Momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector

TL;DR

This paper introduces a novel maximum likelihood method for reconstructing charged particle momentum in nuclear emulsion detectors by analyzing multiple Coulomb scatterings, accounting for energy loss, and validated through simulations and NINJA experiment data.

Contribution

The paper presents a new momentum reconstruction technique that incorporates energy decrease effects, improving accuracy for low-momentum particles in nuclear emulsion detectors.

Findings

Achieves 10% momentum resolution for 500 MeV/c muons

Method reduces bias in low-momentum measurements

Experimental validation shows good agreement with independent measurements

Abstract

This paper describes a new method for momentum reconstruction of charged particles using multiple Coulomb scatterings in a nuclear emulsion detector with a layered structure of nuclear emulsion films and target materials. The method utilizes the scattering angles of particles precisely measured in the emulsion films. The method is based on the maximum likelihood to newly include information on the decrease of the energy as the particle travels through the detector. According to the Monte Carlo simulations, this method can measure momentum with a resolution of 10% for muons of 500 MeV/c passing through the detector perpendicularly. The momentum resolution is evaluated to be 10-20%, depending on the momentum and emission angle of the particle. By accounting for the effect of the energy decrease, the momentum can be reconstructed correctly with less bias, particularly in the low-momentum region. We apply this method to measure the momentum of muon tracks detected in the NINJA experiment where the momentum is also measured independently by using the track range. The two measurements agree well within experimental uncertainties, verifying the method experimentally. This method will extend the measurable phase space of muons and hadrons in the NINJA experiment.