A Combination of CDF and DO Limits on the Branching Ratio of B_s(d) to   mu+ mu- Decays
  We combine the results of CDF and DO searches for the rare decays B_s to mu+ mu- and B_d to mu+ mu-. The experiments use 364 pb-1 and 300 pb-1 of data respectively. The limits on the branching ratios are obtained by normalizing the estimated sensitivity to the decay B+ to J/psi K+, taking into account the fragmentation ratios f_u/f_s(d). The combined results exclude branching ratios of BR(B_s to mu+ mu-) > 1.5x10-7 and BR(B_d to mu+ mu- > 4.0x10-8 at 95% confidence level. These are the most stringent limits on these decays at the present time. 
R. Bernhard, D. Glenzinski, M. Herndon, T. Kamon, V. Krutelyov, G.   Landsberg, F. Lehner, C. J. Lin, S. Mrenna