2024/05/16 by M. Viviani, S. Baeßler, Viviani, M. +59
Engineering · Environmental Science · Physics and Astronomy · #Black Holes and Theoretical Physics #FOS: Physical sciences #Hydrocarbon exploration and reservoir analysis #Methane Hydrates and Related Phenomena #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th)
paper · pdf · doi:10.48550/arxiv.2405.10258
openalex publication_date 2024/05/16 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/30
Recently, the n3He collaboration reported a measurement of the parity-violating (PV) proton directional asymmetry A_\mathrm PV = (1.55± 0.97~\mathrm (st at) ± 0.24~\mathrm (sys))× 10-8 in the capture reaction of 3He( n,\mathrm p)3H at meV incident neutron energies. The result increased the limited inventory of precisely measured and calculable PV observables in few-body systems required to further understand the structure of hadronic weak interaction. In this letter, we report the experimental and theoretical investigation of a parity conserving (PC) asymmetry A_\mathrm PC in the same reaction (the first ever measured PC observable at meV neutron energies). As a result of S- and P-wave mixing in the reaction, the A_\mathrm PC is inversely proportional to the neutron wavelength λ. The experimental value is (λ× A_\mathrm PC)≡β= (-1.97 ± 0.28~(stat)± 0.12~(sys)) × 10-6 Amstrongs. We present results for a theoretical analysis of this reaction by solving the four-body scattering problem within the hyperspherical harmonic method. We find that in the 3He( n,\mathrm p)3H reaction, A_\mathrm PC depends critically on the energy and width of the close 0- resonant state of 4He, resulting in a large sensitivity to the spin-orbit components of the nucleon-nucleon force and even to the three-nucleon force. The analysis of the accurately measured A_\mathrm PC and A_\mathrm PV using the same few-body theoretical models gives essential information needed to interpret the PV asymmetry in the 3He( n, \mathrm p)3H reaction.