Faculty Profiles - SHIMIZU Hirohiko

Papers - SHIMIZU Hirohiko

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New muonic He atom HFS measurements at J-PARC MUSE

Goto Y., Fukumura S., Strasser P., Ino T., Iwai R., Kanda S., Kawamura S., Kitaguchi M., Nishimura S., Oku T., Okudaira T., Shimizu H.M., Shimomura K., Tada H., Torii H.A.

Interactions Vol. 245 ( 1 ) 2024.12

Publisher：Interactions

Muonic He (μHe) is a hydrogen-like atom composed of a helium atom with one of its electrons replaced by a negative muon. Measurements of the ground-state hyperfine structure (HFS) interval of the μHe atom is a sensitive tool to test the three-body atomic system, bound-state quantum electrodynamics (QED) theory, and determine fundamental constants of the negative muon magnetic moment and mass. It allows a test of the CPT theorem in muons by comparing these constants with positive muons. Precise measurements of the ground-state HFS interval using a microwave magnetic resonance technique are now in progress at J-PARC by the MuSEUM collaboration. Furthermore, a new experimental approach to recover the muon polarization lost during the muon cascade process is being investigated by repolarizing μHe atoms using a spin-exchange optical pumping (SEOP) technique. The first laser repolarization experiment was recently performed. An overview of the different features of these new μHe atom HFS measurements and the latest results are presented.

DOI： 10.1007/s10751-024-01912-2

Performance of the Fully Equipped Spin Flip Chopper for the Neutron Lifetime Experiment at J-PARC Open Access

Mishima K., Ichikawa G., Fuwa Y., Hasegawa T., Hino M., Hosokawa R., Ino T., Iwashita Y., Kitaguchi M., Matsuzaki S., Mogi T., Okabe H., Oku T., Okudaira T., Seki Y., Shimizu H.E., Shimizu H.M., Takahashi S., Tanida M., Yamashita S., Yokohashi M., Yoshioka T.

Progress of Theoretical and Experimental Physics Vol. 2024 ( 9 ) 2024.9

Publisher：Progress of Theoretical and Experimental Physics

To solve the "neutron lifetime puzzle,"where measured neutron lifetimes differ depending on the measurement methods, an experiment with a pulsed neutron beam at J-PARC is in progress. In this experiment, neutrons are bunched into 40-cm lengths using a spin flip chopper (SFC), where the statistical sensitivity was limited by the aperture size of the SFC. The SFC comprises three sets of magnetic supermirrors and two resonant spin flippers. In this paper, we discuss an upgrade to enlarge the apertures of the SFC. With this upgrade, the statistics per unit time of the neutron lifetime experiment increased by a factor of 2.8, while maintaining a signal-to-noise ratio of 250-400, which is comparable to the previous one. Consequently, the time r equir ed to r each a pr ecision of 1 s in the neutron lifetime ex- periment was reduced from 590 to 170 days, which is a significant reduction in time. This improvement in the statistics will also contribute to the reduction of systematic uncertain- ties, such as background evaluation, fostering further advancements in the neutron lifetime experiments at J-PARC.

DOI： 10.1093/ptep/ptae123

Circular polarization measurement for individual gamma rays in capture reactions with intense pulsed neutrons Open Access

Endo S., Abe R., Fujioka H., Ino T., Iwamoto O., Iwamoto N., Kawamura S., Kimura A., Kitaguchi M., Kobayashi R., Nakamura S., Oku T., Okudaira T., Okuizumi M., Omer M., Rovira G., Shima T., Shimizu H.M., Shizuma T., Taira Y., Takada S., Takahashi S., Yoshikawa H., Yoshioka T., Zen H.

European Physical Journal A Vol. 60 ( 8 ) 2024.8

Publisher：European Physical Journal A

Measurements of circular polarization of γ-ray emitted from neutron capture reactions provide valuable information for nuclear physics studies. The spin and parity of excited states can be determined by measuring the circular polarization from polarized neutron capture reactions. Furthermore, the γ-ray circular polarization in a neutron capture resonance is crucial for studying the enhancement effect of parity nonconservation in compound nuclei. The γ-ray circular polarization can be measured using a polarimeter based on magnetic Compton scattering. A polarimeter was constructed, and its performance indicators were evaluated using a circularly polarized γ-ray beam. Finally, as a demonstration, the γ-ray circular polarization was measured in 32S(n,γ)33S reactions with polarized neutrons.

DOI： 10.1140/epja/s10050-024-01392-6

Sagnac-type neutron displacement-noise-free interferometeric gravitational-wave detector Open Access

Kawasaki Y., Iwaguchi S., Ishikawa T., Nishizawa A., Kitaguchi M., Yamagata Y., Chen Y., Wu B., Shimizu R., Umemura K., Tsuji K., Shimizu H., Michimura Y., Kobayashi K., Onishi T., Kawamura S.

Classical and Quantum Gravity Vol. 41 ( 11 ) 2024.6

Publisher：Classical and Quantum Gravity

The detection of low-frequency gravitational waves on Earth requires the reduction of displacement noise, which dominates the low-frequency band. One method to cancel test mass displacement noise is a neutron displacement-noise-free interferometer (DFI). This paper proposes a new neutron DFI configuration, a Sagnac-type neutron DFI, which uses a Sagnac interferometer in place of the Mach-Zehnder interferometer. We demonstrate that a sensitivity of the Sagnac-type neutron DFI is higher than that of a conventional neutron DFI with the same interferometer scale. This configuration is particularly significant for neutron DFIs with limited space for construction and limited flux from available neutron sources.

DOI： 10.1088/1361-6382/ad42fa

Combination of crystal growth with optical floating zone and evaluation of Nd<sup>3+</sup>:LaAlO<inf>3</inf> crystals with the dynamic nuclear polarization of <sup>139</sup>La and <sup>27</sup>Al Open Access

Ishizaki K., Ide I., Fujita M., Hotta H., Ito Y., Iinuma M., Ikeda Y., Iwata T., Kitaguchi M., Kohri H., Matsushita T., Miura D., Miyachi Y., Shimizu H.M., Yosoi M.

Review of Scientific Instruments Vol. 95 ( 6 ) 2024.6

Publisher：Review of Scientific Instruments

Producing a polarized lanthanum (La) target with high polarization and long relaxation time is crucial for realizing time-reversal violation experiments using polarized neutron beams. We use a LaAlO3 crystal doped with a small amount of Nd3+ ions for the polarized lanthanum target. Optimizing the amount of Nd3+ ions is considerably important because the achievable polarization and relaxation time strongly depend on this amount. We established a fundamental method to grow single crystals of Nd3+:LaAlO3 using an optical floating zone method that employs halogen lamps and evaluated the crystals with the dynamic nuclear polarization (DNP) method for polarizing nuclear spins. Two crystal samples were grown by ourselves and evaluated with the DNP at 1.3 K and 2.3 T for the first time, except for the target materials of protons. The enhancement of nuclear magnetic resonance signals for 139La and 27Al was successfully observed, and the enhancement factors were eventually 3.5 ± 0.3 and 13 ± 3 for the samples with Nd3+ ions of 0.05 and 0.01 mol. %, respectively. These enhancement factors correspond to absolute vector polarizations of 0.27% ± 0.02% (Nd3+ 0.05 mol. %) and 1.4% ± 0.3% (Nd3+ 0.01 mol. %). Although the obtained polarizations are still low, they are acceptable as a first step. The combination scheme of the crystal growth and the evaluation of the crystals is found to be effectively applicable for optimizing the amount of Nd3+ ions for improving the performance of the polarized target.

DOI： 10.1063/5.0202680

Present Status of Spectroscopy of the Hyperfine Structure and Repolarization of Muonic Helium Atoms at J-PARC Open Access

Fukumura S., Strasser P., Fushihara M., Goto Y., Ino T., Iwai R., Kanda S., Kawamura S., Kitaguchi M., Nishimura S., Oku T., Okudaira T., Shimizu H.M., Shimomura K., Tada H., Torii H.A.

Physics (Switzerland) Vol. 6 ( 2 ) page： 877 - 890 2024.6

Publisher：Physics (Switzerland)

The mass (Formula presented.) of the negative muon is one of the parameters of the elementary particle Standard Model and it allows us to verify the CPT (charge–parity–time) symmetry theorem by comparing (Formula presented.) value with the mass (Formula presented.) of the positive muon. However, the experimental determination precision of (Formula presented.) is (Formula presented.), which is an order of magnitude lower than the determination precision of (Formula presented.) at (Formula presented.). The authors aim to determine (Formula presented.) and the magnetic moment (Formula presented.) with a precision of (Formula presented.) through spectroscopy of the hyperfine structure (HFS) of muonic helium-4 atom (Formula presented.) under high magnetic fields. (Formula presented.) is an exotic atom where one of the two electrons of the (Formula presented.) atom is replaced by a negative muon. To achieve the goal, it is necessary to determine the HFS of (Formula presented.) with a precision of (Formula presented.). This paper describes the determination procedure of the HFS of (Formula presented.) in weak magnetic fields reported recently, and the work towards achieving the goal of higher precision measurement.

DOI： 10.3390/physics6020054

High sensitivity of a future search for effects of P -odd/ T -odd interactions on the 0.75 eV p -wave resonance in n→ +139 La→ forward transmission determined using a pulsed neutron beam Open Access

Nakabe R., Auton C.J., Endo S., Fujioka H., Gudkov V., Hirota K., Ide I., Ino T., Ishikado M., Kambara W., Kawamura S., Kimura A., Kitaguchi M., Kobayashi R., Okamura T., Oku T., Okudaira T., Okuizumi M., Otero Munoz J.G., Parker J.D., Sakai K., Shima T., Shimizu H.M., Shinohara T., Snow W.M., Takada S., Takahashi R., Takahashi S., Tsuchikawa Y., Yoshioka T.

Physical Review C Vol. 109 ( 4 ) 2024.4

Publisher：Physical Review C

Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross section is given as the product of the PV cross section, a spin factor κ, and a ratio of TRIV and PV matrix elements. We determined κ to be 0.59±0.05 for La139+n using both (n,γ) spectroscopy and (n→ +139La→) transmission. This result quantifies for the first time the high sensitivity of the La139 0.75-eV p-wave resonance in a future search for effects of P-odd/T-odd interactions in (n→ +139La→) forward transmission.

DOI： 10.1103/PhysRevC.109.L041602

Spin dependence in the p -wave resonance of la 139 - + n - + Open Access

Okudaira T., Nakabe R., Auton C.J., Endo S., Fujioka H., Gudkov V., Ide I., Ino T., Ishikado M., Kambara W., Kawamura S., Kobayashi R., Kitaguchi M., Okamura T., Oku T., Otero Munoz J.G., Parker J.D., Sakai K., Shima T., Shimizu H.M., Shinohara T., Snow W.M., Takada S., Tsuchikawa Y., Takahashi R., Takahashi S., Yoshikawa H., Yoshioka T.

Physical Review C Vol. 109 ( 4 ) 2024.4

Publisher：Physical Review C

We measured the spin-dependent cross section at a neutron-induced p-wave resonance using a polarized epithermal neutron beam and a polarized nuclear target. Our study focuses on the 0.75 eV p-wave resonance of La139+n, where previous experiments have shown a large enhancement of parity violation. The spin dependence of the neutron absorption cross section of polarized La139 and polarized neutrons determines the partial neutron width of the p-wave resonance. This partial width is a key parameter needed to determine the sensitivity of this system to possible parity-odd and time reversal-odd interactions beyond the standard model. Our findings therefore serve as a foundation for a future search for time reversal violation in this compound nuclear system.

DOI： 10.1103/PhysRevC.109.044606

Predictive factors of post-operative apathy in patients with diffuse frontal gliomas undergoing awake brain mapping

Motomura K., Kawamura A., Ohka F., Aoki K., Nishikawa T., Yamaguchi J., Kibe Y., Shimizu H., Maeda S., Saito R.

Journal of Neuropsychology Vol. 18 ( S1 ) page： 73 - 84 2024.3

Publisher：Journal of Neuropsychology

Patients with diffuse frontal gliomas often present with post-operative apathy after tumour removal. However, the association between apathy and tumour removal of gliomas from the frontal lobe remains unknown. This study aimed to investigate the factors influencing post-operative apathy after tumour removal in patients with diffuse frontal gliomas. We compared the demographics and clinical characteristics of patients with and without post-operative apathy in a cohort of 54 patients who underwent awake brain mapping for frontal gliomas. The frequency of clinical parameters such as left-sided involvement, high-grade tumour types (WHO grades III, IV), main tumour location in the anterior cingulate gyrus (ACC) and/or dorsolateral prefrontal cortex (DLPFC) and orbitofrontal cortex (OFC) was significantly greater in the apathetic group compared to the non-apathetic group. The apathetic group scored significantly lower on neuropsychological assessments such as the Letter Fluency Test among the Word Fluency Tests than the non-pathetic group (p =.000). Moreover, the scores of Parts 3, and 3–1 of the Stroop test were significantly lower in the apathetic group than those in the non-apathetic group (p =.023,.027, respectively). Multivariate model analysis revealed that the appearance of post-operative apathy was significantly related to side of the of lesion [left vs. right, hazard ratio (HR) = 8.00, 95% confidence interval (CI) = 1.36–46.96, p =.021], location of the main tumour in the frontal lobe (ACC/DLPFC/OFC vs. others, HR = 7.99, 95% CI = 2.16–29.59, p =.002), and the Letter Fluency Test (HR =.37, 95% CI =.15–.90, p =.028). Post-operative apathy is significantly associated with ACC and/or DLPFC and OFC in the left hemisphere of diffuse frontal gliomas. Apathy in frontal gliomas is correlated with a decline in the Letter Fluency Test scores. Therefore, this instrument is a potential predictor of post-operative apathy in patients with diffuse frontal gliomas undergoing awake brain mapping.

DOI： 10.1111/jnp.12345

Development of Neutron Interferometer Using Multilayer Mirrors and Measurements of Neutron-Nuclear Scattering Length with Pulsed Neutron Source Open Access

Fujiie T., Hino M., Hosobata T., Ichikawa G., Kitaguchi M., Mishima K., Seki Y., Shimizu H.M., Yamagata Y.

Physical Review Letters Vol. 132 ( 2 ) 2024.1

Publisher：Physical Review Letters

This study entailed the successful deployment of a novel neutron interferometer that utilizes multilayer mirrors. The apparatus facilitates a precise evaluation of the wavelength dependence of interference fringes utilizing a pulsed neutron source. Our interferometer achieved an impressive precision of 0.02 rad within a 20-min recording time. Compared to systems using silicon crystals, the measurement sensitivity was maintained even when using a simplified disturbance suppressor. By segregating beam paths entirely, we achieved successful measurements of neutron-nuclear scattering lengths across various samples. The values measured for Si, Al, and Ti were in agreement with those found in the literature, while V showed a disparity of 45%. This discrepancy may be attributable to impurities encountered in previous investigations. The accuracy of measurements can be enhanced further by mitigating systematic uncertainties that are associated with neutron wavelength, sample impurity, and thickness. This novel neutron interferometer enables us to measure fundamental parameters, such as the neutron-nuclear scattering length of materials, with a precision that surpasses that of conventional interferometers.

DOI： 10.1103/PhysRevLett.132.023402

EUSO-SPB1 mission and science Open Access

Abdellaoui G., Abe S., Adams J.H., Allard D., Alonso G., Anchordoqui L., Anzalone A., Arnone E., Asano K., Attallah R., Attoui H., Pernas M.A., Bachmann R., Bacholle S., Bagheri M., Bakiri M., Baláz J., Barghini D., Bartocci S., Battisti M., Bayer J., Beldjilali B., Belenguer T., Belkhalfa N., Bellotti R., Belov A.A., Benmessai K., Bertaina M., Bertone P.F., Biermann P.L., Bisconti F., Blaksley C., Blanc N., Blin-Bondil S., Bobik P., Bogomilov M., Bolmgren K., Bozzo E., Briz S., Bruno A., Caballero K.S., Cafagna F., Cambié G., Campana D., Capdevielle J.N., Capel F., Caramete A., Caramete L., Caruso R., Casolino M., Cassardo C., Castellina A., Catalano O., Cellino A., Černý K., Chikawa M., Chiritoi G., Christl M.J., Colalillo R., Conti L., Cotto G., Crawford H.J., Cremonini R., Creusot A., Cummings A., de Castro Gónzalez A., de la Taille C., del Peral L., Desiato J., Damian A.D., Diesing R., Dinaucourt P., Djakonow A., Djemil T., Ebersoldt A., Ebisuzaki T., Eser J., Fenu F., Fernández-González S., Ferrarese S., Filippatos G., Finch W., Fornaro C., Fouka M., Franceschi A., Franchini S., Fuglesang C., Fujii T., Fukushima M., Galeotti P., García-Ortega E., Gardiol D., Garipov G.K., Gascón E., Gazda E., Genci J., Golzio A., Gorodetzky P., Gregg R., Green A.

Astroparticle Physics Vol. 154 2024.1

Publisher：Astroparticle Physics

The Extreme Universe Space Observatory on a Super Pressure Balloon 1 (EUSO-SPB1) was launched in 2017 April from Wanaka, New Zealand. The plan of this mission of opportunity on a NASA super pressure balloon test flight was to circle the southern hemisphere. The primary scientific goal was to make the first observations of ultra-high-energy cosmic-ray extensive air showers (EASs) by looking down on the atmosphere with an ultraviolet (UV) fluorescence telescope from suborbital altitude (33 km). After 12 days and 4 h aloft, the flight was terminated prematurely in the Pacific Ocean. Before the flight, the instrument was tested extensively in the West Desert of Utah, USA, with UV point sources and lasers. The test results indicated that the instrument had sensitivity to EASs of ⪆3 EeV. Simulations of the telescope system, telescope on time, and realized flight trajectory predicted an observation of about 1 event assuming clear sky conditions. The effects of high clouds were estimated to reduce this value by approximately a factor of 2. A manual search and a machine-learning-based search did not find any EAS signals in these data. Here we review the EUSO-SPB1 instrument and flight and the EAS search.

DOI： 10.1016/j.astropartphys.2023.102891

Improved Measurements of Muonic Helium Ground-State Hyperfine Structure at a Near-Zero Magnetic Field Open Access

Strasser P., Fukumura S., Iwai R., Kanda S., Kawamura S., Kitaguchi M., Nishimura S., Seo S., Shimizu H.M., Shimomura K., Tada H., Torii H.A.

Physical Review Letters Vol. 131 ( 25 ) 2023.12

Publisher：Physical Review Letters

Muonic helium atom hyperfine structure (HFS) measurements are a sensitive tool to test the three-body atomic system and bound-state quantum electrodynamics theory, and determine fundamental constants of the negative muon magnetic moment and mass. The world's most intense pulsed negative muon beam at the Muon Science Facility of the Japan Proton Accelerator Research Complex allows improvement of previous measurements and testing further CPT invariance by comparing the magnetic moments and masses of positive and negative muons (second-generation leptons). We report new ground-state HFS measurements of muonic helium-4 atoms at a near-zero magnetic field, performed for the first time using a small admixture of CH4 as an electron donor to form neutral muonic helium atoms efficiently. Our analysis gives Δν=4464.980(20) MHz (4.5 ppm), which is more precise than both previous measurements at weak and high fields. The muonium ground-state HFS was also measured under the same conditions to investigate the isotopic effect on the frequency shift due to the gas density dependence in He with CH4 admixture and compared with previous studies. Muonium and muonic helium can be regarded as light and heavy hydrogen isotopes with an isotopic mass ratio of 36. No isotopic effect was observed within the current experimental precision.

DOI： 10.1103/PhysRevLett.131.253003

Demonstration of simultaneous measurement of the spin rotation of dynamically-diffracted neutrons from multiple crystal planes using pulsed neutrons

Itoh S., Fukumura S., Fujiie T., Kitaguchi M., Shimizu H.M.

Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Vol. 1057 2023.12

Publisher：Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment

The strong electric field inside a crystal interacting with dynamically-diffracted neutrons by a single crystal can be used in experiments to search for the electric dipole moment of neutrons. This intra-crystal electric field can be evaluated from the neutron spin rotation derived from the dynamical diffraction. Neutron spin rotations from multiple crystal planes were observed simultaneously using pulsed neutrons with a single SiO2 crystal. The spin rotation of dynamically-diffracted neutrons from (110)-crystal plane with the symmetric Laue configuration was consistent with the spin rotation calculated from the intra-crystal electric field reported by the previous experiments. In addition, the spin rotation was also studied for the (02̄1)-, (011)- and (111̄)-crystal planes, which are asymmetric Laue configurations. There have been no previous studies of spin rotations or intra-crystal electric fields on these crystal planes. The experimental results suggest that spin rotation can occur even on crystal planes where it was previously thought that the spin rotation could not occur due to zero intra-crystal electric field. This information is important to study the sensitivity and the systematic uncertainties in nEDM search experiments by crystal diffractions.

DOI： 10.1016/j.nima.2023.168734

Diffuse scattering model of ultracold neutrons on wavy surfaces Open Access

Imajo S., Akatsuka H., Hatanaka K., Higuchi T., Ichikawa G., Kawasaki S., Kitaguchi M., Mammei R., Matsumiya R., Mishima K., Picker R., Schreyer W., Shimizu H.M.

Physical Review C Vol. 108 ( 3 ) 2023.9

Publisher：Physical Review C

Metal tubes plated with nickel-phosphorus are used in many fundamental physics experiments that use ultracold neutrons (UCN) because of their ease of fabrication. These tubes are usually polished to an average roughness of 25-150nm. However, there is no scattering model that accurately describes UCN scattering on such a rough guide surface with a mean-square roughness greater than 5nm. We, therefore, developed a scattering model for UCN in which scattering from random surface waviness with a size larger than the UCN wavelength is described by a microfacet Bidirectional Reflectance Distribution Function model (mf-BRDF model), and scattering from smaller structures by the Lambert's cosine law (Lambert model). For the surface waviness, we used the statistical distribution of surface slope measured by an atomic force microscope on a sample piece of guide tube as an input of the model. This model was used to describe UCN transmission experiments conducted at the pulsed UCN source in J-PARC. In these experiments, a UCN beam collimated to a divergence angle smaller than ±6° was directed into a guide tube with a mean-square roughness of 6.4 to 17nm at an oblique angle, and the UCN transport performance and its time-of-flight distribution were measured while changing the angle of incidence. The mf-BRDF model combined with the Lambert model with scattering probability pL=0.039±0.003 reproduced the experimental results well. We have thus established a procedure to evaluate the characteristics of UCN guide tubes with a surface roughness of approximately 10nm.

DOI： 10.1103/PhysRevC.108.034605

Current status of the polarized La target development for T-violation search with slow neutron Open Access

Ide I., Fujita M., Hotta H., Iinuma M., Ikeda Y., Ito Y., Iwata T., Kitaguchi M., Kohri H., Miura D., Miyachi Y., Okudaira T., Shimizu H.M., Takanashi Y., Yosoi M.

Proceedings of Science Vol. 433 2023.8

Publisher：Proceedings of Science

We are addressing the development of a polarized lanthanum (139La) target by applying a standard dynamic nuclear polarization (DNP) technique to a single crystal of lanthanum aluminate (LaAlO3) doped with neodymium ions (Nd3+), which is very attractive to search for violating effects of the time-reversal invariance with neutrons. The use of the LaAlO3 crystals as target material is very crucial to extend the spin-lattice relaxation time (T1) through the optimization of the Nd3+ concentration. We have almost established a method for precise control of the Nd3+ amount and this method has allowed us to grow the crystal with 0.01 mol% concentration differently from the 0.05 mol% reached before. Simple DNP experiments using a single-shot dewar at 1.3 K and 2.3 T allowed the evaluation of the T1 and the maximum polarization of these crystals. By that we have found that the 0.01 mol% concentration is the best one among the crystals tested in the past. Both, T1 and the maximum polarization of the 0.01 mol% crystal, have not been exactly obtained because of the long relaxation time, Thus, the preparation of a new DNP system is in progress toward DNP experiments for long-term measurement.

DOI： 10.22323/1.433.0038

Angular distribution of γ rays from a neutron-induced p -wave resonance of Xe 132 Open Access

Okudaira T., Tani Y., Endo S., Doskow J., Fujioka H., Hirota K., Kameda K., Kimura A., Kitaguchi M., Luxnat M., Sakai K., Schaper D.C., Shima T., Shimizu H.M., Snow W.M., Takada S., Yamamoto T., Yoshikawa H., Yoshioka T.

Physical Review C Vol. 107 ( 5 ) 2023.5

Publisher：Physical Review C

A neutron-energy dependent angular distribution was measured for individual γ rays from the 3.2 eV p-wave resonance of Xe131+n, that shows enhanced parity violation owing to a mixing between s- and p-wave amplitudes. The γ-ray transitions from the p-wave resonance were identified, and the angular distribution with respect to the neutron momentum was evaluated as a function of the neutron energy for 7132 keV γ rays, which correspond to a transition to the 1807 keV excited state of Xe132. The angular distribution is considered to originate from the interference between s- and p-wave amplitudes, and will provide a basis for a quantitative understanding of the enhancement mechanism of the fundamental parity violation in compound nuclei.

DOI： 10.1103/PhysRevC.107.054602

Displacement-noise-free interferometeric gravitational-wave detector using unidirectional neutrons with four speeds Open Access

Iwaguchi S., Nishizawa A., Chen Y., Kawasaki Y., Ishikawa T., Kitaguchi M., Yamagata Y., Wu B., Shimizu R., Umemura K., Tsuji K., Shimizu H., Michimura Y., Kawamura S.

Physics Letters, Section A: General, Atomic and Solid State Physics Vol. 458 2023.1

Publisher：Physics Letters, Section A: General, Atomic and Solid State Physics

For further gravitational wave (GW) detections, it is significant to invent a technique to reduce all kinds of mirror displacement noise dominant at low frequencies for ground-based detectors. The neutron displacement-noise-free interferometer (DFI) is one of the tools to reduce all the mirror displacement noise at lower frequencies. In this paper, we describe a further simplified configuration of a neutron DFI in terms of neutron incidence direction. In the new configuration, neutrons enter the interferometer with unidirectional incidence at four speeds as opposed to two bidirectional incidences of opposite directions at two speeds as reported previously. This simplification of the neutron DFI is significant for proof-of-principle experiments.

DOI： 10.1016/j.physleta.2022.128581

Status of the new muonic helium atom HFS measurements at J-PARC MUSE Open Access

Strasser P., Fukumura S., Ino T., Iwai R., Kanda S., Kawamura S., Kitaguchi M., Nishimura S., Oku T., Okudaira T., Seo S., Shimizu H.M., Shimizu K., Shimomura K., Tada H., Tanaka T., Torii H.A., Yamauchi H., Yasuda H.

Journal of Physics: Conference Series Vol. 2462 ( 1 ) 2023

Publisher：Journal of Physics: Conference Series

Measurements of the muonic helium atom hyperfine structure (HFS) are a sensitive tool to test the theory of three-body atomic systems and bound-state quantum electrodynamics (QED) and to determine fundamental constants of the negative muon magnetic moment and mass. The world's most intense pulsed negative muon beam at J-PARC MUSE brings an opportunity to improve previous measurements and test further CPT invariance by comparing the magnetic moments and masses of positive and negative muons. Test measurements at D-line are now in progress utilizing MuSEUM apparatus at zero field. The first results already have better accuracy than previous measurements in the 1980s. Also, the investigation of a new experimental approach to improve HFS measurements by repolarizing muonic helium atoms using a spin-exchange optical pumping (SEOP) technique was started. If successful, this would drastically improve the measurement accuracy.

DOI： 10.1088/1742-6596/2462/1/012023

Measurement of the transverse asymmetry of γ rays in the Sn 117 (n,γ) Sn 118 reaction Open Access

Endo S., Okudaira T., Abe R., Fujioka H., Hirota K., Kimura A., Kitaguchi M., Oku T., Sakai K., Shima T., Shimizu H.M., Takada S., Takahashi S., Yamamoto T., Yoshikawa H., Yoshioka T.

Physical Review C Vol. 106 ( 6 ) 2022.12

Publisher：Physical Review C

Largely enhanced parity-violating effects observed in compound resonances induced by epithermal neutrons are currently attributed to the mixing of parity-unfavored partial amplitudes in the entrance channel of the compound states. Furthermore, it is proposed that the same mechanism that enhances the parity violation also enhances the breaking of time-reversal invariance in the compound nucleus. The entrance-channel mixing induces energy-dependent spin-angular correlations of individual γ rays emitted from the compound nuclear state. For a detailed study of the mixing model, the γ-ray yield in the reaction of Sn117(n,γ)Sn118 was measured using a pulsed beam of polarized epithermal neutrons and Ge detectors. An angular dependence of asymmetric γ-ray yields for the orientation of the neutron polarization was observed.

DOI： 10.1103/PhysRevC.106.064601

Displacement-noise-free neutron interferometer for gravitational wave detection using a single Mach-Zehnder configuration Open Access

Iwaguchi S., Nishizawa A., Chen Y., Kawasaki Y., Kitaguchi M., Morimoto T., Ishikawa T., Wu B., Watanabe I., Shimizu R., Shimizu H., Michimura Y., Kawamura S.

Physics Letters, Section A: General, Atomic and Solid State Physics Vol. 441 2022.7

Publisher：Physics Letters, Section A: General, Atomic and Solid State Physics

The improvement of sensitivity to gravitational waves (GWs) at lower frequencies is still challenging on account of displacement noise. One of the solutions is the neutron displacement-noise-free interferometer (DFI). We focus on a simplification of the detector configuration by taking advantage of the ability to adjust the neutron speed depending on the configuration. The new configuration consists of two beamsplitters and two mirrors, which constitute a single Mach-Zehnder interferometer (MZI). It is simpler than the configuration with two MZIs in previous research. All displacement noise of mirrors and beamsplitters can be canceled in the frequency domain. This cancellation can be explained intuitively using a phasor diagram.

DOI： 10.1016/j.physleta.2022.128150

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