S. Rai Choudhury

Dileptonic decay of Bs meson in SUSY models with large tanβ

Abstract Decay of B s meson into the dileptonic channels of e + e − and μ + μ − are suppressed in the QCD corrected standard model due to the vector and axial nature of the coupling to lepton bilinears. We show that in SUSY theories with large tan β , contributions to the amplitude arising out of exchange of neutral Higgs Bosons considerably enhances the decay of B s into l + l − . In some region of parameter space, the enhancement is more than two orders of magnitude, bringing it well within experimental possibilities in the near future.

Lepton flavor violation in the little Higgs model with T parity

Little Higgs models with T-parity may provide us with a new source of lepton flavor violation, as such, in this paper we consider the anomalous magnetic moment of the muon (g-2){sub {mu}} and the lepton flavor violating decays {mu}{yields}e{gamma} and {tau}{yields}{mu}{gamma} in the little Higgs model with T-parity [A. Goyal, hep-ph/0609095.]. Our results show that the present experimental constraints of {mu}{yields}e{gamma} are a much more useful tool for constraining the new sources of flavor violation, than from the other processes considered here, which are present in T-parity models.

Bd–B¯d mass difference in little Higgs model

Abstract An alternate solution of hierarchy problem in the Standard Model namely, the little Higgs model, has been proposed lately. In this work B d 0 – B ¯ d 0 mass difference in the framework of the little Higgs model is evaluated. The experimental limits on the mass difference is shown to provide meaningful constraints on the parameter space of the model.

Lepton polarization asymmetry in radiative dileptonic B -meson decays in the minimal supersymmetric standard model

In this paper we study the polarization asymmetries of the final state lepton in the radiative dileptonic decay of B meson (Bs → l lγ ) in the framework of Minimal Supersymmetric Standard Model (MSSM) and various other unified models within the framework of MSSM e.g. mSUGRA, SUGRA (where condition of universality of scalar masses is relaxed) etc. Lepton polarization, in addition of having a longitudinal component (PL ), can have two other components, PT and PN , lying in and perpendicular to the decay plane, which are proportional to ml and hence are significant for final state being μ μ or τ τ. We analyse the dependence of these polarization asymmetries on the parameters of the various models.

Lepton number violation in a little Higgs model

The Standard Model (SM) has been remarkably successful in explaining experimental data upto the highest energies available at present. The precision electroweak data suggests that the Higgs boson remains light [1], mH < 219 GeV at 95% CL, upto the Planck’s scale. In SM, the Higgs boson however, gets quadratically divergent contribution to its mass and requires fine tuning of parameters which are sensitive to new physics that may be present at scales much higher than electroweak scale. Fine tuning and naturalness requires this new physics to be at the TeV scale. Supersymmetry (SUSY) provides a particularly elegant solution to the Hierarchy problem where quadratic divergences in Higgs mass are canceled between contributions of SM particles and their superpartners. This has the desired effect of stabilizing the electro-weak scale. In Technicolor theories, the hierarchy problem is deferred by introducing new dynamics at a scale not too much above electroweak scale. Theories of large extra dimensions resolve the hierarchy problem by lowering the Planck’s scale and modifying quantum gravity at the TeV scale. Phenomenological consequences of these theories have been studied in the literature and constraints obtained [2]. Recently there has been a proposal to consider Higgs fields as pseudo-Nambu-Goldstone boson of a Global symmetry which is spontaneously broken at some high scale [3]. The Higgs fields acquire mass through electroweak symmetry breaking triggered by radiative corrections leading to Coleman-Weinberg type of potential. Since the Higgs is protected by approximate global symmetry, it remains light and the quadratic divergent contributions to its mass are canceled by the contributions of heavy gauge bosons and a heavy Fermionic state that are introduced in the model. The Littlest Higgs (LH) [3, 4, 5] model is a minimal model of this class which accomplishes this task to one loop order within a minimal matter content. The LH model consists of an SU(5) non-linear sigma model which is spontaneously broken to its subgroup SO(5) by vacuum expectation value (VEV) of order f. The gauged group [SU(2) � U(1)] 2 is broken at the same time to its diagonal electroweak SM sub

Lepton polarization correlations in B ---> K* tau- tau+

In this work we will study the polarizations of both leptons (

Supersymmetric effects on forward backward asymmetries of B ---> K l+ l-

\tau

τpolarization asymmetry inB→Xsτ+τ−in SUSY models with largetanβ

) in the decay channel

SIGNATURES OF NEW PHYSICS IN DILEPTONIC B-DECAYS

B\to K^* \tau^- \tau^+

Supersymmetry effects on the exclusive semileptonic decays B → π τ + τ − and B → ρ τ + τ −

. In the case of the dileptonic inclusive decay