T-violation Experiment Research Articles

Measurement of muon spin relaxation time in various scintillating materials

A new experimental method to search for T-violating transverse muon polarization (PT ) in the K+ → π 0 μ + ν decay was recently proposed. In this new experiment, the measurements of the μ + momentum vector, the π 0 momentum vector, and the μ + polarization will be performed by the same segmented calorimeter. One of key issues is the choice of a scintillation material which can maintain the μ + spin polarization for several μ + lifetimes. A test experiment to measure the μ + spin relaxation time in various scintillating materials was carried out at J-PARC Material and Life Science Facility (MLF). It was concluded that the residual μ + polarization in CeF3 is high enough to perform the proposed T-violation experiment.

Measurement of residual [formula omitted] polarization in various scintillating materials to search for [formula omitted]-violating [formula omitted] polarization in [formula omitted] decay

A new experimental method to search for T-violating transverse muon polarization (PT) in the K+→π0μ+ν (Kμ3) decay using a segmented CeF3 calorimeter has been proposed. One of the key issues for this experiment is the choice of a scintillation material which can maintain the μ+ spin polarization for several μ+ lifetimes. The residual μ+ polarization in a CeF3 scintillating crystal was previously measured at the J-PARC Material and Life Science Facility (MLF). Unfortunately, due to the small size of the CeF3 material, beam backgrounds contributed significantly to the μSR spectra, and the absolute μ+ polarization could not be determined accurately. In order to solve this problem, a new experiment was performed at the MLF using a large CeF3 crystal, which successfully reduced the beam backgrounds to a negligible level. The residual μ+ polarization in CeF3 was measured by changing the strength of the applied longitudinal field (LF). The polarization was obtained to be 90 ± 2% with LF = 140 Gauss, which is high enough to perform the new T-violation experiment.

The MTV experiment: searching for T-violation in polarized Li-8 at TRIUMF

The MTV experiment (Mott Polarimetry for T-Violation Experiment) is running at TRIUMF, to search for a large T-violating transverse electron-polarization in polarized 8Li β-decay. We aim at reaching precision of 10−4 for the R-correlation, which is defined as a T-violating triple vector correlation in the β-decay rate function. A Mott polarimeter system using a CDC (Cylindrical Drift Chamber) is used to measure the left-right scattering asymmetry in the Mott scattering from a thin metal foil. In the present study, we aim to discuss systematic effects in Mott polarimetry using the CDC.

First result from the MTV experiment at TRIUMF searching T-violation in nuclear beta decay

The MTV experiment (Mott Polarimetry for T-Violation Experiment) is running from 2009 at TRIUMF, which aims to search a large non-standard T-Violation in polarized nuclear beta decay. Existence of transverse polarization of electrons emitted from polarized 8Li nuclei, which are produced at TRIUMF-ISAC and stopped inside an aluminum stopper, is investigated. We utilize a Mott polarimeter consists of a planer drift chamber, measuring backward scattering left-right asymmetry from a thin lead analyzer foil. In this paper, preliminary results from the first physics run performed in 2010 are described.

T-Violation experiment at TRIUMF-ISAC using polarized8Li

Motivated by a search for a new physics beyond the standard model, the MTV experiment (Mott Polarimetry for T-Violation Experiment) is intended to achieve the highest precision test of time-reversal symmetry in polarized nuclear beta decay by measuring a triple correlation (the R -correlation). The first physics run of the MTV experiment was performed in 2010 at TRIUMF-ISAC. This paper gives preliminary results and describes the next generation setup, which involves a cylindrical drift chamber.

A new FPGA-based trigger/DAQ system for the MTV experiment at TRIUMF

A new FPGA based data acquisition (DAQ) and trigger combined system is developed for the MTV experiment (Mott Polarimetry for T-Violation Experiment). The MTV experiment measures backward Mott scattering events by detecting the incident and scattered tracks using a drift chamber. For the backward scattering probability is as small as less than 0.1%, efficient triggering system is required to select the desired events. An intelligent Level-2 trigger system reading hitting pattern together with its digital readout system are built in a custom FPGA system. In this paper, design overview and results from performance tests are described.

The MTV experiment: a test of time reversal symmetry using polarized 8Li

The MTV (Mott Polarimetry for T-Violation Experiment) experiment at TRIUMF-ISAC (Isotope Separator and ACcelerator), which aims to achieve the highest precision test of time reversal symmetry in polarized nuclear beta decay by measuring a triple correlation (R-correlation), is motivated by the search for a new physics beyond the Standard Model. In this experiment, the existence of non-zero transverse electron polarization is examined utilizing the analyzing power of Mott scattering from a thin metal foil. Backward scattering electron tracks are measured using a multi-wire drift chamber for the first time. The MTV experiment was commissioned at ISAC in 2009 using an 80%polarized 8Li beam at 107 pps, resulting in 0.1%statistical precision on the R-parameter in the first physics run performed in 2010. Next generation cylindrical drift chamber (CDC) is now being installed for the future run.

Test of Time Reversal Symmetry using polarized 8Li at TRIUMF-ISAC

A new experimental project called MTV (Mott Polarimetry for T-Violation Experiment), is running at TRIUMF. It aims to achieve the highest precision test of time reversal symmetry in polarized nuclear beta decay by measuring a triple correlation (R-correlation), motivated to search a new physics beyond the standard model. It is because the CKM predicts negligible effects on the u-d quark system. In this experiment, the existence of non-zero transverse electron polarization is examined utilizing the analyzing power of Mott scattering from a thin metal foil. Backward scattering electron tracks are measured using a multi-wire drift chamber event-by-event for the first time. The tracking device eliminates the largest systematic effect, which has been limiting the sensitivity of previous studies. The MTV experiment was commissioned at TRIUMF-ISAC in 2009 using an 80% polarized 8Li beam at 10 Mpps resulting in 3.6% precision on the R-parameter, after performing a feasibility test at KEK-TRIAC in 2008 using an 8% polarized beam at 100 kpps yielding 41% statistical precision. In 2010, a physics production run is scheduled, aiming to reach below 0.1% precision. In this document, the preparation status for the 2010 run and results from the commissioning run are described.

Electron Transverse Polarimeter for the MTV experiment at TRIUMF

A new experimental project called MTV(Mott Polarimetry for T-Violation Experiment)-S1183 has started at TRIUMF, aiming to achieve the highest precision test of time reversal symmetry in polarized nuclear beta decay. In this experiment, existence of T-violating transverse polarization of electrons emitted from polarized nuclei is examined, using a multi-wire drift chamber (MWDC) as an electron tracking detector in order to measure Mott scattering asymmetries. In this paper, technical aspects of the electron polarimetry are described. The Mott polarimeter, MWDC, consists of six sense layers. In order to improve the real backward scattering event purity, a new intelligent triggering system using FPGA module to perform on-line hit pattern recognition was developed. The new triggering system was installed for the first commissioning experiment in November 2009 at TRIUMF-ISAC. In addition to the triggering system, a new buffering DAQ system was also developed in order to achieve the needed high triggering rate at ISAC. Details of their performance are also described.

A Ramsey's method with pulsed neutrons for a T-violation experiment

A Ramsey’s method with pulsed neutrons is discussed for neutron spin manipulation in a time reversal (T) symmetry violation experiment. The neutron spin (sn) is aligned to the direction of a vector product of the nuclear spin (I) and the neutron momentum (kn) for the measurement of a T-odd correlation term, which is represented as sn · (kn × I), during propagation through a polarized nuclear target. The phase control and amplitude modulation of separated oscillatory fields are discussed for the measurement of the T-odd correlation term.

Symmetry Violation under Space Time Reversal and Precision Experiments with Pulsed Neutrons

Symmetry violation experiments with pulsed neutrons are discussed. A T-violation experiment on a neutron phase shift after passing through a polarized nuclear target is proposed. A new application of the experimental method of the symmetry violation experiments to other fields is also proposed.

Motion reversal of polarized neutron-nucleus scattering

A reciprocity relation is discussed for a T-violation experiment on polarized neutron-nucleus scattering. A new method is proposed in which systematic errors due to misalignments in the settings of beam and polarization axes are cancelled by applying a complete motion reversal.

High-precision magnetic field mapping with a three-dimensional Hall probe for a T-violation experiment in K μ3 decay

High-precision magnetic-field mapping was performed for an experiment to search for a violation of time-reversal invariance in the K + → π 0 μ + ν μ decay at the KEK proton synchrotron. A commercially available three-dimensional Hall probe was used in conjunction with a specially designed mapping device and a goniometer system. Details concerning the measurement principle, calibration, actual measurements and analysis are described.

Scintillation ring hodoscope with WLS fiber readout

A simple tracking system for measuring the K + decay vertex along the beam axis in the T-Violation Experiment (E246) at KEK is described. It consists of 32 grooved BC408 plastic scintillator rings with embedded Y11 wavelength-shifting (WLS) optical fibers. Both ends of each multi-clad WLS fiber are directly viewed by a green-extended photomultiplier. Light yield of 46 photoelectrons per minimum ionizing particle in the 5 mm thick ring has been achieved. This configuration gives 1.7 mm position resolution determined purely by the 6 mm width of each ring. Time resolution of 1.0 ns and detection efficiency of 98.4% were obtained.

Neutron polarization for P- and T-violation experiments

The polarization of neutron spin, target nucleus spin and He nuclear spin was developed at KEK for measuring the T-odd term in polarized neutron transmission through a polarized nuclear target. A method to measure the neutron spin rotation was developed for the T-violation experiment. This apparatus has been found to be quite useful for the P-violating neutron spin rotation experiment. The angular distribution of neutron-capture γ-rays was measured for the study of the enhancement mechanism of the P-violation. The results are also discussed.

Test of Time Reversal Invariance using Neutrons

Measurements of neutron electric dipole moment (EDM) have provided the most strict and reliable upper limit on T-violating interactions. It is well known that neutron EDM is sensitive to theoretical models which explain the CP-violation in K-meson. Another approach to T-violation using neutrons is the measurement of T-odd term in p-wave neutron capture reactions in the incident energy region of about eV. In the compound states formed by the p-wave neutron capture reactions, an enhancement of T-violating interaction is theoretically predicted based on the interference of two opposite parity amplitudes. A brief review of neutron EDM measurements and an overview of T-violation experiment in eV-neutron capture reactions are given.

Test of time reversal invariance using neutrons

Measurements of neutron electric dipole moment (EDM) have provided the most strict and reliable upper limit on T-violating interactions. It is well known that neutron EDM is sensitive to theoretical models which explain the CP-violation in K-meson. Another approach to T-violation using neutrons is the measurement of T-odd term in p-wave neutron capture reactions in the incident energy region of about eV. In the compound states formed by the p-wave neutron capture reactions, an enhancement of T-violating interaction is theoretically predicted based on the interference of two opposite parity amplitudes. A brief review of neutron EDM measurements and an overview of T-violation experiment in eV-neutron capture reactions are given.

T-violation neutron experiment and polarized3He

An experimental scheme of the spin detailed balance in polarized neutron transmission through a polarized nuclear target is discussed for the T-violation test. The value of the spin detailed balance is estimated by using the data of the scattering amplitudes. The nuclear polarizations of proton,3He and139La are discussed for the T-violation experiment.

“Artificial vacuum” for T-violation experiment

We point out the possible use of matrix isolation spectroscopy in experimental tests of fundamental physics. As a concrete example we show how this technique might be applied to measuring the T-violation electron electric dipole moment d e. We estimate that a dipole moment could be detected down to d e ∼ 6 × 10 −28 e cm, in comparison to the current limit of d e < 10 −24 e cm.