Using Coherent Pion Photoproduction to Measure Neutron Distributions in Nuclei

Lead Research Organisation: University of Edinburgh
Department Name: Sch of Physics and Astronomy


The properties of neutron distributions in atomic nuclei are currently only known for a small number of nuclei. The neutron distribution in a nucleus is often quantified as a "neutron skin", defined as the difference between the neutron and proton root mean square radii.
High energy photons produced by the MAMI accelerator facility in Mainz, Germany, will allow measurements of the decay of coherently photoproduced neutral pions on several nuclei targets, so neutron distributions for these nuclei can be established. In recent years, the method of pion photoproduction has successfully elucidated the neutron distribution of several nuclei, including the size and shape of the neutron skin of the heavy nucleus, 208Pb.
One of the targets to be used is the doubly magic nucleus, 48Ca, of significant interest due to the proton-neutron asymmetry in the system, allowing insight into several poorly defined nuclear parameters. Models of the 48Ca neutron distribution have given widely varying results, and thus a neutron skin measurement would help to establish which models are closest to reality.
In addition, parameters established from the neutron skin measurements, including the dependency of the neutron skin size on the nuclear symmetry energy, will have a strong impact on models of the equation of state of nucleonic matter. This gives information on several physical phenomena, including the structure and cooling mechanisms of neutron stars, which have recently been confirmed to be a major source of the r-process elements. The neutron skins measured in this experiment will thus have a wide impact, with the run scheduled for Summer 2018.

Studentship Projects

Project Reference Relationship Related To Start End Student Name
ST/R504737/1 30/09/2017 29/09/2021
1961027 Studentship ST/R504737/1 30/09/2017 30/03/2021 Conor Hamill
Description TUNL - Edinburgh 
Organisation Triangle Universities Nuclear Laboratory
Country United States 
Sector Academic/University 
PI Contribution Assisted in performing of the 25Mg(d,p)26Mg experience in August 2018, from which two data sets were acquired. The first data set has been fully analysed by myself, and the results have been published. The second data is in the process of being analysed by me.
Collaborator Contribution Assisted in performing of the 25Mg(d,p)26Mg experience in August 2018, from which two data sets were acquired.
Impact Publication of the paper: Study of the 25Mg(d,p)26Mg reaction to constrain the 25Al(p,gamma)26Si resonant reaction rates in nova burning conditions in EPJA
Start Year 2018