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On the Effects of Finite Temperature and Background Magnetic Fields on the Observables of Heavy Ion Collisions

Taghinavaz, Farid | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 49229 (04)
  4. University: Sharif University of Technology
  5. Department: Physics
  6. Advisor(s): Sadooghi, Neda
  7. Abstract:
  8. The main focus of this dissertation is to investigate the effects of the created background magnetic field on some of the observables that are relevant in heavy ions experiments. Based on the phase diagram of Quantum Chromodynamics, it is expected that in extreme conditions such as high temperature or in dense medium, a new phase of matter arises, which is known as Quark-Gluon Plasma (QGP). Due to the vital role of collective behaviors, this phase behaves similar to a perfect fluid rather than a gas. In addition, the colliding nucleons have potential of creating very strong magnetic fields because of their electric charges and relativistic speeds. Therefore the investigation of the effects of these mighty magnetic fields on relevant phenomena has a certain importance. By pointing out to the collective behaviors in QGP, we have investigated the effects of collective modes on the shear viscosity known as a remarkable macroscopic quantity. Calculation of the shear viscosity has been carried out in the Yukawa model with linear response theory approach in the finite temperature and chemical potential conditions. Thereafter we study the collective behaviors of fermionic particles in Quantum Electrodynamics (QED) theory in the condition of finite temperature and magnetic field. For this purpose, fermion self-energy is calculated up to one-loop order using fermionic Green’s function which is obtained with Ritus method. In addition, the dispersion relation is solved to obtain the fermionic spectrum in the low momentum regime. Based on the results of fermion self-energy, the general form of the complete fermionic Green’s function is obtained at finite temperature and in the presence of a background magnetic field. Eventually, we study the effect of a constanct magnetic field on dilepton production rate as a direct measure of internal events in QGP phase. As there is no exact information of the photon’s mean free path in finite magnetic field, it is assumed that the final dilepton as well as the decaying photons are both affected by the magnetic field. In order to implement the threshold limit for pair production, all figures are sketched above the higher threshold limit which is defined by summing over Landau levels of fermionic particles. Finally, we introduce a novel anisotropy factor to assess the effect of magnetic field on the inhomogenity of the outgoing dilepton
  9. Keywords:
  10. Finite Temperature Field Theory ; Background Magnetic Field ; Transport Coefficients ; Collective Excitations ; Dilepton Production Rate

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