# The 8th International Workshop on the CKM Unitarity Triangle

8-12 September 2014
Vienna University of Technology
Europe/Vienna timezone

## B-->pi form factors from Alpha collaboration

10 Sep 2014, 10:05
20m
EI 10 lecture hall (Vienna University of Technology)

### Speaker

Mr Felix Bahr (DESY Zeuthen)

### Description

We present the current status of the ongoing work of the ALPHA collaboration on the computation of the form factor $f_+ (q^2)$ for the semi-leptonic decay $\textnormal B_\textnormal s \to \textnormal K \ell \nu$. We simulate on lattices generated as part of the Coordinated Lattice Simulations (CLS) effort which have $N_\textnormal f=2$ non-perturbatively $O(a)$ improved Wilson fermions that satisfy $m_\pi L \geq 4$ and have sea pion masses down to $\approx 250 \,\textnormal{MeV}$. The heavy quark is treated in non-perturbative Heavy Quark Effective Theory (HQET). We discuss how to extract physical information from our raw measurement data and present first results in the form of a data point for the form factor at $q^2=21.23\,\textnormal{GeV}^2$ extrapolated to the continuum. We also address the inclusion of next-to-leading order terms in HQET and chiral extrapolation, which have yet to be performed.

 Slides