Journal Article

PUBDB-2023-03985

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Probing the Energy-Smeared $R$ Ratio Using Lattice QCD

Alexandrou, C. ; Bacchio, S. ; De Santis, A. ; Dimopoulos, P. ; Finkenrath, J. ; Frezzotti, R. ; Gagliardi, G. ; Garofalo, M. ; Hadjiyiannakou, K. ; Kostrzewa, B. ; Jansen, K.DESY* ; Lubicz, V. ; Petschlies, M. ; Sanfilippo, F. ; Simula, S. ; Tantalo, N. (Corresponding author) ; Urbach, C. ; Wenger, U. ; Extended Twisted Mass Collaboration (Collaboration Author)

2023
APS College Park, Md.

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Please use a persistent id in citations: doi:10.1103/PhysRevLett.130.241901  doi:10.3204/PUBDB-2023-03985

Report No.: arXiv:2212.08467

Abstract: We present a first-principles lattice QCD investigation of the $R$ ratio between the $e^+e^-$ cross section into hadrons and into muons. By using the method of Ref. [1], that allows one 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 centering the Gaussians in the region around the $ρ$-resonance peak, a tension of about 3 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.

Keyword(s): density: spectral ; correlation function: Euclidean ; muon ; GeV ; lattice ; lattice field theory ; quantum chromodynamics ; tension ; hadron

Note: Version accepted for publication on PRL. Results unchanged

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Contributing Institute(s):

1. Centre f. Quantum Techno. a. Application (CQTA)

Research Program(s):

1. 611 - Fundamental Particles and Forces (POF4-611) (POF4-611)

Experiment(s):

1. No specific instrument

Appears in the scientific report 2023

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Linked articles:

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Preprint Alexandrou, C. ; Bacchio, S. ; De Santis, A.Extern* ; Dimopoulos, P. ; Finkenrath, J. ; Frezzotti, R. ; Gagliardi, G. ; Garofalo, M. ; Hadjiyiannakou, K. ; Kostrzewa, B.Extern* ; Jansen, K.DESY* ; Lubicz, V. ; Petschlies, M. ; Sanfilippo, F. ; Simula, S. ; Tantalo, N. (Corresponding author) ; Urbach, C. ; Wenger, U.
Probing the $R$ -ratio on the lattice
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