ΔF=2\Delta F=2 processes in the MSSM in large tan⁡β\tan\beta limit

We discuss corrections to $\Delta M_{B_d}$, $\Delta M_{B_s}$ and to the CP violation parameter $\epsilon$ in two examples of (generalized) minimal flavour violation models: 2HDM and MSSM in the large $\tan\beta$ limit. We show that for $H^+$ not too heavy, $\Delta M_{B_s}$ in the MSSM with heavy sparticles can be substantially smaller than in the SM due the charged Higgs box contributions and in particular due to the growing like $\tan^4\beta$ contribution of the double penguin diagrams involving neutral Higgs boson exchanges.Comment: 5 pages, 2 Postscript figures, to appear in the proceedings of the 9th International Conference on Supersymmetry and Unification of Fundamental Interactions SUSY'01, June 11-17, Dubna, Russi

SUSY_FLAVOR library for rare decays in the MSSM

SUSY_FLAVOUR 2.0 is a FORTRAN code calculating over 30 low-energy flavour- and CP-related observables in the R-parity conserving MSSM. The code admits for the most general flavour structure of the SUSY breaking terms and complex flavour-diagonal couplings. It includes the numerically important resummation of chirally enhanced effects and it is fast enough for scanning over a large SUSY-parameter space. The program can be obtained from http://www.fuw.edu.pl/susy_flavor.Comment: 3 pages, 1 table, proceedings for EPS-HEP201

Complete One-Loop MSSM Predictions for B --> lepton lepton' at the Tevatron and LHC

During the last few years the Tevatron has dramatically improved the bounds on rare B-meson decays into two leptons. In the case of B_s --> mu+ mu-, the current bound is only ten times greater than the Standard Model expectation. Sensitivity to this decay is one of the benchmark goals for LHCb performance and physics. The Higgs penguin dominates this rate in the region of large tan(beta) of the MSSM. This is not necessarily the case in the region of low tan(beta), since box and Z-penguin diagrams may contribute at a comparable rate. In this article, we compute the complete one-loop MSSM contribution to B --> l+l'- for l,l' = e, mu. We study the predictions for general values of tan(beta) with arbitrary flavour mixing parameters. We discuss the possibility of both enhancing and suppressing the branching ratios relative to their Standard Model expectations. In particular, we find that there are "cancellation regions" in parameter space where the branching ratio is suppressed well below the Standard Model expectation, making it effectively invisible to the LHC.Comment: 30 pages, 4 figures; v.3: corrected factors of (2 pi) in (2.11), (3.1), (A.11), (A.13-14

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

Supersymmetry and FCNC effects

We consider Flavour Changing Neutral Current processes in the framework of the supersymmetric extension of the Standard Model. FCNC constraints on the structure of sfermion mass matrices are reviewed. Furthermore, we analyze supersymmetric contributions to FCNC transitions which remain in the limit of flavour-conserving sfermion mass matrices. Implications of the FCNC constraints on the structure of sfermion mass matrices for SUSY breaking and sfermion mass generation are discussed. We conclude that the supersymmetric flavour problem is intriguing but perhaps not as severe as it is commonly believed.Comment: 45 pages, 19 figures, uses epsfig.sty, (axodraw.sty included) To appear in the Review Volume ``Heavy Flavours II'', eds. A.J. Buras and M. Lindner, Advanced Series on Directions in High Energy Physics, World Scientific Publishing Co., Singapore. Revision made on November 19, 1997 amounts to including "note added" concerning bounds on delta_LR from charginos, and a few correlated minor changes. Misprint in eq. (A.5) correcte