Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets

TL;DR

This study measures charged pion production from long cylindrical targets hit by protons at various energies, comparing experimental data with Monte Carlo simulations to improve understanding of particle yields for different target materials.

Contribution

It provides the first detailed comparison of pion production from long targets with predictions from MARS and GEANT4 simulations, extending previous thin-target measurements.

Findings

Data show differences between measured yields and simulations.

Results vary with target material and proton energy.

Provides correction factors for long-target pion production.

Abstract

The HARP collaboration has presented measurements of the double-differential pi+/pi- production cross-section in the range of momentum 100 MeV/c <= p 800 MeV/c and angle 0.35 rad <= theta <= 2.15 rad with proton beams hitting thin nuclear targets. In many applications the extrapolation to long targets is necessary. In this paper the analysis of data taken with long (one interaction length) solid cylindrical targets made of carbon, tantalum and lead is presented. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. The secondary pions were produced by beams of protons with momenta 5 GeV/c, 8 GeV/c and 12 GeV/c. The tracking and identification of the produced particles were performed using a small-radius cylindrical time projection chamber (TPC) placed inside a solenoidal magnet. Incident protons were identified by an elaborate system of beam detectors. Results are obtained for the double-differential yields per target nucleon d2 sigma / dp dtheta. The measurements are compared with predictions of the MARS and GEANT4 Monte Carlo simulations.