Conveners
Electromagnetic and weak probes: I
- Olga Evdokimov (University of Illinois at Chicago (US))
Electromagnetic and weak probes: II
- Charles Gale (McGill University)
Direct photons are produced in various processes in pp, p-A and A-A collision and are sensitive to details of the space-time evolution the medium produced in heavy-ion collisions. The low $p_{\rm T}$ part of the direct photon spectrum is expected to be dominated by thermal direct photons - thermal radiation of hot matter, i.e., of the quark-gluon plasma and the hadron gas. At RHIC energies it...
In recent years data from small collision systems at LHC and RHIC have revealed
evidence for collective behavior of the produced hadrons. Collective behavior in
small systems clearly points towards a strongly coupled system being formed in
these collisions. If so, the matter formed must also radiate thermal or low
momentum direct photons. PHENIX is ideally positioned to search for any...
In this talk, we present a systematic study of direct soft photon observables from the RHIC Beam Energy Scan (BES) to the LHC energies. We utilize the power of photons as clean and penetrating probes of the strongly-coupled nuclear matter created in relativistic heavy-ion collisions, together with the fact that the rapidly expanding Quark-Gluon Plasma (QGP) imprints its evolution on the photon...
The matter formed in central heavy-ion collisions at a few GeV per nucleon is commonly understood as resonance matter, a gas of nucleons and excited baryon states with a substantial contribution from mesonic, mostly pionic excitations. Yet, in the initial phase of the reaction the system is compressed to beyond nuclear ground state density and hence substantial modifications of the hadron...
We present an overview of recent results on in-medium spectral functions and transport coefficients of hadrons using the Functional Renormalization Group approach. Our method is based on a recently developed analytic continuation procedure that allows to calculate real-time quantities like spectral functions at finite temperature and chemical potential. Results for the quark, the sigma and the...
The production of low-mass dielectrons is one of the most promising tools for the understanding of the chiral symmetry restoration and of the thermodynamical properties of the Quark-Gluon plasma (QGP) created in heavy-ion collisions. At low invariant mass, the dielectron production is sensitive to the properties of vector mesons in the medium and modifications related to the chiral symmetry...
Insensitive to the strong interaction, the electroweak W and Z bosons are clean observables for the initial state of heavy-ion collisions. Their measurement in p-Pb and Pb-Pb collisions provides constraints on the nuclear parton distribution functions (nPDFs) of (anti)quarks. In particular, the W and Z rapidity-differential production cross sections and the decay lepton charge asymmetry as a...
Yields of W and Z bosons can be used to probe the nuclear parton distribution functions of quarks and antiquarks. New results on W boson and Drell-Yan production in pPb collisions at a nucleon-nucleon center-of-mass energy of 8.16 TeV using the CMS detector will be presented. The muon decay channel is used to study both positive and negative W bosons as a function of muon pseudorapidity....
In this talk, we employ new field-theoretical tools to study photons [1] and, for the first time, jets in a non-equilibrium quark-gluon plasma. Jet broadening and photon emission takes place through radiation which is suppressed by repeated and coherent interaction with the medium. We analyze this physics in a medium that is not in thermal equilibrium. This can provide independent means of...
Light-by-light (LbyL) scattering ($\gamma\gamma \rightarrow \gamma\gamma$) is a fundamental quantum-mechanical process with tiny cross sections. Studies of LbyL scattering, using the large photon fluxes from ultraperipheral PbPb collisions at sqrt(s_N) = 5.02 TeV at the LHC, will be reported based on the evidence of a signal corresponding to an integrated luminosity of 391 $\mu b^{-1}$. The...
Top quarks have been recently measured for the first time in nuclear collisions. With most of the integrated luminosity of the LHC PbPb program to be recorded in the coming years and the impressive projections for the future HL-LHC, HE-LHC or FCC, top quark observables will be measured with good precision and become an excellent probe of the QGP. We argue here that the unique properties of the...
