Speranza, Enrico (2018)
Virtual photon polarization and dilepton anisotropy in pion-nucleon and heavy-ion collisions.
Technische Universität Darmstadt
Ph.D. Thesis, Primary publication
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Virtual photon polarization and dilepton anisotropy in pion-nucleon and heavy-ion collisions | ||||
Language: | English | ||||
Referees: | Friman, Prof. Dr. Bengt ; Galatyuk, Prof. Dr. Tetyana | ||||
Date: | 5 June 2018 | ||||
Place of Publication: | Darmstadt | ||||
Date of oral examination: | 26 June 2017 | ||||
Abstract: | The goal of this Thesis is to study photon polarization and dilepton anisotropies as a tool to understand hadronic and heavy-ion collisions. First, the anisotropies of the dilepton angular distribution for the reaction $\pi N \rightarrow Ne^+ e^-$ are studied. We employ consistent effective interactions for baryon resonances up to spin-5/2, where non-physical degrees of freedom are eliminated, to compute the anisotropy coefficients for isolated intermediate baryon resonances. It is shown that the spin and parity of the intermediate baryon resonance is reflected in the angular dependence of the anisotropy coefficient. We then compute the anisotropy coefficient including the $N(1520)$ and $N(1440)$ resonances, which are essential at the collision energy of the recent data obtained by the HADES collaboration on this reaction. We conclude that the anisotropy coefficient provides useful constraints for unravelling the resonance contributions to this process. In order to study the medium effects on the dilepton polarization observables, we present a general framework for studying the angular anisotropy of dileptons produced from polarized virtual photons in relativistic heavy-ion collisions. The connection between the anisotropy coefficients and the medium evolution via flow velocity and temperature profile is obtained. We consider the dilepton production from quark-antiquark annihilation in the quark-gluon plasma phase and pion annihilation in the hadronic phase through electromagnetic interactions. The thermal and flow effects on the anisotropy coefficients are studied in the case of a static uniform medium, and a system with an expansion longitudinal and transverse to the beam axis. It is shown that the anisotropy coefficients are non-zero in a thermalized medium, and depend on the flow of the medium as well as on the transverse momentum and invariant mass of the virtual photon. The present framework can be implemented in a realistic hydrodynamic simulation of relativistic heavy-ion collisions in order to study the effect of non-trivial medium properties on dilepton anisotropy. |
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URN: | urn:nbn:de:tuda-tuprints-74602 | ||||
Classification DDC: | 500 Science and mathematics > 530 Physics | ||||
Divisions: | 05 Department of Physics > Institute of Nuclear Physics | ||||
Date Deposited: | 12 Jun 2018 05:34 | ||||
Last Modified: | 09 Jul 2020 02:07 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/7460 | ||||
PPN: | 43250415X | ||||
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