Kießig, Clemens (2011): Quasiparticles in Leptogenesis: A hardthermalloop study. Dissertation, LMU München: Faculty of Physics 

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Abstract
We analyse the effects of thermal quasiparticles in leptogenesis using hardthermalloopresummed propagators in the imaginary time formalism of thermal field theory. We perform our analysis in a leptogenesis toy model with three righthanded heavy neutrinos N_1, N_2 and N_3. We consider decays and inverse decays and work in the hierarchical limit where the mass of N_2 is assumed to be much larger than the mass of N_1, that is M_2 >> M_1. We neglect flavour effects and assume that the temperatures are much smaller than M_2 and M_3. We pay special attention to the influence of fermionic quasiparticles. We allow for the leptons to be either decoupled from each other, except for the interactions with neutrinos, or to be in chemical equilibrium by some strong interaction, for example via gauge bosons. In two additional cases, we approximate the full hardthermalloop lepton propagators with zerotemperature propagators, where we replace the zerotemperature mass by the thermal mass of the leptons m_l(T) in one case and the asymptotic mass of the positivehelicity mode \sqrt{2} m_l(T) in the other case. We calculate all relevant decay rates and CPasymmetries and solve the corresponding Boltzmann equations we derived. We compare the final lepton asymmetry of the four thermal cases and the vacuum case for three different initial neutrino abundances; zero, thermal and dominant abundance. The final asymmetries of the thermal cases differ considerably from the vacuum case and from each other in the weak washout regime for zero abundance and in the intermediate regime for dominant abundance. In the strong washout regime, where no influences from thermal corrections are commonly expected, the final lepton asymmetry can be enhanced by a factor of two by hiding part of the lepton asymmetry in the quasisterile minusmode in the case of strongly interacting lepton modes.
Item Type:  Thesis (Dissertation, LMU Munich) 

Keywords:  Leptogenesis, Thermal Field Theory, Finite Temperature Field Theory, Hard Thermal Loop Resummation, Quasiparticle, Plasmino 
Subjects:  600 Natural sciences and mathematics 600 Natural sciences and mathematics > 530 Physics 
Faculties:  Faculty of Physics 
Language:  English 
Date Accepted:  29. June 2011 
1. Referee:  Raffelt, Georg 
Persistent Identifier (URN):  urn:nbn:de:bvb:19133231 
MD5 Checksum of the PDFfile:  cee692fc26417b01c9e575837036b44e 
Signature of the printed copy:  0001/UMC 19646 
ID Code:  13323 
Deposited On:  23. Aug 2011 07:23 
Last Modified:  16. Oct 2012 08:52 