Search for $B^{+}\rightarrow K^{+} \tau^{+}\tau^{-}$ at the BaBar experiment

TL;DR

This study searches for the rare decay $B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ using BABAR data, finds no significant signal, and sets an upper limit on its branching fraction, contributing to understanding flavor-changing neutral currents.

Contribution

First search for $B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ decay at BABAR, providing experimental upper limits on its branching fraction.

Findings

No evidence for the decay was observed.

Measured branching fraction is approximately 1.31 x 10^{-3}.

Upper limit on the branching fraction is 2.25 x 10^{-3} at 90% CL.

Abstract

We search for the rare flavor-changing neutral current process $B^{+}\rightarrow K^{+}\tau^{+}\tau^{-}$ using data from the BABAR experiment. The data sample, collected at the center-of-mass energy of the $\Upsilon{(4S)}$ resonance, corresponds to a total integrated luminosity of 424 fb$^{-1}$ and to 471 million $B\overline{B}$ pairs. We reconstruct one $B$ meson, produced in the $\Upsilon{(4S)}\rightarrow B^{+} B^{-}$ decay, in one of many hadronic decay modes and search for activity compatible with a $B^{+}\rightarrow K^{+} \tau^{+}\tau^{-}$ decay in the rest of the event. Each $\tau$ lepton is required to decay leptonically into an electron or muon and neutrinos. Comparing the expected number of background events with the data sample after applying the selection criteria, we do not find evidence for a signal. The measured branching fraction is ($1.31^{+0.66}_{-0.61}$( stat.)$^{+0.35}_{-0.25}$( sys.)$) \times 10^{-3}$ with an upper limit, at the 90\% confidence level, of $\mathcal{B}(B^{+}\rightarrow K^{+}\tau^{+}\tau^{-})$$< 2.25\times 10^{-3}$.