Second order perturbative corrections to electron wavefunction are calculated here at generalized temperature, for the first time. This calculation is important to prove the renormalizeability of QED through order by order cancellation of singularities at higher order. This renormalized wavefunction could be used to calculate the particle processes in the extremely hot systems such as the very early universe and the stellar cores. We have to re-write the second order thermal correction to electron mass in a convenient way to be able to calculate the wavefunction renormalization constant. A procedure for integrations of hot loop momenta before the cold loop momenta integration is maintained throughout to be able to remove hot singularities in an appropriate way. Our results, not only includes the intermediate temperatures T ∼ m (where m is the electron mass), the limits of high temperature T >> m and low temperature T << m are also retrievable. A comparison is also done with the existing results.

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Magnetic moment of electron at finite temperature is directly related to the modified electron mass in the background heat bath. Magnetic moment of electron gets modified at finite temperature also, when it couples with the magnetic field, through its temperature dependent physical mass. We show that the second order corrections to the magnetic moment of electron is a complicated function of temperature. We calculate the selfmass induced thermal contributions to the magnetic moment of electron, up to the two loop level, for temperatures valid around the era of primordial nucleosynthesis. A comparison of thermal behavior of the magnetic moment is also quantitatively studied in detail, around the temperatures below and above the nucleosynthesis temperature.

Abstract:The production of ∆ 0 (1232)-resonances in p+ 12 C collisions at 4.2 GeV/c was analyzed with 4π acceptance. The mass distribution of ∆ 0 (1232) was reconstructed using an angular criterion. The fraction of charged π − -mesons coming from ∆ 0 (1232) decay was estimated and compared to those obtained in earlier works. The momentum, transverse momentum, kinetic energy, and rapidity distributions as well as invariant cross sections of ∆ 0 (1232)-resonances were reconstructed in the laboratory frame. The mean kinematical characteristics of the reconstructed ∆ 0 (1232) were compared to those of participant protons in experiment and within some of the models. The freeze-out temperature of ∆ 0 (1232) estimated in the present analysis was compared with those obtained using different methods for ∆(1232) produced with other sets of colliding nuclei at various incident energies. The relative number of nucleons excited to ∆ 0 (1232) at freeze-out conditions in p+ 12 C collisions was estimated.

We recalculate the two loop corrections in the background heat bath using real time formalism. The procedure of the integrations of loop momenta with dependence on finite temperature before the momenta without it, has been followed. We determine the mass and wavefunction renormalization constants in the low temperature limit of QED, for the first time with this preferred order of integrations. The correction to electron mass and spinors in this limit is important in the early universe at the time of primordial nucleosynthesis as well as in astrophysics.