Luminosity Spectrum Reconstruction at Linear Colliders

TL;DR

This paper presents a method to accurately reconstruct the luminosity spectrum at future e+e- colliders using a parametric model and reweighting technique, achieving 5% precision without bias in physics measurements.

Contribution

It introduces a novel approach combining a parametric luminosity spectrum model with reweighting to measure the spectrum from Bhabha events at 3 TeV CLIC.

Findings

Reconstructed the energy spectrum within 5% accuracy.

No significant bias introduced in smuon pair production analysis.

Method accounts for ISR, FSR, and cross-section effects.

Abstract

A good knowledge of the luminosity spectrum is mandatory for many measurements at future e+e- colliders. As the beam-parameters determining the luminosity spectrum cannot be measured precisely, the luminosity spectrum has to be measured through a gauge process with the detector. The measured distributions, used to reconstruct the spectrum, depend on Initial State Radiation, cross-section, and Final State Radiation. To extract the basic luminosity spectrum, a parametric model of the luminosity spectrum is created, in this case the spectrum at the 3 TeV Compact Linear Collider (CLIC). The model is used within a reweighting technique to extract the luminosity spectrum from measured Bhabha event observables, taking all relevant effects into account. The centre-of-mass energy spectrum is reconstructed within 5% over the full validity range of the model. The reconstructed spectrum does not result in a significant bias or systematic uncertainty in the exemplary physics benchmark process of smuon pair production.