# The 35th International Symposium on Lattice Field Theory

18-24 June 2017
Palacio de Congresos
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# Contribution Parallel

Andalucía I
Weak Decays and Matrix Elements

# $B_s \to K \ell\nu$ form factors with 2+1 flavors

## Speakers

• Prof. Steven GOTTLIEB

## Content

Using the MILC 2+1 flavor asqtad quark action ensembles, we are calculating the form factors $f_0$ and $f_+$ for the semileptonic $B_s \rightarrow K \ell\nu$ decay. A total of six ensembles with lattice spacing from $\approx0.12$ to 0.06 fm are being used. At the coarsest and finest lattice spacings, the light quark mass $m_l$ is one-tenth the strange quark mass $m_s$. At the intermediate lattice spacing, the ratio $m_l/m_s$ ranges from 0.05 to 0.2. The valence $b$ quark is treated using the Sheikholeslami-Wohlert Wilson-clover action with the Fermilab interpretation. The other valence quarks use the asqtad action. When combined with (future) measurements from the LHCb experiment, these calculations will provide another way to determine the CKM matrix element $|V_{ub}|$.