The design of the ILD forward region

TL;DR

This paper analyzes how relocating the BeamCal closer to the interaction point affects background levels, revealing significant increases in beamstrahlung and backscattered particle depositions, impacting detector performance.

Contribution

It provides a detailed study of background changes due to the reduced L* and the resulting implications for detector design and operation.

Findings

Beamstrahlung depositions increase by 20% at BeamCal

Backscattered electron and positron backgrounds nearly double

Photon counts in the tracker significantly rise

Abstract

Following the decision to reduce the L* from 4.4 m to 4.1 m, the BeamCal had to be moved closer to the interaction point. Results of a study of how this affects the beamstrahlung and backward scattering backgrounds show that the e+e- pair background depositions from beamstrahlung at the BeamCal rises by 20%. The background from backscattered electrons and positrons in the inner pixel layers rises almost by a factor two, so does the number of photons in the tracker.