Measurement of $π^0$ Production in $\barν_μ$ Charged-Current Interactions in the NOvA Near Detector

TL;DR

This work delivers a high-statistics measurement of antineutrino-induced CC $\pi^0$ production on a hydrocarbon target using the NOvA Near Detector, reporting differential cross sections in pion and muon kinematics as well as $Q^2$ and $W_{EXP}$ for $E_ν$ near 2 GeV. The analysis combines a detailed event reconstruction, a CNN-assisted photon identification, and a template-based sideband fit to constrain backgrounds, followed by unfolding to extract cross sections. The results show GENIE with the NOvA Tune v2 configuration best describes the data, but reveal a systematic underestimation in the $\Delta(1232)$ resonance-dominated region, highlighting deficiencies in how resonance production is modeled by competing generators and underscoring the impact of intranuclear interactions. The measurements provide important inputs for refining neutrino interaction models, reducing systematic uncertainties in oscillation measurements that rely on accurate background predictions for $\pi^0$ production.

Abstract

We present a high-statistics measurement of muon antineutrino-induced charged-current neutral pion production on a hydrocarbon target using the NOvA Near Detector. The differential cross sections as functions of the momenta and angles of the outgoing pion and muon, the squared four-momentum transfer, and the invariant mass of the hadronic system at an average neutrino energy of 2~GeV are measured and compared with predictions from various neutrino interaction models. The results agree with the GENIE prediction but suggest that other models underestimate the cross section in the $Δ$(1232) resonance region. These results represent the most precise measurement of antineutrino-induced neutral pion production to date.

Figures (16)

• Figure 1: Neutrino flux components at the NOvA near detector in antineutrino running mode. The muon antineutrino fraction is about 92%.
• Figure 2: Distributions of EMscore for leading (left) and subleading (right) prongs. Event quality preselection, muon selection, prong multiplicity, and minimum number of prong hit cuts have been applied. The vertical dashed lines indicate the signal region selection thresholds. The CCN$\pi^0$ event category includes the signal, while CC0${\pi^0}$, NC, and Other are background event categories.
• Figure 3: Reconstructed $\pi^{0}\rightarrow\gamma\gamma$ mass distribution after applying the preselection, muon selection, prong multiplicity, prong hit count, and EMscore requirements. The vertical dashed lines separate the signal region from two background-dominated (low-mass and high-mass) regions used to constrain the backgrounds.
• Figure 4: NCID score distribution after applying the preselection, muon selection, prong multiplicity, prong hit count, EMscore, $m_{\gamma\gamma}\geq$ 190 MeV/$c^2$, and NProngs $>$ 3 cuts. The vertical dashed lines indicate the region used for the template fit.
• Figure 5: Signal and sideband samples used in the template fit, integrated over all kinematic bins. Top row: NProngs $=$ 3; bottom row: NProngs $>$ 3. Left: distributions in signal region; middle and top right: sideband distributions for $\rm{CC}0\pi^0$; bottom right: NC sideband.