Twisted mass QCD in the charm sector

TL;DR

This paper reports lattice QCD calculations of charm quark mass and D meson decay constants using twisted mass fermions with two dynamical flavors, highlighting the impact of renormalisation uncertainties.

Contribution

First lattice QCD determination of charm quark mass and decay constants using twisted mass fermions with two dynamical flavors at multiple lattice spacings.

Findings

Charm quark mass around 1.48 GeV with uncertainties.

Decay constants f_D and f_{D_s} measured with ~10-15% errors.

Renormalisation uncertainties dominate the error budget.

Abstract

We present preliminary results for the charm quark mass $m_c$ and the $D$ and $D_s$ mesons decay constants $f_D$ and $f_{D_s}$ from a lattice QCD calculation with ${\rm N_f}$ = 2 dynamical fermions. We use the twisted mass fermionic action defined at maximal twist so that physical quantities are automatically ${\cal O}(a)$ improved. Two lattice spacings are considered. The charm quark mass has been renormalised in the RI-MOM scheme. After a matching to the $\msb$ scheme, we obtain from the simulation at a fine lattice ($a \sim 0.09$ fm) $m_c^{\msb}(m_c) = 1.481 \pm 0.022 \pm 0.092$ GeV, $f_D = 205 \pm 13 \pm 17$ MeV, $f_{D_s} = 271 \pm 6 \pm 6$ MeV and from the simulation at the finer lattice ($a \sim 0.07$ fm) $m_c^{\msb}(m_c) = 1.474 \pm 0.041 \pm 0.132$ GeV, $f_D = 230 \pm 31 \pm 8$ MeV and $f_{D_s} = 264 \pm 5 \pm 8$ MeV. We chose three renormalisation conditions to determine $m_c$: the spread between the final results contributes to the systematic error. At both lattice spacings, particularly at the finer one, the error on $m_c$ is dominated by present uncertainty on the renormalisation constant $Z_P$, which should be reduced before performing a reliable continuum limit.