N. Muramatsu
A5068927152- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Nuclear physics research studies
- Particle Accelerators and Free-Electron Lasers
- Atomic and Subatomic Physics Research
- Dark Matter and Cosmic Phenomena
- Particle Detector Development and Performance
- Superconducting Materials and Applications
- Black Holes and Theoretical Physics
- Nuclear Physics and Applications
- Neutrino Physics Research
- Advanced NMR Techniques and Applications
- Computational Physics and Python Applications
- Radiation Detection and Scintillator Technologies
- Medical Imaging Techniques and Applications
- Advanced X-ray Imaging Techniques
- Particle accelerators and beam dynamics
- Astrophysics and Cosmic Phenomena
- Cold Atom Physics and Bose-Einstein Condensates
- Quantum, superfluid, helium dynamics
- Electron and X-Ray Spectroscopy Techniques
- Asthma and respiratory diseases
- X-ray Spectroscopy and Fluorescence Analysis
- Atomic and Molecular Physics
Meiji Pharmaceutical University
2024-2025
Niigata University
2024-2025
Tohoku University
2015-2024
Nanjing University of Aeronautics and Astronautics
2023
Osaka University
2007-2020
Japan Atomic Energy Agency
2003-2020
Advanced Science Research Center
2002-2020
The University of Tokyo
2017-2020
High Energy Accelerator Research Organization
1997-2020
Yamagata University
2020
The gamman-->K(+)K(-)n reaction on 12C has been studied by measuring both K+ and K- at forward angles. A sharp baryon resonance peak was observed 1.54+/-0.01 GeV/c(2) with a width smaller than 25 MeV/c(2) Gaussian significance of 4.6sigma. strangeness quantum number (S) the is +1. It can be interpreted as molecular meson-baryon or alternatively an exotic five-quark state (uuddsmacr;) that decays into neutron. consistent lowest member antidecuplet baryons predicted chiral soliton model.
We report the observation of two narrow structures in mass spectra pi+-Y(nS) (n=1,2,3) and pi+-hb(mP)(m$ (m=1,2) pairs that are produced association with a single charged pion Y(5S) decays. The measured masses widths averaged over five final states M_1=(10607.2+-2.0) MeV/c2, Gamma_1=(18.4+-2.4) MeV M_2=(10652.2+-1.5) Gamma_2=(11.5+-2.2) MeV. results obtained 121.4 1/fb data sample collected Belle detector vicinity resonance at KEKB asymmetric-energy e+e- collider.
Experiment E949 at Brookhaven National Laboratory has observed three new events consistent with the decay K+→π+ν¯ν in pion momentum region 140<Pπ<199 MeV/c an exposure of 1.71×1012 stopped kaons estimated total background 0.93±0.17(stat)+0.32−0.24(syst) events. This brings number to seven. Combining this observation previous results, assuming spectrum predicted by standard model, results a branching ratio B(K+→π+ν¯ν)=(1.73+1.15−1.05)×10−10. An interpretation for alternative models...
Three events for the decay K+→π+ν¯ν have been observed in pion momentum region below K+→π+π0 peak, 140<Pπ<199 MeV/c, with an estimated background of 0.93±0.17(stat.)+0.32−0.24(syst.) events. Combining this observation previously reported results yields a branching ratio B(K+→π+ν¯ν)=(1.73+1.15−1.05)×10−10 consistent standard model prediction.Received 18 August 2008DOI:https://doi.org/10.1103/PhysRevLett.101.191802©2008 American Physical Society
We report a measurement of the process $\ensuremath{\gamma}{\ensuremath{\gamma}}^{*}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{0}$ with $759\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample recorded Belle detector at KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. The pion transition form factor, $F({Q}^{2})$, is measured for kinematical region $4\text{ }{\mathrm{GeV}}^{2}\ensuremath{\lesssim}{Q}^{2}\ensuremath{\lesssim}40\text{ }{\mathrm{GeV}}^{2}$, where...
We perform a full amplitude analysis of B0→ψ′K+π− decays, with ψ′→μ+μ− or e+e−, to constrain the spin and parity Z(4430)−. The JP=1+ hypothesis is favored over 0−, 1−, 2− 2+ hypotheses at levels 3.4σ, 3.7σ, 4.7σ 5.1σ, respectively. based on 711 fb−1 data sample that contains 772×106 BB¯ pairs collected Υ(4S) resonance by Belle detector asymmetric-energy e+e− collider KEKB.7 MoreReceived 20 June 2013DOI:https://doi.org/10.1103/PhysRevD.88.074026© 2013 American Physical Society
We measure the branching fraction of B−→τ−¯ντ using full Υ(4S) data sample containing 772×106 B¯¯¯B pairs collected with Belle detector at KEKB asymmetric-energy e+e− collider. Events are tagged by reconstructing one B mesons decaying into hadronic final states, and candidates detected in recoil. find evidence for a significance 3.0 standard deviations including systematic errors B(B−→τ−¯ντ)=[0.72+0.27−0.25(stat)±0.11(syst)]×10−4.Received 16 November...
Differential cross sections and photon beam asymmetries for the gamma p rightarrow K+ Lambda Sigma0 reactions have been measured in energy range from 1.5 GeV to 2.4 angular Theta_{cm} = 0 60 of scattering angle center mass system at SPring-8/LEPS facility. The both found be positive increase with energy. differential agree data by CLAS collaboration cosTheta_{cm}<0.9 within experimental uncertainties, but discrepancy SAPHIR K+Lambda reaction is large cosTheta_{cm}>0.9. In reaction,...
We report on a search for heavy neutrinos in B-meson decays. The results are obtained using data sample that contains 772x10^6 BB-bar pairs collected at the Upsilon(4S) resonance with Belle detector KEKB asymmetric-energy e+e- collider. No signal is observed and upper limits set mixing of left-handed Standard Model mass range 0.5 - 5.0 GeV/c^2.
We report a search for the rare decays $B\ensuremath{\rightarrow}{h}^{(*)}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, where ${h}^{(*)}$ stands ${K}^{+}$, ${K}_{S}^{0}$, ${K}^{*+}$, ${K}^{*0}$, ${\ensuremath{\pi}}^{+}$, ${\ensuremath{\pi}}^{0}$, ${\ensuremath{\rho}}^{+}$, ${\ensuremath{\rho}}^{0}$ and $\ensuremath{\phi}$. The results are obtained from $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample that contains $772\ifmmode\times\else\texttimes\fi{}{10}^{6}B\overline{B}$...
We present a precise measurement of the CP violation parameter sin2phi_1 and direct A_f using final data sample 772x10^6 B\bar B pairs collected at Upsilon(4S) resonance with Belle detector KEKB asymmetric-energy e+e- collider. One neutral meson is reconstructed in J/psi K0S, psi(2S) chi_c1 K0S or K0L CP-eigenstate its flavor identified from decay products accompanying meson. From distribution proper time intervals between two decays, we obtain following parameters:...
Evidence of a heavy neutrino, $\nu_H$, in the $K^+\to\mu^+\nu_H$ decays was sought using E949 experimental data with an exposure $1.70\times 10^{12}$ stopped kaons. With major background from radiative $K^+\to\mu^+\nu_\mu\gamma$ decay understood and suppressed, upper limits (90% C.L.) on neutrino mixing matrix element between muon $|U_{\mu H}|^2$, were set at level $10^{-7}$ to $10^{-9}$ for mass region 175 300 MeV/$c^2$.
The photo-production of ϕ mesons from Li, C, Al, and Cu at forward angles has been measured Eγ=1.5–2.4GeV. number events for incoherent is found to have a target mass dependence A0.72±0.07 in the kinematical region |t|⩽0.6GeV2/c2. total cross section ϕ–nucleon interaction, σϕN, estimated as 35−11+17mb using A-dependence yield Glauber-type multiple scattering theory. This value much larger than σϕN free space, suggesting that properties might change nuclear medium.
An additional event near the upper kinematic limit for K+-->pi(+)nunu; has been observed by experiment E949 at Brookhaven National Laboratory. Combining previously reported and new data, branching ratio is B(K+-->pi(+)nunu;)=(1.47(+1.30)(-0.89))x10(-10) based on three events in pion momentum region 211<P<229 MeV/c. At measured central value of ratio, had a signal-to-background 0.9.
Additional evidence for the rare kaon decay K+-->pi+nu(nu) has been found in a new data set with comparable sensitivity to previously reported result. One event was observed pion momentum region examined, 211<P<229 MeV/c, bringing total combined two. Including all taken, backgrounds were estimated contribute 0.15+/-0.05 events. The branching ratio is B(K+-->pi+nu(nu)) = 1.57(+1.75)(-0.82)x10(-10).
The γd→K+K−pn reaction has been studied to search for the evidence of Θ+ by detecting K+K− pairs at forward angles. Fermi-motion-corrected nK+ invariant mass distribution shows a narrow peak 1.524±0.002+0.003 GeV/c2. statistical significance calculated from shape analysis is 5.1 σ, and differential cross section γn→K−Θ+ estimated be 12±2 nb/sr in photon energy range 2.0 2.4 GeV LEPS angular assuming isotropic production γn center-of-mass system. obtained results support existence Θ+.9...
Differential cross sections for γp→K+Λ(1405) and γp→K+Σ0(1385) reactions have been measured in the photon energy range from 1.5 to 2.4 GeV angular of 0.8<cos(Θ)<1.0 K+ scattering angle center-of-mass system. This data is first measurement Λ(1405) photoproduction section. The line shapes Σ+π− Σ−π+ decay modes were different with each other, indicating a strong interference isospin 0 1 terms Σπ amplitudes. ratios production Σ0(1385) two ranges: near threshold (1.5<Eγ<2.0 GeV) far it...
We report results of a study doubly charmed baryons and strange baryons. The analysis is performed using $980\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ data sample collected with the Belle detector at KEKB asymmetric-energy ${e}^{+}{e}^{\ensuremath{-}}$ collider. search for ${\mathrm{\ensuremath{\Xi}}}_{cc}^{+(+)}$ ${\mathrm{\ensuremath{\Lambda}}}_{c}^{+}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}({\ensuremath{\pi}}^{+})$...
We report the first evidence for ${\ensuremath{\eta}}_{b}(2S)$ using ${h}_{b}(2P)\ensuremath{\rightarrow}{\ensuremath{\eta}}_{b}(2S)\ensuremath{\gamma}$ transition and observation of ${h}_{b}(1P)\ensuremath{\rightarrow}{\ensuremath{\eta}}_{b}(1S)\ensuremath{\gamma}$ ${h}_{b}(2P)\ensuremath{\rightarrow}{\ensuremath{\eta}}_{b}(1S)\ensuremath{\gamma}$ transitions. The mass width ${\ensuremath{\eta}}_{b}(1S)$ are measured to be...
A search for $K^-pp$ bound state (the lightest kaonic nucleus) has been performed using the $\gamma d \rightarrow K^+ \pi^- \rm{X}$ reaction at E$_\gamma$=1.5-2.4 GeV LEPS/SPring-8. The differential cross section of $K^+ \pi^-$ photo-production off deuterium measured first time in this energy region, and a bump structure was searched inclusive missing mass spectrum. statistically significant not observed region from 2.22 to 2.36 GeV/$c^2$, upper limits production were determined be 0.1$-$0.7...
An event consistent with the signature expected for rare kaon decay ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$ has been observed. In pion momentum region examined, $211<P<230\mathrm{MeV}/c$, backgrounds are estimated to contribute $0.08\ifmmode\pm\else\textpm\fi{}0.03$ events. If is due ${K}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}\ensuremath{\nu}\overline{\ensuremath{\nu}}$, branching ratio...
Beam polarization asymmetries for the p(gamma-->,K+)Lambda and p(gamma-->,K+)Sigma(0) reactions are measured first time E(gamma)=1.5-2.4 GeV 0.6<cos((theta(c.m.)(K+))<1.0 by using linearly polarized photons at Laser-Electron-Photon facility SPring-8 (LEPS). The observed positive gradually increase with rising photon energy. data not consistent theoretical predictions based on tree-level effective-Lagrangian approaches. Including new results in development of models is, therefore, crucial...
Photoproduction of a phi meson on protons was studied by means linearly polarized photons at forward angles in the low-energy region from threshold to Egamma = 2.37 GeV. The differential cross sections t -|t|min do not increase smoothly as increases but show local maximum around 2.0 angular distributions demonstrate that mesons are photoproduced predominantly helicity-conserving processes, and is likely due unnatural-parity processes.
Experiment E949 at Brookhaven National Laboratory studied the rare decay \$K^+\to\pi^+\nu\bar{\nu}$ and other processes with an exposure of $1.77\times 10^{12}$ $K^+$'s. The data were analyzed using a blind analysis technique yielding one candidate event estimated background $0.30\pm0.03$ events. Combining this result observation two events by predecessor experiment E787 gave branching ratio ${\calB}(K^+\to\pi^+\nu\bar{\nu})=(1.47^{+1.30}_{-0.89})\times 10^{-10}$, consistent Standard Model...