Speaker
Description
Neutrinoless double-$\beta$ decay (0$\nu \beta \beta$) is the most sensitive
experimental probe to answer the question whether neutrinos have Majorana or Dirac
nature. The observation of (0$\nu \beta \beta$) would not only establish the Majorana
nature of neutrinos, but also provide a measurement of effective mass and probe the
neutrino mass hierarchy. The latest precise neutrino oscillation data of the mass
differences and mixings among the three neutrino mass eigenstates, along with
cosmology data provide slight preferences of the “normal hierarchy” (NH) over the
“inverted hierarchy” (IH) in the structures of the neutrino mass eigenstates. In this
work, we address issue of the required exposures (target mass × data taking time) of
(0$\nu \beta \beta$) projects vs the expected background B0 before the experiments
are performed. The background reduction can substantially alleviate the necessity of
unrealistic large exposure as the normal mass hierarchy (NH) is probed. The
nondegenerate (ND)-NH can be covered with an exposure of order of 100 ton-year,
which is only an order of magnitude larger than those planned for next-generation
projects—provided that the background could be reduced by order of 10−6 relative to
the current best levels[1]. It follows that background suppression will be playing
increasingly important and investment-effective role to covering ND-NH
in future 0νββ experiments.
[1] M. K. Singh et al., Phy. Rev, D
| Session | Neutrino Physics |
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