Active-sterile neutrino mixing constraint using reactor antineutrinos with the ISMRAN set-up

Abstract

In this work, we present an analysis of the sensitivity to the active-sterile neutrino mixing with the Indian Scintillator Matrix for Reactor Anti-Neutrino (ISMRAN) experimental set-up at very short baseline. In this article, we have considered the measurement of electron antineutrino induced events employing a single detector which can be placed either at a single position or moved between near and far positions from the given reactor core. Results extracted in the later case are independent of the theoretical prediction of the reactor anti-neutrino spectrum and detector related systematic uncertainties. Our analysis shows that the results obtained from the measurement carried out at a combination of the near and far detector positions are improved significantly at higher $\Delta m^{2}_{41}$ compared to the ones obtained with the measurement at a single detector position only. It is found that the best possible combination of near and far detector positions from a 100 MW$_{th}$ power DHRUVA research reactor core are 7 m and 9 m, respectively, for which ISMRAN set-up can exclude in the range 1.4 $eV^{2} \leq \Delta m^{2}_{41} \leq$ 4.0 $eV^{2}$ of reactor antineutrino anomaly region along with the present best-fit point of active-sterile neutrino oscillation parameters. At those combinations of detector positions, the ISMRAN set-up can observe the active sterile neutrino oscillation with a 95$\%$ confidence level provided that $\sin^{2}2\theta_{14}\geq 0.09$ at $\Delta m^{2}_{41}$ = 1 eV$^{2}$ for an exposure of 1 ton-yr. The active-sterile neutrino mixing sensitivity can be improved by about 22\% at the same exposure by placing the detector at near and far distances of 15 m and 17 m, respectively, from the compact proto-type fast breeder reactor (PFBR) facility which has a higher thermal power of 1250 MW$_{th}$.