quenching in such systems (which would not be expected if jets are traversing a medium). This study has been done using the JEWEL event generator with a ``brick"-like medium. This simplified...
The sPHENIX collaboration has been taking data since 2023 at the Relativistic Heavy Ion Collider in BNL to study the Quark-Gluon Plasma and cold-QCD. A detector complex consisting of the solenoid magnet, a hadron calorimeter, an electromagnetic calorimeter, a time projection chamber, a MAPS-based vertex detector, and the intermediate silicon tracker (INTT). A tracking system formed by the...
Energy correlators characterize the energy flow in scattering events produced at colliders. They have recently received a lot of interest both theoretically and experimentally, and a range of promising applications have been proposed, including the study of hadronization, as a potential probe for identifying the emergent scales in a Quark-Gluon Plasma as well as studying the deadcone effect....
We employ the AdS/CFT correspondence to study the jet quenching effect in Quark-gluon plasma in heavy-ion collisions ubder magnetic field and chemical potential. The nuclear modification factor $R_{AA}$ and elliptic flow parameter $v_{2}$ are studied in different-centrality collisions at RHIC and LHC. Our numerical results agree with data. Magnetic field and chemical potential of the medium...
Color coherence plays a crucial role in the description of jet evolution in vacuum. Stimulated gluon emission suffered by energetic jets traversing deconfined QCD matter is also affected by color coherence effects. Through multiple soft scatterings with the medium constituents, an antenna will lose its color correlation, causing its legs to behave as independent emitters after the so-called...
There must be electromagnetic fields created during high-energy heavy-ion collisions. However, as the quark-gluon plasma (QGP) starts to evolve hydrodynamically (around 1fm/c), these fields become very likely weak comparing to the energy scales of the strong interaction. In this talk, I will introduce the weak magnetic effect in the standard hydrodynamical formulation, which emerges in QGP...
Energy-Energy correlators (EEC) have been identified as robust observables for quantifying the properties of quark gluon plasma (QGP) created in high energy nuclear collision experiments. Despite the remarkable precision obtained in proton-proton (pp) collision by utilizing the Effective Field Theory (EFT) framework, comparable accuracy in heavy-ion collisions (HIC) remains elusive. In this...
The PHENIX experiment pioneered measurements of nuclear modification factor of neutral pions and photons, providing strong evidence of the formation of Quark-Gluon Plasma (QGP) in Au+Au collisions at RHIC. In 2014 large amount of 200 GeV Au+Au data were collected, vastly exceeding the statistics of all similar data taken earlier.
This makes it possible to extend the transverse momentum...
The new sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is currently in its inaugural physics run with proton-proton and gold-gold collisions. sPHENIX is a large acceptance and high rate experiment, equipped with hermetic electromagnetic and hadronic calorimeter systems, the latter of which is unique at RHIC. These systems, along with an efficient trigger system, enable...
A maximum is unexpectedly shown at intermediate p_T for the baryon-to-meson yield ratio of a function of transverse momentum p_T both in p+p similar to the case in A+A. It has been widely discussed. To understand such production mechanisms in small systems, ALCIE proposes using jet constraints to separate the particles produced in hard processes from those produced in the underlying event in...
The PHENIX collaboration has measured jet cross-section and jet substructure in p+p collisions at $\sqrt{s}=~200 GeV$. Jets are reconstructed from charged particle tracks and electromagnetic calorimeter clusters using the anti-$k_T$ algorithm with a jet radius $R~=~0.3$, transverse momentum within $8 < p_T < 40~GeV$ and pseudorapidity $|\eta| < 0.15$. We will present the jet cross-section,...
We study bottomonium evolution in QGP using an open quantum systems approach. Previous works [1,2] study quarkonia using Lindblad equation in Brownian regime i.e, at zero frequency limit of the medium correlators. Finite frequency effects of the medium are important [3,4] for quarkonia dynamics when the binding energy is of the order of temperature (beyond the Brownian regime). We include...
This work presents a phenomenological study on the angle between the Standard and the Winner-Take-All (WTA) jet axes ($\Delta R$) in high-energy nuclear collisions. Our theoretical results calculated by the LBT model show that the $\Delta R$ distribution in Pb+Pb at $\sqrt{s}=5.02$ TeV is narrower than that in p+p, which agrees well with the recent ALICE measurements. The narrowing of $\Delta...
We present a theoretical study of the medium modifications of the $p_{\rm T}$ balance ($x_{\rm J}$) of dijets in Xe+Xe collisions at $\sqrt{s_{\rm NN}}=5.44$ TeV. The initial production of dijets is carried out by the POWHEG+PYTHIA8 prescription, which matches the next-to-leading order (NLO) QCD matrix elements with the parton shower (PS) effect. The in-medium evolution in nucleus-nucleus...
Heavy quarkonia production is one of the substantial probes to study the properties of the quark-gluon plasma. The observation of the sequential suppression of heavy quarkonia yields in small and large collision systems intensely stimulates relevant theoretical developments. The SHINCHON, which stands for Simulation for Heavy IoN Collision with Heavy-quark and ONia, employs a theoretical...
The new sPHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is currently in its inaugural physics run with proton-proton and gold-gold collisions. sPHENIX is equipped with a state-of-the-art four-component tracking system, featuring two silicon vertex trackers based on Monolithic Active Pixel Sensors (MAPS) and silicon strip sensors, respectively, a compact Time Projection...
We present the first theoretical investigation of Fox-Wolfram moments (FWMs) for multi-jet productions in relativistic heavy ion collisions. In this work jet productions in p+p collisions are computed with a Monte Carlo event generator SHERPA, while the Linear Boltzmann Transport model is utilized to simulate the multiple scattering of energetic partons in the hot and desne QCD matter. The...
The question whether or not small systems form a QGP has remained unresolved for the past decade. In the soft sector, hydrodynamic modelling can describe experimental data, but with large error bars. In the near future, collisions of O-16 nuclei will provide new experimental data in a system which is theoretically under more control than for example pPb. However, theoretical uncertainties...
The modifications imprinted on jets due to their interaction with QGP are assessed by comparing samples of jets produced in AA collisions and pp collisions. The standard procedure compares jets with the same reconstructed transverse momentum ($p_T$), ignoring the effect of $p_T$ migration and thus confounding QGP induced modifications by comparing jets that started out differently. Brewer et...
