Speaker
Description
A new complete method, based on the Wigner distributions of photons, how to calculate differential distributions of dileptons created via photon-photon fusion in semicentral ($b<2R_{AA}$) AA collisions is reviewed [1]. The formalism is used to calculate different distributions of invariant mass, dilepton transverse momentum and acoplanarity for different regions of centrality. The results of calculation are compared with recent STAR, ALICE and ATLAS experimental data. Very good agreement with the data is achieved without free parameters and without including additional mechanisms such as a possible rescattering of leptons in the quark-gluon plasma.
We will also refer to our earlier paper [2] where we discussed competition with thermal radiation. We verify that the combination of photon fusion, thermal radiation and final-state hadron decays gives a fair description of the low-$P_T$ invariant-mass as well as $P_T$ spectra as recently measured by the STAR collaboration in $\sqrt{s_{NN}}=200$ GeV Au+Au collisions for different centrality classes.
[1] Mariola Kłusek-Gawenda, Wolfgang Schaefer, Antoni Szczurek,
Phys. Lett. B814 (2021) 136114.
[2] Mariola Kłusek-Gawenda, Ralf Rapp, Wolfgang Schaefer, Antoni Szczurek,
Phys. Lett. B790 (2019) 339-344.
