Study of hadron interactions in a lead-emulsion target

TL;DR

This study investigates hadron interactions in a lead-emulsion target using high-energy beams, measuring interaction characteristics and validating simulation models relevant for neutrino oscillation experiments.

Contribution

It provides detailed experimental data on hadron interactions and nuclear fragment emissions, validating Monte Carlo simulations for background estimation in neutrino experiments.

Findings

Interaction lengths and secondary particle distributions match simulations.

Nuclear fragment emission probabilities are >50% for P > 4 GeV/c.

Results support background estimation in tau neutrino detection.

Abstract

Topological and kinematical characteristics of hadron interactions have been studied using a lead-emulsion target exposed to 2, 4 and 10 GeV/c hadron beams. A total length of 60 m $\pi^-$ tracks was followed using a high speed automated emulsion scanning system. A total of 318 hadron interaction vertices and their secondary charged particle tracks were reconstructed. Measurement results of interaction lengths, charged particle multiplicity, emission angles and momenta of secondary charged particles are compared with a Monte Carlo simulation and appear to be consistent. Nuclear fragments emitted from interaction vertices were also detected by a newly developed emulsion scanning system with wide-angle acceptance. Their emission angle distributions are in good agreement with the simulated distributions. Probabilities of an event being associated with at least one fragment track are found to be greater than 50% for beam momentum $P > 4$ GeV/c and are well reproduced by the simulation. These experimental results validate estimation of the background due to hadron interactions in the sample of $\tau$ decay candidates in the OPERA $\nu_{\mu} \to \nu_{\tau}$ oscillation experiment.