First Constraint on P-odd/T-odd Cross Section in Polarized Neutron Transmission through Transversely Polarized $^{139}$La
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| Main Authors: | , , , , , , , , , , , , , , , , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866911613506813952 |
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| author | Nakabe, Rintaro Auton, Clayton J. Endo, Shunsuke Fujioka, Hiroyuki Gudkov, Vladimir Hirota, Katsuya Ide, Ikuo Ino, Takashi Ishikado, Motoyuki Kambara, Wataru Kawamura, Shiori Kimura, Atsushi Kitaguchi, Masaaki Kobayashi, Ryuju Okamura, Takahiro Oku, Takayuki Okudaira, Takuya Okuizumi, Mao Munoz, J. G. Otero Parker, Joseph D. Sakai, Kenji Shima, Tatsushi Shimizu, Hirohiko M. Shinohara, Takenao Snow, William M. Takada, Shusuke Takahashi, Ryuta Takahashi, Shingo Tsuchikawa, Yusuke Yoshioka, Tamaki |
| author_facet | Nakabe, Rintaro Auton, Clayton J. Endo, Shunsuke Fujioka, Hiroyuki Gudkov, Vladimir Hirota, Katsuya Ide, Ikuo Ino, Takashi Ishikado, Motoyuki Kambara, Wataru Kawamura, Shiori Kimura, Atsushi Kitaguchi, Masaaki Kobayashi, Ryuju Okamura, Takahiro Oku, Takayuki Okudaira, Takuya Okuizumi, Mao Munoz, J. G. Otero Parker, Joseph D. Sakai, Kenji Shima, Tatsushi Shimizu, Hirohiko M. Shinohara, Takenao Snow, William M. Takada, Shusuke Takahashi, Ryuta Takahashi, Shingo Tsuchikawa, Yusuke Yoshioka, Tamaki |
| contents | We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized $^{139}$La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of $^{139}$La including tensor polarization terms up to third-rank. The formalism is applied to existing transmission data originally obtained to measure the spin-dependent cross section near the $0.75$~eV $p$-wave resonance. Since these data were not optimized for P-odd/T-odd observables, the attainable sensitivity is intrinsically limited; nevertheless, they provide a useful test of the formalism on real experimental data. No statistically significant TRIV signal is observed. By analyzing the global $χ^2$ structure in the parameter space, we obtain an upper limit of $|W_T|<15~\mathrm{eV}$ at the 90\% confidence level. This corresponds to an upper limit on the resonance-averaged TRIV cross section of $|Δσ_{\not{T}\not{P}}|<8.3\times10^2~\mathrm{b}$. These results validate the present theoretical framework and provide guidance for future dedicated TRIV searches in polarized neutron transmission experiments. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2509_06542 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | First Constraint on P-odd/T-odd Cross Section in Polarized Neutron Transmission through Transversely Polarized $^{139}$La Nakabe, Rintaro Auton, Clayton J. Endo, Shunsuke Fujioka, Hiroyuki Gudkov, Vladimir Hirota, Katsuya Ide, Ikuo Ino, Takashi Ishikado, Motoyuki Kambara, Wataru Kawamura, Shiori Kimura, Atsushi Kitaguchi, Masaaki Kobayashi, Ryuju Okamura, Takahiro Oku, Takayuki Okudaira, Takuya Okuizumi, Mao Munoz, J. G. Otero Parker, Joseph D. Sakai, Kenji Shima, Tatsushi Shimizu, Hirohiko M. Shinohara, Takenao Snow, William M. Takada, Shusuke Takahashi, Ryuta Takahashi, Shingo Tsuchikawa, Yusuke Yoshioka, Tamaki Nuclear Experiment High Energy Physics - Experiment We report the first constraint on time-reversal invariance violating (TRIV) effects in polarized neutron transmission through a transversely polarized $^{139}$La target. We formulate the transmission asymmetry within the density matrix formalism, explicitly incorporating the forward scattering amplitude of $^{139}$La including tensor polarization terms up to third-rank. The formalism is applied to existing transmission data originally obtained to measure the spin-dependent cross section near the $0.75$~eV $p$-wave resonance. Since these data were not optimized for P-odd/T-odd observables, the attainable sensitivity is intrinsically limited; nevertheless, they provide a useful test of the formalism on real experimental data. No statistically significant TRIV signal is observed. By analyzing the global $χ^2$ structure in the parameter space, we obtain an upper limit of $|W_T|<15~\mathrm{eV}$ at the 90\% confidence level. This corresponds to an upper limit on the resonance-averaged TRIV cross section of $|Δσ_{\not{T}\not{P}}|<8.3\times10^2~\mathrm{b}$. These results validate the present theoretical framework and provide guidance for future dedicated TRIV searches in polarized neutron transmission experiments. |
| title | First Constraint on P-odd/T-odd Cross Section in Polarized Neutron Transmission through Transversely Polarized $^{139}$La |
| topic | Nuclear Experiment High Energy Physics - Experiment |
| url | https://arxiv.org/abs/2509.06542 |