Conveners
Parallel Session T13: Electroweak probes: I
- Sasha Milov
Parallel Session T13: Electroweak probes: II
- Itzhak Tserruya (Weizmann Institute of Science (IL))
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 present the first combination of light-by-light scattering ($\gamma\gamma\rightarrow \gamma\gamma$) cross-section measurements at LHC, using lead-lead data recorded by the ATLAS and CMS Collaborations at $5.02\,\text{TeV}$ and corresponding to integrated luminosities of 2.2 and $0.39\,\text{nb}^{-1}$, respectively. The combined cross-section is $115\pm 19\,\text{nb}$, with the two...
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...
Due to the minimal interactions with the medium constituents, thermal dileptons emitted throughout the medium evolution are suggested as excellent probe of the hot QCD medium created in relativistic heavy-ion collisions. The invariant mass distribution of thermal dileptons can reveal the temperature of their emitting source without suffering from the blue-shift effect. By analyzing the...
We examine the spectrum of bremsstrahlung photons that results from the stopping of the initial net charge distributions in ultra-relativistic nucleus-nucleus collisions at the LHC. This effect has escaped detection so far since it becomes sizeable only at very low transverse momentum and at sufficiently forward rapidity. We compute the spectra of photon yields from different models of initial...
The unique forward coverage of the LHCb spectrometer allows the valence quark distributions of protons and nuclei to be probed with unprecedented precision. In this high-$x$ region, both the flavor content and structure of the nucleon's parton distribution functions remain relatively poorly known. New LHCb measurements of $Z$+charm jet production could be indicative of a valence-like...
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 p–Pb and Pb–Pb 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...
Z bosons and the Drell-Yan process are considered as essential probes to study the initial state effects in nuclear collisions. The CMS experiment has measured differential cross sections of Z bosons decaying to pairs of leptons in lead-lead collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV. The second order Fourier coefficient of the azimuthal distribution of Z bosons are...
PHENIX has used the versatility of RHIC to map out low $p_T$ direct photon production as function of collision system size and beam energy. For systems with a size corresponding to a $dN_{ch}/d\eta$ larger than 20-30, we observe a large yield of direct photons, a large azimuthal anisoptropy with respect to the reaction plane, and a characteristic centrality dependence of $dN_\gamma/dy \propto...
Heavy ion collision experiments at the Relativistic Heavy Ion Collider (RHIC) and the Large Hadron Collider (LHC) have resulted in the creation of an exotic state of matter: the quark-gluon plasma (QGP). Over the past two decades, our understanding of the QGP has evolved significantly, from measurements of nuclear modification functions of jets due to energy loss in medium to the realization...
Electromagnetic probes are one of promising tools to investigate properties of the hot and dense matter created in high-energy heavy-ion collisions. However, even the state-of-the-art phenomenological models which can correctly explain spectra and anisotropic flows of charged hadrons underpredict yield and elliptic flow of photons [1]. It is known as “photon puzzle”.
Here, we propose...
The High Acceptance DiElectron Spectrometer (HADES) is dedicated to the measurement of electromagnetic probes from heavy ion collisions and to study the in-medium behaviour of dileptons in the moderate temperature and high density regime of the QCD phase diagram. This region recently gained more attention as conditions turn out to be similar as in neutron-star mergers. Dileptons as penetrating...
