First Observation of the Decay $B \to J/\psi \phi K$

TL;DR

This paper reports the first observation of the decay B->J/psi phi K, demonstrating a rare process involving s sbar quark pair creation, with a measured branching fraction based on data from the CLEO detector.

Contribution

First experimental observation of the B->J/psi phi K decay, highlighting a new decay mode involving s sbar quark pair creation in B mesons.

Findings

10 candidates observed with low background

Branching fraction measured as (8.8+3.5-3.0(stat)+/-1.3(syst))×10^-5

First decay requiring additional s sbar quark pair creation

Abstract

We present the first observation of the decay B->J/psi phi K. Using 9.6 million B meson pairs collected with the CLEO detector, we have observed 10 fully reconstructed B->J/psi phi K candidates, whereas the estimated background is 0.5+/-0.2 events. We obtain a branching fraction of Br(B->J/psi phi K) = (8.8+3.5/-3.0(stat)+/-1.3(syst))*10^-5. This is the first observed $B$ meson decay requiring the creation of an additional s sbar quark pair.