Limiting the effective mass and new physics parameters from $0\nu \beta \beta$

In the light of the recent result from KamLAND-Zen (KLZ) and GERDA Phase-II, we update the bounds on the effective mass and the new physics parameters, relevant for neutrinoless double beta decay ($0\nu \beta \beta$). In addition to the light Majorana neutrino exchange, we analyze beyond standard model contributions that arise in left-right symmetry and R-parity violating supersymmetry. The improved limit from KLZ constrains the effective mass of light neutrino exchange down to sub-eV mass regime 0.06 eV. Using the correlation between the ${}^{136}\mathrm{Xe}$ and ${}^{76}\mathrm{Ge}$ half-lives, we show that the KLZ limit individually rules out the positive claim of observation of $0\nu \beta \beta$ for all nuclear matrix element compilation. For the left-right symmetry and R-parity violating supersymmetry, the KLZ bound implies a factor of 2 improvement of the effective mass and the new physics parameters. The future ton scale experiments such as, nEXO will further constrain these models, in particular, will rule out standard as well as Type-II dominating LRSM inverted hierarchy scenario.

Figure 1

The half-life $T_{1/2}^{0\nu }({}^{76}\mathrm{Ge})$ vs $T_{1/2}^{0\nu }({}^{136}\mathrm{Xe})$. The brown shaded region represents the effect of NME uncertainty. The gray horizontal band represents the positive claim. The vertical lines represent the recent KLZ limit and the older KLZ limit, $\mathrm{KLZ}+\mathrm{EXO}$ combined limit. The horizontal brown dot-dashed line represents the present limit from GERDA Phase-II [42].

Figure 2

The half-life $T_{1/2}^{0\nu }$ vs the light neutrino mass for NH (upper panel) and for IH (lower panel) for different $W_R$ masses. The area between blue dot-dashed lines represents the total contributions (standard light $\mathrm{neutrino}+\text{heavy neutrino exchange}$) for Type-II dominance.

Figure 3

The effective mass of $0\nu \beta \beta$ vs the effective mass of $\beta$-decay. The yellow and red region correspond to the light neutrino exchange and RR contribution. The blue region represents the total contribution. The future ton-scale experiment nEXO can rule out the IH scenario for the adopted benchmark points.

Figure 4

The variation of $M_{W_R}$ vs the gauge coupling $g_R$, that satisfy the KLZ bound [39] and the future sensitivity of nEXO [60].

Figure 5

The variation of ${\lambda }_{113}^{\prime }{\lambda }_{131}^{\prime }$ vs the common sbottom mass $m_0$ that satisfy the KLZ bound [39] and saturate the future sensitivity of nEXO [60]. The difference of the sbottom mass from $m_0$ is 60 GeV and the mixing $\sin 2\theta ={10}^{-4}$.

Figure 6

The variation of ${\lambda }_{111}^{\prime }$ vs the down type squark mass $m_0$ that satisfy the KLZ bound [39] and saturate the future sensitivity of nEXO [60]. The gluino mass has been set to 2.0 TeV.