Study of the N⁎ momentum distribution for experimental η-mesic 3He searches

• Published in: Nuclear physics. A Vol. 996; p. 121698
• Main Authors: Kelkar, N.G., Bedoya Fierro, D., Kamada, H., Skurzok, M.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2020
• Subjects: Momentum distribution; N⁎ resonance; Search for eta mesic nuclei; Search for eta mesic nuclei; Momentum distribution; N⁎ resonance
• ISSN: 0375-9474
• DOI: 10.1016/j.nuclphysa.2020.121698

The proximity of the η N threshold to the mass of the N⁎(1535) allows us to consider the η-nucleus interaction below the η threshold as a series of excitations, decays of the N⁎ on the constituent nucleons and the eventual decay of the N⁎ to a nucleon and a pion. Experimental searches for η-mesic nuclei rely on this model in their analysis of data where an η-mesic nucleus could have been formed. However, the momentum distribution of an N⁎ is often approximated to be the same as that of a nucleon inside the nucleus. Our aim is to obtain an estimate of the error introduced by this assumption and hence we calculate the momentum distribution of the N⁎ formed inside 3He. This distribution is found to be narrower than that of a nucleon inside 3He. The latter affects the outgoing particles kinematics and reduces the determined acceptance of their experimental registration by the detection setup. This reduction is crucial for the determination of cross sections in the search for η-mesic helium.