Correction of beam-beam effects in luminosity measurement in the forward region at CLIC

TL;DR

This paper presents methods to correct beam-beam effects in luminosity measurements at CLIC using Monte Carlo simulations, achieving high precision in the corrected measurements at 3 TeV energy.

Contribution

It introduces novel correction procedures for beam-beam effects in luminosity measurements, validated through simulations at CLIC's 3 TeV energy.

Findings

Correction precision of 1.4 permille at high energies

Correction precision of 2.7 permille at lower energies

Effective correction of angular and spectrum distortions

Abstract

Procedures for correcting the beam-beam effects in luminosity measurements at CLIC at 3 TeV center-of-mass energy are described and tested using Monte Carlo simulations. The angular counting loss due to the combined Beamstrahlung and initial-state radiation effects is corrected based on the reconstructed velocity of the collision frame of the Bhabha scattering. The distortion of the luminosity spectrum due to the initial-state radiation is corrected by deconvolution. At the end, the counting bias due to the finite calorimeter energy resolution is numerically corrected. To test the procedures, BHLUMI Bhabha event generator, and Guinea-Pig beam-beam simulation were used to generate the outgoing momenta of Bhabha particles in the bunch collisions at CLIC. The systematic effects of the beam-beam interaction on the luminosity measurement are corrected with precision of 1.4 permille in the upper 5% of the energy, and 2.7 permille in the range between 80 and 90% of the nominal center-of-mass energy.