Electroweak one-loop corrections to the process of fermion pair production in electron-positron annihilation

Numerical results for the total cross section, polarization asymmetry, as well as forward-backward asymmetry are presented. Calculations were carried out for longitudinal polarization of the initial electron-positron beams, as well as for the unpolarized case in the one-loop approximation for the standard electroweak Glashow – Weinberg – Salam model without considering quark fields. As a renormalization scheme, we used a non-minimal on-shell scheme with simultaneous renorma lization of the fields. In addition to considering the radiation of soft photons, numerical analysis of hard bremsstrahlung was performed. Analysis of the effect of the cut-off parameters of the phase region of the three-particle final state was made, which are the acollinearity angle between the final leptons, the detecting threshold energies of the final particles, and the radiation energy of the soft photons. An algorithm for obtaining ultraviolet convergent expressions is described. The calculations were carried out in the formalism of the Passarino – Veltman functions in the light-lepton approximation.

Mass and energy dependence of the transverse momentum densities in covariant parton model

The parton densities which are dependent on transverse momentum, open a way to understand better the structure of quarks and gluons in a more complete way. We are investigating a method based on the covariant quark model which enables us to extract the transverse momentum dependent (TMD) densities from the usual parton densities which are just dependent on the longitudinal momentum. In continuation, we obtain the dependence of the TMDs on binding energy and the mass of quarks. We do some calculations to obtain the TMDs in the unpolarized case while the mass and binding energy of partons are varying. Considering these effects, the results for TMDs are in good agreement with the results of the recent related models.

TMD FACTORIZATION AND EVOLUTION FOR TMD CORRELATION FUNCTIONS

We discuss the application of transverse momentum dependent (TMD) factorization theorems to phenomenology. Our treatment relies on recent extensions of the Collins-Soper-Sterman (CSS) formalism. Emphasis is placed on the importance of using well-defined TMD parton distribution functions (PDFs) and fragmentation functions (FFs) in calculating the evolution of these objects. We explain how parametrizations of unpolarized TMDs can be obtained from currently existing fixed-scale Gaussian fits and previous implementations of the CSS formalism in the Drell-Yan process, and provide some examples. We also emphasize the importance of agreed-upon definitions for having an unambiguous prescription for calculating higher orders in the hard part, and provide examples of higher order calculations. We end with a discussion of strategies for extending the phenomenological applications of TMD factorization to situations beyond the unpolarized case.

Investigation of the Muon Catalyzed Fusion in the Spin Polarized Condition

The cross-sections of the muonic atom interactions in the muon catalyzed fusion (μCF) cycle are spin dependent. In this paper we answer an interesting question about the efficiency of μCF: "Dose the efficiency of μCF increase by spin polarization of the injected beam of muons in the spin polarized D/T mixture?" To answer this question we investigate the spin polarization effects on the kinetics of the μCF cycle by simulating the collisional processes of the μt atoms by the Monte–Carlo method. The themalization and spin-flip rates are determined and used to simulate the kinetics of μCF in the spin polarized condition. Then, the total number of fusions per muon in two cases, spin polarized and unpolarized conditions, are compared. We have shown the spin polarization condition is rapidly converted to the unpolarized case in μCF cycle and its effects can be ignored, especially if the concentration of tritium increases.