Light quark masses and pseudoscalar decay constants fromN_f= 2 lattice QCD with twisted mass fermions

Abstract

We present the results of a lattice QCD calculation of the average up-down and strange quark masses and of the light meson pseudoscalar decay constants with N f = 2 dynamical fermions. The simulation is carried out at a single value of the lattice spacing with the twisted mass fermionic action at maximal twist, which guarantees automatic O(a)-improvement of the physical quantities. Quark masses are renormalized by implementing the non perturbative RI-MOM renormalization procedure. Our results for the light quark masses are m MS ud (2 GeV) = 3.85 ± 0.12 ± 0.40 MeV, m MS s (2 GeV) = 105±3±9 MeV and m s /m ud = 27.3±0.3±1.2. We also obtain f K = 161.7±1.2±3.1 MeV and the ratio f K /f π = 1.227±0.009±0.024. From this ratio, by using the experimental determination of Γ(K → µν µ (γ))/Γ(π → µν µ (γ)) and the average value of |V ud | from nuclear beta decays, we obtain |V us | = 0.2192(5)(45), in agreement with the determination from K l3 decays and the unitarity constraint.

A proposal for B-physics on current lattices

“…The latter was obtained in the standard way (see ref. [28][29][30]) from the same ETMC gauge configuration ensembles, but with a rather different analysis method where the meson masses rather than the renormalized quark masses were kept fixed as a → 0, resulting in somewhat different statistical (no use of Z P ) and systematic errors as compared to the present study. For the present computation of f hu/d (μ (1) h ) = f D the quality of the continuum and chiral extrapolation of our lattice data is shown in figure 7.…”

“…From the set of the ETMC simulation data [28][29][30] with parameters detailed in table 1, we extract the values of the hℓ pseudoscalar meson masses that correspond to theμ h values listed in (2.9). With these masses we construct the lattice ratios (2.1) on which a combined continuum and chiral fit is performed.…”

“…As a first test of the method, we have computed in (the continuum limit of) QCD with N f = 2 light dynamical quarks the (renormalized) b-quark mass as well as the B-meson decay constants, f B and f Bs , employing the gauge configurations recently produced by the ETM Collaboration with maximally twisted Wilson fermion action [28][29][30].…”

A mixed action analysis of η and η′ mesons

“…However, this complication can be avoided by using a mixed action approach for the valence strange and charm quarks. Formally, we introduce so-called Osterwalder-Seiler (OS) twisted valence strange and charm quarks [11,35]. The Dirac operator for a single valence quark flavour q reads…”

“…(6). Instead, meson masses are used: in previous studies it was found that matching kaon masses determined from the operator (4) to the unitary kaon masses is best in the sense that the residual lattice artifacts in the results computed in a mixed action approach are small [36]. We will call this procedure kaon matching.…”