Test Of Time-reversal Invariance Research Articles

Polarized proton-deuteron scattering as a test of time-reversal invariance

Scattering of protons with transversal polarization $p_y^p$ on deuterons with tensor polarization $P_{xz}$ provides a null-test signal for time-reversal (T) invariance violating but parity (P) conserving effects. We calculate the corresponding null-test observable at beam energies 100-1000 MeV within the spin-dependent Glauber theory considering T-violating P-conserving nucleon-nucleon interactions. The S-wave component of the deuteron wave function as well as the D-wave are taken into account and the latter is found to play an important role for the magnitude and the energy dependence of the observable in question. Specifically, with inclusion of the D wave the maximum of the obtained signal is shifted to higher beam energies, i.e. to 700-800 MeV.

The physics program of PAX at COSY

The construction of the PAX installation was inspired by the idea to make a beam of polarized antiprotons available for the experiments at the HESR FAIR. A spin filtering experiment with transversally polarized protons was realized using the new PAX installation at COSY. The results of this measurement are in perfect agreement with the FILTEX experiment. Hence, filtering is a viable method to produce a stored beam of polarized antiprotons. Another experiment which can be pursued using the PAX installation is the test of Time Reversal Invariance at COSY (TRIC). The goal of the TRIC experiment is to improve the present upper limit on violation of the T-odd P-even interaction by an order of magnitude using a genuine null observable available in a double polarized pd scattering. The status of the PAX spin filtering experiments as well as present understanding of the possible systematic uncertainties in TRIC are presented in this contribution.

Double-Polarized pd Scattering and Test of Time-reversal Invariance

The integrated proton-deuteron cross section σ˜ for the case of transversal polarization ppy of the proton and tensor polarization Pxz of the deuteron provides a null test signal for time-reversal invariance violating but P-parity conserving effects. The corresponding experiment is planned at COSY to measure the observable σ˜. Here we consider in general case the status of the null-test observable in pd scattering, calculate σ˜ within the Glauber theory of the double-polarized pd scattering at 100 - 1000 MeV and study the contribution of the deuteron S- and D-waves for several type of the T-odd NN interactions.

Test of Time-Reversal Invariance at COSY (TRIC)

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10[Formula: see text] is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry A[Formula: see text]. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be determined by the lifetime of the beam. Consequently, the accuracy of the current measurement of the circulating proton beam is crucial for this experiment. Thus, the cooler synchroton ring serves as an ideal forward spectrometer, as a detector, and an accelerator.

Test of Time Reversal Invariance and COSY

Test of Time Reversal Invariance in pd scattering is planned at the COoler-SYnchrotron COSY-Jülich using the PAX internal target station. Feasibility test, performed in September 2012, have shown possibility to perform such an experiment using COSY and PAX. In parallel to the PAX upgrade a new high precision beam current measurement system will be constructed by the end of 2014. After these modifications, it will be possible to improve the current upper limit on a strength of T-odd P-even NN potential by an order of magnitude.

Test of time-reversal invariance at COSY (TRIC)

At the Cooler Synchrotron COSY a novel (P-even, T-odd) null test of time-reversal invariance to an accuracy of 10 − 6 is planned as an internal target transmission experiment. The parity conserving time-reversal violating observable is the total cross-section asymmetry Ay,xz. This quantity is measured using a polarized proton beam with an energy of 135 MeV and an internal tensor polarized deuteron target from the PAX atomic beam source. The reaction rate will be measured by means of an integrating beam current transformer. Thus, in this experiment the cooler synchroton ring serves as ideal forward spectrometer, as a detector, and an accelerator.

Spin physics at COSY and beyond

Hadron physics aims at a fundamental understanding of all particles and their interactions that are subject to the strong force. Experiments using hadronic probes bear the potential to shed light on open questions that address the structure of hadrons and their interaction, as well as the symmetries of nature. The COoler SYnchrotron COSY at the Forschungszentrum Jülich accelerates protons and deuterons with momenta up to 3.7 GeV/c. In combination with internal polarized Hydrogen and Deuterium targets, the availability of electron and stochastically cooled polarized proton and deuteron beams allows for precision measurements. This report highlights selected recent results from the ongoing spin physics programs at the COSY facility. Spin physics projects reaching into the future, such as the quest for polarized antiprotons, the search for permanent electric dipole moments of protons and deuterons, and a test of time reversal invariance using COSY, are presented as well.

TESTS OF SYMMETRIES WITH NUCLEI

I review here the status of tests of discrete symmetries in nuclear beta decay, including neutron decay. The focus is given on tests of maximal parity violation, tests of time reversal invariance as well as searches for parity and time reversal invariant exotic interactions. Along with the most sensitive results, I present also some recent achievements of precision beta decay experiments as well as selected ongoing project.

Fundamental Symmetries and Conservation Laws

I discuss recent progress in low-energy tests of symmetries and conservation laws, including parity nonconservation in atoms and nuclei, electric dipole moment tests of time-reversal invariance, β-decay correlation studies, and decays violating separate (family) and total lepton number.

Aligned nuclear targets for the test of time reversal invariance

The new aligned nuclear targets are proposed for investigation of time reversal invariance violation (TRIV) in the neutron-nuclei interactions with the use of five-fold correlation. The nuclei121Sb,123Sb and127I can be aligned in these targets by brute force method at 20 mK. The construction of127I single crystal target is considered with the use of dilution refrigerator that is precooled by two stage pulse-tube refrigerator without any cryoliquids. The use of above targets at new neutron spallation sources (SNS, USA and JSNS, Japan) will provide a way of TRIV observation or allow to decrease the present limit on intensity of parity conserving time violating interation by two orders of magnitude.

Measurement of the polarization vector of the e+ from the decay of polarized μ+ as a test of time reversal invariance

The complete polarization vector of the positrons from the decay of polarized muons has been measured for the first time with one experimental setup. The μPT experiment at the Paul Scherrer Institute determines the three polarization components simultaneously with the same apparatus by making use of three different effects (spatial and temporal dependence of annihilation-in-flight with polarized electrons as well as muon decay asymmetry). The use of a stroboscopic method greatly reduces systematic errors. The energy dependence of the transverse polarization component PT1, which lies in the plane spanned by muon spin and positron momentum, yields the low energy parameter η and thus an improved model-independent value of the Fermi coupling constant. A non-zero value of the transverse component PT2, which is perpendicular to the above-mentioned plane, would be the first observation of time reversal violation in a purely leptonic decay. The preliminary results are PT1 = (5 +/- 16) × 10−3, PT2 = (1 +/- 16) × 10−3 and PL = (1.09 +/- 0.15).

Polarized muon decay: Measurement of the polarization vector of the decay positrons as a test of time reversal invariance

The μ PT experiment at the Paul Scherrer Institut has determined the three polarization components of positrons from polarized muon decay simultaneously with the same apparatus by making use of three different effects (spatial and temporal dependence of annihilation-in-flight with polarized electrons and muon decay asymmetry). The use of a stroboscopic method greatly reduces systematic errors. The energy dependence of the transverse polarization component P T 1 , which lies in the plane spanned by muon-spin and positron momentum, yields the low energy parameter η and thus an improved model-independent value of the Fermi coupling constant. A non-zero value of the transverse component P T 2 , which is perpendicular to the above mentioned plane, would be the first observation of time reversal violation in a purely leptonic decay. The preliminary results are P T 1 = (5 ± 16) × 10 −3, P T 2 = (1 ± 16) × 10 −3and P L = 1.09 ± 0.15.

Test of time reversal invariance with TRINE

The new detector TRINE (time reversal invariance neutron experiment) was developed to test the time reversal invariance in the neutron decay. The precision of former experiments can be improved by one order of magnitude with an improved proton detection, a better background suppression and an angular resolving measurement using multiwire proportional chambers in coincidence with plastic scintillators, and the higher neutron flux and polarization available today. The concept of the detector and the status of the project is discussed.

Dynamic nuclear polarization in crystals of Nd 3+:LaAlO 3, a polarized 139La target for a test of time-reversal invariance

Dynamic nuclear polarization (DNP) has been performed in a magnetic field of 2.35 T at a temperature below 0.3 K in crystals of Nd 3+ : LaAlO 3 . A Q-meter NMR-system was used to measure the polarization of the 27Al and 139La nuclei and allowed to characterize the quality of the crystals. The 139La polarizations of +47.5% and −56.5% achieved represent an important step in the development of a polarized 139La target for a test of time reversal invariance in low-energy neutron reactions.

Time reversal in polarized neutron decay: the emiT experiment

The standard electro-weak model predicts negligible violation of time-reversal invariance in light quark processes. We report on an experimental test of time-reversal invariance in the beta decay of polarized neutrons as a search for physics beyond the standard model. The emiT collaboration has measured the time-reversal-violating triple-correlation in neutron beta decay between the neutron spin, electron momentum, and neutrino momentum often referred to as the D coefficient. The first run of the experiment produced 14 million events which are currently being analyzed. However, a second run with improved detectors should provide greater statistical precision and reduced systematic uncertainties.

The polarized atomic-beam target for the EDDA experiment and the time-reversal invariance test at COSY

For the the EDDA experiment, which was set up to measure the p̄-p̄ excitation function during the acceleration ramp of the cooler synchrotron COSY at Jülich, a polarized atomic-beam target was designed regarding the restrictions imposed by the geometry of the EDDA detector. Later, when the time-reversal invariance experiment is to be performed, the EDDA detector will serve as efficient internal polarimeter and the source has to deliver tensor polarized deuterons. The modular design of this polarized atomic-beam target that allows to meet these conditions will be discussed in comparison to other existing polarized atomic-beam targets.

Observation of a large parity nonconserving analyzing power in Xe.

A large parity nonconserving longitudinal analyzing power was discovered in polarized-neutron transmission through Xe. An analyzing power of 4.3\ifmmode\pm\else\textpm\fi{}0.2% was observed in a $p$-wave resonance at ${E}_{n}=3.2$ eV. The measurement was performed with a liquid Xe target of natural isotopic abundance that was placed in the polarized epithermal neutron beam, flight path 2, at the Manuel Lujan Neutron Science Center. This apparatus was constructed by the TRIPLE Collaboration, and has been used for studies of parity symmetry in compound nuclear resonances. Part of the motivation of the experiment was to discover a nucleus appropriate for a sensitive test of time-reversal invariance in polarized-neutron transmission. The large analyzing power of the observed resonance may make it possible to design a test of time reversal invariance using a polarized-Xe target.

Isotopic identification of the parity-violating neutron p-wave resonance at energy E0=3.2 eV in Xe.

Two-dimensional pulse height and time-of-flight (TOF) spectra were measured at the IBR-30 pulsed neutron source to make the isotopic identification of the parity-violating $p$-wave resonance at ${E}_{0}=3.2$ eV recently observed in Xe. Analysis of the TOF spectra corresponding to the characteristic low-energy gamma-rays established the $^{131}\mathrm{Xe}$ isotope as the origin of the 3.2-eV resonance. This new finding poses a challenge for the development of a polarized solid $^{131}\mathrm{Xe}$ target for a test of time-reversal invariance with neutrons.

Tests of time-reversal invariance in nuclear and particle physics.

There is a theorem that states that there can be no null test of time-reversal invariance (T symmetry) in exclusive reactions; that is, T symmetry does not require any single observable to vanish. This theorem is extended to inclusive reactions. Also, a general argument, that an experimental observable vanishes from T symmetry if a corresponding operator changes sign under time reversal, is shown to be invalid.

Experimental determination of the symmetry of the order parameter in YBCO

At present, the symmetry of the order parameter in the high temperature superconductor YBCO is quite controversial. Recent experiments using SQUIDs and Josephson junctions appear to support competing theories, with some experiments supporting a dx2−y2 pairing symmetry for the order parameter and others a s-wave pairing symmetry. We note that a number of factors such as trapped flux, magnetic field gradients and SQUID asymmetries could lead such measurements astray. We use a Scanning SQUID Microscope and a time-reversal invariance test to resolve these experimental problems. We find the order parameter in YBCO has a time-reversal invariant dx2−y2 symmetric component. We estimate the amplitude of anyimaginary s-wave symmetric component to be less than 4% and anyreal s-wave component to be less than 82%.