Centre-of-momentum frame analysis of $η$ production in DUNE

TL;DR

The paper addresses uncertainties in neutrino–nucleus interactions, particularly in the resonance region, by introducing center-of-momentum variables $θ_{c.m.}$ and $E_{c.m.}$ to isolate FSI from IS in η production for CC νμ–Argon at the DUNE near detector. Using GENIE v3.06.00 with multiple nuclear models and FSI treatments, η is reconstructed via $oldsymbol{η} ightarrow 2γ$ and $oldsymbol{η} ightarrow 3π^0$, and the analysis focuses on the 1p1η final state. The results show that $θ_{c.m.}$ is strongly sensitive to FSI and largely insensitive to IS under the hA model, while $E_{c.m.}$ cuts can suppress FSI and isolate RES contributions, with some IS dependence in the hN model and an evident influence from the off-axis neutrino flux. These c.m. variables thus provide a tool for validating and improving RES and FSI modeling, with practical relevance for cross-section precision, detector calibration, and potential color transparency studies in DUNE.

Abstract

A deep understanding of neutrino-nucleus interaction is crucial for the precise measurement of neutrino oscillation parameters and cross section measurements. Various nuclear effects, such as initial state effects (IS) and Final state interactions (FSI), make neutrino interactions more complicated. To probe the impacts of the nuclear effects, a separate study of FSI and IS is required. A set of variables known as Centre-of-momentum (c.m.) variables ($θ_{c.m.}$ and $E_{c.m.}$) provides a unique approach to isolate the FSI effect with minimal sensitivity to IS. This work presents the importance of c.m. variables in neutrino-induced eta ($η$) meson production in the DUNE near detector. $θ_{c.m.}$ is an important parameter to improve the FSI modeling, while $E_{c.m.}$ helps in isolating high-purity neutrino-Hydrogen events. The study of $η$ production in neutrino interactions helps in understanding the theoretical descriptions of higher resonance states.

Figures (15)

• Figure 1: Schematic illustration of $N^+$ decay in its rest frame (without FSI), in lab frame, and c.m. frame (after FSI) Li:2025iiv.
• Figure 2: Cross section normalized $\theta_{c.m.}$ distribution for decay channel only $\eta \rightarrow 2\gamma$ (dotted) and both $\eta \rightarrow 2\gamma$, and $\eta \rightarrow 3\pi^0$ (solid) for hA (blue) and hN (Red) FSI models.
• Figure 3: Cross section normalized distribution of $\theta_{c.m.}$ for Argon-FSI-ON/OFF and Deuterium.
• Figure 4: Area-normalized distribution of TKI variables for the 1p1$\eta$ channel on argon and deuterium ($\eta$ cannot be produced in $\nu$–H interactions in GENIE). The difference between Ar-FSI-off and Ar indicates the dependence on FSI, while the difference between Ar-FSI-off and $^2$H shows the IS dependence for $\delta p_T$ and $\delta \alpha_T$. However, $\delta \phi_T$ shows minimal dependence on both IS and FSI.
• Figure 5: Area normalized distribution of $\theta_{c.m.}$ for Argon-FSI-ON/OFF and Deuterium considering $\nu_{\mu}$CC1p1$\eta$ events (left) and resonance events (right).