Neutrinoless double beta decay via light neutralinos in R-parity violating supersymmetry

Abstract

We perform a study of neutrinoless double beta (0νββ) decay mediated by the lightest neutralino of arbitrary mass in the minimal supersymmetric Standard Model (MSSM) under the presence of R-parity violating trilinear interactions. In this scenario, the exchange of the lightest neutralino can result in 0νββ decay of either long-range or short-range behaviour, depending on the neutralino mass. Using nuclear matrix elements calculated in the interacting boson model, we use an interpolation between the long- and short-range behaviours with an approximate formula. The non-observation of 0νββ decay is then used to place constraints on the supersymmetry parameter space, compatible with constraints from collider experiments. We compare these constraints to bounds from pion decays, CKM unitarity and big bang nucleosynthesis.

Searching for light neutralinos with a displaced vertex at the LHC

“…Besides the bounds on the lightest neutralino mass, the various RPV couplings are also constrained from both collider and low-energy observables [31]. In this work, we focus on the single coupling λ 111 , for which the most stringent current bounds stem from neutrinoless double beta decay [32][33][34][35] as well as monolepton searches at the LHC [36]. Details of the neutrinoless double beta decay bounds are described in section 4, while a reinterpretation of the monolepton search for our scenario is presented in section A.…”

“…The neutrinoless double beta decay limits were obtained by comparing the theoretical calculations from ref. [35] of the RPV SUSY contribution to 0νββ half-life, mediated by light neutralinos and selectrons 2 (see figure 1 and rotate it by 90 degrees clockwise to visualize the Feynman diagram contributing to 0νββ decay) with the experimental current limits on the 0νββ half-life T exp 1/2 > 1.8 × 10 26 yr for the isotope 76 Ge. On the other hand, the monolepton limits are based on our reinterpretation of the AT-LAS search described in appendix A, which corresponds to the red solid curve in figure 5.…”

“… Figure 3 in ref [35]. shows the calculation of the contribution of light neutralinos and selectrons to the 0νββ half-life for λ 111 = 10 −3 and mẽ L = 2 TeV (green dashed line).…”

“…shows the calculation of the contribution of light neutralinos and selectrons to the 0νββ half-life for λ 111 = 10 −3 and mẽ L = 2 TeV (green dashed line). We have re-scaled these results for different values of λ 111 and mẽ L using the proportionality relation (T 0νββ 1/2 ) −1 ∝ |λ 2 111 /m 4 ẽL | 2 (see equation (4.5) in ref [35]…”

Unraveling the $0νββ$ Decay Mechanisms

“…For simplicity we take m χ 1 = 2 GeV and m χ i → ∞ for i = 1. Lighter neutralino masses in connection to 0νββ have also recently been studied [101]. We set the coupling constant to λ 111 = 2×10 −4 .…”