Momentum Measurement of Charged Particles in FASER's Emulsion Detector at the LHC

TL;DR

This paper introduces a novel method to measure charged particle momentum in the FASER neutrino emulsion detector using multiple Coulomb scattering, enabling high-precision measurements from GeV to TeV energies.

Contribution

The paper presents a new momentum measurement technique based on multiple Coulomb scattering tailored for the FASER neutrino emulsion detector, validated through simulations and test beam data.

Findings

Method accurately measures momenta from a few GeV to TeV energies.

Validation with Monte Carlo simulations shows reliable performance.

Background muons' reconstructed momenta align with expectations.

Abstract

We present a momentum measurement method based on multiple Coulomb scattering (MCS) in the FASER$\nu$ emulsion detector. The measurement of charged-particle momenta is essential for studying neutrino interactions in the TeV energy range at the FASER experiment. This method exploits the sub-micron spatial resolution and long tracking length of the FASER$\nu$ detector, enabling momentum determination from a few GeV up to a few TeV. The performance was evaluated using Geant4-based Monte Carlo simulations and validated with muon test beam data in the momentum range 100-300 GeV. As a first probe of the method for higher momentum muons, background muons recorded by the FASER$\nu$ detector were examined, showing reconstructed momenta consistent with expectations from their angular spread.