New Physics Searches via Beam Normal Spin Asymmetry in Bhabha Scattering

TL;DR

This paper explores how beam normal spin asymmetry in Bhabha scattering can detect new physics beyond the Standard Model, especially scalar and vector mediators, offering a promising background-free search method.

Contribution

It introduces the use of beam normal spin asymmetry as a sensitive probe for BSM mediators in Bhabha scattering, highlighting a zero crossing point as a clean signal.

Findings

Scalar and vector mediators can be constrained beyond current limits.

The zero crossing in the asymmetry provides a background-free detection point.

Projected bounds significantly extend existing search ranges.

Abstract

We examine the sensitivity of the beam normal spin asymmetry in Bhabha scattering to beyond the Standard Model (BSM) mediators, in the context of the JLab polarized positron program. A key property of this observable is that the Standard Model contribution exhibits a zero crossing at a fixed scattering angle, providing a clean, effectively background-free point for these searches. We consider scalar, vector, and axial vector mediators and present projected bounds, finding that scalar and vector scenarios allow a significant extension of the search ranges beyond existing constraints.