Heavy semileptonics with a fully relativistic mixed action

TL;DR

This paper discusses a relativistic mixed action approach using twisted mass valence quarks for heavy semileptonic decays, achieving high-precision form factors at zero momentum transfer.

Contribution

It introduces a novel fully relativistic mixed action strategy with twisted mass quarks for heavy quark calculations on CLS ensembles.

Findings

Form factors at $q^2=0$ are at the percent statistical precision level.

Preliminary results for $D o K$ and $D o ext{ extmu} o ext{ extmu}$ decays are presented.

The approach reduces discretisation errors in heavy quark lattice calculations.

Abstract

The first phase of a heavy quark program based on twisted mass valence quarks has been presented at last years's lattice conference. The CLS $N_f=2+1$ ensembles were used for their fine lattice spacing, while twisting the masses is expected to reduce discretisation errors even further and allow for a fully relativistic calculation. We present our strategy and preliminary results on three point functions, corresponding to $D\to K$ and $D\to\pi$ semileptonic decays. The form factors for $m_u=m_d=m_s$ quark masses obtained as a first step are shown here to be at the percent level in statistical precision at $q^2=0$.