Conveners
Heavy Ions
- Manuel Colocci (University and INFN, Bologna (IT))
Heavy Ions
- Martin Spousta (Charles University in Prague)
Heavy Ions
- Yvonne Pachmayer (University of Heidelberg)
Heavy Ions
- Yen-Jie Lee (Massachusetts Institute of Technology)
Heavy Ions
- Yen-Jie Lee (Massachusetts Institute of Technology)
Heavy Ions
- Giulia Manca (Istituto Nazionale di Fisica Nucleare)
Heavy Ions
- Giulia Manca (Istituto Nazionale di Fisica Nucleare)
Heavy Ions
- Yvonne Pachmayer (University of Heidelberg)
Heavy Ions
- Manuel Colocci (University and INFN, Bologna (IT))
Heavy Ions
- Martin Spousta (Charles University in Prague)
ALICE is the experiment at the LHC specifically designed to study the properties of the quark-gluon plasma (QGP), a deconfined state of matter created in ultrarelativistic heavy-ion collisions. In this context, light-flavour particle production measurements play a key role, as they can probe statistical hadronization and partonic collectivity. Recent measurements in small collision systems (pp...
One of the main goals of the STAR experiment is to map the QCD phase diagram. The flow harmonics of azimuthal anisotropy ($v_{2}$ and $v_{3}$) of particles are sensitive to the initial dynamics of the medium. The first phase of RHIC Beam Energy Scan Phase-I (BES-I) program demands a precision measurement of $v_{2}$ and $v_{3}$ specifically for $\phi$ mesons and multi-strange hadrons in the low...
Strange and multi-strange hadrons have a small hadronic cross-section compared to light hadrons, making them an excellent probe for understanding the initial stages of relativistic heavy-ion collisions and dynamics of QCD matter. Isobar collisions, $^{96}_{44}$Ru+$^{96}_{44}$Ru and $^{96}_{40}$Zr+$^{96}_{40}$Zr, at $\sqrt{s_{\mathrm {NN}}}$ = 200 GeV have been performed at RHIC. These...
One of the key challenges of hadron physics today is understanding the origin of strangeness enhancement in high-energy hadronic collisions, i.e. the increase of (multi)strange hadron yields relative to non-strange hadron yields with increasing charged-particle multiplicity. In particular, what remains unclear is the relative contribution to this phenomenon from hard and soft QCD processes and...
The LHCb spectrometer has the unique capability to function as a fixed-target experiment by injecting gas into the LHC beampipe while proton or ion beams are circulating. The resulting beam+gas collisions cover an unexplored energy range that is above previous fixed-target experiments, but below the top RHIC energy for AA collisions. Here we present new results on antiproton and charm...
The MoEDAL experiment deployed at IP8 on the LHC ring was the first dedicated search experiment to take data at the LHC in 2010. It was designed to search for Highly Ionizing Particle (HIP) avatars of new physics such as magnetic monopoles, dyons, Q-balls, multiply charged particles, and massive slowly moving charged particles in p-p and heavy-ion collisions. We will report on our most...
In heavy ion collisions, the quark gluon plasma, a new state of matter where quarks and gluons are no longer confined in a nucleus, is created. High energy partons created during the initial collision are observed to lose energy though interactions with the plasma. The details of how the energy is transported away from the partons is not fully understood and of great interest. Jet spectra...
Several new features have been recently observed in high-multiplicity small collision systems that are reminiscent of the observations attributed to the creation of a quark-gluon plasma, QGP, in Pb-Pb collisions. These include long-range angular correlations on the near and away side of two-particle correlations, non-vanishing second order Fourier coefficients in multiparticle cumulant...
In this work, we introduce both gluon and quark degrees of freedom for describing the partonic cascades inside the medium. We present numerical solutions for the set of coupled evolution equations with splitting kernels calculated for the static, exponential and Bjorken expanding media to arrive at medium-modified parton spectra for quark and gluon initiated jets respectively. We discuss novel...
The sPHENIX detector at the BNL Relativistic Heavy Ion Collider (RHIC) is currently under construction and on schedule for first data in early 2023. Built around the BaBar superconducting solenoid, the central detector consists of a silicon pixel vertexer, a silicon strip detector with single event timing resolution, a compact TPC, novel EM calorimetry, and two layers of hadronic calorimetry....
The LHeC and the FCC-he will measure DIS cross sections and the partonic structure of protons and nuclei in an unprecedented range of small $๐ฅ$. In this kinematic region the non-linear dynamics expected in the high energy regime of QCD should be relevant in a region of small coupling. In this talk we will demonstrate the unique capability of these high-energy colliders for unravelling dynamics...
Automated perturbative computations of cross sections for hard processes in asymmetric hadronic/nuclear $A+B$ collisions at the next-to-leading (NLO) order in $\alpha_s$ will offer a wide range of applications, such as more robust predictions for new experimental programs, the phenomenology of heavy-ion collisions, and the interpretation of the LHC and RHIC data. Such a goal can be achieved...
In this contribution the nuclear modification factor ($R_\mathrm{AA}$) of prompt charm hadrons and heavy-flavour hadrons decaying to leptons measured in Pb-Pb collisions at $\sqrt{s_\mathrm{NN}}=5.02$ TeV by the ALICE Collaboration are presented. The measurement of heavy-flavour leptons in Xe-Xe collisions is also discussed. Heavy quarks are a very suitable probe to investigate the...
We report the first measurement of the azimuthal angular correlation between jets and $D^0$ mesons in pp and PbPb collisions. The measurement is performed using jets with $p_\mathrm{T}> 60$ GeV and $D^0$ mesons with $p_\mathrm{T} > 4$ GeV. The azimuthal angle difference between jets and $D^0$ mesons($0<\Delta\phi<\pi$) is sensitive to medium-induced charm diffusion, charm quark energy loss,...
Heavy quarks are primarily produced via initial hard scatterings, and thus carry information about the early stages of the Quark-Gluon Plasma (QGP). Measurements of the azimuthal anisotropy of the final-state heavy flavor hadrons provide information about the initial collision geometry, its fluctuation, and more importantly, the mass dependence of energy loss in QGP. Due to the larger bottom...
In this contribution, the final measurements of the centrality dependence of $R_{\rm AA}$ of non-prompt $\mathrm{D}^0$ and electrons from beauty hadron decays in Pb--Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV will be presented. These measurements provide important constraints to the in-medium mass-dependent energy loss and hadronization of the beauty quark. The integrated non-prompt...
Measurements of jet constituent distributions for light- and heavy flavor jets are used successfully for experimental QCD studies with high energy pp collisions at the LHC. These studies are now extended to explore the flavor dependence of the jet quenching phenomenon. The jet quenching, one of the signatures of the quark-gluon plasma, is well established through experimental measurements at...
Beauty quark is one of the best probes of the Quark Gluon Plasma. Its large mass allows to probe the QGP transport properties in the heavy flavor sector through energy loss and diffusion. However, the hadronization of beauty is not as well understood as that of charm due to the smaller cross-section. Clarifying the hadronization mechanism is crucial for understanding the transport properties...
We have investigated the many-body equations of $D$ and $\bar{B}$ mesons in a thermal medium by applying an effective field theory based on chiral and heavy-quark spin symmetries. Exploiting these symmetries within the kinetic theory, we have derived an off-shell Fokker-Planck equation which incorporates information of the full spectral function of these states.
I will present the latest...
Electromagnetic probes such as photons and dielectrons are a unique tool to study the space-time evolution of the hot and dense matter created in ultra-relativistic heavy-ion collisions. They are produced by a variety of processes during all stages of the collision with negligible final-state interactions. At low dielectron invariant mass ($m_{\rm ee}$), thermal radiation from the hot hadron...
The strong electromagnetic field generated by the colliding nuclei in heavy-ion collisions can be represented by a spectrum of photons, leading to photon-induced interactions. While such interactions are traditionally studied in ultra-peripheral collisions (UPC) without any nuclear overlap, significant enhancements of dilepton pairs and J/$\psi$ production at very low transverse momentum...
Electroweak W and Z bosons created in hard-scattering processes at the early stage of the collisions are efficient probes of the initial state of the collisions. While the measurements of W and Z bosons in pโPb and PbโPb collisions provide insights on the nuclear modification of the parton distribution functions, the results in pp collisions are a stringent test of perturbative QCD-based...
Ultrarelativistic Heavy Ions of large charge Z are accompanied by a large flux of
Weizs\"ackerโWilliams photons. This opens up the opportunity to study a variety of photo-induced nuclear processes, as well as photon-photon processes.
We would like to present a formalism which allows to calculate differential distributions of
leptons produced in semi-central (impact parameter < 2 $\times$...
We review recent CMS results on diffractive and exclusive processes in heavy ion collisions, including photon-induced processes in ultraperipheral collisions.
Photon-photon and photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultra-peripheral collisions with impact parameters larger than twice the nuclear radius. Since a few years, both the photoproduction of the J/$\psi$ vector meson and the production of dileptons via...
Measurements of direct photons can provide valuable information on the properties and dynamics of the quark-gluon plasma (QGP) by comparing them to model calculations that describe the whole evolution of the system created in heavy-ion collisions, from the initial conditions to the pre-equilibrium, QGP, and hadronic phases.
In the ALICE experiment, photons can be reconstructed either by using...
We review recent CMS results on hard probes of heavy ion collisions, including jet and electroweak boson production.
Jets are generated in hard interactions in high energy nuclear collisions, propagating through the quark-gluon plasma (QGP) as the jet shower evolves. The interaction of jet shower components with the QGP, known as jet quenching, generates several observable phenomena that provide incisive probes of the structure and dynamics of the QGP. In particular, measurements of the medium-induced...
The energy loss of jets (jet quenching) is one of the most important signatures of the deconfined state of quarks and gluons (quark-gluon plasma) created in Pb-Pb collisions at the LHC. The measurement of jets recoiling from a trigger hadron uniquely enables the exploration of medium-induced modification of jet production. Jet deflection via multiple soft scatterings with the medium...
We report high-statistics measurements of semi-inclusive distributions of charged jets recoiling from high-$E_{\text{T}}$ direct photon ($\gamma_{\text{dir}}$) and $\pi^{0}$ triggers in $p$+$p$ and central Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV. In a semi-inclusive approach, event bias is induced solely by the choice of trigger; separately utilizing $\gamma_{\text{dir}}$ and $\pi^{0}$...
We compute the in-medium jet broadening to leading order in energy in the opacity expansion. At leading order in $\alpha_s$ the elastic energy loss gives a jet broadening that grows with $\ln E$. The next-to-leading order in $\alpha_s$ result is a jet narrowing, due to destructive LPM interference effects, that grows with $\ln^2 E$. We find that in the opacity expansion the jet broadening...
Azimuthal angle ($\Delta\phi$) and transverse momentum ($p_\mathrm{T}$) correlations of isolated photons and associated jets, which are sensitive to medium induced parton momentum broadening, are reported for the first time with the latest high statistics pp and PbPb data recorded with the CMS detector at $\sqrt{s_{_{\mathrm{NN}}}} =$ 5.02 TeV. The fully corrected photon+jet azimuthal...
We review recent CMS results on collective flow in heavy ion collisions.
This talk presents ATLAS measurements of collective, flow phenomena in a variety of collision systems, including pp collisions at 13 TeV, Xe+Xe collisions at 5.44 TeV, and Pb+Pb collisions at 5.02 TeV. These include measurements of vn-[pT] correlations in Xe+Xe and Pb+Pb, which carry important information about the initial-state geometry of the Quark-Gluon Plasma and can potentially shed light...
The study of collective phenomena in ultrarelativistic heavy-ion collisions is nowadays to a great extent built on the so-called flow amplitudes $v_n$ and symmetry planes $\Psi_n$. Both appear as two distinct degrees of freedom in the parametrization of the azimuthal distribution of the produced particles, which is used in the study of the quark-gluon plasma (QGP). Investigating the complex...
With a unique geometry covering the forward rapidity region, the LHCb detector provides unprecedented kinematic coverage at low Bjorken-$x$ down to $x \sim 10^{-5}$ or lower. The excellent momentum resolution, vertex reconstruction and particle identification allow precision measurements down to very low hadron transverse momentum. In this contribution we present the latest studies of the...
Femtoscopy is a tool that can be used to measure the space-time dimensions of the particle-emitting source created in heavy-ion collisions using two-particle correlations. Additionally to the measurement of the system size, one can extract the average pair-emission asymmetry between two particles with different masses. In this context, the measurement of femtoscopic correlations between...
The study of femtoscopic correlations in high-energy collisions is a powerful tool to investigate the space-time structure of the particle emitting region formed in such collisions, as well as to probe interactions that the involved particles may suffer after being emitted. This talk presents an overview of recent results on the two-particle femtoscopic correlations measurements using charged...
Measurements of heavy-flavor hadron production in heavy-ion collisions provide a powerful tool to study both initial-state effects on heavy-quark production and final-state interactions between heavy-quarks and the quark-gluon plasma. These measurements are performed with the ATLAS detector at the LHC and capitalize on the large statistics of the Run 2 Pb+Pb dataset. This talk presents new...
We review recent CMS results on heavy flavour hadron production, including quarkonia, in heavy ion collisions.
Charmonium production is a probe sensitive to deconfinement in nucleus-nucleus collisions. The production of J/$\psi$ via regeneration within the QGP or at the phase boundary has been identified as an important ingredient for the description of the observed centrality and $p_{T}$ dependence at the LHC. $\psi$(2S) production relative to J/$\psi$ is one possible discriminator between the two...
Measurements of quarkonia production in peripheral and ultra-peripheral heavy-ion collisions are sensitive to photon-photon and photon-nucleus interactions, the partonic structure of nuclei, and to the mechanisms of vector-meson production. LHCb has studied both coherent and incoherent production of $J/\psi$ mesons in peripheral and ultra-peripheral collisions using PbPb data at forward...
Polarization and spin-alignment measurements represent an important tool for the understanding of the particle production mechanisms occurring in protonโproton collisions. When considering heavy-ion collisions, quarkonium polarization could also be used to investigate the characteristics of the hot and dense medium (quark-gluon plasma) created at the LHC energies. In ALICE, this observable was...
We present the current global analysis of nuclear parton distribution functions (PDFs) with the nCTEQ approach. Recent LHC data on W/Z-boson, single-inclusive hadron (SIH) and heavy quark/quarkonium (HQ) production are shown to constrain not only the gluon density down to $x\geq10^{-5}$, but to also influence the strange quark density. The consistency with neutrino deep-inelastic scattering...
The production of quarkonia in hadronic collisions provides a unique testing ground for understanding quantum chromodynamics (QCD) since it involves both the perturbative and non-perturbative regimes of this theory. As the quarkonia formation is not yet fully understood, a variety of new experimental data serve as new insights and help to constrain the models. Additionally to the inclusive...
The suppression of bottomonium states is closely related to the interaction with the QGP, supposedly created in heavy ion (AA) collisions. The different binding energies of bottomonium states provide a unique pattern of yield modification which is useful to study thermal properties of the QGP. Previous results from CMS have shown the evidence of sequential suppression for $\Upsilon$(1S),...
J/$\psi$ is an important probe to study the properties of the quark-gluon plasma (QGP) created in heavy-ion collisions. Measurements of J/$\psi$ yield suppression in Au+Au collisions at $\sqrt{s_\mathrm{NN}}$ = 200 GeV suggest that J/$\psi$ production in heavy-ion collisions is affected by the interplay of several effects, including dissociation and regeneration in the QGP, and cold nuclear...
Quarkonium production is a direct probe of deconfinement in heavy-ion collisions. For J/$\psi$, a bound state of $c\bar{c}$ quarks, the (re-)generation is found to be the dominant production mechanism at low transverse momentum ($p_{T}$) and in central collisions at the LHC energies.
In addition, the non-prompt component of J/$\psi$ production from b-hadron decays allows one to access the...
Charm and bottom quark production is an important experimental observable that sheds light on the heavy quark interaction with the nuclear medium. With high statistics datasets, tracking and PID at very low transverse momentum, and excellent vertexing capabilities, LHCb performs precision measurements of a rich set of heavy flavor hadrons, including B mesons, open charm hadrons and charmonia....
Recent experimental measurements display an enhanced production of charmed baryons in high-energy nucleus-nucleus collisions. Quite surprisingly the same is found in proton-proton collisions, in which the relative yields of charmed baryons do not agree with the expectations based on e+e- collisions and with the predictions of those QCD event generators in which the hadronization stage is tuned...
Hadronic resonances having short lifetimes are very useful to study the hadron-gas phase that characterizes the late-stage evolution of high energy nuclear collisions. Indeed, regeneration and rescattering processes occurring in the hadron gas modify the measured yields of hadronic resonances and can be studied by measuring resonance yields as a function of system size and by comparing to...
We consider the experimental data on yields of protons, strange ฮโs, and multistrange baryons (ฮ, ฮฉ), and antibaryons production on nuclear targets, and the experimental ratios of multistrange to strange antibaryon production, at the energy region from SPS up to LHC, and compare them to the results of the Quark-Gluon String Model calculations. In the case of heavy nucleus collisions, the...
In the recent years ALICE has carried out many measurements of the production of light nuclei in pp and p-Pb collisions and at different energies. A clear dynamics with multiplicity arises when combining all these measurements, however the theory interpretation of this evolution is still debated. In this presentation, the measurements of the ratio between the production yields of nuclei and...
The rapidity dependence of particle production contains information on the partonic structure of the projectile and target and is, in particular at LHC energies, sensitive to non-linear QCD evolution in the initial state. At LHC, collision final states have been mainly studied in the central kinematic region, however, there is a rich opportunity for measurements in the forward direction, which...
Recent multiplicity-dependent studies of particle production in pp and p-Pb collisions have shown similar features as in heavy-ion collisions. Measurements using resonances could help to understand the possible onset of collective-like phenomena and a non-zero lifetime of the hadronic phase in a small collision system. Measurements of the differential yields of resonances with different...
Relativistic heavy-ion beams at the LHC are accompanied by a large flux of equivalent photons, leading to multiple photon-induced processes. This talk presents a series of measurements of such processes performed by the ATLAS Collaboration. New measurements of exclusive dilepton production (electron, muon, and tau pairs) are discussed. These processes provide strong constraints on the nuclear...
Measurements of hard processes in heavy-ion collisions provide powerful and broad information on the dynamics of the hot, dense plasma formed in relativistic nucleus-nucleus collisions. This talk gives an overview of the latest jet measurements with the ATLAS detector at the LHC, utilizing the high statistics 5.02 TeV Pb+Pb data collected in 2015 and 2018. This talk presents multiple...
A significant goal of high-energy nuclear collisions is to determine the Quantum Chromodynamics (QCD) phase diagram for the strongly interacting matter. The most experimentally accessible way to characterize the QCD phase diagram is to scan in temperature (T) and the baryon chemical potential (\mu_B). The hadronic matter exists in a state where the fundamental constituents, quarks and gluons,...
Heavy-ion collisions are a powerful device to probe the phase diagram of the strongly interacting matter. An issue of special interest is the transition between hadronic gas and quark-gluon plasma, especially the possible presence of the critical point. One of the methods of the critical point search is analyzing fluctuations and correlations of produced particles. An increase in the...
We present the measurement of two-particle angular correlations in hadronic $e^{+}e^{โ}$ collisions data collected by the Belle detector at KEKB. Two high-statistics datasets, with center-of-mass energies $\sqrt{s} = 10.52$ GeV ($89.5 ~\mathrm{fb}^{โ1}$) and $10.58$ GeV on the $\Upsilon(4S)$ resonance ($333.2~\mathrm{fb}^{โ1}$), are analyzed. In various heavy-ion and proton-proton collisions,...
The first measurement of two-particle angular correlations of charged particles emitted in high energy $e^+e^-$ annihilation up to $\sqrt{s}=$ 209 GeV is presented. The archived hadronic $e^+e^-$ scattering data at a center-of-mass energy of 91-209 GeV were collected with the ALEPH detector at LEP between 1992 and 2000. The correlation functions are measured over a broad range of...
Collective behaviour of final-state hadrons, and multiparton interactions are studied in high-multiplicity ep scattering at a centre-of-mass energy $\sqrt{s}$ = 318 GeV with the ZEUS detector at HERA. Two- and four-particle azimuthal correlations, as well as multiplicity, transverse momentum, and pseudorapidity distributions for charged- particle multiplicities $N_{\rm ch}$ โฅ 20 are measured....
