Meson decays and physics beyond standard model

Abstract

In this thesis we discuss possible effects of new physics beyond the Standard Model (SM) associated with high energy scales. We make special emphasis on their manifestations in low energy processes such as meson decays. In particular, we examine the possible resolution of the recently observed polarization anomaly in B0 ( B0 ) ---> c/JK*0 ( [(*0 ) decay within R-parity violating (Jftp) supersymmetry (SUSY). We show that a combination of the superpotential X -trilinear Jftp-interactions and soft SUSY breaking bilinear 1ftp sneutrinoHiggs rnixing terms, proportional to P,2, can potentially generate the effective operators with the chiral structure necessary to account for this anomaly. However, we demonstrate that the existing experimental data on Es ---> J-L+ J-L- -decay lead to stringent upper lirnits on the Wilson coefficients of these operators, which are about two orders of magnitude below the values required for the resolution of the B-decay polarization anomaly, and, therefore, this anomaly can hardly be explained within the JftpSUSY framework. We also derive new limits on the products of the soft bilinear and the superpotential trilinear Jftp-parameters of the form P,2 )...', previously unconstrained in the literature. We study the contribution of massive dominantly sterile neutrinos, N, to the Lepton Number and Lepton Flavor Violating (LNV, LFV) semileptonic decays of T and B, D, K - mesons. We focus on special domains of sterile neutrino masses m N where it is close to its mass-shell. This leads to an enormous resonant enhancement of the decay rates of these processes. This allows us to derive stringent limits on the sterile neutrino mass m N and its mixing matrix elements IUeN I, IUJ.LNI, IUeNU7 NI, IU7 NU7 NI carrying out ajoint analysis of the existing experimental bounds on the decay rates of the studied processes. In difference from other approaches in the literature our approach to extraction of these lirnits is free from any ad hoc assumptions on the relative size of the sterile neutrino mixing parameters. Special attention was paid to the limits on meson decays with two electrons or positrons in final state, derived from non-observation of Ov/3/3-decay. We point out that observation of these decays may, in particular, shed light on CP violation in the neutrino sector. In the last part of the thesis, we study relations between lepton ftavor violating decays of the vector mesons p, w, cp ---t e¡_¿ and nuclear¡_¿- e-conversion. The theoretical tools for this study is given by an effective Lagrangian approach without referring to any specific realization of the physics beyond the standard m o del responsible for lepton ftavor violation (LFV). On this basis we extract the effective LFV decay couplings of vector mesons from the existing experimental bounds on nuclear¡_¿-- e- conversion and estimate upper lirnits on the LFV decays rates ofvector mesons p, w, cp ---t e¡_¿. In particular, we derived an upper limit on the LFV branching ratio of cp mesons which is 15 orders of magnitude less much more stringent than an experimental bound recently presented by the SND Collaboration. In general, our theoreticallimits on the LFV decays of vector mesons malee the prospects for their observation rather pessirnistic.