Theory and phenomenology of two-Higgs-doublet models

SuSpect: A Fortran code for the supersymmetric and Higgs particle spectrum in the MSSM

The rare decay B → K*(→ Kπ)μ+μ− is regarded as one of the crucial channels for B physics as the polarization of the K* allows a precise angular reconstruction resulting in many observables that offer new important tests of the Standard Model and its extensions. These angular observables can be expressed in terms of CP-conserving and CP-violating quantities which we study in terms of the full form factors calculated from QCD sum rules on the light-cone, including QCD factorization corrections. We investigate all observables in the context of the Standard Model and various New Physics models, in particular the Littlest Higgs model with T-parity and various MSSM scenarios, identifying those observables with small to moderate dependence on hadronic quantities and large impact of New Physics. One important result of our studies is that new CP-violating phases will produce clean signals in CP-violating asymmetries. We also identify a number of correlations between various observables which will allow a clear distinction between different New Physics scenarios.

Symmetries and Asymmetries of B -> K* mu+ mu- Decays in the Standard Model and Beyond

We study model-independently the implications of nonstandard scalar and pseudoscalar interactions for the decays $\stackrel{\ensuremath{\rightarrow}}{b}s\ensuremath{\gamma},$ $\stackrel{\ensuremath{\rightarrow}}{b}sg,$ $\stackrel{\ensuremath{\rightarrow}}{b}s{\mathcal{l}}^{+}{\mathcal{l}}^{\ensuremath{-}}$ $(\mathcal{l}=e,\ensuremath{\mu})$ and ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}.$ We find sizable renormalization effects from scalar and pseudoscalar four-quark operators in the radiative decays and at $O({\ensuremath{\alpha}}_{s})$ in hadronic b decays. Constraints on the Wilson coefficients of an extended operator basis are worked out. Further, the ratios ${R}_{H}=\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{B}H{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}})/\mathcal{B}(\stackrel{\ensuremath{\rightarrow}}{B}{\mathrm{He}}^{+}{e}^{\ensuremath{-}}),$ for ${H=K}^{(*)}{,X}_{s},$ and their correlations with the ${B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}$ decay are investigated. We show that the standard model prediction for these ratios defined with the same cut on the dilepton mass for electron and muon modes, ${R}_{H}{=1+O(m}_{\ensuremath{\mu}}^{2}{/m}_{b}^{2}),$ has a much smaller theoretical uncertainty $(\ensuremath{\lesssim}1%)$ than the one for the individual branching fractions. The present experimental limit ${R}_{K}l~1.2$ puts constraints on scalar and pseudoscalar couplings, which are similar to the ones from current data on $\mathcal{B}{(B}_{s}\ensuremath{\rightarrow}{\ensuremath{\mu}}^{+}{\ensuremath{\mu}}^{\ensuremath{-}}).$ We find that new physics corrections to ${R}_{{K}^{*}}$ and ${R}_{{X}_{s}}$ can reach 13% and 10%, respectively.

More model-independent analysis of b→s processes

We show -- by explicit computation of first-order corrections -- that the QCD factorization approach previously applied to hadronic two-body decays and to form factor ratios also allows us to compute non-factorizable corrections to exclusive, radiative B meson decays in the heavy quark mass limit. This removes a major part of the theoretical uncertainty in the region of small invariant mass of the photon. We discuss in particular the decays B\to K^* \gamma and B\to K^* l^+l^- and complete the calculation of corrections to the forward-backward asymmetry zero. The new correction shifts the asymmetry zero by 30%, but the result confirms our previous conclusion that the asymmetry zero provides a clean phenomenological determination of the Wilson coefficient C_9.

Systematic approach to exclusive B ->V l^+l^-, V gamma decays

Photonic penguins at two loops and mt-dependence of BR[B→Xsl+l−]

http://cds.cern.ch/record/385343/files/9904413.pdf

Christoph Bobeth

Papers

Photonic penguins at two loops and mt-dependence of BR[B→Xsl+l−]

Matching conditions for b→sγ and b→s gluon in extensions of the Standard Model