Bulletin of the American Physical Society
6th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Sunday–Friday, November 26–December 1 2023; Hawaii, the Big Island
Session 1WCA: Neutron Fundamental Physics IInvited Workshop
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Chair: Kenji MISHIMA, KEK Room: Hilton Waikoloa Village Kings 3 |
Sunday, November 26, 2023 9:00AM - 9:30AM |
1WCA.00001: Enhancement of discrete symmetry violations in neutron-induced compound nuclei Invited Speaker: Takuya Okudaira The fundamental parity violation caused by the hadronic weak interaction is enhanced by up to 10^6 times in neutron absorption reactions of 139^La, 131^Xe, 117^Sn, and other nuclei. This enhancement can be explained by the mixing between s-wave and p-wave amplitudes of the compound nuclear state (s-p mixing model). Similarly, T-violation can also be enhanced in these systems through the same mechanism, suggesting the possibility of conducting a sensitive search for T-violation using compound nucleus reactions. The NOPTREX collaboration is planning an experiment to explore unknown T-violation by measuring the T-odd cross-section between a polarized epithermal neutron beam and a polarized target. Recently, fundamental studies for the T-violation search experiment have been conducted, including the measurement of the angular correlation of (n,gamma) reactions, enhanced P-violation, and the spin-dependent cross-section between polarized neutrons and a polarized target. In my presentation, I will provide an overview of these experiments and present several new results. |
Sunday, November 26, 2023 9:30AM - 10:00AM |
1WCA.00002: The Progress of UCN Source Development for a Neutron EDM Measurement by the TUCAN Collaboration Invited Speaker: Shinsuke Kawasaki To explain the asymmetry between matter and antimatter in the universe, a new source of CP violation is necessary. The presence of a non-zero permanent electric dipole moment (EDM) in a fundamental particle, such as a neutron, breaks the time-reversal symmetry and implies CP violation if we assume CPT conservation. |
Sunday, November 26, 2023 10:00AM - 10:30AM |
1WCA.00003: The neutron electric dipole moment experiment at Los Alamos National Laboratory Invited Speaker: Steven M Clayton The electric dipole moment of the neutron (nEDM) is exceedingly small in the standard model of particle physics. However, beyond standard model theories allow for larger values of the nEDM, possibly within the reach of upcoming experiments. This talk will present an overview and status of the nEDM experiment under development at the Los Alamos National Laboratory (LANL) ultracold neutron source and targeting a measurement uncertainty of 3×10-27 e·cm. The experiment features a double-cell geometry, 199Hg co-magnetometry, external optical magnetometers, precision holding field and gradient coils, and a large, state-of-the-art magnetically shielded enclosure. The overall status of the experiment and some details of the apparatus will be described. |
Sunday, November 26, 2023 10:30AM - 11:00AM |
1WCA.00004: Precision Neutron Lifetime Measurement with the UCNtau Experiment Invited Speaker: Chen-Yu Liu Neutrons are stable inside atomic nuclei. Outside the confines of the nucleus, they decay into a proton, electron, and antineutrino, with a lifetime of approximately 880 s. The rate of decay can be precisely calculated, using the theory of electroweak interactions, with an uncertainty on the order of 1e-4. Recent measurements using bottled neutrons have achieved uncertainties below 1 s (0.1%), but other measurements observing neutron decay in flight disagree by 10 s. Attempts to resolve this discrepancy have spawned much experimental effort as well as exotic theoretical conjectures, thus far without a clear conclusion. In this talk, I will discuss the challenges of precision measurement of the neutron lifetime, illustrating the UCNtau experiment. It eliminates the dominant loss mechanisms present in previous bottle experiments by levitating polarized ultracold neutrons above the surface of a large Halbach magnetic trap. Using this approach, our latest result, 877.75 +/- 0.28 (stat) +0.22/-0.16 (sys) s [PRL 127, 162501 (2021)], is the most precise measurement of the lifetime. This result, together with improved measurements of the axial coupling constant, will provide a determination of the CKM matrix element Vud, independent of nuclear decays, and address the recent tension in the test of CKM unitarity. |
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