Electroweak response functions: from 12-Carbon to Neutron Matter

Abstract: I will report on an ab initio calculation of the 12-Carbon charge form factor and sum rules of electromagnetic and neutral-current response functions. The longitudinal elastic form factor and the electromagnetic sum rules are found to be in satisfactory agreement with available experimental data. The transverse electromagnetic and neutral current sum rules receive large contributions from the two-body currents. In the Electromagnetic case they are needed for a better agreement with experimental data; this fact may have implications for the anomaly observed in recent neutrino quasi-elastic charge-changing scattering data off 12-Carbon. The role played by nuclear correlations is discussed in both 12-Carbon and neutron matter case. In particular, I will show how the neutrino mean free path in cold neutron matter turns out to be strongly affected by both short and long range correlations, leading to a sizable increase with respect to the prediction of the Fermi gas model.