Neutron Dark Matter Decays and Correlation Coefficients of Neutron Beta Decays

Abstract

As we have pointed out in (arXiv:1806.10107 [hep-ph]), the existence of neutron dark matter decay modes "n -> chi + anything", where "chi" is a dark matter fermion, for the solution of the neutron lifetime problem changes priorities and demands to describe the neutron lifetime "tau_n = 888.0(2.0)s", measured in beam experiments and defined by the decay modes "n -> p + anything", in the Standard Model (SM). The latter requires the axial coupling constant "lambda" to be equal to "lambda = - 1.2690" (arXiv:1806.10107 [hep-ph]). Since such an axial coupling constant is excluded by experimental data reported by the PERKEO II and UCNA Collaborations, the neutron lifetime "tau_n = 888.0(2.0)s" can be explained only by virtue of interactions beyond the SM, namely, by the Fierz interference term of order "b ~ - 10^{-2}" dependent on scalar and tensor coupling constants. We give a complete analysis of all correlation coefficients of the neutron beta decays with polarized neutron, taking into account the contributions of scalar and tensor interactions beyond the SM with the Fierz interference term "b ~ - 10^{-2}". We show that the obtained results agree well with the contemporary experimental data that does not prevent the neutron with the rate of the decay modes "n -> p + anything", measured in beam experiments, to have dark matter decay modes "n -> chi + anything".