Speaker
Description
The absolute machine luminosity is a crucial parameter for high-precision measurements at future colliders. Its determination relies on the precise prediction of the cross section of some reference process, which is calculated within the Standard Model (SM). It is therefore crucial to have under control the uncertainties induced by possible New Physics (NP) effects on this reference process. We here investigate the possible NP contamination on small-angle Bhabha scattering at future electron-positron machines, by considering that NP contributions can arise due to either heavy degrees of freedom or light mediators with small couplings to SM particles.
In the first scenario, we parametrise the effects in a model-independent way through the Standard Model Effective Field Theory (SMEFT), while in the second case we consider different models. We show how four-electron SMEFT operators affect the Bhabha cross section in a non-negligible way and discuss possible strategies to reduce this contamination.