Speaker
Description
Our recent work has shown that a novel, much higher granularity
forward calorimetry concept can enable much more detailed and precise
reconstruction than the baseline designs based on LEP luminometers, together
with the capability of electron/positron/photon separation.
This new calorimeter concept is designed primarily to maximize the acceptance
for $e^+e^- \to \gamma \gamma$ as an alternative luminosity process, where it serves
to define the inner edge of the acceptance (there is no outer edge - as the
complete detector is used in the measurement), while continuing to provide
the standard luminosity measurement from small angle Bhabhas. It will also
serve as a general forward electromagnetic calorimeter helping ensure hermeticity
and detecting individual electrons/positrons/photons.
In this contribution we will highlight the Bhabha rejection capability in the
context of the $e^{+}e^{-} \to \gamma \gamma$ luminosity measurement and investigate the
utility of a Bhabha ``mini-tracker'' consisting of a few planes of
upstream thin silicon detectors. This will further refine the $e^{+}$/$e^{-}$ polar angle measurement, improve Bhabha rejection (for gamma gamma), and,
last-but-not-least, help mitigate the beam-induced electromagnetic deflection
that biases the Bhabha acceptance by providing high precision longitudinal
vertex information in Bhabha events than can be used in diagnosing this
beam/final-state $e^{+}/e^{-}$ effect.
