Probing the energy-smeared R-ratio on the lattice
Abstract
We present a first-principles lattice QCD investigation of the -ratio between the 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 -ratio convoluted with Gaussian smearing kernels of widths of about MeV and central energies from MeV up to GeV. Our theoretical results are compared with the corresponding quantities obtained by smearing the KNT19 compilation [2] of -ratio experimental measurements with the same kernels and, by centring the Gaussians in the region around the -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 -ratio in Gaussian energy bins on the lattice at the level of accuracy required in order to perform precision tests of the Standard Model.
Keywords
Cite
@article{arxiv.2212.08467,
title = {Probing the energy-smeared R-ratio on the lattice},
author = {Constantia Alexandrou and Simone Bacchio and Alessandro De Santis and Petros Dimopoulos and Jacob Finkenrath and Roberto Frezzotti and Giuseppe Gagliardi and Marco Garofalo and Kyriakos Hadjiyiannakou and Bartosz Kostrzewa and Karl Jansen and Vittorio Lubicz and Marcus Petschlies and Francesco Sanfilippo and Silvano Simula and Nazario Tantalo and Carsten Urbach and Urs Wenger},
journal= {arXiv preprint arXiv:2212.08467},
year = {2023}
}
Comments
Version accepted for publication on PRL. Results unchanged