| dc.description.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. | |
