Neutrinoless double-beta decay and physics beyond the standard model

Abstract

Neutrinoless double beta decay is the most powerful tool to probe not only for Majorana neutrino masses but for lepton number violating physics in general. We discuss relations between lepton number violation, double beta decay and neutrino mass, review a general Lorentz invariant parametrization of the double beta decay rate, highlight a number of different new physics models showing how different mechanisms can trigger double beta decay, and finally discuss possibilities to discriminate and test these models and mechanisms in complementary experiments.

Sterile neutrinos in leptonic and semileptonic decays

“…Although neutrinoless double beta decay [38] remains the key observable (the most recent results on neutrinoless double beta decay having been obtained by the GERDA experiment [39]), the LHC is beginning to be competitive, as demonstrated by the phenomenological studies of [40,41] and recent CMS results [42]. However, we have not taken these LNV processes into account, since they are not correlated with the observables of interest for our study.…”

Effect of steriles states on lepton magnetic moments and neutrinoless double beta decay

“…In addition to accommodating neutrino data [37][38][39][40][41], these extensions must comply with unitarity bounds [42,43], laboratory bounds [44], electroweak precision tests [23,45,46], LHC constraints (as those arising from Higgs decays) [24][25][26][27][28], bounds from rare decays [14,15,21,22] as well as cosmological constraints [10,47]. New sources of lepton number violation can trigger neutrinoless double beta decay (see, for example, [29]), and the sterile states can contribute to the decay rate: the additional mixings and possible new Majorana phases might enhance the effective mass, potentially rendering it within experimental reach, or even leading to the exclusion of certain regimes due to conflict with the current bounds (the most recent results on neutrinoless double beta decay have been obtained by the GERDA experiment [48]). …”

“…Sterile neutrinos could also have a relevant rôle in flavour conserving observables, as is the case of electric and magnetic lepton moments, neutrinoless double beta decay [29], and several lepton number violating (LNV) decays, as for example B − → h + − − (h denoting a meson) among others currently being explored by the LHC collaborations (see, for example, [30] and references therein). Although the anomalous magnetic moment of the electron, which is now experimentally determined to an impressive precision [31], exhibits a striking agreement with the SM theoretical prediction, the same does not occur for the…”

Double beta decay and neutrino mass models

“…m S 1,2,1/2 is the mass of S 1,2,1/2 . Following the method adopted in [1,31] and using the experimental bound [3][4][5] …”

“…Experimental limits on half-lives of neutrinoless double beta decay (0νββ) give stringent bounds on many Lepton Number Violating (LNV) extensions of the Standard Model (SM); for a recent review see, for example [1]. Recent experimental results give limits for 76 Ge [2] and 136 Xe [3][4][5] in excess of 10 25 ys, which place an upper limit on the effective Majorana mass m ν 1 of the order of roughly m ν < ∼ (0.2 − 0.4) eV, depending on calculations of nuclear matrix element [6][7][8].…”