Tau neutrino as a probe of charged non-standard interactions at DUNE

TL;DR

This work analyzes charged-current non-standard interactions (CC-NSI) that modify pion decay and thereby affect tau-neutrino appearance in a DUNE-like experiment. Using a WEFT/LEFT EFT description with a focus on the non-diagonal parameter $|\epsilon_{\mu\tau}|$, it models the NSI-modified production via the NSI probability $P_{\mu\tau}^{\text{NSI}}=|S_{\tau\mu}^{\text{SM}}-p_{\mu}\epsilon_{\mu\tau}^{*}S_{\tau\tau}^{\text{SM}}|^{2}$ with $p_{\mu}\approx 27$, and propagates these effects through near and far detectors with a Gaussian energy-migration kernel across 40 energy bins up to 20 GeV. A near detector analysis yields a strong improvement over current bounds, with $|\epsilon_{\mu\tau}|<4.5\times10^{-5}$, while the far detector reaches $|\epsilon_{\mu\tau}|<4\times10^{-3}$, demonstrating that the tau-neutrino channel at DUNE provides a unique and competitive probe of CC-NSI beyond existing pion-decay limits. The results highlight the complementary role of $\nu_{\tau}$ measurements alongside $\nu_e$ and $\nu_\mu$ channels and motivate refined parameter handling and dedicated $\nu_\tau$ analyses in future work.

Abstract

In this work, we study the influence of charged-current non-standard interactions (CC-NSI) at a DUNE-like experiment. We are particularly interested in the tau neutrino channel accessible at DUNE, given the higher energy neutrino flux expected to be achieved by the experiment. We focus on CC-NSI that may affect the pion decay, the primary source of neutrinos for DUNE. We show that the expected sensitivity at the near detector may supersede the present bounds coming directly from pion decay by one order of magnitude.

Figures (6)

• Figure 1: Expected number of events after 3.5 years in neutrino mode (left), 3.5 years in antineutrino mode (middle), 1 year in high energy mode (right). Dashed lines represent the true number of events, while solid lines represent the reconstructed ones.
• Figure 2: Expected number of events after 3.5 years in neutrino mode (left), 3.5 years in antineutrino mode (middle), 1 year in high energy mode (right). Dashed lines represent the standard scenario ($\epsilon_{\mu\tau}=0$), while solid lines are for $\epsilon_{\mu\tau}=1.2\times10^{-2}$.
• Figure 3: Stacked histograms for neutrino (left) and antineutrino (right) modes. The black curve is for the case of null $\epsilon_{\mu\tau}=0$, while the green (red) curve is for $\epsilon_{\mu\tau}=-6\times 10^{-3} (-1.2 \times 10^{-2})$.
• Figure 4: Sensitivity on CC-NSI parameter $\epsilon_{\mu\tau}$ for the different experiments considered in this work. The orange (blue) regions are for one (two) $\sigma$ C.L.
• Figure 5: Probabilities for tau appearance for positive and negative values of $\epsilon_{\mu\tau}$.