Abstract
We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO. Assuming the Majoron model of neutrino decay, we obtain constraints on the couplings between Majoron and neutrino as well as on the lifetime/mass of the most massive neutrino state i.e., tau _{3} / m_{3} or tau _{2} / m_{2}, respectively, for the normal or the inverted mass orderings. We obtain the constraints on the lifetime tau _{2} / m_{2} ge 1.4 times 10^{-9}~{mathrm{s/eV}} in the inverted mass ordering for both KamLAND and JUNO at 90% CL. In the normal ordering in which the bound can be obtained for JUNO only, the constraint is milder than the inverted ordering case, tau _{3} / m_{3} ge 1.0 times 10^{-10} s/eV at 90% CL. We find that the dependence of lightest neutrino mass (=m_{{{mathrm{lightest}}}}), m_1 (m_3) for the normal (inverted) mass ordering, on the constraints for the different types of couplings (scalar or pseudo-scalar) is rather strong, but the m_{{{mathrm{lightest}}}} dependence on the lifetime/mass bound is only modest.
Highlights
It appears that most of the foregoing analyses of ν3 lifetime were done under the assumption of invisible decay, namely, the case that decay products are unobservable
We study visible neutrino decay at the reactor neutrino experiments KamLAND and, JUNO
We obtain the constraints on the lifetime τ2/m2 ≥ 1.4 × 10−9 s/eV in the inverted mass ordering for both KamLAND and JUNO at 90% CL
Summary
In most of the existing literatures, the bounds on neutrino decay have been calculated for NO, and Table 1 contains the bound for the NO which uses the ν3/ν3 decay mode only. These bounds, which utilize the artificial neutrino beams, are very loose compared with the solar neutrino bounds [24,25,26,27,28,29,30,31,32]. 2.9 × 10−10 (90% CL) 2.8 × 10−12 (90% CL) 1.5 × 10−11 (90% CL) 7.5 × 10−11 (95% CL) (1.95 − 2.6) × 10−10 (90% CL) 1.6 × 10−10 (90% CL)
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