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

Abstract We present results of measurement of the P -odd asymmetry α P- odd of γ -quanta emission in the nuclear reaction 10 B( n , α ) 7 Li * → γ + 7 Li(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 α P ‐ odd 10 B = + ( 0.8 ± 3.9 ) × 1 0 - 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 f π 10 B ≤ 2.4 × 1 0 - 7 (at 90% c.l.). This constraint does not contradict the estimation obtained from the nuclear reaction 6 Li( n , α ) 3 H: f π 6 Li ≤ 1.1 × 1 0 - 7 (at 90% c.l.). However, both these constraints contradict the “best” value of the Quark model by Desplanques, Donoughe, and Holstein f π DDH = 4.6 × 1 0 - 7 .