Searches for parity-violation effects in the γ transition 7Li*→γ(M1)→7Li(Eγ=0.478 MeV)

Theoretical calculations and preliminary measurements of the p-odd asymmetry of photon emission from the deexcitation of the first excited 7Li level populated in the reaction 10B(n,α)7Li*→γ(M1)→7Li induced by a polarized-neutron beam have been performed. Theoretical results indicate that weak neutral currents contribute substantially to parity violation in this process. Special features of the spectrum of 7Li nuclear states result in that the effect under discussion is caused predominantly by the pseudoscalar-potential-induced mixing of bound states with the states of the α+t continuum. The results of preliminary measurements demonstrate a strong potential of the proposed experimental procedure. Upon the upgrade of some elements of the apparatus used, this procedure will permit achieving a precision on the order of 10-8in determining the anisotropy of the angular distribution if emitted photons. This will make it possible to measure the predicted effect or, at least, to set a rather low upper limit on it. As a result, the process being considered proves very promising in what is concerned with searches for the contribution of neutral currents