Abstract
We study the impact of new physics contributions to neutrinoless double beta decay arising from right-handed current in comparison with the standard mechanism. If the light neutrinos obtain their masses from Type-II seesaw within left-right symmetric model, where the Type-I contribution is suppressed to negligible extent, the right-handed PMNS matrix is the same as its left-handed counterpart, making it highly predictable and testable at next-generation experiments. It is very attractive, especially with recent cosmological constraint favoring the normal hierarchy under which the neutrinoless double beta decay is too small to be observed unless new physics appears as indicated by the recent diboson excess observed at ATLAS. The relative contributions from left- and right-handed currents can be reconstructed with the ratio between lifetimes of two different isotopes as well as the ratio of nuclear matrix elements. In this way, the theoretical uncertainties in the calculation of nuclear matrix elements can be essentially avoided. We also discuss the interplay of neutrinoless double beta decay measurements with cosmology, beta decay, and neutrino oscillation.
Highlights
JHEP10(2015)077 for right-handed neutrino mass and mixing, WR mass and its mixing with the left-handed counterpart as well as the corresponding gauge coupling gR
We study the impact of new physics contributions to neutrinoless double beta decay arising from right-handed current in comparison with the standard mechanism
If the result of observation turns out to be the opposite, namely neutrinoless double beta decay is observed but cannot be explained by the standard mechanism, it clearly indicates physics beyond SM. Both hints from the diboson excess observed at ATLAS for heavy W around 2 TeV and cosmological preference for normal hierarchy (NH) with tiny mass scale and invisible neutrinoless double beta decay even at next-generation experiments, we examine the effect of Type-II seesaw contributions to neutrinoless double beta decay arising from purely right-handed current within LRSM
Summary
The effective Majorana mass parameter of neutrinoless double beta decay that predicted by the standard mechanism is displayed in figure 1 with light-red (green) band for NH (IH), respectively. The horizontal bands are bounds from neutrinoless double beta decay measurements which can provide crucial information about the absolute scale of light neutrino mass and Majorana CP phases. Iii) Cosmological observations which provide constraints on the sum of light neutrino masses mΣ ≡ i mi They have been shown as vertical bands in figure 1. Note that these constraints have only touched down to the quasi-degenerate region, m1 m2 m3 and mlightest > ∆m2a, with the beta-decay and cosmological constraints approximately at i mi/3 mlightest mβ ≥ |mνee| which is the same for both hierarchies. Type-II seesaw dominance which is fully predictable and can be tested at next-generation experiments
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