First measurement of sub-GeV $\nu_{\mu}$ charged-current coherent pion production on the argon nucleus in MicroBooNE

Abstract

I present a measurement of the $\nu_{\mu}$ charged-current (CC) coherent pion production cross section on the argon nucleus, performed using data collected by the MicroBooNE liquid argon time projection chamber (LArTPC) exposed to the Booster Neutrino Beam (BNB) at Fermilab. The analysis utilizes the full MicroBooNE dataset corresponding to an exposure of $1.31 \times 10^{21}$ protons on target (POT), with a mean neutrino energy of approximately $0.8$~GeV.

The flux-averaged cross section for this process is measured to be \[ \sigma = (9.7 \pm 1.3~\text{(stat)} \pm 1.2~\text{(syst)}) \times 10^{-40}~\text{cm}^2/\text{Ar}. \] This result constitutes the first measurement of CC coherent pion production on an argon nucleus at sub-GeV neutrino energies.

Coherent pion production is a rare neutrino-nucleus interaction in which the neutrino scatters coherently off the entire nucleus, leaving it in its ground state while producing a forward-going muon and pion with little momentum transfer. Owing to its clean two-body kinematics, the process provides a well-constrained experimental signature that can be isolated through topological and angular selections. In this work, the signal is extracted using a data-driven template-fitting method that minimizes dependence on theoretical models, thereby improving the robustness of the measurement against generator uncertainties.

Beyond representing a first-of-its-kind result on the argon nucleus, this measurement offers a benchmark for future neutrino experiments employing liquid-argon detectors. The simplicity and kinematic predictability of coherent pion events make them valuable for constraining the $\nu_{\mu}$-component of neutrino flux uncertainties and validating reconstruction performance in oscillation experiments such as DUNE. The results presented here thus contribute to the broader effort to achieve precise and model-independent neutrino cross-section measurements on argon nucleus, a critical ingredient for reducing systematic uncertainties in long-baseline neutrino oscillation physics.