Toward inclusive observables with staggered quarks: the smeared $R$~ratio

TL;DR

This paper advances the computation of inclusive hadronic observables in lattice QCD by applying spectral reconstruction to the smeared R ratio using staggered quarks, comparing different lattice ensembles and addressing staggered quark effects.

Contribution

It demonstrates the feasibility of computing the smeared R ratio with staggered quarks using spectral reconstruction and compares results across different lattice formulations and ensembles.

Findings

Staggered-quark results are consistent with domain-wall results on comparable ensembles.

Spectral reconstruction effectively computes the smeared R ratio in lattice QCD.

Strategies for mitigating opposite-parity effects in staggered quark calculations are discussed.

Abstract

Inclusive hadronic observables are ubiquitous in particle and nuclear physics. Computation of these observables using lattice QCD is challenging due the presence of a difficult inverse problem. As a stepping stone to more complicated observables, we report on progress to compute the smeared $R$~ratio with staggered quarks using the spectral reconstruction algorithm of Hansen, Lupo, and Tantalo. We compare staggered-quark results on two ensembles to domain-wall results on a single ensemble and to the Bernecker-Meyer parameterization. This work utilizes two ensembles generated by the MILC collaboration using highly improved staggered quarks and one ensemble generated by the RBC/UKQCD collaboration using domain-wall quarks. Possible strategies for controlling opposite-parity effects associated with staggered quarks are discussed.