Electroweak Physics with Polarized Electron Beams in a SuperKEKB Upgrade

Abstract

Consideration is being given to upgrading the SuperKEKB e${}^{+}$e${}^{-}$ collider with polarized electron beams, which would open a new program of precision electroweak physics at a centre-of-mass energy of 10.58GeV, the mass of the ${\rm Y}(4S)$. These measurements include ${\sin }^2{\theta }_W$ obtained via left-right asymmetry measurements of e${}^{+}$e${}^{-}$ transitions to pairs of electrons, muons, taus, charm and b-quarks. The precision obtainable at SuperKEKB will match that of the LEP/SLC world average and will thereby probe the neutral current couplings with unprecedented precision at a new energy scale sensitive to the running of the couplings. At SuperKEKB the measurements of the individual neutral current vector coupling constants to b-quarks and c-quarks and muons in particular will be substantially more precise than current world averages and the current 3$\sigma$ discrepancy between the SLC A${}_{LR}$ measurements and LEP A${}_{FB}^b$ measurements of ${\sin }^2{\theta }_W^{eff}$ will be addressed. This paper will include a discussion of the necessary upgrades to SuperKEKB. This program opens an exciting new window in searches for physics beyond the Standard Model.

Contribution to Proceedings of Flavor Physics and CP Violation Conference, Victoria BC, 2019

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