Eur. Phys. J. A (2014) 50: 48
https://doi.org/10.1140/epja/i2014-14048-3

Regular Article - Experimental Physics

Electroweak measurements of neutron densities in CREX and PREX at JLab, USA

¹ Indiana University, Bloomington, Indiana, USA
² University of Massachusetts, Amherst, Massachusetts, USA
³ Thomas Jefferson National Accelerator Facility, Newport News, VA, USA

^* e-mail: rom@jlab.org

Received: 11 July 2013
Revised: 18 September 2013
Accepted: 27 September 2013
Published online: 27 February 2014

Abstract

Measurement of the parity-violating electron scattering asymmetry is an established technique at Jefferson Lab and provides a new opportunity to measure the weak charge distribution and hence pin down the neutron radius in nuclei in a relatively clean and model-independent way. This is because the Z boson of the weak interaction couples primarily to neutrons. We will describe the PREX and CREX experiments on ²⁰⁸Pb and ⁴⁸Ca , respectively; these are both doubly magic nuclei whose first excited state can be discriminated by the high-resolution spectrometers at JLab. The heavier lead nucleus, with a neutron excess, provides an interpretation of the neutron skin thickness in terms of properties of bulk neutron matter. For the lighter ⁴⁸Ca nucleus, which is also rich in neutrons, microscopic nuclear theory calculations are feasible and are sensitive to poorly constrained 3-neutron forces.