Measurement of the $B_s^0 \to \phi \phi$ branching fraction and search for the decay $B^0 \to \phi \phi$

TL;DR

This paper reports the most precise measurement of the $B_s^0 o \,phi \,phi$ branching fraction using 3.0 fb$^{-1}$ of data, and sets a new upper limit for the $B^0 o \,phi \,phi$ decay, improving previous results significantly.

Contribution

It provides the most accurate measurement of the $B_s^0 o \,phi \,phi$ branching fraction and the most stringent upper limit for $B^0 o \,phi \,phi$, advancing experimental constraints in B-meson decays.

Findings

Measured $B_s^0 o \,phi \,phi$ branching fraction as (1.84 ± 0.05 (stat) ± 0.07 (syst) ± 0.11 (f_s/f_d) ± 0.12 (norm)) × 10^{-5}

Set an upper limit on $B^0 o \,phi \,phi$ branching fraction at < 2.8 × 10^{-8} (90% CL)

Achieved a fivefold reduction in statistical uncertainty for the $B_s^0 o \,phi \,phi$ measurement

Abstract

Using a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the $B_s^0 \to \phi \phi$ branching fraction is measured to be \[ \mathcal{B}(B_s^0 \to \phi \phi) = ( 1.84 \pm 0.05 (\text{stat}) \pm 0.07 (\text{syst}) \pm 0.11 (f_s/f_d) \pm 0.12 (\text{norm}) ) \times 10^{-5}, \] where $f_s/f_d$ represents the ratio of the $B_s^0$ to $B^0$ production cross-sections, and the $B^0 \to \phi K^*(892)^0$ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. A search for the decay $B^0 \to \phi \phi$ is also made. No signal is observed, and an upper limit on the branching fraction is set as \[ \mathcal{B}(B^0 \to \phi \phi) < 2.8 \times 10^{-8} \] at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.