[Paper Review] Neutrinoless Double Beta Decay of 134Xe

F. Šimkovic, P. Domin+1 more|ArXiv.org|Apr 24, 2002

Neutrino Physics Research3 citations

TL;DR

This paper investigates the theoretical feasibility of neutrinoless double beta decay (0νββ) in ¹³⁴Xe, analyzing light and heavy Majorana neutrino exchange and R-parity violating SUSY mechanisms. Using renormalized Quasiparticle Random Phase Approximation (RQRPA), it finds that ¹³⁴Xe's sensitivity to lepton number violation is only 2–3 times weaker than ¹³⁶Xe, making it a strong candidate for future experiments despite its lower Q-value.

ABSTRACT

In view of recent great progress achieved in the experimental study of the neutrinoless double beta decay (0nbb-decay) of 134Xe we discuss theoretical aspects of this process. The light and heavy Majorana neutrino exchange as well as the trilinear R-parity breaking contributions to 0nbb-decay are considered. We show that the sensitivity of the studied process to the signal of lepton number violation is only by factor 2-3 weaker in comparison with the 0nbb-decay of 136Xe. The current limits on effective neutrino mass (light and heavy) and trilinear R-parity violating parameter lambda'_111 deduced from lower limits on the 0nbb-decay half-lifes of various nuclei are reviewed and perspectives of the experimental verification of recently announced evidence of the 0nbb-decay of 76Ge are discussed.

Motivation & Objective

• To assess the theoretical viability of 0νββ decay in ¹³⁴Xe given recent experimental limits.
• To compare the sensitivity of ¹³⁴Xe with ¹³⁶Xe for detecting lepton number violation via light and heavy Majorana neutrino exchange.
• To evaluate the potential of ¹³⁴Xe for probing trilinear R-parity violating SUSY parameters.
• To review current experimental bounds on effective neutrino mass and R-parity violating couplings from various nuclei.
• To discuss the prospects for confirming or refuting the claimed 0νββ decay signal in ⁷⁶Ge.

Proposed method

• Calculates nuclear matrix elements for 0νββ decay in ¹³⁴Xe using the renormalized Quasiparticle Random Phase Approximation (RQRPA).
• Applies the standard formula for 0νββ decay half-life involving phase space factors and matrix elements for light and heavy Majorana neutrino exchange.
• Evaluates the R-parity violating mechanism via gluino exchange, using matrix elements from one- and two-pion exchange contributions.
• Uses the effective Hamiltonian and nucleon current contributions, including induced currents, to refine matrix element calculations.
• Compares theoretical half-lives for ¹³⁴Xe with those of ¹³⁶Xe and other isotopes to assess relative sensitivity.
• Reviews and compiles current experimental limits on effective neutrino mass and R-parity violating parameters from multiple experiments.

Experimental results

Research questions

• RQ1 How does the nuclear matrix element for 0νββ decay in ¹³⁴Xe compare to that in ¹³⁶Xe?
• RQ2 What is the relative sensitivity of ¹³⁴Xe to lepton number violation compared to ¹³⁶Xe?
• RQ3 Can the 0νββ decay of ¹³⁴Xe probe effective Majorana neutrino masses and R-parity violating parameters with comparable sensitivity to other isotopes?
• RQ4 What are the implications of the reported 0νββ decay signal in ⁷⁶Ge for the theoretical framework of 0νββ decay?
• RQ5 How do current experimental limits on 0νββ decay half-lives constrain effective neutrino masses and R-parity violating couplings?

Key findings

• The nuclear matrix elements for 0νββ decay in ¹³⁴Xe are found to be significantly larger than those for ¹³⁶Xe, leading to comparable sensitivity to lepton number violation.
• The sensitivity of ¹³⁴Xe to effective light Majorana neutrino mass is only 2–3 times weaker than that of ¹³⁶Xe, despite its lower Q-value.
• The current experimental limit on the 0νββ decay half-life of ¹³⁴Xe (T₁/₂ ≥ 5.8×10²⁵ years) provides competitive bounds on effective neutrino mass and R-parity violating parameters.
• Upper bounds on the trilinear R-parity violating coupling λ′₁₁₁ from ¹³⁴Xe are already stronger or comparable to those from ⁴⁸Ca.
• The claimed 0νββ decay signal in ⁷⁶Ge (best-fit half-life ~1.5×10²⁵ years) implies an effective Majorana neutrino mass of 0.52 eV, though this conflicts with preferred low-mass scenarios.
• Future experiments like NEMO-III, MAJORANA, and GENIUS are expected to reach sensitivities sufficient to confirm or rule out the ⁷⁶Ge signal within the next decade.