Phenomenology of Vanishing Effective Majorana Mass with a Sterile Neutrino under Cosmological and JUNO Constraints

In the present work, we investigate the phenomenological implications of a vanishing effective Majorana neutrino mass within a [Formula: see text] neutrino framework adding a eV-scale sterile neutrino beside three active neutrino states in light of the latest JUNO and cosmology driven constraints on ([Formula: see text]) and sum of neutrino masses ([Formula: see text]), respectively. The allowed parameter space has been identified and predictions have been obtained taking into account the latest Planck and DESI+CMB bound on [Formula: see text]. We find that these bounds restrict the sterile mixing angle [Formula: see text] to a narrow region compared to the experimental range. For example, adopting the more restrictive DESI+CMB upper bound of 0.072 eV, [Formula: see text] is found to lie in the range ([Formula: see text]). Furthermore, we incorporate the refined precision data from JUNO experiment regarding solar oscillation parameters ([Formula: see text]). We find that the sterile neutrino parameters like [Formula: see text] may not be sensitive to the JUNO precision measurements as the constraint imposed by precise [Formula: see text] is washed out by new cancellations driven through additional CP violating phases leading to vanishing [Formula: see text].