Search for the Rare Decays B^+ -> mu^+ mu^- K^+, B^0 -> mu^+ mu^- K^*0(892), and B^0_s -> mu^+ mu^- phi at CDF

TL;DR

This paper reports on a search for rare B meson decays involving muon pairs at the CDF detector, measuring branching fractions and setting upper limits, contributing to understanding flavor-changing neutral currents in particle physics.

Contribution

The study provides new measurements of branching fractions for B^+ and B^0 decays to muon pairs, and sets the most stringent upper limit on B_s^0 decay to muon pairs to date.

Findings

Measured branching fractions for B^+ and B^0 decays are consistent with world averages.

Observed excesses with significances up to 4.5 sigma in some decay modes.

Set the most stringent upper limit on B_s^0 to muon pairs decay.

Abstract

We search for b to s\mu^+\mu^- transitions in B meson (B^+, B^0, or B^0_s) decays with 924pb^{-1} of p pbar collisions at sqrt(s)=1.96 TeV collected with the CDF II detector at the Fermilab Tevatron. We find excesses with significances of 4.5, 2.9, and 2.4 standard deviations in the B^+ to \mu^+\mu^-K^+, B^0 to \mu^+\mu^-K^*(892)^0, and B_s^0 to \mu^+\mu^-\phi decay modes, respectively. Using B to J/psi h (h = K^+, K^*(892)^0, phi) decays as normalization channels, we report branching fractions for the previously observed B^+ and B^0 decays, BR(B^+ to \mu^+\mu^-K^+)=(0.59\pm0.15\pm0.04) x 10^{-6}, and BR(B^0 to \mu^+\mu^-K^*(892)^0)=(0.81\pm0.30\pm0.10) x 10^{-6}, where the first uncertainty is statistical, and the second is systematic. These measurements are consistent with the world average results, and are competitive with the best available measurements. We set an upper limit on the relative branching fraction BR(B_s^0 to \mu^+\mu^-\phi)/BR(B_s^0 to J/\psi\phi) <2.6(2.3)\times10^{-3} at the 95(90)% confidence level, which is the most stringent to date.