Measurement of the production cross-section of positive pions in p-Al collisions at 12.9 GeV/c

TL;DR

This paper reports a precise measurement of the positive pion production cross-section in proton-aluminium collisions at 12.9 GeV/c, crucial for neutrino flux calculations in the K2K experiment.

Contribution

It provides the first detailed double-differential cross-section data for positive pions in p-Al collisions at this energy, with improved accuracy and normalization.

Findings

Cross-section measured with better than 6% normalization accuracy.

Data covers pion momenta from 0.75 to 6.5 GeV/c.

Angular range from 30 to 210 mrad.

Abstract

A precision measurement of the double-differential production cross-section, ${{d^2 \sigma^{\pi^+}}}/{{d p d\Omega}}$, for pions of positive charge, performed in the HARP experiment is presented. The incident particles are protons of 12.9 GeV/c momentum impinging on an aluminium target of 5% nuclear interaction length. The measurement of this cross-section has a direct application to the calculation of the neutrino flux of the K2K experiment. After cuts, 210000 secondary tracks reconstructed in the forward spectrometer were used in this analysis. The results are given for secondaries within a momentum range from 0.75 GeV/c to 6.5 GeV/c, and within an angular range from 30 mrad to 210 mrad. The absolute normalization was performed using prescaled beam triggers counting protons on target. The overall scale of the cross-section is known to better than 6%, while the average point-to-point error is 8.2%.