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Register a new userA Reconsideration of the b -> s gamma Decay in the Minimal Flavor Violating MSSM
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We present a MSSM study of the b -> s gamma decay in a Minimal Flavor Violating (MFV) framework, where the form of the soft SUSY breaking terms is determined by the Standard Model Yukawa couplings. In particular, we address the role of gluino contributions, which are set to zero in most studies of the MFV MSSM. Gluino contributions can play an important role in the MFV MSSM whenever mu * tan(beta) is large. In fact, similarly to chargino contributions, gluino contributions are tan(beta) enhanced and can easily dominate charged Higgs contributions for large values of tan(beta). Even though each of the separate contributions to b -> s gamma can be sizeable by itself, surprisingly no absolute lower bound can be placed on any of the relevant SUSY masses, since patterns of partial cancellations among the three competing contributions (Higgs, chargino and gluino) can occur throughout the MSSM parameter space.
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We present the fortran code SusyBSG version 1.1, which computes the branching ratio for the decay B -> Xs gamma in the MSSM with Minimal Flavor Violation. The computation takes into account all the available NLO contributions, including the complete supersymmetric QCD corrections to the Wilson coefficients of the magnetic and chromomagnetic operators.
In this work we compute the leading logarithmic corrections to the b -> s gamma decay in a dimensional scheme which does not require any definition of the gamma5 matrix. The scheme does not exhibit unconsistencies and it is therefore a viable alternative to the tHooft Veltman scheme, particularly in view of the next-to-leading computation. We confirm the recent results of Ciuchini et al.
In recent years, several deviations from the Standard Model predictions in semileptonic decays of $B$-meson might suggest the existence of new physics which would break the lepton-flavour universality. In this work, we have explored the possibility of using muon sneutrinos and right-handed sbottoms to solve these $B$-physics anomalies simultaneously in $R$-parity violating minimal supersymmetric standard model. We find that the photonic penguin induced by exchanging sneutrino can provide sizable lepton flavour universal contribution due to the existence of logarithmic enhancement for the first time. This prompts us to use the two-parameter scenario $(C^{rm V}_9, , C^{rm U}_9)$ to explain $b to s ell^+ ell^-$ anomaly. Finally, the numerical analyses show that the muon sneutrinos and right-handed sbottoms can explain $b to s ell^+ ell^-$ and $R(D^{(ast)})$ anomalies simultaneously, and satisfy the constraints of other related processes, such as $B to K^{(ast)} u bar u$ decays, $B_s-bar B_s$ mixing, $Z$ decays, as well as $D^0 to mu^+ mu^-$, $tau to mu rho^0$, $B to tau u$, $D_s to tau u$, $tau to K u$, $tau to mu gamma$, and $tau to mumumu$ decays.
The lepton flavor violating $Z^{prime}totaumu$ decay is studied in the context of several extended models that predict the existence of the new gauge boson named $Z^prime$. A calculation of the strength of the lepton flavor violating $Z^primemutau$ coupling is presented by using the most general renormalizable Lagrangian that includes lepton flavor violation. We used the experimental value of the muon magnetic dipole moment to bound this coupling, from which the $mathrm{Re}(Omega_{Lmutau}Omega^ast_{Rmutau})$ parameter is constrained and it is found that $mathrm{Re}(Omega_{Lmutau}Omega^ast_{Rmutau})sim 10^{-2}$ for a $Z^prime$ boson mass of 2 TeV. Alongside, we employed the experimental restrictions over the $tautomugamma$ and $tautomumu^+mu^-$ processes in the context of several models that predict the existence of the $Z^prime$ gauge boson to bound the mentioned coupling. The most restrictive bounds come from the calculation of the three-body decay. For this case, it was found that the most restrictive result is provided by a vector-like coupling, denoted as $|Omega_{mutau}|^2$, for the $Z_chi$ case, finding around $10^{-2}$ for a $Z^prime$ boson mass of 2 TeV. We used this information to estimate the branching ratio for the $Z^primetotaumu$ decay. According to the analyzed models the least optimistic result is provided by the Sequential $Z$ model, which is of the order of $10^{-2}$ for a $Z^prime$ boson mass around 2 TeV.
Recently the radiative B decay to the strange axial-vector mesons, B --> K1(1270) gamma, has been observed with rather large branching ratio. This process is particularly interesting as the subsequent K1 decay into its three body final state allows us to determine the polarization of the photon, which is mostly left- (right-)handed for Bbar (B) in the SM while various new physics models predict additional right- (left-)handed components. A new method is proposed to determine the polarization, exploiting the full Dalitz plot distribution, which seems to reduce significantly the statistical errors. This polarization measurement requires however a detailed knowledge of the K1--> K pi pi strong interaction decays, namely, the various partial wave amplitudes into the several possible quasi two-body channels, as well as their relative phases. The pattern of partial waves is especially complex for the K1(1270). We attempt to obtain the information through the combination of an experimental input and a theoretical one, provided by the 3P0 quark-pair-creation model.
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