Abstract
We investigate invisible decays of the third neutrino mass eigenstate in future accelerator neutrino experiments using muon-decay beams such as MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT). MOMENT has outstanding potential to measure the deficit or excess in the spectra caused by neutrino decays, especially in νμ and {overline{nu}}_{mu } disappearance channels. Such an experiment will improve the constraints of the neutrino lifetime τ3. Compared with exclusion limits in the current accelerator neutrino experiments T2K and NOvA under the stable ν assumption, we expect that MOMENT gives the bound of τ3/m3 ≥ 10−11 s/eV at 3σ, which is better than their recent limits: τ3/m3 ≥ 7 × 10−13 s/eV in NOvA and τ3/m3 ≥ 1.41 × 10−12 s/eV in T2K. The non-decay scenario is expected to be excluded by MOMENT at a confidence level > 3σ, if the best fit results in T2K and NOvA are confirmed. We further find that reducing systematic uncertainties is more important than the running time. Finally, we find some impact of τ3/m3 on the precision measurement of other oscillation parameters.
Highlights
JHEP04(2019)004 and the coupling which gives rise to neutrino decay: νi → νjR + χ, where χ is a light iso-singlet scalar and νiR is a right-handed fermion [14, 15]
We investigate invisible decays of the third neutrino mass eigenstate in future accelerator neutrino experiments using muon-decay beams such as MuOn-decay MEdium baseline NeuTrino beam experiment (MOMENT)
Compared with exclusion limits in the current accelerator neutrino experiments T2K and NOvA under the stable ν assumption, we expect that MOMENT gives the bound of τ3/m3 ≥ 10−11 s/eV at 3σ, which is better than their recent limits: τ3/m3 ≥ 7 × 10−13 s/eV in NOvA and τ3/m3 ≥ 1.41 × 10−12 s/eV in T2K
Summary
The latest results from MiniBooNE have an excess for reconstructed oscillation spectra [44], suggesting the existence of sterile neutrinos. We notice the fact that the probability with neutrino decays goes above or below the curve corresponding to the stable-neutrino assumption. This is because the suppression term dominates the damping ones. Moving to the smaller τ3/m3, Uα∗3(δ)Uβ3(δ)Uα3(δ)Uβ∗3(δ) exp(−2Γ3L) gets smaller earlier than the damping terms because of the factor of 2 in the exponential When this effect does not dominate the damping one, the probability goes upper around the minima. We see an overall decrease in P (νe → νμ), while the impact of neutrino decays on P (νμ → νe) is similar to that for e disappearance channels — it smoothens out the probability (damping effects). Based on the size of variations, we reach the conclusion that the μ-flavour disappearance channel is the more important than the other channels in the measurement of τ3/m3
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
