Probing the energy-smeared R-ratio on the lattice

Abstract

We present a first-principles lattice QCD investigation of the $R$-ratio between the $e^{+}{e}^{-}$ cross-section into hadrons and that into muons. By using the method of Ref.[1], that allows to extract smeared spectral densities from Euclidean correlators, we compute the $R$-ratio convoluted with Gaussian smearing kernels of widths of about $600$ MeV and central energies from $220$ MeV up to $2.5$ GeV. Our theoretical results are compared with the corresponding quantities obtained by smearing the KNT19 compilation [2] of $R$-ratio experimental measurements with the same kernels and, by centring the Gaussians in the region around the $\rho$-resonance peak, a tension of about three standard deviations is observed. From the phenomenological perspective, we have not included yet in our calculation QED and strong isospin-breaking corrections and this might affect the observed tension. From the methodological perspective, our calculation demonstrates that it is possible to study the $R$-ratio in Gaussian energy bins on the lattice at the level of accuracy required in order to perform precision tests of the Standard Model.

Version accepted for publication on PRL. Results unchanged

References in corpus (10)

• The $g-2$ of charged leptons, $\alpha (M_Z^2)$ and the hyperfine splitting of muonium
• Lattice calculation of the short and intermediate time-distance hadronic vacuum polarization contributions to the muon magnetic moment using twisted-mass fermions
• Window observable for the hadronic vacuum polarization contribution to the muon $g-2$ from lattice QCD
• Data-driven evaluations of Euclidean windows to scrutinize hadronic vacuum polarization
• On the extraction of spectral densities from lattice correlators
• Reconstructing QCD Spectral Functions with Gaussian Processes
• Isospin-breaking effects in the two-pion contribution to hadronic vacuum polarization
• Bayesian Approach to Inverse Problems: an Application to NNPDF Closure Testing
• Inverse problems, real-time dynamics and lattice simulations
• Spectral-weight sum rules for the hadronic vacuum polarization

Cited by in corpus (9)

• The anomalous magnetic moment of the muon in the Standard Model: an update
• Measurement of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ cross section from threshold to 1.2 GeV with the CMD-3 detector
• Measurement of the pion form factor with CMD-3 detector and its implication to the hadronic contribution to muon (g-2)
• A phenomenological estimate of isospin breaking in hadronic vacuum polarization
• Muon $g-2$: Lattice calculations of the hadronic vacuum polarization
• The curvature of the pseudo-critical line in the QCD phase diagram from mesonic lattice correlation functions
• Modeling the $R$-ratio and hadronic contributions to $g-2$ with a Treed Gaussian Process
• Revisiting Affleck-Dine Leptogenesis with light sleptons
• Topological susceptibility and excess kurtosis in SU(3) Yang-Mills theory