TY - JOUR
T1 - Hadronic vacuum polarization
T2 - Comparing lattice QCD and data-driven results in systematically improvable ways
AU - Davier, Michel
AU - Fodor, Zoltán
AU - Gérardin, Antoine
AU - Lellouch, Laurent
AU - Malaescu, Bogdan
AU - Stokes, Finn M.
AU - Szabó, Kálmán K.
AU - Toth, Balint C.
AU - Varnhorst, Lukas
AU - Zhang, Zhiqing
N1 - Publisher Copyright:
© 2024 authors. Published by the American Physical Society. Published by the American Physical Society under the terms of the "https://creativecommons.org/licenses/by/4.0/"Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.
PY - 2024/4/1
Y1 - 2024/4/1
N2 - The precision with which hadronic vacuum polarization (HVP) is obtained determines how accurately important observables, such as the muon anomalous magnetic moment aμ or the low-energy running of the electromagnetic coupling α, are predicted. The two most precise approaches for determining HVP are dispersive relations combined with e+e-→hadrons cross section data and lattice QCD. However, the results obtained in these two approaches display significant tensions, whose origins are not understood. Here we present a framework that sheds light on this issue and - if the two approaches can be reconciled - allows them to be combined. Via this framework, we test the hypothesis that the tensions can be explained by modifying the R-ratio in different intervals of center-of-mass energy s. As ingredients, we consider observables that have been precisely determined in both approaches. These are the leading hadronic contributions to aμ, to the so-called intermediate window observable, and to the running of α between spacelike virtualities 1 and 10 GeV2 (for which only a preliminary lattice result exists). Our tests take into account all uncertainties and correlations, as well as uncertainties on uncertainties in the lattice results. For instance, using this framework we show that results obtained in the two approaches can be made to agree, for all three observables, by modifying the ρ peak in the experimental spectrum. More specifically, we show that this requires a common ∼5% increase in the contributions of the peak to each of the three observables. This result is robust against the presence or absence of the running of α in the comparison. However, such an increase is much larger than the uncertainties on the measured R-ratio. We also discuss a variety of generalizations of the methods used here, as well as the limits in the information that can be extracted from the R-ratio via a finite set of observables.
AB - The precision with which hadronic vacuum polarization (HVP) is obtained determines how accurately important observables, such as the muon anomalous magnetic moment aμ or the low-energy running of the electromagnetic coupling α, are predicted. The two most precise approaches for determining HVP are dispersive relations combined with e+e-→hadrons cross section data and lattice QCD. However, the results obtained in these two approaches display significant tensions, whose origins are not understood. Here we present a framework that sheds light on this issue and - if the two approaches can be reconciled - allows them to be combined. Via this framework, we test the hypothesis that the tensions can be explained by modifying the R-ratio in different intervals of center-of-mass energy s. As ingredients, we consider observables that have been precisely determined in both approaches. These are the leading hadronic contributions to aμ, to the so-called intermediate window observable, and to the running of α between spacelike virtualities 1 and 10 GeV2 (for which only a preliminary lattice result exists). Our tests take into account all uncertainties and correlations, as well as uncertainties on uncertainties in the lattice results. For instance, using this framework we show that results obtained in the two approaches can be made to agree, for all three observables, by modifying the ρ peak in the experimental spectrum. More specifically, we show that this requires a common ∼5% increase in the contributions of the peak to each of the three observables. This result is robust against the presence or absence of the running of α in the comparison. However, such an increase is much larger than the uncertainties on the measured R-ratio. We also discuss a variety of generalizations of the methods used here, as well as the limits in the information that can be extracted from the R-ratio via a finite set of observables.
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U2 - 10.1103/PhysRevD.109.076019
DO - 10.1103/PhysRevD.109.076019
M3 - Article
AN - SCOPUS:85193945011
SN - 2470-0010
VL - 109
JO - Physical Review D
JF - Physical Review D
IS - 7
M1 - 076019
ER -