Indirect search for supersymmetry in rare B decays

QCD corrections to the gluino induced contribution to b --> s gamma are shown to be important in order to extract reliable bounds on the off-diagonal elements of the squark mass matrices.Comment: 4 pages including 2 postscript figure

Towards the NNLL precision in Bˉ→Xsγ\bar B \to X_s \gamma

The present NLL prediction for the decay rate of the rare inclusive process $\bar B \to X_s \gamma$ has a large uncertainty due to the charm mass renormalization scheme ambiguity. We estimate that this uncertainty will be reduced by a factor of 2 at the NNLL level. This is a strong motivation for the on-going NNLL calculation, which will thus significantly increase the sensitivity of the observable $\bar B \to X_s \gamma$ to possible new degrees of freedom beyond the SM. We also give a brief status report of the NNLL calculation.Comment: 5 pages, 2 figures, contribution to the proceedings of EPS-HEP 200

Smooth invariant densities for random switching on the torus

We consider a random dynamical system obtained by switching between the flows generated by two smooth vector fields on the 2d-torus, with the random switchings happening according to a Poisson process. Assuming that the driving vector fields are transversal to each other at all points of the torus and that each of them allows for a smooth invariant density and no periodic orbits, we prove that the switched system also has a smooth invariant density, for every switching rate. Our approach is based on an integration by parts formula inspired by techniques from Malliavin calculus.Comment: 19 page

Reduction of Charm Quark Mass Scheme Dependence in Bˉ→Xsγ\bar B \to X_s \gamma at the NNLL Level

The uncertainty of the theoretical prediction of the $\bar B \to X_s \gamma$ branching ratio at NLL level is dominated by the charm mass renormalization scheme ambiguity. In this paper we calculate those NNLL terms which are related to the renormalization of $m_c$, in order to get an estimate of the corresponding uncertainty at the NNLL level. We find that these terms significantly reduce (by typically a factor of two) the error on ${BR}(\bar B \to X_s \gamma)$ induced by the definition of $m_c$. Taking into account the experimental accuracy of around 10% and the future prospects of the $B$ factories, we conclude that a NNLL calculation would increase the sensitivity of the observable $\bar B \to X_s \gamma$ to possible new degrees of freedom beyond the SM significantly.Comment: 13 pages including 3 figure

B→XsgammaB \to X_s gamma in the Standard Model

We give a summary about the various contributions which have to be calculated in order to obtain the next-to-leading logarithmic result for the branching ratio $BR(B \to X_s \gamma)$. Combining all these ingredients, which were obtained by different groups, a complete next-to-leading-logarithmic prediction of the inclusive decay rate was recently presented in the literature. The theoretical uncertainty in the partonic decay rate is now at the 10% level, i.e., less than half of the error in the previous leading-logarithmic result. We also mention the impact of non-perturbative corrections which scale like $1/m_b^2$ and discuss in some more detail the recently discovered corrections which scale like $1/m_c^2$. It turns out that the $1/m_b^2$- and the $1/m_c^2$ terms lead to corrections to the branching ratio $BR(B \to X_s \gamma)$ well below the 10% level.Comment: 11 pages including 2 postscript figure

B\to X_s\gamma, X_s l^+ l^- decays and constraints on the mass insertion parameters in the MSSM

In this paper, we study the upper bounds on the mass insertion parameters $(\delta^{q}_{AB})_{ij}$ in the minimal supersymmetric standard model (MSSM). We found that the information from the measured branching ratio of $B \to X_s l^+ l^-$ decay can help us to improve the upper bounds on the mass insertions parameters \left (\delta^{u,d}_{AB})_{3j,i3}. Some regions allowed by the data of $Br(B \to X_s \gamma)$ are excluded by the requirement of a SM-like $C_{7\gamma}(m_b)$ imposed by the data of $Br(B \to X_s l^+ l^-)$.Comment: 16 pages, 5 eps figure files, typos remove

Non-Canonical Perturbation Theory of Non-Linear Sigma Models

We explore the O(N)-invariant Non-Linear Sigma Model (NLSM) in a different perturbative regime from the usual relativistic-free-field one, by using non-canonical basic commutation relations adapted to the underlying O(N) symmetry of the system, which also account for the non-trivial (non-flat) geometry and topology of the target manifold.Comment: 11 pages, 1 figure, LaTe

NNLL QCD Contribution of the Electromagnetic Dipole Operator to Gamma(anti-B -> X(s) gamma)

We present an independent calculation of that part of the O(\alpha_s^2) contribution to the decay width \Gamma(\bar B -> X_s \gamma) which arises from the self-interference term of the electromagnetic dipole operator O_7. Using a different method, we find complete agreement with a previous calculation. This NNLL contribution is an important ingredient for the complete NNLL prediction of \Gamma(\bar B -> X_s \gamma) which will resolve the charm quark mass ambiguity appearing at NLL accuracy.Comment: 15 pages, uses axodraw.st