Neutrino-induced coherent $\pi^{+}$ production in C, CH, Fe and Pb at $\langle E_{\nu}\rangle \sim 6$ GeV

TL;DR

This study measures neutrino-induced coherent pion production across various targets at around 6 GeV, revealing higher cross sections than existing models predict and an evolving atomic number dependence at higher energies.

Contribution

It provides the first simultaneous measurements of this process in multiple targets and compares the results to theoretical models, highlighting discrepancies and energy-dependent scaling.

Findings

Measured cross sections exceed model predictions at multi-GeV energies.

Observed A-scaling increases from ~A^{1/3} to ~A^{2/3} with energy.

Cross-section ratios suggest energy-dependent nuclear effects.

Abstract

MINERvA has measured the $\nu_{\mu}$-induced coherent $\pi^{+}$ cross section simultaneously in hydrocarbon (CH), graphite (C), iron (Fe) and lead (Pb) targets using neutrinos from 2 to 20 GeV. The measurements exceed the predictions of the Rein-Sehgal and Berger-Sehgal PCAC based models at multi-GeV $\nu_{\mu}$ energies and at produced $\pi^{+}$ energies and angles, $E_{\pi}>1$ GeV and $\theta_{\pi}<10^{\circ}$. Measurements of the cross-section ratios of Fe and Pb relative to CH reveal the effective $A$-scaling to increase from an approximate $A^{1/3}$ scaling at few GeV to an $A^{2/3}$ scaling for $E_{\nu}>10$ GeV.