New sensitivity goal for neutrinoless double beta decay experiments

Vishnudath K N,Sandhya Choubey,Srubabati Goswami

doi:10.1103/physrevd.99.095038

Abstract

We study the implications of the Dark-LMA (DLMA) solution to the solar neutrino problem for neutrinoless double beta decay ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$). We show that, while the predictions for the effective mass governing $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ remain unchanged for the inverted mass scheme, that for normal ordering becomes higher for the DLMA parameter space and moves into the ``desert region'' between the two. This sets a new goal for the sensitivity reach for the next-generation experiments if no signal is found for the inverted ordering by the future search programs.

Highlights

Fermions can be of two types: Dirac or Majorana
While the predictions for the effective mass governing 0νββ remain unchanged for the inverted mass scheme, that for normal ordering becomes higher for the DLMA parameter space and moves into the “desert region” between the two
Inverted ordering: Ipn tffiffihffiffiiffisffiffiffifficffiffiaffise, for very smpaffilffilffiffiffivffiffiaffiffilffiffiuffi es of m3 such that m3 ≪ Δm2atm, m2 ≈ m1 ≈ Δm2atm, the effective mass is given as qffiffiffiffiffiffiffiffiffiffiffiffi mββIO ≈ Δm2atmðjc212c213 þ s212c213e2iα2 jÞ: In this region, mββ is independent of m3 and is bounded from above and below by a maximum and minimum value given by [28], qffiffiffiffiffiffiffiffiffiffiffiffi mββIO max 1⁄4 jc213 Δm2atmj ðα2 1⁄4 0; πÞ; qffiffiffiffiffiffiffiffiffiffiffiffi mββIO min 1⁄4 jc213 cos 2θ12 Δm2atmj ðα2 1⁄4 π=2Þ: The maximum value is independent of θ12, while for the minimum value, we can see from Table I that the 3σ range for j cos 2θ12j is the same for both the LMA and DLMA solutions

Summary

INTRODUCTION

Fermions can be of two types: Dirac or Majorana. A Majorana particle is a self-conjugate fermion. While the IO band for the effective mass in 0νββ experiments remains nearly same for LMA and DLMA solutions, the NO band gets shifted upward for DLMA into the desert region mentioned above. As a result, this may make it possible for the next-generation experiments to start probing 0νββ for NO as well. This opens up unheralded regions of the effective neutrino mass to be probed by future 0νββ experiments This provides a way of testing the longstanding DLMA solution to the solar neutrino problem, irrespective of the value of the NSI parameters. The importance of precision determination of θ12 on the effective mass determined by 0νββ experiments has been highlighted earlier [22,23], the ramifications of the DLMA solution for 0νββ is being investigated in this work for the first time

PREDICTIONS FOR 0νββ

SENSITIVITY IN THE FUTURE EXPERIMENTS

Findings

CONCLUSION