Conveners
Heavy Ions: Session I - Premiere
- Barbara Antonina Trzeciak (Czech Technical University in Prague)
- Dennis Perepelitsa (University of Colorado Boulder)
Heavy Ions: Session II - Premiere
- Arturo Fernandez Tellez (Autonomous University of Puebla (MX))
Heavy Ions: Session III - Premiere
- Andrea Rossi (Universita e INFN, Padova (IT))
Heavy Ions: Session IV - Premiere
- Barbara Antonina Trzeciak (Czech Technical University in Prague)
Heavy Ions: Session III - Replay
- There are no conveners in this block
Heavy Ions: Session I - Replay
- There are no conveners in this block
Heavy Ions: Session II - Replay
- There are no conveners in this block
Heavy Ions: Session IV - Replay
- There are no conveners in this block
W and Z bosons are clean probes of the initial-state effects in hadronic collisions, being formed in the hard scatterings taking place in the initial stages, and being insensitive to the presence of any strongly-interacting medium. This is especially true at the LHC energies, where having a clear picture of the initial state is mandatory to properly interpret the later stages characterising...
Vector meson photo-production in ultra-peripheral Pb-Pb collisions is sensitive to nuclear parton distribution functions, and probe models of vector meson production in nuclear interactions with strong electromagnetic fields. In pPb collisions, measurements of the Z production in the forward (pPb) and backward (Pbp) configurations are sensitive to the nPDFs in different kinematic domains, such...
Electroweak bosons produced in lead-lead (Pb+Pb) collisions are an excellent tool to constrain initial-state effects which affect the rates of hard-scattering processes in nucleus-nucleus interactions. The production yields of massive electroweak bosons, observed via their leptonic decay channels, offer a high-precision test of the binary collision scaling expected in Pb+Pb and a way to...
Results from RHIC for Au-Au and from LHC for Pb-Pb collisions are compiled in terms of $R_{AA}$, $R_{CP}$ and ratio of the $p_T$ spectra, normalized with the corresponding $dN_{ch}/d\eta$, for each centrality to the most peripheral one ($R^N_{CP}$). The studies are focused on the $p_T$ range in the region of maximum suppression evidenced in the experiment. The $R_{CP}$ for 4 GeV/c < $p_T$ <...
We present the results for PbPb collisions at 2.76 TeV LHC energy from a parton shower integrated with a hydrodynamic evolution. The initial hard (jet) partons are produced along with soft partons in the initial state EPOS approach. The EPOS initial state typically contains multiple hard scatterings in each event. The soft partons melt into a thermalized medium, which is described with a 3...
Fragmentation (or in general, hadronization) is the transition from a colored and energetic parton to a colorless hadron is a rich and dynamical process in QCD quantified by the fragmentation function. Fast moving hadrons (or jets) are produced by the fragmentation of colored quarks or gluons that are produced during hard collisions at short distances. The determination of a characteristic...
Jets are an important tool to study the hot, dense matter produced in Pb+Pb collisions at the LHC. They are produced at the early stages of the collisions and are expected to be modified as they propagate through the hot and dense medium. This leads to energy loss as well as modification of the jet structure. This talk presents the latest jet measurements from Run 2 heavy-ion collisions data...
We present a study of the impact of the expansion of deconfined medium on single-gluon emission spectra and the jet suppression factor ($𝑄_{𝐴𝐴}$) within the BDMPS-Z formalism. These quantities are calculated for three types of media (static medium, exponentially decaying medium and Bjorken expanding medium). The distribution of medium-induced gluons and the jet $𝑄_{𝐴𝐴}$ are calculated using...
Collisions of ultra-relativistic heavy ions are used to create strongly interacting matter in the regime of high-energy densities and temperatures. Under these conditions color confinement of quarks and gluons in hadrons breaks down and a new state of matter called Quark-Gluon Plasma is formed. Properties of this medium can be inferred based on observed modifications of produced jets. ...
I am going to report on recent study, at a qualitative level, production of jet pairs in ultrarelativistic nuclear collisions within a framework combining High Energy Factorisation (HEF) and in-medium propagation of jet particles that takes into account stochastic transverse forces as well as medium-induced radiation. We find that the resulting di-jet observables feature the behaviour...
We review recent CMS results on hard probes of heavy ion collisions, including jet and electroweak boson production.
I will present a new class of jet/event substructure observable called collinear drop and its use in the search for novel signatures of jet modifications and medium responses. It is demonstrated using Monte Carlo simulations generated with Jewel how underlying jet-medium interactions can be systematically examined using collinear-drop observables. Studies using LEP open data and applications...
The LHeC and the FCC-eh will open a new realm in our understanding of nuclear structure and the dynamics in processes involving nuclei, in an unexplored kinematic domain. In this talk we will review the most recent studies as shown in the update of the 2012 LHeC CDR to be delivered in March 2020. We will discuss the determination of nuclear parton densities in the framework of global fits and...
We present the comprehensive study of shadowing in deep-inelastic scattering off nuclei in kinematical regions accessible by future experiments at electron-ion colliders.
The calculations of shadowing are performed within the color dipole formalism using a rigorous Green function technique. This allows incorporating naturally the effects of quantum coherence and color transparency, which are...
z-Scaling of inclusive spectra as a manifestation of self-similarity and fractality of hadron interactions is illustrated. The scaling for negative particle production in Au+Au collisions from BES-I at RHIC is demonstrated. The scaling variable z depends on momentum fractions of colliding objects carried by the interacting constituents and momentum fractions of the scattered and recoil...
Recent studies show that initial state fluctuations have important contributions to the collective medium form on small collisions systems at LHC energies. In general fluctuations of the initial state should play an important role for small collision systems since in general, their effects increase as the system size reduces. In this work, we present a study of the contribution of the initial...
The electromagnetic moments of the tau lepton are highly sensitive to new physics but are challenging to measure due to the short tau lifetime. Given observed tensions for other lepton generations it is crucial to pin down the moments of the tau. We propose a strategy using heavy ion collisions at the LHC as an intense source of photon collisions in order to surpass 15 year old lepton collider...
We present our calculation [1] of electromagnetic effects, induced by the spectator charge on Feynman-$x_F$ distributions of charged pions in peripheral $Pb+Pb$ collisions at CERN SPS energies, including realistic initial space-time-momentum conditions for pion emission. The calculation is performed in the framework of the fire-streak model, adopted to the production of both $\pi^-$ and...
Quantum tomography reconstructs higher dimensional features of quantum mechanical
systems from lower dimensional experimental information. The method is practical and directly processes experimental data while bypassing field-theoretic formalism. Quantum tomography can probe entanglement while avoiding model assumptions such as factorization. We review recent work applying quantum tomography...
We review recent CMS results on diffractive and exclusive processes in heavy ion collisions, including photon-induced processes in ultra-peripheral collisions.
We investigate the exclusive photoproduction of $J/\psi$-mesons in ultraperipheral
heavy ion collisions in the color dipole approach.
We first test a number of dipole cross sections fitted to inclusive $F_2$-data against the total cross section of exclusive $J/\psi$-production on the free nucleon.
We then use the color-dipole formulation of Glauber-Gribov theory to calculate
the...
Ultra-peripheral nucleus-nucleus and proton-nucleus collisions (UPC) are mediated by strong
electromagnetic fields, offering the opportunity to study photon-nucleus and photon-proton
processes at RHIC. In particular, coherent $J/\psi$ photoproduction in photon-nucleus interactions
is sensitive to nuclear effects on the gluon density, and exclusive $J/\psi$ photoproduction
in photon-proton...
The electromagnetic field of a fast charged particle, described as a flux of quasi-real photons whose intensity is proportional to its squared electric charge, provides copious photonuclear interactions in the case of lead ions circulating in the LHC. If the impact parameter of the colliding ions is larger than the sum of their radii, photon-induced processes dominate the interaction rate via...
Dielectrons and dimuons are a powerful probe of the quark-gluon plasma (QGP) created in ultra-relativistic heavy-ion collisions, since they do not interact strongly and are emitted during all stages of the collisions.
At low invariant mass, the dilepton spectrum is sensitive to in-medium modification of the $\rho$ meson spectral function and to effects related to the chiral symmetry...
We calculate cross sections for di-lepton photoproduction in ultrarelativistic heavy-ion collisions from low (SPS) to high (LHC) energy.
We study the invariant-mass distributions of dileptons produced in ultrarelativistic heavy-ion collisions at very low pair transverse momenta, $P_T < 0.15$ GeV. Specifically, we investigate the interplay of thermal radiation with initial photon annihilation...
Bound states of a heavy quark-antiquark-pair, quarkonia, are unique model systems to probe the deconfinement property of strongly interacting matter created in heavy-ion collisions. At the LHC, a unique comprehensive and precise set of measurements is available for the heavy bottom-antibottom vector states, which is a complementary probe to the lighter charmonium system thanks to its heavier...
The $\Upsilon$ states are a clean probe of the properties of quark-gluon plasma, which can be created in heavy-ion collisions. Each of the $\Upsilon$ states dissociates at a different temperature in the plasma due to Debye-like screening of color charges. In order to understand the Cold Nuclear Matter effects, the $\Upsilon$ production has to be studied in small colliding systems such as p+Au...
Among the many possible probes to study the quark-gluon plasma (QGP), a high energy-density medium formed in relativistic heavy-ion collisions, heavy quarks are particularly interesting as they are expected to be produced in the initial stages of the collisions, by hard partonic scatterings, and to experience the full evolution of the medium. In particular, charmonia (bound c$\overline{\rm c}$...
We present LHCb results on production of quarkonia and of open-heavy-flavour hadrons in proton-lead collisions, using data collected at sqrt(s_NN) = 5 and 8.16 TeV. Measurements are performed in the forward pseudorapidity region (2<eta<5), covering both forward (pPb configuration) and backward (Pbp configuration) rapidities. Measurements for charmonium states include prompt and from-b-decay...
The last decade of hadron spectroscopy has unveiled a wealth of states that do not have the properties expected of particles composed of 2 or 3 valence quarks. Among the most intriguing of these exotics is the X(3872), which various models attempt to describe as a hadronic molecule, a compact tetraquark, an unexpected charmonium state, or their mixtures. Heavy-ion collisions, as well as...
New results on the production of light nuclei, including deuterons, tritons, $^3$He, $^4$He and the corresponding anti-nuclei in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV and $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV will be presented and compared with theoretical predictions to provide insight into their production mechanisms in heavy-ion collisions.
Furthermore, new measurements...
We review recent CMS results on heavy flavour hadron production, including quarkonia, in heavy ion collisions, as well as particle correlations.
Open heavy flavours are effective probes of the hot and dense matter, the quark-gluon plasma (QGP), produced in ultra-relativistic heavy-ion collisions. Due to the very short time scale characterising their production, they experience the whole evolution of the system. In particular, measurements of open heavy-flavour production in Pb-Pb collisions at the LHC energies, including nuclear...
At RHIC energies, charm quarks are primarily produced at early stages of ultra-relativistic heavy-ion collisions, in hard partonic scatterings. This makes them an excellent probe of the Quark-Gluon Plasma (QGP) since they experience the whole evolution of the hot and dense medium. STAR is able to study the production of charm quarks and their interaction with the QGP through direct...
In hadronic collisions, beauty quarks are produced in hard scattering processes with large momentum transfer. Their production provides a very important test of perturbative QCD calculations in pp collisions. Measurements in p-Pb collisions are crucial to investigate the effects of cold nuclear matter on their production. In heavy-ion collisions, the measurement of beauty hadron production is...
The exploration of the QCD phase diagram in the region of high net-baryon density has gained strong interest in recent years. Among the reasons for that are the observation of multi-messenger signals emitted by binary neutron star mergers and the quest for the existence of a first order phase transition to a deconfined and/or chirally restored phase another one. HADES is a second-generation...
Correlation femtoscopy has become a standard technique for measuring and probing the space-time evolution of heavy-ion collisions. Usually, two-particle correlation functions are fitted to a Gaussian form. However, the real shape of the correlation function is often strongly non-Gaussian and better described by a Lévy-stable distribution. A Lévy index much below 2 has recently been observed...
The precise knowledge of the size of the source producing primary hadrons and resonances in pp collisions at the LHC can be employed to study the onset of collective phenomena in such systems. Indeed, the multiplicity and transverse momentum dependence of the pion and kaon source sizes, extracted by the femtoscopy analysis, was often interpreted as due to collective effects in heavy-ion...
The first measurement of two-particle angular correlation functions is reported in high-multiplicity $e^{+} e^{-}$ collisions recorded at $\sqrt{s}=10.52$ and $10.58$ GeV with the Belle detector at KEKB. The main goal of this measurement based on high-statistics low energy data is to search for the long-range (large pseudorapidity difference $\Delta\eta$) near-side (small azimuthal angle...
Two-particle azimuthal correlations have been measured in neutral current deep inelastic $ep$ scattering with virtuality $Q^2 > 5$ GeV$^2$ at a centre-of-mass energy $\sqrt{s}=318$ GeV recorded with the ZEUS detector at HERA. The correlations of charged particles have been measured in the range of laboratory pseudorapidity $-1.5 < \eta < 2$ and transverse momentum $0.1 < p_T < 5$ GeV and...
This talk presents recent measurements form the ATLAS collaboration that study features of the azimuthal distributions for charged particles in $pp$ and $p$+Pb collisions. The measurement of the azimuthal anisotropy of charged hadrons in $p$+Pb collisions up to a transverse momentum of 50 GeV is presented. In A+A collisions non-zero flow coefficients at high-$p_{T}$ are understood to arise...
Recent experimental results in proton-proton and in proton-nucleus collisions at Large Hadron Collider energies show a strong similarity to those observed in nucleus-nucleus collisions, where the formation of a quark-gluon plasma is expected. We discuss the comparison between small colliding systems and nucleus-nucleus collisions, for: a) the strangeness suppression factor γ_s and yields of...
In the presence of the large initial angular momentum occurring in non-central heavy-ion collisions, vector mesons can be produced in a polarized state. This might be either due to spin-orbital-angular-momentum interaction or by hadronization from polarized quarks. Experimentally, vector meson polarization is measured from the angular distribution of the decay daughters with respect to a...
Hadronic resonances with different lifetimes are very useful to probe the hadronic phase of heavy-ion collisions. Due to their relatively short lifetimes compared to the duration of the hadronic phase, resonances are good candidates to investigate the interplay between particle re-scattering and regeneration in the hadronic phase. In addition, having different masses, quantum numbers and quark...
Geometry and dynamics of the particle-emitting source in heavy-ion collisions can be inferred via femtoscopy method. Two-particle correlations at small relative momentum exploit Quantum Statistics (QS) and the Final State Interactions (FSI) which allow one to study the space-time characteristics of the source of the order of 10^{−15} m and 10^{−23} s. The RHIC Beam Energy Scan (BES) program...
ATLAS measurements of flow harmonics ($v_n$) and their fluctuations in Pb+Pb and Xe+Xe collisions covering a wide range of transverse momenta, pseudorapidity and collision centrality are presented. The measurements are performed using data from Xe+Xe collisions at 5.44 TeV and Pb+Pb collisions at 2.76 and 5.02 TeV. The $v_{n}$ are measured up to $n=6$ using the two-particle correlations,...
Collisions of relativistic heavy ions at the LHC are carried out to understand the fundamental properties of one of the extreme phases of QCD matter, the quark-gluon plasma (QGP). Anisotropic flow is one of the most sensitive probes to study the QGP transport properties, such as the shear viscosity over entropy density ratio (η/s), the value of which was found to be close to a universal lower...
