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arXiv · 2304.02031

Anomalous Tau Neutrino Appearance from Light Mediators in Short-Baseline Neutrino Experiments

P. S. Bhupal Dev·Bhaskar Dutta·Tao Han·Doojin Kim
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Abstract

We point out a new mechanism giving rise to anomalous tau neutrino appearance at the near detectors of beam-focused neutrino experiments, without extending the neutrino sector. The charged mesons ($\pi^\pm, K^\pm$) produced and focused in the target-horn system can decay to a (neutrino-philic) light mediator via the helicity-unsuppressed three-body decays. If such a mediator carries non-vanishing hadronic couplings, it can also be produced via the bremsstrahlung of the incident proton beam. The subsequent decay of the mediator to a tau neutrino pair results in tau neutrino detection at the near detectors, which is unexpected under the standard three-flavor neutrino oscillation paradigm. We argue that the signal flux from the charged meson decays can be significant enough to discover the light mediator signal at the on-axis liquid-argon near detector of the DUNE experiment, due to the focusing of charged mesons. In addition, we show that ICARUS-NuMI, an off-axis near detector of the NuMI beam, as well as DUNE, can observe a handful of tau neutrino events induced by beam-proton bremsstrahlung.

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P. S. Bhupal Dev, Bhaskar Dutta, Tao Han, Doojin Kim. 2023-04-04. Anomalous Tau Neutrino Appearance from Light Mediators in Short-Baseline Neutrino Experiments. https://arxiv.org/abs/2304.02031

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