Speaker
Description
The electric and magnetic polarizabilities ( 𝛼$_{𝐸1}$ and 𝛽$_{𝑀1}$ ) are fundamental quantities encoding the internal structure of nucleons. They characterize the response of the nucleon to an external electromagnetic field and can be probed using Compton scattering processes. From chiral effective field theories ( 𝜒 EFTs) [1,2], the angular distributions of the Compton differential cross section for light nuclei (A=1-6) provide an important way of extracting the nucleon electromagnetic polarizabilities experimentally. However, due to the difficulties in experimental measurements, 𝛼$_{𝐸1}$ and 𝛽$_{𝑀1}$ of nucleons, particularly of the neutron, are still not precisely determined [3-5].
Compton scattering measurements using a liquid He-3 target are planned for determining neutron electromagnetic polarizabilities. These measurements will be carried out using the nearly monoenergetic gamma-ray beam at the High Intensity Gamma-Ray Source (HI𝛾S) facility at Triangle Universities Nuclear Laboratory (TUNL). This experiment will be the first Compton-scattering measurement performed on He-3 , mainly because of limitations of cryogenic techniques, which have been recently overcome. Compared to Compton Scattering experiments on liquid deuterium [6] and He-4 [7,8], the elastic Compton cross section of He-3 arises from a different combination of the nucleon contributions. This can provide another way to extract the polarizabilities of the neutron and another test under the EFT formalism [9], although nuclear effects need to be taken into account. The proposed experiment will measure the angular differential cross section for Compton scattering from He-3 at 100 MeV using a circularly polarized photon beam at HI𝛾S. In this poster, we will present the techniques and proposed setup of this experiment as well as theoretical predictions for the sensitivity to the polarizability in the angular distribution of the cross section.
This research is supported by the U.S. Department of Energy under Contracts DE-FG02-03ER41231, DE-SC0016581, DE-SC0005367, DE-FG02-97ER41033, DE-SC0016656, and National Science Foundation 2232117.
[1] H. W. Griesshammer, J. A. McGovern, D. R. Phillips and G. Feldman, Prog. Part. Nucl. Phys. 67, 841 (2012);
[2] H.W. Griesshammer, J.A. McGovern and D.R. Phillips, invited talk at the 8th International Workshop on Chiral Dynamics (Pisa, Italy, June 2015);
[3] J. A. McGovern, D. R. Phillips and H. W. Griesshammer, Eur. Phys. J. A 49,12 2013);
[4] L. S. Myers et al. [COMPTON@MAX-lab], Phys. Rev. Lett. 113, no.26, 262506 (2014);
[5] L. S. Myers et al. Phys. Rev. C 92, no.2, 025203 (2015);
[6] D. Godagama, PhD Dissertation, DOI: 10.13023/etd.2022.281 (2022);
[7] M. Sikora et al. (Compton@HIGS Collaboration), Phys. Rev. C96, 055209 (2017);
[8] X. Li et al.(Compton@HIGS Collaboration), Phys. Rev. C 101, 034618 (2020);
[9] A. Margaryan, B. Strandberg, H.W. Griesshammer, J.A. McGovern, D.R. Phillips and D. Shukla, Eur. Phys. J. A54, 125 (2018)
