Constraints on a Parity-even/Time-Reversal-odd Interaction

Time-Reversal-Invariance non-conservation has for the first time been unequivocally demonstrated in a direct measurement, one of the results of the CPLEAR experiment. What is the situation then with regard to time-reversal-invariance non-conservation in systems other than the neutral kaon system? Two classes of tests of time-reversal-invariance need to be distinguished: the first one deals with parity violating (P-odd)/time-reversal-invariance non-conserving (T-odd) interactions, while the second one deals with P-even/T-odd interactions (assuming CPT conservation this implies C-conjugation non-conservation). Limits on a P-odd/T-odd interaction follow from measurements of the electric dipole moment of the neutron. This in turn provides a limit on a P-odd/T-odd pion-nucleon coupling constant which is 10^-4 times the weak interaction strength. Limits on a P-even/T-odd interaction are much less stringent. The better constraint stems also from the measurement of the electric dipole moment of the neutron. Of all the other tests, measurements of charge-symmetry breaking in neutron-proton elastic scattering provide the next better constraint. The latter experiments were performed at TRIUMF (at 477 and 347 MeV) and at IUCF (at 183 MeV). Weak decay experiments (the transverse polarization of the muon in K+ -> pi0 mu+ nu and the transverse polarization of the positrons in polarized muon decay) have the potential to provide comparable or possibly better constraints.Comment: 7 Pages LaTeX, 2 PostScript figures, uses aipproc.sty. Written version of Invited Paper presented at the 3rd International Symposium on Symmetries in Subatomic Physics, Adelaide, SA, Australia, March 13-17, 200

Symmetries and Symmetry Breaking

Several new proton-proton parity violation experiments are presently either being performed or are being prepared for execution in the near future. Similarly, a new measurement of the parity-violating gamma-ray asymmetry in polarized neutron capture on the proton is being developed with a ten-fold improvement over previous measurements. These experiments are intended to provide stringent constraints on the set of seven effective weak meson-nucleon coupling constants. Time-reversal-invariance non-conservation has now been unequivocally demonstrated in a direct measurement at CPLEAR. Tests may also be made of time-reversal-invariance non-conservation in systems other than the kaon system. There exist two classes of time-reversal invariance breaking interactions: P-odd/T-odd and P-even/T-odd interactions. Constraints on the first ones stem from measurements of the electric dipole moment of the neutron, while constraints on the second ones stem from the same and measurements of charge symmetry breaking in neutron-proton elastic scattering and from $K$ semi-leptonic decays. A series of precision experiments, either ongoing or being prepared, will determine the neutral weak current of the proton by measuring the parity-violating normalized asymmetry in electron-proton elastic scattering. A direct comparison between the electromagnetic and neutral weak ground state currents of the nucleon will allow a delineation of the contributions to these currents of the various quark flavours, including quarks which belong exclusively to the nucleon sea. An extension of these precision experiments to very low momentum transfer would permit stringent limits to be placed on physics beyond the standard model.Comment: 11 Pages LaTeX, including 5 PostScript figures. Uses esprc1.sty. Invited Paper presented at 16th International Conference on Few-Body Problems in Physics, Taipei, March 6-10, 200

Charge Independence and Charge Symmetry

Charge independence and charge symmetry are approximate symmetries of nature, violated by the perturbing effects of the mass difference between up and down quarks and by electromagnetic interactions. The observations of the symmetry breaking effects in nuclear and particle physics and the implications of those effects are reviewed.Comment: 41 pages, report # DOE/ER/40427-17-N94, Chapter for a book titled "Symmetries and Fundamental Interactions in Nuclei" eds. E.M. Henley and W. Haxton, to be published by World Scientifi

From Hadronic Parity Violation to Parity-Violating Electron Scattering and Tests of the Standard Model

After almost five decades of study of parity violation in hadronic systems, the determination of the seven weak meson-nucleon couplings is still incomplete. Whereas parity violation in nuclear systems is complicated by the intricacies of QCD, measurements of parity violation in the much simpler proton-proton system are more straightforward to interpret. We now have three such precision pp experiments at 13.6, at 45, and 221 MeV. Today there are also better possibilities for theoretical interpretation using effective field theory. In electron-proton scattering, parity violating ep experiments such as SAMPLE, G0, HAPPEX, and PVA4 have already shown that the strange quark contributions to the charge and magnetization distributions of the nucleon are tiny. When analyzed together, the results have also greatly improved knowledge of the proton's "weak charge" (Q^p_weak = 1-4sin^2\theta_W at tree level). The Q^p_weak experiment at JLab will further improve this, determining the proton's weak charge to a precision of about 4%. Such a precision will either establish conformity with the Standard Model of quarks and leptons or point to New Physics. Following the upgrade of CEBAF at JLab to 12 GeV, a parity violating electron-electron (Moller) scattering experiment similar to SLAC E158, will measure the weak charge of the electron and hence sin^2\theta_W at low energy with a precision comparable to the most precise individual measurements at the Z0 pole (to about +/- 0.00025). This experiment will be complementary to Q^p_weak in terms of sensitivity to New Physics.Comment: 12 pages, 8 figures, LaTeX. Invited talk at the International Symposium on Cosmology and Particle Astrophysics (CosPA07), Taipei, Taiwan, Nov 13-15, 200

Constraints on a Parity-Conserving/Time-Reversal-Non-Conserving Interaction

Time-Reversal-Invariance non-conservation has now been unequivocally demonstrated in a direct measurement at CPLEAR. What about tests of time-reversal-invariance in systems other than the kaon system? Tests of time-reversal-invariance belong to two classes: searches for parity violating (P-odd)/time-reversal-invariance-odd (T-odd) interactions, and for P-even/T-odd interactions (assuming CPT conservation this implies C-conjugation non-conservation). Limits on a P-odd/T-odd interaction follow from measurements of the electric dipole moment of the neutron (with a present upper limit of 6 x 10^-26 e.cm [95% C.L.]). It provides a limit on a P-odd/T-odd pion-nucleon coupling constant which is less than 10^-4 times the weak interaction strength. Experimental limits on a P-even/T-odd interaction are much less stringent. Following the standard approach of describing the nucleon-nucleon interaction in terms of meson exchanges, it can be shown that only charged rho-meson exchange and A_1 meson exchange can lead to a P-even/T-odd interaction. The better constraints stem from measurements of the electric dipole moment of the neutron and from measurements of charge-symmetry breaking in neutron-proton elastic scattering. The latter experiments were executed at TRIUMF (497 and 347 MeV) and at IUCF (183 MeV). Weak decay experiments may provide limits which will possibly be comparable. All other experiments, like gamma decay experiments, detailed balance experiments, polarization - analyzing power difference determinations, and five-fold correlation experiments with polarized incident nucleons and aligned nuclear targets, have been shown to be at least an order of magnitude less sensitive.Comment: 15 pages LaTeX, including 5 PostScript figures. Uses ijmpe1.sty. To appear in International Journal of Modern Physics E (IJMPE). Slight change in short abstrac

The Precision nEDM Measurement with UltraCold Neutrons at TRIUMF

The TRIUMF Ultra-Cold Advanced Neutron (TUCAN) collaboration aims at a precision neutron electric dipole moment (nEDM) measurement with an uncertainty of $10^{-27}\,e\cdot\mathrm{cm}$, which is an order-of-magnitude better than the current nEDM upper limit and enables us to test Supersymmetry. To achieve this precision, we are developing a new high-intensity ultracold neutron (UCN) source using super-thermal UCN production in superfluid helium (He-II) and a nEDM spectrometer. The current development status of them is reported in this article.Comment: Proceedings of the 24th International Spin Symposium (SPIN 2021), 18-22 October 2021, Matsue, Japa

Testing Discrete Symmetries At Triumf

3> p ). One expects effects at the most of the order of the fine-structure constant ff, requiring an experimental precision of a few parts in 10 4 . Because polarization calibration standards to date have not reached such precision, a type of null experiment has to be performed: the difference in the zero-crossing angles of A n and A p is measured and then multiplied by the average slope of A n and A p at the zero-crossing angles to deduce \DeltaA j A n - A p . Work supported in part by the Natural Sciences and Engineering Research Council of Canada. y For the E369 Collaboration: R.Abegg, A.R.Berdoz, J.Birchall, J.R.Campbell, C.A. Davis, P.P.J. Delheij, L. Gan, P.W. Green, L.G. Greeniaus, D.C. Healey, R. Helmer, N. Kolb, E. Korkmaz, L. Lee, C.D.P. Levy, J. Li, C.A. Miller, A.K. Opper, S.A. Page, H.

Parity Violation Experiments At Intermediate Energies

n can be described in terms of a meson exchange model involving a strong interaction vertex and a weak interaction vertex (in a one boson exchange model). The strong interaction vertex is thought to be understood and is represented by the standard meson exchange parameterization of the N-N interaction. The weak interaction vertex is calculated from the Weinberg-Salam model assuming that the W- and Z-bosons are exchanged between the intermediate mesons (ß, ae, and !) and constituent quarks of the nucleon. The interaction can then be described in terms of seven weak meson-nucleon coupling constants. The exchange of neutral scalar mesons is suppressed by CP conservation by a factor of a few times 10 3 (Barton's theorem). The six weak meson-nucleon coupling constants (f ß , h 0 ae , h 1 ae , h 2 ae