Testing T invariance in the interaction of slow neutrons with aligned nuclei

Abstract

The study of five-fold (P even, T odd) correlation in the interaction of slow polarized neutrons with aligned nuclei is a possible way of testing the time reversal invariance due to the expected enhancement of T violating effects in compound resonances. Possible nuclear targets are discussed which can be aligned both dynamically as well as by the "brute force" method at low temperature. A statistical estimation is performed of the five-fold correlation for low lying p wave compound resonances of the 121 Sb, 123 Sb and 127 I nuclei. It is shown that a significant improvement can be achieved for the bound on the intensity of the fundamental parity conserving time violating (PCTV) interaction. PACS: 24.80.+y Nuclear tests of fundamental interactions and symmetries

Time reversal invariance violating and parity conserving effects in neutron-deuteron scattering

“…Here, C / P n , C / T / P n , and C / T P n are low energy constants for PV, TVPV, and TVPC interactions, correspondingly, with a separated factor 1/m N to match dimensions of the final result and suppression factor is well known [8][9][10]18] for TVPC matrix elements in nuclei.…”

“…This correlation leads to the difference [3,4] between the total neutron cross sections for neutron polarized perpendicular to the neutron momentum and averaged over elongated target states…”

“…According to CPT theorem, the violation of CP invariance implies the TRIV. In spite of the fact that almost all known possible mechanisms of CP violation also violate parity, TVPC interactions have been a subject of experimental and theoretical studies for decades (see, for example, [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] and references therein), because they directly manifest phenomena beyond the Standard model. The most experimental constraints for this interactions were obtained by using low energy nuclear physics processes, which cover a large variety of nuclear reactions and nuclear decays.…”

“…These effects can be enhanced [9,18] by a factor of 10 6 , and therefore, could be measured at new spallation neutron facilities, such as the SNS at the Oak Ridge National Laboratory or the J-SNS at J-PARC, Japan.…”

Fundamental Neutron Physics

“…Although EDM limits can also be used to constrain P -even T -odd interactions in many models, in general only direct measurements can set model-independent bounds [207]. A JINR-ITEP collaboration is preparing to perform a search for the P -even T -odd fivefold correlation with low energy neutrons on p-wave resonances using microwave-induced dynamical nuclear alignment to order the nuclei [208][209][210]. A shift in the zero crossing of the forward-backward asymmetry in unpolarized neutron capture on p-wave resonances has also been considered as a signal for P -even, T -odd interactions [211] but it is not a null test and although the statistical precision of the bound from 113 Cd is at the 10 −4 level, one must accumulate a number of results either in different nuclei or in different resonances in the same nucleus in order to construct a statistically meaningful bound from such measurements [212].…”