K^+ -> pi^+ nu nu-bar and K_L -> pi^0 nu nu-bar Decays in the General MSSM

We reanalyze the rare decays K^+ -> pi^+ nu nu-bar and K_L -> pi^0 nu nu-bar in a general MSSM with conserved R-parity. Working in the mass eigenstate basis and performing adaptive scanning of a large space of supersymmetric parameters, 16 parameters in the constrained scan and 63 in the extended scan, we find that large departures from the Standard Model expectations are possible while satisfying all existing constraints. Both branching ratios can be as large as a few times 10^{-10} with Br(K_L -> pi^0 nu nu-bar) often larger than Br(K^+ -> pi^+ nu nu-bar) and close to its model independent upper bound. We give examples of supersymmetric parameters for which large departures from the SM expectations can be found and emphasize that the present 90% C.L. experimental upper bound on Br(K^+ -> pi^+ nu nu-bar) gives a non trivial constraint on the MSSM parameter space. Unlike previous analyses, we find that chargino box diagrams can give, already for moderately light charged sleptons, a significant contribution. As a byproduct we find that the ranges for the angles beta and gamma in the unitarity triangle are relaxed due to the presence of new CP-violating phases in K^0 - K^0-bar and B^0_d - B^0_d-bar mixing to 12 degrees <= beta <= 27 degrees and 20 degrees <= gamma <= 110 degrees.Comment: 36 pages, 27 figures, latex, uses axodraw.st

Complete (O_7,O_8) contribution to B -> X_s gamma at order alpha_s^2

We calculate the set of O(alpha_s^2) corrections to the branching ratio and to the photon energy spectrum of the decay process B -> X_s gamma originating from the interference of diagrams involving the electromagnetic dipole operator O_7 with diagrams involving the chromomagnetic dipole operator O_8. The corrections evaluated here are one of the elements needed to complete the calculations of the B -> X_s gamma branching ratio at next-to-next-to-leading order in QCD. We conclude that this set of corrections does not change the central value of the Standard Model prediction for Br(B -> X_s gamma) by more than 1 %.Comment: 19 pages, 8 figure

Updated NNLO QCD predictions for the weak radiative B-meson decays

Weak radiative decays of the B mesons belong to the most important flavor changing processes that provide constraints on physics at the TeV scale. In the derivation of such constraints, accurate standard model predictions for the inclusive branching ratios play a crucial role. In the current Letter we present an update of these predictions, incorporating all our results for the O(alpha_s^2) and lower-order perturbative corrections that have been calculated after 2006. New estimates of nonperturbative effects are taken into account, too. For the CP- and isospin-averaged branching ratios, we find B_{s gamma} = (3.36 +_ 0.23) * 10^-4 and B_{d gamma} = 1.73^{+0.12}_{-0.22} * 10^-5, for E_gamma > 1.6GeV. Both results remain in agreement with the current experimental averages. Normalizing their sum to the inclusive semileptonic branching ratio, we obtain R_gamma = ( B_{s gamma} + B_{d gamma})/B_{c l nu} = (3.31 +_ 0.22) * 10^-3. A new bound from B_{s gamma} on the charged Higgs boson mass in the two-Higgs-doublet-model II reads M_{H^+} > 480 GeV at 95%C.L.Comment: journal version, 5 pages, no figure

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

B->X_s l^+l^- in the MSSM at NNLO

We present the results of the calculation of QCD corrections to the matching conditions for the Wilson coefficients of operators mediating the transition b->s l^+l^- in the context of the MSSM. Within a scenario with decoupled heavy gluino the calculated contributions together with those present already in the literature allow for the first time a complete NNLO analysis of B->X_s l^+l^-. We study the impact of the QCD corrections and the reduction of renormalization scale dependencies for the dilepton invariant mass distribution and the forward-backward asymmetry in the inclusive decay B->X_s l^+l^- restricting the analysis to the "low-s" region and small values of tan(beta). The NNLO calculation allows to decrease the theoretical uncertainties related to the renormalization scale dependence below the size of supersymmetric effects in B->X_s l^+l^- depending on their magnitude. While it will be difficult to distinguish the MSSM expectations for the branching ratio from the Standard Model ones, this can become possible in the dilepton invariant mass distribution depending on the MSSM parameters and \hat{s}. In this respect the position of the zero of the forward-backward asymmetry s_0 is even more promising.Comment: 35 pages, 10 figure

Magnetic dipole operator contributions to the photon energy spectrum in anti-B -> X(s) gamma at O(alpha(s)^2)

We compute the O(\alpha_s^2) contributions to the photon energy spectrum of the inclusive decay \bar{B} -> X_s \gamma associated with the magnetic penguin operator O_7. They are an essential part of the ongoing NNLO calculation of this important decay. We use two different methods to evaluate the master integrals, one based on the differential equation approach and the other on sector decomposition, leading to identical results which in turn agree with those of a recent independent calculation by Melnikov and Mitov. We study the numerical relevance of this set of NNLO contributions in the photon energy spectrum and discuss the change of bottom quark mass scheme.Comment: 18 pages, uses axodraw.st