Violation Of Time-reversal Invariance Research Articles

Stuart Jay Freedman

Stuart Jay Freedman

Discover potential in a search for time-reversal invariance violation in nuclei

Time reversal invariance violating (TRIV) effects in low energy physics could be very important in searching for new physics, being complementary to neutron and atomic electric dipole moment (EDM) measurements. In this relation, we discuss a sensitivity of some TRIV observables to different models of time-reversal (CP) violation and their dependencies on nuclear structure. As a measure of a sensitivity of TRIV effects to the value of TRIV nucleon coupling constant, we introduce a coefficient of a “discovery potential”, which shows a possible factor for improving the current limits of the EDM experiments by measuring nuclear TRIV effects.

Memory function of turbulent fluctuations in soft-mode turbulence

Modal relaxation dynamics has been observed experimentally to clarify statistical-physical properties of soft-mode turbulence, the spatiotemporal chaos observed in homeotropically aligned nematic liquid crystals. We found a dual structure, dynamical crossover associated with violation of time-reversal invariance, the corresponding time scales satisfying a dynamical scaling law. To specify the origin of the dual structure, the memory function due to nonthermal fluctuations has been defined by a projection-operator method and obtained numerically using experimental results. The results of the memory function suggest that the nonthermal fluctuations can be divided into Markov and non-Markov contributions; the latter is called the turbulent fluctuation (TF). Consequently, the relaxation dynamics is separated into three characteristic stages: bare-friction, early, and late stages. If the dissipation due to TFs dominates over that of the Markov contribution, the bare-friction stage contracts; the early and late stages then configure the dual structure. The memory effect due to TFs results in a time-reversible relaxation at the early stage, and the disappearance of the memory by turbulent mixing leads to a simple exponential relaxation at the late stage. Furthermore, the memory effect due to TFs is shown to originate from characteristic spatial coherency called the patch structure.

Nuclear electric dipole moment of three-body systems

Background: The existence of the electric dipole moment (EDM) of stable nuclei would be a direct evidence of the time reversal invariance violation (TRIV). Therefore, its measurement could be considered as a complement to the search for neutron and atomic EDMs.Purpose: To clarify theoretical issues related to calculations of EDMs in many-body systems we calculated the EDMs of the simplest nuclei.Method: For calculations of three-nucleon systems EDMs we used TRIV potentials based on the meson exchange theory, as well as the ones derived by using effective field theories (EFT) with and without explicit pions. Nuclear wave functions were obtained by solving Faddeev equations in configuration space for the complete Hamiltonians comprising both TRIV and realistic strong interactions.Results: The expressions for EDMs of ${}^{3}\text{He}$ and ${}^{3}\text{H}$ are given in terms of meson exchange couplings and low energy constants of EFT potentials.Conclusions: The obtained results are compared with the previous calculations of ${}^{3}\text{He}$ EDM and with time reversal invariance violating effects in neutron-deuteron scattering. The model dependence on strong interactions is discussed.

Dipole resonances and the nuclear Schiff moment

The nuclear Schiff moment creates a mechanism of transfer of the violation of parity and time-reversal invariance by weak interaction in nuclei into the atomic electric dipole moment. We point out an additional contribution to the Schiff moment generated by the mixing of single-particle states through the low-lying nuclear dipole resonances. An estimate shows that this contribution is by order of magnitude comparable to single-particle contributions and can be enhanced if the low-lying resonance has collective nature.

Unidirectionality of time induced by T violation

The physical nature of time has been an enigma for centuries. Despite the progress made in linking various arrows of time together, the underlying reason for the observed direction of time has remained a deep mystery. However, an increasing number of experiments are confirming a violation of time reversal invariance (T) in meson decay processes. T violation represents a fundamental break in the symmetry between the past and future. I show here that such processes induce destructive interference between different paths that the universe can take through time. The interference eliminates all paths except for two that represent continuously forwards and continuously backwards time evolution. These results illustrate that there are previously-unknown large-scale physical effects arising from the T violation processes in meson decay. Moreover these effects offer a solution to the age-old problem of the cause of the unidirectionality of time.

Time reversal invariance violation in neutron-deuteron scattering

Time reversal invariance violating (TRIV) effects for low energy elastic neutron deuteron scattering are calculated for meson exchange and EFT-type of TRIV potentials in a Distorted Wave Born Approximation, using realistic hadronic strong interaction wave functions, obtained by solving three-body Faddeev equations in configuration space. The relation between TRIV and parity violating observables are discussed.

T Violation and the Unidirectionality of Time

An increasing number of experiments at the Belle, BNL, CERN, DAΦNE and SLAC accelerators are confirming the violation of time reversal invariance (T). The violation signifies a fundamental asymmetry between the past and future and calls for a major shift in the way we think about time. Here we show that processes which violate T symmetry induce destructive interference between different paths that the universe can take through time. The interference eliminates all paths except for two that represent continuously forwards and continuously backwards time evolution. Evidence from the accelerator experiments indicates which path the universe is effectively following. This work may provide fresh insight into the long-standing problem of modeling the dynamics of T violation processes. It suggests that T violation has previously unknown, large-scale physical effects and that these effects underlie the origin of the unidirectionality of time. It may have implications for the Wheeler-DeWitt equation of canonical quantum gravity. Finally it provides a view of the quantum nature of time itself.

Exceptional Points in a Microwave Billiard with Time-Reversal Invariance Violation

We report on the experimental study of an exceptional point (EP) in a dissipative microwave billiard with induced time-reversal invariance (T) violation. The associated two-state Hamiltonian is non-Hermitian and nonsymmetric. It is determined experimentally on a narrow grid in a parameter plane around the EP. At the EP the size of T violation is given by the relative phase of the eigenvector components. The eigenvectors are adiabatically transported around the EP, whereupon they gather geometric phases and in addition geometric amplitudes different from unity.

Kaon experiments at J-PARC

The newly constructed high-intensity proton synchrotron, J-PARC ( J apan P roton A ccelerator R esearch C omplex), has completed its first stage of construction and started accelerator commissioning. Many experiments using slowly extracted proton beam are proposed and being prepared. Among them, two experiments to study Kaon decays, KOTO to search for a K L → π 0 ν ν ¯ decay and TREK for violation of Time-Reversal invariance, are under preparation. In this article, current status of the experiments is reported.

Random matrices and chaos in nuclear physics: Nuclear reactions

The application of random-matrix theory (RMT) to compound-nucleus (CN) reactions is reviewed. An introduction into the basic concepts of nuclear scattering theory is followed by a survey of phenomenological approaches to CN scattering. The implementation of a random-matrix approach into scattering theory leads to a statistical theory of CN reactions. Since RMT applies generically to chaotic quantum systems, that theory is, at the same time, a generic theory of quantum chaotic scattering. It uses a minimum of input parameters (average S-matrix and mean level spacing of the CN). Predictions of the theory are derived with the help of field-theoretical methods adapted from condensed-matter physics and compared with those of phenomenological approaches. Thorough tests of the theory are reviewed, as are applications in nuclear physics, with special attention given to violation of symmetries (isospin, parity) and time-reversal invariance.

Measurement of the transverse polarization of electrons emitted in neutron decay: A search for weak exotic couplings

First results are presented from an experiment that aims at the simultaneous determination of both transversal polarization components of electrons emitted in the decay of free neutrons—two observables that have never before been addressed experimentally. A non-zero value of the R correlation coefficient, due to the e - polarization component perpendicular to the plane spanned by the spin of the decaying neutron and the electron momentum, would signal a violation of time reversal invariance. The value of the N correlation coefficient, given by the transverse e - polarization component within that plane, is expected to be finite. The measurement of N, both, probes the Standard Model and serves as an important systematic check of the experimental apparatus with respect to the R correlation measurement. Data taking using the polarized cold neutron beam FUNSPIN from the SINQ spallation source at the Paul Scherrer Institute, Villigen, Switzerland, has been completed. Preliminary results of the data analysis are presented. Two options for a possible future experiment leading to the accuracy of about 3 × 10 - 4 are discussed.

Induced Violation of Time-Reversal Invariance in the Regime of Weakly Overlapping Resonances

We measure the complex scattering amplitudes of a flat microwave cavity (a "chaotic billiard"). Time-reversal (T) invariance is partially broken by a magnetized ferrite placed within the cavity. We extend the random-matrix approach to T violation in scattering, determine the parameters from some properties of the scattering amplitudes, and successfully predict others. Our work constitutes the most precise test of the random-matrix theoretical approach to T violation so far available.

Measurement of relaxation rates in Al and Mg alloys for the precise transverse polarization experiment TREK at J-PARC

Abstract The J-PARC TREK experiment will search for violation of time reversal invariance (T) in the K + → π 0 μ + ν decay. The transverse muon polarization ( P T ) in stopped kaon decay will be measured with high precision ( 10 - 4 ) . An active polarimeter will be employed to stop muons and to detect decay positron asymmetry at the same time. The selection of the stopper material is an important issue. In a longitudinal and transverse field μ SR experiment at TRIUMF, the muon spin relaxation rates have been measured for alloys of Al and Mg to find the best candidate stopper material. Almost all the alloys tested showed no significant relaxation.

DIRECT TEST OF TIME REVERSAL INVARIANCE VIOLATION IN B-MESONS

In this letter we reinterpret and reanalyze the available data of the B-meson factories showing the existence of direct experimental evidence of time reversal invariance violation in B-mesons. This reinterpretation consists of using the available observables to define a new observable which, in a model-independent way and without assuming CPT invariance, compares a transition between a B0 and a here-defined Bα-state, with its time reversed transition. The observable then offers a direct way to probe time reversal invariance and it is therefore independent of any conclusion obtained from current experimental information on CP violation and CPT invariance. As far as we are concerned, this is the first direct evidence of time reversal invariance violation in B-mesons and also the first one obtained from decaying particles whose mean lifetime difference is negligible.

Weak pion production off the nucleon

We develop a model for the weak pion production off the nucleon, which besides the delta pole mechanism [weak excitation of the $\ensuremath{\Delta}(1232)$ resonance and its subsequent decay into $N\ensuremath{\pi}$], includes also some background terms required by chiral symmetry. We refit the ${C}_{5}^{A}({q}^{2})$ form factor to the flux-averaged ${\ensuremath{\nu}}_{\ensuremath{\mu}}p\ensuremath{\rightarrow}{\ensuremath{\mu}}^{\ensuremath{-}}p{\ensuremath{\pi}}^{+}$ ANL ${q}^{2}$-differential cross section data, finding a substantially smaller contribution of the delta pole mechanism than traditionally assumed in the literature. Within this scheme, we calculate several differential and integrated cross sections, including pion angular distributions, induced by neutrinos and antineutrinos and driven both by charged and neutral currents. In all cases we find that the background terms produce quite significant effects, and that they lead to an overall improved description of the data, as compared to the case where only the delta pole mechanism is considered. We also show that the interference between the delta pole and the background terms produces parity-violating contributions to the pion angular differential cross section, which are intimately linked to $T$-odd correlations in the contraction between the leptonic and hadronic tensors. However, these latter correlations do not imply a genuine violation of time-reversal invariance because of the existence of strong final state interaction effects.

Evaluating the PT-violation contributions and the T-invariant masking spin-angle correlations in 10B(n, α1γ)7Li reaction

A three-vector apt(σn[kα × sγ]) correlation of the neutron beam polarization directions σn, α-particle momentum kα, and γ-quantum circular polarizations sγ in 10B(n, α1γ)7Li reaction (Eγ = 478 keV) is proposed as a means of searching for the simultaneous time-reversal invariance and space parity (PT-invariance) violation. An expression for apt coefficient in the αγ cascade is presented. Masking effects, sensitivity of the proposed experiment, and its realization prospects are discussed.

Search forT-violating transverse muon polarization in theK+→π0μ+νdecay

At the 12-GeV proton synchrotron of KEK, an experiment (KEK-PS-E246) was performed to measure the transverse muon polarization (${P}_{T}$) in ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}{\ensuremath{\mu}}^{+}\ensuremath{\nu}$ decays as a direct search of violation of time reversal invariance ($T$-violation). ${P}_{T}$ is a very sensitive probe of $CP$ violation beyond the standard model. A stopped positive kaon beam was used. An elaborate high-acceptance detector, in conjunction with a 12-sector superconducting toroidal spectrometer, was utilized. The stopped kaon method provided several advantages in performing a high-precision experiment. The decay was identified by detecting a ${\ensuremath{\mu}}^{+}$ with the spectrometer and a ${\ensuremath{\pi}}^{0}$ with a CsI(Tl) calorimeter surrounding the target as two photons as well as one photon with high energy. For the ${P}_{T}$ measurement, ${\ensuremath{\pi}}^{0}$ events in the forward (fwd) and backward (bwd) regions in the calorimeter were relevant. Systematic errors were greatly suppressed by exploiting the rotational and fwd-bwd symmetry of the system. Polarization measurement was done in terms of asymmetry measurement of decay positrons of stopped muons in the polarimeter. A longitudinal field method was applied for the ${P}_{T}$ polarization component. In the data analysis a novel technique of the two-analysis method was employed. Two independent analyses were performed following their own policy and criteria and good events were selected. Then, the two analyses were combined. A data quality check was carefully done by looking at the null asymmetry ${A}_{0}$, the sensitivity function ${A}_{N}$, the kinematical attenuation coefficient, and the decay-plane distributions. The asymmetry measurement for finite-size muon stoppers was performed ``differentially'' using the position information by the chamber in front of the polarimeter. From the measurements during 1996--2000, we accumulated $11.8\ifmmode\times\else\texttimes\fi{}{10}^{6}$ good events after the two-analysis combination, and deduced ${P}_{T}=\ensuremath{-}0.0017\ifmmode\pm\else\textpm\fi{}0.0023(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0011(\mathrm{syst})$, corresponding to the $T$-violating parameter $\mathrm{Im}\ensuremath{\xi}=\ensuremath{-}0.0053\ifmmode\pm\else\textpm\fi{}0.0071(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.0036(\mathrm{syst})$. From these results the upper limits of $|{P}_{T}|l0.0050$ (90% C.L.) and $|\mathrm{Im}\ensuremath{\xi}|l0.016$ (90% C.L.) were deduced. Systematic errors were carefully studied and estimated. Almost all of the errors were canceled by the 12-sector summation and/or fwd-bwd subtraction, and the total systematic error was concluded to be as a half of the statistical error. The present result set constraints on model parameters of several theoretical models. For the three-Higgs-doublet model, e.g., a limit $|\mathrm{Im}({\ensuremath{\alpha}}_{1}{\ensuremath{\gamma}}_{1}^{*})|l544({M}_{{H}_{1}}/\mathrm{GeV}{)}^{2}$ was obtained. Implications for several other models are discussed.

Plate with a hole obeys the averaged null energy condition

During the recent years experiments with neutral kaons have yielded remarkably sensitive results which are pertinent to such fundamental phenomena as CPT invariance (protecting causality), time-reversal invariance violation, coherence of wave functions, and entanglement of kaons in pair states. We describe the phenomenological developments and the theoretical conclusions drawn from the experimental material. An outlook to future experimentation is indicated.

Two Coils Resonant Ramsey's Method for the Measurement of Time Reversal Invariance Violation in Neutron Transmission.

It is proposed within the framework of Ramsey’s method to register two-dimensional spectra, depending on the neutron phase and neutron energy, for measuring parity (P) and time (T) violating amplitudes of the interaction of polarized neutrons with polarized 139La nuclei in region of the p-wave resonance. The form of the phase spectrum and corresponding expressions for the asymmetries are obtained on the basis of a formalism of a spin density matrix. It is shown that the ratio of the P,T,-violating to P-violating imaginary amplitudes can be obtained from the measurements of the neutron phase spectrum with polarized and unpolarized 139La target.