Form factors of the $D \to \pi$ and $D \to K$ semileptonic decays with $N_f = 2$ twisted mass lattice QCD

TL;DR

This paper presents lattice QCD calculations of the form factors for D -> pi and D -> K semileptonic decays, achieving good agreement with experimental data and previous lattice results.

Contribution

First lattice QCD study using N_f=2 twisted mass fermions to compute D meson decay form factors across the full q^2 range with controlled systematic errors.

Findings

Form factors agree with experimental data across all q^2.

Zero momentum transfer form factors: f^{D->pi}(0)=0.65(6)(6), f^{D->K}(0)=0.76(5)(5).

Results align with recent N_f=2+1 lattice calculations.

Abstract

We present lattice results for the vector and scalar form factors of the semileptonic decays D -> \pi \ell \nu_ell and D -> K \ell \nu_\ell in the physical range of values of squared four momentum transfer q^2, obtained with N_f=2 maximally twisted Wilson fermions simulated at three different lattice spacings (a ~ 0.102 fm, 0.086 fm, 0.068 fm) with pion masses as light as 270 MeV and m_\pi L \gtrsim 4. The form factors are extracted using a double ratios strategy, which allows a good statistical accuracy and is independent of the vector current renormalization constant. The chiral/continuum extrapolation is performed through a simultaneous fit in the three variables (m_\pi, q^2, a) using HMChPT formulae with additional O(a^2) terms that parametrically account for the lattice spacing dependence. Our results are in very good agreement with the experimental data in the full q^2 range for both D -> \pi \ell \nu_\ell and D -> K \ell \nu_\ell. At zero momentum transfer we obtain f^{D->pi}(0) = 0.65(6)_{stat}(6)_{syst} and f^{D->K}(0) = 0.76(5)_{stat}(5)_{syst}, where the systematic error does not include the effects of quenching the strange and the charm quarks. Our findings are in good agreement with recent lattice calculations at N_f = 2+1.