Renormalization of the weak hadronic current in the nuclear medium - art. no. 055501

The renormalization of the weak charge-changing hadronic current as a funct ion of the reaction energy release is studied at the nucleonic level. We ha ve calculated the average quenching factors for each type of current (vecto r, axial vector, and induced pseudoscalar). The obtained quenching in the a xial vector part is, at zero momentum transfer, 19% for the 1s0d shell and 23% in the 1p0f shell. We have extended the calculations also to heavier sy stems such as Ni-56, and Sn-100, where we obtain stronger quenchings, 44% a nd 59%, respectively. Gamow-Teller-type transitions are discussed, along wi th the higher-order matrix elements. The quenching factors are constant up to roughly 60 MeV momentum transfer. Therefore the use of energy-independen t quenching factors in beta decay is justified. We also found that going be yond the zeroth and first order operators (in inverse nucleon mass) does no t give any substantial contribution. The extracted renormalization to the r atio C-P/C-A at q = 100 MeV is -3.5%, -7.1%, -28.6%, and +8.7% for mass 16, 40, 56, and 100, respectively.