Time-reversal invariance violation in neutron-nucleus scattering

Fadeev, Pavel; Flambaum, V. V.

doi:10.1103/physrevc.100.015504

Cited by 16 publications

(18 citation statements)

References 82 publications

(134 reference statements)

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“…Using the most recent experimental data [30], the authors of Ref. [29] obtained g p = 3.4 ± 0.8 and g n = 0.9 ± 0.6. In the following, we use central points g p = 3.4 and g n = 0.9 for the single-particle model estimates of the magnitude of the anapole moment.…”

Section: Theorymentioning

confidence: 99%

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Nuclear spin-dependent parity-violating effects in light polyatomic molecules

et al. 2020

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Measurements of nuclear spin-dependent parity-violating (NSD-PV) effects provide an excellent opportunity to test nuclear models and to search for physics beyond the Standard Model. Molecules possess closely spaced states with opposite parity which may be easily tuned to degeneracy to greatly enhance the observed parity-violating effects. A high-sensitivity measurement of NSD-PV effects using light triatomic molecules is in preparation [E. B. Norrgard et al., Commun. Phys. 2, 77 (2019)]. Importantly, by comparing these measurements in light nuclei with prior and ongoing measurements in heavier systems, the contribution to NSD-PV from Z 0 -boson exchange between the electrons and the nuclei may be separated from the contribution of the nuclear anapole moment. Furthermore, light triatomic molecules offer the possibility to search for new particles, such as the postulated Z boson. In this work, we detail a sensitive measurement scheme and present high-accuracy molecular and nuclear calculations needed for interpretation of NSD-PV experiments on triatomic molecules composed of light elements, Be, Mg, N, and C. The ab initio nuclear structure calculations, performed within the no-core shell model provide a reliable prediction of the magnitude of different contributions to the NSD-PV effects in the four nuclei. These results differ significantly from the predictions of the standard single-particle model and highlight the importance of including many-body effects in such calculations. In order to extract the NSD-PV contributions from measurements, a parity-violating interaction parameter W PV , which depends on the molecular structure, needs to be known with a high accuracy. We have calculated these parameters for the triatomic molecules of interest using the relativistic coupled-cluster approach. In order to facilitate the interpretation of future experiments we provide uncertainties on the calculated parameters. A scheme for measurement using laser-cooled polyatomic molecules in a molecular fountain is presented, along with an estimate of the expected sensitivity of such an experiment. This experimental scheme, combined with the presented state-of-the-art calculations, opens exciting prospects for a measurement of the anapole moment and the PV effects due to the electron-nucleon interactions with unprecedented accuracy and for a new path towards detection of signatures of physics beyond the Standard Model.

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Section: Theorymentioning

confidence: 99%

“…[8,28] these constants were expressed in terms of a meson-exchange model, and in Ref. [29] the results based on different calculations of meson-nucleon interactions are presented. Using the most recent experimental data [30], the authors of Ref.…”

Section: Theorymentioning

confidence: 99%

Nuclear spin-dependent parity-violating effects in light polyatomic molecules

et al. 2020

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“…Statistical spectroscopy has been used to successfully analyze the widths of the distributions of observed parity-odd asymmetries in several heavy nuclei in the isolated resonance regime corresponding to eV-keV neutron energies [8]. The present theory involving the mixing of nearby swave and p-wave resonances that accounts for this amplification of parity-odd amplitudes also predicts a similar amplification of Time Reversal Invariance Violating (TRIV) amplitudes [9]. Parity-(P) and Time-(T) odd effects in forward transmission provide null tests for time reversal invariance [10].…”

Section: Introductionmentioning

confidence: 76%

A modular apparatus for use in high-precision measurements of parity violation in polarized eV neutron transmission

Schaper

Auton

Barrón‐Palos

et al. 2020

Nuclear Instruments and Methods in Physics Research Section A:

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We describe a modular apparatus for use in parity-violation measurements in epithermal neutron-nucleus resonances with high instantaneous neutron fluxes at the Manuel Lujan Jr. Neutron Scattering Center at Los Alamos National Laboratory. This apparatus is designed to conduct high-precision measurements of the parity-odd transmission asymmetry of longitudinally polarized neutrons through targets containing nuclei with p-wave neutronnucleus resonances in the 0.1-10 eV energy regime and to accommodate a future search for time reversal violation in polarized neutron transmission through polarized nuclear targets. The apparatus consists of an adjustable neutron and gamma collimation system, a 3 He-4 He ion chamber neutron flux monitor, two identical cryostats for target cooling, an adiabatic eV-neutron spin flipper, a near-unit efficiency 6 Li-7 Li scintillation detector operated in current mode, a flexible CAEN data acquisition system, and a neutron spin filter based on spin-exchange optical pumping of 3 He gas. We describe the features of the apparatus design devoted to the suppression of systematic errors in parity-odd asymmetry measurements. We describe the configuration of the apparatus used to conduct a precision measurement of parity violation at the 0.7 eV p-wave resonance in 139 La which employs two identical 139 La targets, one to polarize the beam on the p-wave resonance using the weak interaction and one to analyze the polarization.

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“…[38,39,42] we calculated the PV matrix elements. The matrix elements of the P,T-violating interactions have been obtained in our papers [14,43,44].…”

Section: The Function (Cmentioning

confidence: 99%

“…The same mechanism of enhancement can also be extended to effects which violate both parity and timereversal invariance (PTRIV) [10][11][12][13][14]. PTRIV effects in the transmission of polarized neutrons through a polarized target have been suggested in Refs.…”

Section: Introductionmentioning

confidence: 99%

Parity and Time Reversal Invariance Violation in Neutron-Nucleus Scattering

Flambaum,

Mansour

2021

Preprint

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Parity violating (PV) as well as parity and time-reversal invariance violating (PTRIV) effects are enhanced a million times in neutron reactions near p-wave compound resonances. We present the calculation of such effects using a statistical theory based on the properties of chaotic eigenstates and discuss a possibility to extract the strength constants of PTRIV interactions from the experimental data, including nucleon-nucleon and pion-nucleon CP-violating interactions, the QCD θ-term and the quark chromo-EDM. PV effects have random sign for all target nuclei except for 232 Th, where PV effects of a positive sign have been observed for ten statistically significant p-wave resonances, with energy smaller than 250 eV. This may be an indication of a possible regular (non-chaotic) contribution to PV effects. We link this regular effect to the doublets of opposite parity states in the rotation spectra of nuclei with an octupole deformation and suggest other target nuclei where this hypothesis may be tested. We also discuss a permanent sign contribution produced by doorway states. An estimate of the ratio of PTRIV effects to PV effects is presented. Although a polarised target is not needed for the measurement of PV effects, for the interpretation of the results, it may be convenient to do both PV and PTRIV experiments with a polarised target.

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Time-reversal invariance violation in neutron-nucleus scattering

Cited by 16 publications

References 82 publications

Nuclear spin-dependent parity-violating effects in light polyatomic molecules

Nuclear spin-dependent parity-violating effects in light polyatomic molecules

A modular apparatus for use in high-precision measurements of parity violation in polarized eV neutron transmission

Parity and Time Reversal Invariance Violation in Neutron-Nucleus Scattering

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