Description
Conveners:
Laura Fabbietti (TU München)
Gunther Roland (MIT)
Jasmine Brewer (CERN)
Jeremi Niedziela (DESY)
Contact: eps23-conveners-t05 @desy.de
The physics of ultraperipheral ultrarelativistic heavy-ion collisions
gives an excellent opportunity to study photon-photon interaction.
Vast moving charged particles (nuclei) are surrounded by an electromagnetic field that can be considered as a source of (almost real) photons. The photon flux scales as the square of the nuclear charge, so $^{208}$Pb has a considerable advantage over...
Measurements of direct photons provide valuable information on the properties of the quark-gluon plasma because they are colour-neutral and created during all phases of the collision. Sources of photons include initial hard scatterings, Bremsstrahlung and the fragmentation process, jet-medium interactions, and radiation from the medium. Direct thermal photons, produced by the plasma, are...
Photonuclear reactions are induced by the strong electromagnetic field generated by ultrarelativistic heavy-ion collisions. These processes have been extensively studied in ultraperipheral collisions, in which the impact parameter is larger than twice the nuclear radius. In recent years, the observation of coherent J/$\psi$ photoproduction has been claimed in nucleus--nucleus (A--A) collisions...
One of the main challenges in nuclear physics is studying the structure of the atomic nucleus. Recently, it has been shown that high-energy heavy-ion collisions at RHIC and the LHC can complement low-energy experiments. Heavy-ion collisions provide a snapshot of the nuclear distribution at the time of collisions, offering a unique and precise probe of the nuclear structure.
This talk...
Light-flavour hadrons represent the bulk of particles produced in high-energy hadronic collisions at the LHC.
Measuring their pseudorapidity dependence provides information on the partonic structure of the colliding hadrons. It is, in particular at LHC energies sensitive to non-linear QCD evolution in the initial state.
In addition, measurements of light-flavour hadron production in small...
The study of strange particle production in heavy-ion collisions plays an important role in understanding the dynamics of the strongly interacting system created in the collision. The enhanced production of strange hadrons in heavy-ion collisions relative to that in pp collisions is historically one of the signatures of the formation of the quark-gluon plasma. The study of strangeness...
Charmonia have long been recognized as a valuable probe of the nuclear matter in extreme conditions, such as the strongly interacting medium created in heavy-ion collisions and known as quark-gluon plasma (QGP). At LHC energies, the regeneration process due to the abundantly produced charm quarks, was found to considerably affect measured charmonium observables. Comprehensive production...
Electromagnetic probes such as photons and dielectrons (e$^{+}$e$^{-}$ pairs) 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 at all stages of the collision with negligible final-state interactions. At intermediate dielectron invariant mass ($m_{\rm ee} > 1$ GeV/$c^{2}$), thermal radiation...
Hypernuclei are bound states of nucleons and hyperons. The study of their properties, such as their lifetimes and binding energies, provide information on the hadronic interaction between hyperons and nucleons which are complementary to those obtained from correlation measurements. Precise modeling of this interaction is a fundamental input for the calculation of the equation of state of...
The investigation of the quark content of hadrons has been a major goal of non-perturbative strong interaction physics. In the last decade, several resonances in the mass range 1000-2000 MeV/$c^2$ have emerged that cannot be explained by the quark model. The internal structure of exotic resonances such as $\rm f_0$, $\rm f_1$, and $\rm f_2$ is currently unknown. Different scenarios are...
Short-lived hadronic resonances are unique tools for studying the hadron-gas phase that is created in the late stages of relativistic heavy-ion collisions. Measurements of the yield ratios between resonances and the corresponding stable particles are sensitive to the competing rescattering and regeneration effects. These measurements in small collision systems, such as pp and p-Pb, are a...
We present a selection of very recent results by the CMS collaboration on heavy-ion physics at the LHC (CERN).
The center-of-mass energies available at modern accelerators, such as the Large Hadron Collider (LHC), and at future generation accelerators, such as the Electron-Ion Collider (EIC) and Future Circular Collider (FCC), offer us a unique opportunity to investigate hadronic matter under the most extreme conditions ever reached. One of the most intriguing phenomena of strong interaction is the...
This talk presents the latest ATLAS measurements of collective phenomena in various 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 measurement of vn-[pT] correlations in pp, Xe+Xe, and Pb+Pb, which carry important information about the initial-state geometry of the Quark-Gluon Plasma, provide an insight as to...
Studies have yielded strong evidence that a deconfined state of quarks and gluons, the quark--gluon plasma, is created in heavy-ion collisions. This hot and dense matter exhibits almost zero friction and a strong collective behavior. An unexpected collective behavior has also been observed in small collision systems. In this talk, the origin of collectivity in small collision systems is...
Event classifiers based either on the charged-particle multiplicity or on event topologies, such as spherocity and Underlying Event, have been extensively used in proton-proton (pp) collisions by the ALICE Collaboration at the LHC. These event classifiers became very useful tools since the observation of fluid-like behavior in high multiplicity pp collisions, for example radial and anisotropic...
Recent measurements of high multiplicity pp collisions at LHC energies have revealed that these systems exhibit features similar to quark-gluon plasma, such as presence of radial and elliptic flow, and strangeness enhancement, traditionally believed to be only achievable in heavy nucleus-nucleus collisions at high energy. To pinpoint the origin of these phenomena and to bring all collision...
Hard probes as heavy quarks (charm and beauty) and jets are valuable tools for investigating the properties of the quark-gluon plasma (QGP) formed in ultra-relativistic heavy-ion collisions. In particular, measurements of the nuclear modification factor $R_{\rm AA}$ of these probes allow us to characterise the in-medium energy loss of heavy quarks, light quarks and gluons while traversing the...
Jets are excellent probes for studying the deconfined matter formed in heavy ion collisions. This talk presents the new observables to study how jets interact with the QGP. First, we introduce a new infrared and collinear safe measurement of the jet energy flow within jets reconstructed with different resolution parameters $R$. Changing the jet $R$ varies the relative contribution of competing...
