Masaaki Kitaguchi
A5013466758- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Radiation Detection and Scintillator Technologies
- Nuclear reactor physics and engineering
- Particle physics theoretical and experimental studies
- Nuclear physics research studies
- Advanced NMR Techniques and Applications
- High-Energy Particle Collisions Research
- Quantum Chromodynamics and Particle Interactions
- Magnetic confinement fusion research
- High-pressure geophysics and materials
- NMR spectroscopy and applications
- Dark Matter and Cosmic Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Pulsars and Gravitational Waves Research
- Muon and positron interactions and applications
- Particle accelerators and beam dynamics
- Geophysics and Sensor Technology
- Superconducting Materials and Applications
- Advanced MRI Techniques and Applications
- Atomic and Molecular Physics
- Crystallography and Radiation Phenomena
- Radiation Therapy and Dosimetry
- Neutrino Physics Research
Nagoya University
2016-2025
Obayashi (Japan)
2017-2024
High Energy Accelerator Research Organization
2006-2024
Japan Proton Accelerator Research Complex
2022-2024
Osaka University
2023
Kyoto University
2004-2022
Japan Atomic Energy Agency
2022
Kyushu University
2005-2022
The University of Tokyo
2002-2022
Campbell Collaboration
2022
The invariant mass spectra of e+e- pairs produced in 12 GeV proton-induced nuclear reactions are measured at the KEK Proton Synchrotron. On low-mass side meson peak, a significant enhancement over known hadronic sources has been observed. spectra, including excess, well reproduced by model that takes into account density dependence vector modification, as theoretically predicted.
Invariant mass spectra of e(+) e(-) pairs have been measured in 12 GeV p + A reactions to detect possible in-medium modification vector mesons. Copper and carbon targets are used study the nuclear-size dependence invariant distributions. significant excess on low-mass side phi meson peak is observed low betagamma(= beta/square root(1-beta(2))) region mesons (betagamma < 1.25) with copper targets. However, high betagamma > 1.25), spectral shapes well described by Breit-Wigner shape when...
The violation of Baryon Number, $\mathcal{B}$, is an essential ingredient for the preferential creation matter over antimatter needed to account observed baryon asymmetry in universe. However, such a process has yet be experimentally observed. HIBEAM/NNBAR %experiment program proposed two-stage experiment at European Spallation Source (ESS) search number violation. will include high-sensitivity searches processes that violate by one or two units: free neutron-antineutron oscillation...
At the J-PARC Muon Science Facility (MUSE), MuSEUM collaboration is now performing new precision measurements of ground state hyperfine structure (HFS) both muonium and muonic helium atoms. High-precision ground-state HFS are recognized as one most sensitive tools for testing bound-state quantum electrodynamics theory to precisely probe standard model determine fundamental constants positive muon magnetic moment mass. The same technique can also be employed measure HFS, obtain negative mass,...
Muonic helium is a hydrogenlike atom composed of with one its two electrons replaced by negative muon. Its ground-state hyperfine structure sensitive tool for testing the theory three-body atomic systems and bound-state quantum electrodynamics determining fundamental constants muon magnetic moment mass. New precise measurements are now in progress at J-PARC Muon Science Facility (MUSE). Zero-field have already been carried out, results more than previous 40 years ago. High-field preparation....
We measured the invariant mass spectra of electron-positron pairs in target rapidity region 12-GeV p+A reactions. have observed a significant difference below omega meson between p+C and p+Cu interactions. This indicates that spectral shape mesons is modified at normal nuclear-matter density.
Experiments aiming at 'day long operation high performance' have been carried out in TRIAM-1M. The record value of the discharge duration was updated to 5 h and 16 min. Steady-state tokamak is studied under localized plasma wall interaction conditions. distributions heat load, particle recycling flux impurity source are investigated understand co-deposition pumping. formation sustainment an internal transport barrier (ITB) enhanced current drive mode has by controlling lower hybrid driven...
We describe an experimental search for deviations from the inverse-square law of gravity at nanometer length scale using neutron scattering noble gases on a pulsed slow beam line. By measuring momentum transfer (q) dependence differential cross section xenon and helium comparing to their well-known analytical forms, we place upper bound strength new interaction as function λ which improves upon previous results in region λ<0.1 nm, remains competitive larger-λ region. A pseudoexperimental...
We installed a source for ultracold neutrons at new, dedicated spallation target TRIUMF. The was originally developed in Japan and uses superfluid-helium converter cooled to 0.9$\,$K. During an extensive test campaign November 2017, we extracted up 325000 after one-minute irradiation of the target, over three times more than previously achieved with this source. corresponding ultracold-neutron density whole production guide volume is 5.3$\,$cm$^{-3}$. storage lifetime initially 37$\,$s...
We are developing a neutron polarizer with polarized $^3$He gas, referred to as spin filter, based on the Spin Exchange Optical Pumping (SEOP) for scattering experiments at Materials and Life Science Experimental Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC). A gas-filling station was constructed J-PARC, several cells long relaxation times have been fabricated using station. laboratory has prepared in MLF beam hall polarizing cells, compact pumping systems laser powers...
Ultracold neutrons (UCNs) can be bound by the potential of terrestrial gravity and a reflecting mirror. The wave function state has characteristic modulations. We carried out an experiment to observe vertical distribution UCNs above such mirror at Institut Laue-Langevin in 2011. observed modulation is good agreement with that prediction quantum mechanics using Wigner function. spatial resolution detector system estimated 0.7 micro meter. This first observation gravitationally states...
Angular distribution of individual $\gamma$-rays, emitted from a neutron-induced compound nuclear state via radiative capture reaction ${}^{139}$La(n,$\gamma$) has been studied as function incident neutron energy in the epithermal region by using germanium detectors. An asymmetry $A_{\mathrm{LH}}$ was defined $(N_{\mathrm L}-N_{\mathrm H})/(N_{\mathrm L}+N_{\mathrm H})$, where $N_{\mathrm L}$ and H}$ are integrals low high resonance respectively, we found that angular dependence...
[Figure: see text].
Plasma start-up and sustainment without an inductive field have been studied in the TST-2@K spherical tokamak using high power RF sources (8.2?GHz/up to 170?kW). Steady state discharges with a plasma current of 4?kA were achieved. The line integrated density was about 3 ? 1017?m?2 electron temperature 160?eV. A truncated equilibrium introduced reproduce magnetic measurements. It found that positive Pfirsch?Schl?ter open region at outboard boundary makes significant contribution current....
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 large parity (PV) neutron-induced compound nuclear processes. In these processes, TRIV cross section is given as product PV section, spin factor κ, and ratio matrix elements. We determined κ to be 0.59±0.05 139La+n using both (n,γ) spectroscopy (→n+139→La) transmission. This result...
An $sp$-mixing model, which describes a compound nuclear reaction by mixing partial waves, predicts correlation term in this reaction. A detailed study of the model is required to feasibility new type time reversal symmetry violation search experiment. The ${\mathbit{\ensuremath{\sigma}}}_{n}\ifmmode\cdot\else\textperiodcentered\fi{}({\mathbit{k}}_{n}\ifmmode\times\else\texttimes\fi{}{\mathbit{k}}_{\ensuremath{\gamma}})$ $^{139}\mathrm{La}(\stackrel{P\vec}{n},\ensuremath{\gamma})$ has been...
A neutron-energy dependent angular distribution was measured for individual $\ensuremath{\gamma}$ rays from the 3.2 eV $p$-wave resonance of $^{131}\mathrm{Xe}+n$, that shows enhanced parity violation owing to a mixing between $s$- and amplitudes. The $\ensuremath{\gamma}$-ray transitions were identified, with respect neutron momentum evaluated as function energy 7132 keV rays, which correspond transition 1807 excited state $^{132}\mathrm{Xe}$. is considered originate interference...
Inverse Compton scattering of polarized laser photons by energetic electrons is an excellent method to generate gamma rays. A 100% can rays, but polarization varies depending on the angle In this study, we experimentally measure spatial distribution circularly rays using a magnetized iron that circular MeV Measurements asymmetry gamma-ray transmission relative at each clearly show are near central axis, and they change from linear as increases. simple way obtain highly use collimator...