Description
DaRveX isan abbreviation of "Decay at Rest nue+Pb Cross(X) section measurement".
Until now, no good detection method for electron neutrino (${\nu_e}$) in MeV energy region has been developed although there are interesting physics channels in the low energy $\nu_{e}$ such as measurement of supernova, neutrino oscillation and $\nu_e-$nucleus interactions. Lead (Pb) has a novel potential as the target of the low energy $\nu_{e}$ since the cross section is expected to be very large and the delayed coincidence method is available to reduce the backgrounds.
The mercury proton beam target in J-PARC/MLF is a great source of neutrinos. A number of $\pi^+$ are created in the target, and they decay to $\mu^+$. The $\mu^+$ soon stops in the target and then decays to $\nu_e$. We are preparing measurement of the “Decay at Rest $\nu_e$” in the MLF experiment area using plastic scintillator-based detector with lead planes.
Neutron and gamma ray related to the beam collision are major backgrounds of the $\nu_e$ measurement since they are synchronized with $\nu_e$ timing. We have performed an onsite-background measurement in the MLF experiment area in the summer of 2021 and observed high background level for the neutrino measurement. Then we plan to measure the effectiveness of background shields we are designing (Boron shields for thermal neutron and thick lead shields for gamma-rays) making use of the real backgrounds. in spring of 2022. We are also developing the neutrino detector aiming to start the data taking in 2023.
In this presentation, we report the results of the background measurement and plan of the neutrino observation.
