STUDIES OF NEUTRINO OSCILLATIONS, NEUTRINO LESS DOUBLE-BETA DECAY, AND THEIR IMPLICATIONS FOR PARTICLE PHYSICS AND COSMOLOGY

Abstract

Background: Neutrinos are among the most enigmatic particles in the Standard Model, playing a pivotal role in our understanding of fundamental physics and cosmology. The discovery of neutrino oscillations established that neutrinos possess non-zero mass, challenging the original Standard Model framework. Equally significant is the search for neutrinoless double-beta decay (0νββ), a process that, if observed, would confirm the Majorana nature of neutrinos and demonstrate lepton number violation.

Objective: This study investigates the interplay between neutrino oscillations and neutrinoless double-beta decay, exploring their combined implications for particle physics and cosmology. By analyzing current experimental results and theoretical models, we aim to constrain key parameters, including the neutrino mass hierarchy, CP-violating phase, and effective Majorana mass.

Methods: A mixed-methods approach was adopted, integrating theoretical modeling of oscillation probabilities via the PMNS matrix with analysis of experimental data from leading neutrino oscillation experiments (T2K, NOvA, DUNE, Hyper-Kamiokande) and double-beta decay searches (GERDA, KamLAND-Zen, CUORE, LEGEND). Monte Carlo simulations were used to assess experimental sensitivities and evaluate the correlation between oscillation parameters and 0νββ half-life measurements. Cosmological constraints from cosmic microwave background (CMB) data and large-scale structure surveys were also incorporated.

Results: Global fits of oscillation data favor a normal mass hierarchy, though inverted ordering remains viable within current uncertainties. No conclusive signal of neutrinoless double-beta decay has yet been observed, with half-life lower limits exceeding 10²⁶ years in the most sensitive detectors. These results constrain the effective Majorana neutrino mass to the sub-0.1 eV range. Cosmological observations place complementary upper limits on the sum of neutrino masses, further refining theoretical models.

Conclusion: The combined study of neutrino oscillations and neutrinoless double-beta decay offers a powerful framework for probing neutrino mass generation mechanisms, CP violation in the lepton sector, and the potential origin of the universe’s matter-antimatter asymmetry. Future high-sensitivity experiments will be critical for resolving the neutrino mass ordering and determining whether neutrinos are Majorana particles, with profound implications for both particle physics and cosmology.