T. Kawasaki
A5082113220- Particle physics theoretical and experimental studies
- Quantum Chromodynamics and Particle Interactions
- High-Energy Particle Collisions Research
- Particle Detector Development and Performance
- Neutrino Physics Research
- Dark Matter and Cosmic Phenomena
- Particle Accelerators and Free-Electron Lasers
- Radiation Detection and Scintillator Technologies
- Black Holes and Theoretical Physics
- Atomic and Subatomic Physics Research
- Computational Physics and Python Applications
- Medical Imaging Techniques and Applications
- Superconducting Materials and Applications
- Astrophysics and Cosmic Phenomena
- Nuclear physics research studies
- Radiation Therapy and Dosimetry
- Cosmology and Gravitation Theories
- Advanced NMR Techniques and Applications
- Radio Astronomy Observations and Technology
- CCD and CMOS Imaging Sensors
- Electron and X-Ray Spectroscopy Techniques
- Particle accelerators and beam dynamics
- Advanced Electron Microscopy Techniques and Applications
- Nuclear Physics and Applications
- Gamma-ray bursts and supernovae
Kitasato University
2016-2025
Korea Institute of Science & Technology Information
2020-2022
Korea University
2020
Niigata University
2010-2019
Kitasato University Hospital
2019
Beihang University
2016-2019
University of the Basque Country
2013-2019
University of Cincinnati
2013-2019
Chonnam National University
2018-2019
Duke University
2019
The cross section for ee+ e- → π+ π- J/ψ between 3.8 and 5.5 GeV is measured with a 967 fb(-1) data sample collected by the Belle detector at or near Υ(nS) (n = 1,2,…,5) resonances. Y(4260) state observed, its resonance parameters are determined. In addition, an excess of production around 4 observed. This feature can be described Breit-Wigner parametrization properties that consistent Y(4008) was previously reported Belle. study decays, structure observed in M(π(±)J/ψ) mass spectrum 5.2σ...
We report a measurement of the branching fraction ratios R(D(*)) Bbar -> D(*) tau- nubar_tau relative to D()* l- nubar_l (where l = e or mu) using full Belle data sample 772 x 10^6 BBbar pairs collected at Y(4S) resonance with detector KEKB asymmetric-energy e+e- collider. The measured values are R(D)= 0.375 +- 0.064(stat.) 0.026(syst.) and R(D*) 0.293 0.038(stat.) 0.015(syst.). analysis uses hadronic reconstruction tag-side B meson purely leptonic tau decays. results consistent earlier...
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.
We report the first measurement of $\ensuremath{\tau}$ lepton polarization ${P}_{\ensuremath{\tau}}({D}^{*})$ in decay $\overline{B}\ensuremath{\rightarrow}{D}^{*}{\ensuremath{\tau}}^{\ensuremath{-}}{\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ as well a new ratio branching fractions...
The cross section for ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}\ensuremath{\psi}(2S)$ between threshold and $\sqrt{s}=5.5\text{ }\text{ }\mathrm{GeV}$ is measured using $673\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ of data on off the $\ensuremath{\Upsilon}(4S)$ resonance collected with Belle detector at KEKB. Two resonant structures are observed in...
We report a measurement of the ratio ${\cal R}(D^*) = {\cal B}(\bar{B}^0 \rightarrow D^{*+} \tau^- \bar{\nu}_{\tau})/{\cal \ell^- \bar{\nu}_{\ell})$, where $\ell$ denotes an electron or muon. The results are based on data sample containing $772\times10^6$ $B\bar{B}$ pairs recorded at $\Upsilon(4S)$ resonance with Belle detector KEKB $e^+ e^-$ collider. select $B^0 \bar{B}^0$ by reconstructing both $B$ mesons in semileptonic decays to $D^{*\mp} \ell^{\pm}$. measure R}(D^*)= 0.302 \pm...
We present a measurement of angular observables and test lepton flavor universality in the $B\ensuremath{\rightarrow}{K}^{*}{\ensuremath{\ell}}^{+}{\ensuremath{\ell}}^{\ensuremath{-}}$ decay, where $\ensuremath{\ell}$ is either $e$ or $\ensuremath{\mu}$. The analysis performed on data sample corresponding to an integrated luminosity $711\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ containing $772\ifmmode\times\else\texttimes\fi{}1{0}^{6}$ $B\overline{B}$ pairs, collected at...
The experimental results on the ratios of branching fractions R(D)=B(B[over ¯]→Dτ^{-}ν[over ¯]_{τ})/B(B[over ¯]→Dℓ^{-}ν[over ¯]_{ℓ}) and R(D^{*})=B(B[over ¯]→D^{*}τ^{-}ν[over ¯]→D^{*}ℓ^{-}ν[over ¯]_{ℓ}), where ℓ denotes an electron or a muon, show long-standing discrepancy with standard model predictions, might hint at violation lepton flavor universality. We report new simultaneous measurement R(D) R(D^{*}), based data sample containing 772×10^{6} BB[over ¯] events recorded ϒ(4S) resonance...
With the full data sample of $772 \times 10^6$ $B{\bar B}$ pairs recorded by Belle detector at KEKB electron-positron collider, decay $\bar{B} \rightarrow D^* \tau^- \bar{\nu}_\tau$ is studied with hadronic $\tau$ decays $\tau^- \pi^- \nu_\tau$ and \rho^- \nu_\tau$. The polarization $P_\tau(D^*)$ in two-body measured, as well ratio branching fractions $R(D^{*}) = \mathcal{B}(\bar {B} \bar{\nu}_\tau) / \mathcal{B}(\bar{B} \ell^- \bar{\nu}_\ell)$, where $\ell^-$ denotes an electron or a muon....
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 present results from a study of $X(3872)\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}J/\ensuremath{\psi}$ decays produced via exclusive $B\ensuremath{\rightarrow}KX(3872)$ decays. determine the mass to be ${M}_{X(3872)}=(3871.85\ifmmode\pm\else\textpm\fi{}0.27(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.19(\mathrm{syst}))\text{ }\text{ }\mathrm{MeV}$, 90% confidence level upper limit on natural width ${\ensuremath{\Gamma}}_{X(3872)}<1.2\text{ product branching fraction...
We present the results of an amplitude analysis anti-B0 -> J/psi K- pi+ decays. A new charged charmoniumlike state Zc(4200)+ decaying to is observed with a significance 6.2 sigma. The mass and width are 4196 +31-29 +17-13 MeV/c^2 370 +70-70 +70-132 MeV, respectively; preferred assignment quantum numbers J^P = 1^+. In addition, we find evidence for Zc(4430)+ pi+. based on 711 fb^-1 data sample collected by Belle detector at asymmetric-energy e+ e- collider KEKB.
We report a study of the processes ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}J/\ensuremath{\psi}{D}^{(*)}{\overline{D}}^{(*)}$. In $J/\ensuremath{\psi}{D}^{*}{\overline{D}}^{*}$ we observe significant enhancement in ${D}^{*}{\overline{D}}^{*}$ invariant mass spectrum, which interpret as new charmoniumlike state and denote $X(4160)$. The $X(4160)$ parameters are $M=({4156}_{\ensuremath{-}20}^{+25}\ifmmode\pm\else\textpm\fi{}15)\text{ }\text{ }\mathrm{MeV}/{c}^{2}$...
We present the results of a search for rare decays $B\to h\nu\overline{\nu}$, where $h$ stands $K^+,\:K^0_{\mathrm{S}},\:K^{\ast +},\:K^{\ast 0},\:\pi^+,\:\pi^0,\:\rho^+$ and $\rho^{0}$. The are obtained with $772\times10^{6}$ $B\overline{B}$ pairs collected Belle detector at KEKB $e^+ e^-$ collider. reconstruct one $B$ meson in semileptonic decay require single but nothing else on signal side. observe no significant set upper limits branching fractions. K^0_{\mathrm{S}}\nu\overline{\nu}$,...
We report the first observations of spin-singlet bottomonium states hb(1P) and hb(2P). The are produced in reaction e+e−→hb(nP)π+π− using a 121.4 fb−1 data sample collected at energies near Υ(5S) resonance with Belle detector KEKB asymmetric-energy e+e− collider. determine M[hb(1P)]=(9898.2+1.1+1.0−1.0−1.1) MeV/c2 M[hb(2P)]=(10 259.8±0.6+1.4−1.0) MeV/c2, which correspond to P-wave hyperfine splittings ΔMHF=(+1.7±1.5) (+0.5+1.6−1.2) respectively. significances hb(2P) 5.5σ 11.2σ, find that...
We present a determination of the magnitude Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$ using decay $B\to D\ell\nu_\ell$ ($\ell=e,\mu$) based on 711 fb$^{-1}$ $e^+e^-\to \Upsilon(4S)$ data recorded by Belle detector and containing $772 \times 10^6$ $B\bar{B}$ pairs. One $B$ meson in event is fully reconstructed hadronic mode while other, signal side, partially from charged lepton either $D^+$ or $D^0$ total 23 modes. The isospin-averaged branching fraction found to be...
We report measurement of the cross section $e^+e^-\to \pi^+\pi^-\psi(2S)$ between 4.0 and $5.5 {\rm GeV}$, based on an analysis initial state radiation events in a $980 \rm fb^{-1}$ data sample recorded with Belle detector. The properties $Y(4360)$ $Y(4660)$ states are determined. Fitting mass spectrum $\pi^+\pi^-\psi(2S)$ two coherent Breit-Wigner functions, we find solutions identical width but different couplings to electron-positron pairs: $M_{Y(4360)} = (4347\pm 6\pm 3) MeV}/c^2$,...
We report the results of a search for charmonium-like state produced in process gamma --> omega J/psi 3.9-4.2 GeV/c^2 mass region. observe significant enhancement, which is well-described by resonant shape with M = (3915 +/- 3 2) MeV/c^2 and total width Gamma (17 10 3) MeV. This enhancement may be related to one or more three states so far reported 3.90-3.95
We report a study of $B\to (J/\psi \gamma) K$ and (\psi' \gamma)K$ decay modes using $772\times 10^{6}$ $B\bar{B}$ events collected at the \Upsilon(4S)$ resonance with Belle detector KEKB energy-asymmetric $e^+ e^-$ collider. observe $X(3872) \to J/\psi \gamma$ first evidence for $\chi_{c2} in (X_{c\bar{c}}\gamma) decays, while search \psi' no significant signal is found. measure branching fractions, $\mathcal{B}(B^{\pm} X(3872) K^{\pm}) \mathcal{B}(X(3872) J/\psi\gamma)$ $=$...
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.
The process $\gamma \gamma \to \phi \jpsi$ is measured for $\phi masses between threshold and 5 GeV/${\it c}^2$, using a data sample of 825 fb$^{-1}$ collected with the Belle detector. A narrow peak $8.8^{+4.2}_{-3.2}$ events, significance 3.2 standard deviations including systematic uncertainty, observed. mass natural width structure (named X(4350)) are to be $(4350.6^{+4.6}_{-5.1}(\rm{stat})\pm 0.7(\rm{syst})) \hbox{MeV}/{\it c}^2$ $(13^{+18}_{-9}(\rm{stat})\pm 4(\rm{syst})) \hbox{MeV}$,...
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 $772\ifmmode\times\else\texttimes\fi{}{10}^{6}B\overline{B}$...