B+ and Ds+ Decay Constants from Belle and Babar

TL;DR

This paper discusses measurements of B+ and Ds+ decay constants from Belle and Babar experiments, comparing them to lattice QCD calculations and highlighting a notable discrepancy for Ds+.

Contribution

It provides experimental measurements of decay constants and compares them with theoretical predictions, revealing a significant difference for Ds+ decay constant.

Findings

Measured B+ and Ds+ decay constants from experiments

Identified a 2.1 sigma discrepancy for Ds+ decay constant

Compared experimental results with lattice QCD calculations

Abstract

The Belle and Babar experiments have measured the branching fractions for B+ -> tau+ nu and Ds+ -> mu+ nu decays. From these measurements one can extract the B+ and Ds+ decay constants, which can be compared to lattice QCD calculations. For the Ds+ decay constant, there is currently a 2.1 sigma difference between the calculated value and the measured value.