Search for B^0 -> l^+ l^- at Belle

TL;DR

This paper reports a search for rare B^0 meson decays into lepton pairs using Belle data, setting upper limits on branching fractions and leptoquark mass, with no candidate events observed.

Contribution

First search for B^0 -> e^+ e^-, mu^+ mu^-, and e^{+-} mu^{-+} decays at Belle, establishing new upper limits and constraining leptoquark models.

Findings

No candidate events observed.

Upper limits on branching fractions set.

Lower limit on leptoquark mass established.

Abstract

We report the results of a search for the decay B^0 -> e^+ e^-, mu^+ mu^- and e^{+-} mu^{-+} based on an analysis of 78 fb^{-1} of data collected by the Belle detector at KEKB. No candidate events have been found. Upper limits on the branching fractions are calculated at the 90% confidence level: B(B^0 -> e^+ e^-) < 1.9 x 10^{-7}, B(B^0 -> mu^+ mu^-) < 1.6 x 10^{-7}, and B(B^0 -> e^{+-} mu^{-+})< 1.7 x 10^{-7}. A limit on the Pati-Salam leptoquark mass M_{LQ}> 46 TeV/c^2 is obtained at the 90% confidence level.