Left-right asymmetry calculation comparisons and projected sensitivity to the weak mixing angle in polarized Bhabha scattering at 10.58 GeV

Abstract

Consideration is being given to upgrading the SuperKEKB electron-positron collider with the introduction of electron-beam polarization. This would enable a unique precision electroweak physics program that opens new ways to search for physics beyond the Standard Model. The upgrade would enable Belle II to make a number of high precision measurements, one of which is the left-right cross-section asymmetry in the $e^{+}{e}^{-}\to e^{+}{e}^{-}$ Bhabha scattering process. The expected level of precision in such a measurement will require the theoretical values of the asymmetry to be calculated at least to the next-to-leading order (NLO) level, and the implementation of simulation event generators with a similar level of precision. In this study, we compare the calculations of the ReneSANCe Monte Carlo generator with those of an independent NLO calculation to determine the level of agreement in this process. A 2.3% difference between the calculations is found and attributed to some higher-order effects being accounted for in the ReneSANCe generator. Using the published Belle II efficiency for selecting Bhabha events and assuming a 40 ab${}^{-1}$ dataset having 70% polarization, the projected uncertainty on the weak mixing angle, sin${}^2{\theta }_W$ , is calculated using ReneSANCe to be $\pm$0.00032 or better. Combining this with left-right asymmetry measurements from muons and taus under the assumption of lepton universality yields a projected overall uncertainty of $\pm$0.00019 on sin${}^2{\theta }_W$ with SuperKEKB upgraded to have polarized electron beams.

References in corpus (10)

• Precision Electroweak Measurements on the Z Resonance
• Low Q^2 Weak Mixing Angle Measurements and Rare Higgs Decays
• Measurement of the integrated luminosity of the Phase 2 data of the Belle II experiment
• Measurement of the integrated luminosity of data samples collected during 2019-2022 by the Belle II experiment
• Polarized NLO EW $e^{+}{e}^{-}$ cross section calculations with ReneSANCe-v1.0.0
• Lepton pair production at NNLO in QED with EW effects
• Quadratic electroweak corrections for polarized Moller scattering
• Two-loop electroweak vertex corrections for polarized Møller scattering
• Measurement of the Drell-Yan forward-backward asymmetry and of the effective leptonic weak mixing angle in proton-proton collisions at $\sqrt{s}$ = 13 TeV
• NLO radiative corrections for Forward-Backward and Left-Right Asymmetries at a B-Factory