Hadronic physics with domain-wall valence and improved staggered sea quarks

TL;DR

Hadronic physics with domain-wall valence and improved staggered sea quarks addresses the feasibility of simulating light dynamical quarks in lattice QCD using a hybrid approach with Asqtad sea quarks and domain-wall valence quarks, aiming for the correct continuum limit. The authors tune the fifth-dimension length $L_5$ and the bare valence mass $(am)_q^{\text{DWF}}$ to minimize the residual mass $m_{\text{res}}$ and to match pseudoscalar masses $m_\pi$ between sea and valence sectors, enabling computation of $F_1(-t)$ and $g_A$. They report dipole-like behavior of $F_1(-t)$ with a growing transverse radius $r_{\text{MS}}$ as $m_\pi^2$ decreases and show that $g_A$ approaches the experimental value in larger volumes, illustrating finite-size effects are volume-dependent. Overall, the results support the viability of the hybrid scheme for realistic hadronic observables and motivate further studies with larger volumes and refined actions.

Abstract

With the advent of chiral fermion formulations, the simulation of light valence quarks has finally become realistic for numerical simulations of lattice QCD. The simulation of light dynamical quarks, however, remains one of the major challenges and is still an obstacle to realistic simulations. We attempt to meet this challenge using a hybrid combination of Asqtad sea quarks and domain-wall valence quarks. Initial results for the proton form factor and the nucleon axial coupling are presented.

Figures (6)

• Figure 1: Residual quark mass as a function of $L_5$ for the two samples (heavy and light) of $25$ configurations each.
• Figure 2: The pion mass with heavy and light quarks, $m_{\pi,\text{heavy}}$ and $m_{\pi,\text{light}}$, and the nucleon mass with heavy and light quarks, $m_{\text{N,heavy}}$ and $m_{\text{N,light}}$, as a function of $L_5$.
• Figure 3: The same quantities as in Figure \ref{['fig:masses-L_5']}, but with a Jackknife analysis of the mass differences vs. $L_5=16$.
• Figure 4: The proton form factor, $F_1(-t)$, as a function of the virtuality, $t=q^2$.
• Figure 5: Transverse root-mean squared radius $r_{\text{MS}}$ of the nucleon as a function of the pion mass squared.