The 3He(\vec n,p)3H parity-conserving asymmetry
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arXiv
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| Natura: | Preprint |
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2024
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| author | Viviani, M. Baeßler, S. Barrón-Palos, L. Birge, N. Bowman, J. D. Calarco, J. Cianciolo, V. Coppola, C. E. Crawford, C. B. Dodson, G. Fomin, N. Garishvili, I. Gericke, M. T. Girlanda, L. Greene, G. L. Hale, G. M. Hamblen, J. Hayes, C. Iverson, E. B. Kabir, M. L. Kievsky, A. Marcucci, L. E. McCrea, M. Plemons, E. Ramírez-Morales, A. Mueller, P. E. Novikov, I. Penttila, S. I. Scott, E. M. Watts, J. Wickersham, C. |
| author_facet | Viviani, M. Baeßler, S. Barrón-Palos, L. Birge, N. Bowman, J. D. Calarco, J. Cianciolo, V. Coppola, C. E. Crawford, C. B. Dodson, G. Fomin, N. Garishvili, I. Gericke, M. T. Girlanda, L. Greene, G. L. Hale, G. M. Hamblen, J. Hayes, C. Iverson, E. B. Kabir, M. L. Kievsky, A. Marcucci, L. E. McCrea, M. Plemons, E. Ramírez-Morales, A. Mueller, P. E. Novikov, I. Penttila, S. I. Scott, E. M. Watts, J. Wickersham, C. |
| contents | Recently, the n$^3$He collaboration reported a measurement of the parity-violating (PV) proton directional asymmetry $A_{\mathrm {PV}} = (1.55\pm 0.97~\mathrm {(st\ at)} \pm 0.24~\mathrm {(sys)})\times 10^{-8}$ in the capture reaction of ${}^3$He$(\vec {n},{\mathrm p}){}^3$H 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 $(λ\times A_{\mathrm {PC}})\equivβ= (-1.97 \pm 0.28~\mathrm{(stat)}\pm 0.12~\mathrm{(sys)}) \times 10^{-6}$ 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 ${}^3$He$(\vec {n},{\mathrm p}){}^3$H reaction, $A_{\mathrm {PC}}$ depends critically on the energy and width of the close $0^-$ resonant state of ${}^4$He, 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 ${}^3$He$(\vec {n}, {\mathrm p}){}^3$H reaction. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2405_10258 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | The 3He(\vec n,p)3H parity-conserving asymmetry Viviani, M. Baeßler, S. Barrón-Palos, L. Birge, N. Bowman, J. D. Calarco, J. Cianciolo, V. Coppola, C. E. Crawford, C. B. Dodson, G. Fomin, N. Garishvili, I. Gericke, M. T. Girlanda, L. Greene, G. L. Hale, G. M. Hamblen, J. Hayes, C. Iverson, E. B. Kabir, M. L. Kievsky, A. Marcucci, L. E. McCrea, M. Plemons, E. Ramírez-Morales, A. Mueller, P. E. Novikov, I. Penttila, S. I. Scott, E. M. Watts, J. Wickersham, C. Nuclear Experiment Nuclear Theory Recently, the n$^3$He collaboration reported a measurement of the parity-violating (PV) proton directional asymmetry $A_{\mathrm {PV}} = (1.55\pm 0.97~\mathrm {(st\ at)} \pm 0.24~\mathrm {(sys)})\times 10^{-8}$ in the capture reaction of ${}^3$He$(\vec {n},{\mathrm p}){}^3$H 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 $(λ\times A_{\mathrm {PC}})\equivβ= (-1.97 \pm 0.28~\mathrm{(stat)}\pm 0.12~\mathrm{(sys)}) \times 10^{-6}$ 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 ${}^3$He$(\vec {n},{\mathrm p}){}^3$H reaction, $A_{\mathrm {PC}}$ depends critically on the energy and width of the close $0^-$ resonant state of ${}^4$He, 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 ${}^3$He$(\vec {n}, {\mathrm p}){}^3$H reaction. |
| title | The 3He(\vec n,p)3H parity-conserving asymmetry |
| topic | Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2405.10258 |