Measurement of P-odd asymmetry of γ-quanta emission in the nuclear reaction 10B(n,α)7Li*→γ+7Li(g.s.)

We present results of measurement of the P-odd asymmetry αP-odd of γ-quanta emission in the nuclear reaction 10B(n,α)7Li*→γ+7Li(g.s.) with polarized cold neutrons. The experiment was carried out using a new version of the integral measuring method. The frequency of neutron spin-flip is higher in this method than the typical reactor power noise frequency; this condition decreases experimental uncertainties. The result is αP‐odd10B=+(0.8±3.9)×10-8; “zero” experiments are taken into account. Using this value, we constrain the weak neutral current constant in the framework of the cluster model to fπ10B≤2.4×10-7 (at 90% c.l.). This constraint does not contradict the estimation obtained from the nuclear reaction 6Li(n,α)3H: fπ6Li≤1.1×10-7 (at 90% c.l.). However, both these constraints contradict the “best” value of the Quark model by Desplanques, Donoughe, and Holstein fπDDH=4.6×10-7.