  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".
