Observation of the annihilation decay mode $B^{0}\to K^{+}K^{-}$

TL;DR

This paper reports the first observation of the rare decay mode $B^{0} o K^{+}K^{-}$ using LHCb data, and provides an improved measurement of the $B_s^0 o ext{pi}^+ ext{pi}^-$ branching fraction, enhancing understanding of B meson decays.

Contribution

The paper presents the first observation of the $B^{0} o K^{+}K^{-}$ decay and refines the measurement of the $B_s^0 o ext{pi}^+ ext{pi}^-$ branching fraction using LHCb data.

Findings

First observation of $B^{0} o K^{+}K^{-}$ decay with >5 sigma significance.

Measured branching fraction for $B^{0} o K^{+}K^{-}$: $(7.80 imes 10^{-8})$.

Improved measurement of $BR(B_s^0 o ext{pi}^+ ext{pi}^-)$.

Abstract

A search for the $B^{0}\to K^{+}K^{-}$ decay is performed using $pp$-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1 and 2 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than five standard deviations. The analysis also results in an improved measurement of the branching fraction for the $B_s^0\to \pi^+\pi^-$ decay. The measured branching fractions are $BR(B^0\to K^+K^-) = (7.80 \pm 1.27 \pm 0.81 \pm 0.21) \times 10^{-8}$ and $BR(B_s^0\to\pi^+\pi^-) = (6.91 \pm 0.54 \pm 0.63 \pm 0.19 \pm 0.40) \times 10^{-7}$. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the $B^0\to K^+\pi^-$ branching fraction used as a normalization. For the $B_s^0$ mode, the fourth accounts for the uncertainty on the ratio of the probabilities for $b$ quarks to hadronize into $B_s^0$ and $B^0$ mesons.