Exploiting the Symmetries of P and S wave for B --> K^* mu^+ mu^-

After summarizing the current theoretical status of the four-body decay B --> K^*(--> K pi) mu^+ mu^-, we apply the formalism of spin-symmetries to the full angular distribution, including the S-wave part involving a broad scalar resonance K0^*. While we recover in the P-wave sector the known relation between the angular observables Pi('), we find in the S-wave sector two new relations connecting the coefficients of the S-wave angular distribution and reducing the number of independent S-wave observables from six to four. Included in the experimental data analysis, these relations can help to reduce the background from S-wave pollution. We further point out the discriminative power of the maximum of the angular observable P2 as a charm-loop insensitive probe of right-handed currents. Moreover, we show that in absence of right-handed currents the angular observables P4' and P5' fulfill the relation P4' = beta P5' at the position where P2 reaches its maximum.Comment: 13 pages, 3 figures; journal versio

Probing new physics in electroweak penguins through B_d and B_s decays

An enhanced electroweak penguin amplitude due to the presence of unknown new physics can explain the discrepancies found between theory and experiment in the B -> pi K decays, in particular in A_CP(B^- -> pi^0 K^-) - A_CP(\bar{B}^0 -> pi^+ K^-), but the current precision of the theoretical and experimental results does not allow to draw a firm conclusion. We argue that the \bar{B}_s -> phi rho^0 and \bar{B}_s -> phi pi^0 decays offer an additional tool to investigate this possibility. These purely isospin-violating decays are dominated by electroweak penguins and we show that in presence of a new physics contribution their branching ratio can be enhanced by about an order of magnitude, without violating any constraints from other hadronic B decays. This makes them very interesting modes for LHCb and future B factories. In arXiv:1011.6319 we have performed both a model-independent analysis and a study within realistic New Physics models such as a modified-Z^0-penguin scenario, a model with an additional Z' boson and the MSSM. In this article we summarise the most important results of our study.Comment: 8 pages, 5 figures, LaTeX. Talk given at Discrete2010, Rome, 6-11 December 2010; References adde

Rare hadronic B decays in the MSSM and in other models of new physics

In this thesis we study several aspects of new physics (NP) in rare hadronic B decays: First we analyse tan(beta)-enhanced corrections in the Minimal Supersymmetric Standard Model (MSSM). We generalise the known resummation formulas beyond the decoupling limit and study novel effects in couplings involving genuine SUSY particles. In the second part of the thesis we discuss the possibility of probing NP in electroweak penguins via the purely isospin-violating decays B_s->phi,pi(rho)