Samina S. Masood. Physics Department University of Houston Clear Lake

Transcription

1 Samina S. Masood Physics Department University of Houston Clear Lake

2 Introduction Properties of particles are modified when they propagate through a statistical medium Physically measureable parameters of a theory become function of properties of the medium such as temperature, chemical potential and magnetic field. Propagating particles also effect the electromagnetic properties of the medium itself Renormalization techniques are used to compute temperature, chemical potential and the magnetic field dependence of electron mass, charge, wavefunction, coupling constant and the magnetic moment Change in the effective mass of electron in a medium will directly effect the magnetic moment of electron, beta decay rate, neutrino capture and also the properties of neutrinos

3 Introduction Nucleosynthesis occurs through beta processes and is affected by the high hot and extremely dense media Particle properties, their decay rates and scattering crossections highly depend on the medium properties in extreme statistical conditions Nuclear matter formation is affected by the Finite Temperature and Density (FTD) of the background Beta decay rates become function of statistical parameters and contribute to nucleosynthesis Fusion of hydrogen into helium may also be corrected by the temperature and magnetic field effects in neutron stars

4 Calculation Scheme Renormalization techniques are used to find the properties of particles in this medium. The Feynman rules of vacuum theory are used with the statistically corrected propagators for bosons, and for fermions, where the corresponding energies of electrons (positrons) are defined as: and Where μ is the chemical potential, positive sign for particles and negative sign for antiparticles

5 Calculation Scheme In the presence of strong magnetic field and a polarized medium, energy can be written as Magnetic field in z-direction and n indicates the Landau levels Renormalization of QED gives temperature, density and magnetic field dependent contribution to electron mass, charge and wavefunction. Electron mass contributes to the magnetic moment of electron, beta decay rate, energy density and even the helium abundance Similar calculational techniques are used to calculate the number density, average energy, refractive energy and the form factors of neutrino

6 Temperature dependence of Helium yield in the early universe Using second order contributions to the electron mass at low temperature (T < m), leading order contributions to the helium yield can be computed as The leading order contributions at high temperature (T > m) comes out to be The high temperature contributions are not very encouraging as they reduce the helium abundance at high temperature and the last term on the right hand side of equation induces very strong temperature dependence at lower temperatures and helium yield becomes negative before the nucleosynthesis is started

7 0.003 Δτ/τ ΔTν/Tν ΔY T/m Δρ/ρ ΔTν/T Δλ/λ

8 First Order Thermal Corrections

9 Second Order Thermal Corrections

10 Temperature and Density dependence of beta decay Magnetic field and the polarized medium effects are being incorporated.

11 Results The existence of hot and dense polarized media develops a relevance of QED background effects to stellar systems Properties of particles such as the effective masses, number densities, charge and magnetic moment are modified Electromagnetic properties of a medium such as QED coupling constant, electric permittivity, magnetic permeability and polarization also changes Properties of neutrinos are significantly modified in QED medium

12 Results Beta decay rate is affected by the electron mass, neutrino properties and the phase space due to the Fermi-Dirac distribution function for fermion and Bose- Einstein distribution function for the bosons Radiative corrections are very important to compute perturbative corrections to estimate T, μ and B dependence of the decay rates and their effect on compact stars Polarization effect may help to find out the pulsar frequency more precisely

13 Results Higher order contributions to the nucleosynthesis are not so simple and cannot really be evaluated without numerical computations The second order behavior is expected to be similar to the oneloop level almost constant for low temperatures The two-loop contribution is much smaller than one loop and ensures renormalizabilty of the theory itself Numerical calculations of the thermal corrections at the higher loop level will be helpful WMAP data is still being interpreted and the latest observational probes such as Planck and James Webb Space Telescope are expected to provide further fine-tuning in precision values of parameters

14 The helium synthesis slows down at higher temperatures but is accelerated at higher densities

15 QUESTIONS?

16 References Samina Saleem (Masood), Phys. Rev. D36, 2602 (1987). Samina Masood, BAP. :arxiv: [hep-ph]. Samina Masood,e Renormalization of QED Near Decoupling Temperaturei, (submitted for publication) Samina S.Masood,Phys.Rev.D48, 3250(1993) and references therein. Samina S.Masood, Astroparticle Phys. 4, 189 (1995). Samina S. Masood, et.al; Rev.Mex.Fis. 48, 501 (2002). M.Chaichian, et.al; Phys.Rev.Lett. Phys. Rev. Lett (2000). Samina S. Masood,e Magnetic Moment of Neutrino in the strong magnetic O eldi, arxiv: hep-ph/ SaminaS.Masood,e ScatteringofLeptonsinHotandDenseMediai,arXiv: hep-ph/ Samina S.Masood and Mahnaz Qader,Phys.Rev.D46,5110(1992).

17 References K.AhmedandSaminaSaleem(Masood)Phys.RevD35,1861(1987). K.Ahmed and Samina Saleem (Masood), 4020(1987). K.Ahmed and Samina Saleem (Masood),Ann.Phys.164,460(1991) and references therein. Mahnaz Qader, Samina S.Masood and K.Ahmed, Phys.Rev.D44,3322(1991). Mahnaz Qader, Samina S.Masood and K.Ahmed, D46,5633(1992)and ref- erences therein. Samina Masood and Mahnaz Haseeb, Int.J.Mod.Phys. A27 (2012) ; Samina Masood and Mahnaz Haseeb, Int.J.Mod.Phys. A23 (2008) Mahnaz Haseeb and Samina Masood, Chin.Phys. C35 (2011) ; Mahnaz Haseeb and Samina Masood, Phys.Lett. B704 (2011) and references therein. Samina S.Masood, Phys.Rev.D44,3943(1991). Samina S.MasoodN D47,648(1993) and references therein.

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19 Onion like structure before core collapse

20 Questions and Discussion