Y. Hasegawa
A5011782519- Particle physics theoretical and experimental studies
- High-Energy Particle Collisions Research
- Particle Detector Development and Performance
- Quantum Chromodynamics and Particle Interactions
- X-ray Diffraction in Crystallography
- Crystallization and Solubility Studies
- Dark Matter and Cosmic Phenomena
- Computational Physics and Python Applications
- Neutrino Physics Research
- Astrophysics and Cosmic Phenomena
- Medical Imaging Techniques and Applications
- Cosmology and Gravitation Theories
- Radiation Detection and Scintillator Technologies
- Atomic and Subatomic Physics Research
- Particle Accelerators and Free-Electron Lasers
- Distributed and Parallel Computing Systems
- Nuclear physics research studies
- Superconducting Materials and Applications
- Gamma-ray bursts and supernovae
- Black Holes and Theoretical Physics
- Muon and positron interactions and applications
- advanced mathematical theories
- Particle accelerators and beam dynamics
- Radio Astronomy Observations and Technology
- Advanced Data Storage Technologies
Shinshu University
2016-2025
Ōtani University
2007-2025
Fermi National Accelerator Laboratory
2024
University of Chicago
2024
European Organization for Nuclear Research
2023-2024
AGH University of Krakow
2019-2024
Rutherford Appleton Laboratory
2023-2024
A. Alikhanyan National Laboratory
2024
Jagiellonian University
2024
Atlas Scientific (United States)
2024
We report the first observation of a charmoniumlike state recoiling from J/psi in inclusive process e+e- -->J/psi+anything at mass (3.943+/-0.006+/-0.006) GeV/c{2}. also observe decay this into D*D[over ] and determine its intrinsic width to be less than 52 MeV/c{2} 90% C.L. These results are obtained 357 fb{-1} data sample collected with Belle detector near Upsilon(4S) resonance, KEKB asymmetric-energy collider.
We report a high-statistics measurement of the branching fraction for tau^- --> pi^- pi^0 nu_tau and invariant mass spectrum produced system using 72.2 fb^-1 data recorded with Belle detector at KEKB asymmetric-energy e^+ e^- collider. The obtained is (25.24 +/- 0.01 0.39)%, where first error statistical second systematic. unfolded used to determine resonance parameters rho(770), rho'(1450), rho"(1700) mesons. also use this estimate hadronic (2pi) contribution anomalous magnetic moment muon...
A search for muon neutrinos from neutralino annihilations in the Sun has been performed with IceCube 22-string neutrino detector using data collected 104.3 days of live time 2007. No excess over expected atmospheric background observed. Upper limits have obtained on annihilation rate captured neutralinos and converted to weakly interacting massive particle (WIMP) proton cross sections WIMP masses range 250-5000 GeV. These results are most stringent date Sun.
From a Dalitz plot analysis of $B\ensuremath{\rightarrow}K{\ensuremath{\pi}}^{+}{\ensuremath{\psi}}^{\ensuremath{'}}$ decays, we find signal for $Z(4430{)}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\psi}}^{\ensuremath{'}}$ with mass $M=({4443}_{\ensuremath{-}12\ensuremath{-}13}^{+15+19})\text{ }\text{ }\mathrm{MeV}/{c}^{2}$, width $\ensuremath{\Gamma}=({107}_{\ensuremath{-}43\ensuremath{-}56}^{+86+74})\text{ }\mathrm{MeV}$, product branching fraction...
A search for TeV-PeV muon neutrinos from unresolved sources was performed on AMANDA-II data collected between 2000 and 2003 with an equivalent live time of 807 days. This diffuse analysis sought to find extraterrestrial neutrino flux nonthermal components. The signal is expected have a harder spectrum than the atmospheric backgrounds. Since no excess events seen in over background, upper limit...
We present the results of searches for high-energy muon neutrinos from 41 gamma-ray bursts (GRBs) in northern sky with IceCube detector its 22-string configuration active 2007/2008. The cover both prompt and a possible precursor emission as well model-independent, wide time window -1 h to +3 around each GRB. In contrast previous large GRB population, we do not utilize standard Waxman-Bahcall flux but calculate individual neutrino spectra all GRBs burst parameters measured by satellites. none...
We present a precise measurement of the left-right cross section asymmetry (${A}_{\mathrm{LR}}$) for $Z$ boson production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions. The was performed at center-of-mass energy 91.26 GeV with SLD detector SLAC Linear Collider (SLC). luminosity-weighted average polarization SLC electron beam (63.0 \ifmmode\pm\else\textpm\fi{} 1.1)%. Using sample 49 392 decays, we measure ${A}_{\mathrm{LR}}$ to be 0.1628 0.0071 (stat) 0.0028 (syst) which determines effective...
A search for diffuse neutrinos with energies in excess of 105 GeV is conducted AMANDA-II data recorded between 2000 and 2002. Above 107 GeV, the Earth essentially opaque to neutrinos. This fact, combined limited overburden detector (roughly 1.5 km), concentrates these ultra-high-energy at horizon. The primary background this analysis bundles downgoing, high-energy muons from interaction cosmic rays atmosphere. No statistically significant above expected seen data, an upper limit set on...
The AMANDA-II detector, operating since 2000 in the deep ice at geographic South Pole, has accumulated a large sample of atmospheric muon neutrinos 100 GeV to 10 TeV energy range. zenith angle and distribution these events can be used search for various phenomenological signatures quantum gravity neutrino sector, such as violation Lorentz invariance (VLI) or decoherence (QD). Analyzing set 5511 candidate collected during 1387 days livetime from 2006, we find no evidence effects upper limits...
We present a measurement of the decay B−→τ−ν¯τ using data sample containing 657×106 BB¯ pairs collected at Υ(4S) resonance with Belle detector KEKB asymmetric-energy e+e− collider. A B+B− are tagged by reconstructing one B+ meson decaying semileptonically. detect candidate in recoil. obtain signal significance 3.6 standard deviations including systematic uncertainties, and measure branching fraction to be B(B−→τ−ν¯τ)=[1.54−0.37+0.38(stat)−0.31+0.29(syst)]×10−4. This result confirms evidence...
We report measurements of the exclusive cross section for e+e−→D0D*−π+ as a function center-of-mass energy from D0D*−π+ threshold to 5.2 GeV with initial-state radiation. No evidence is found Y(4260)→D0D*−π+ decays. The analysis based on data sample collected Belle detector at or near 10.58 an integrated luminosity 695 fb−1 KEKB asymmetric-energy e+e− collider.Received 4 August 2009DOI:https://doi.org/10.1103/PhysRevD.80.091101©2009 American Physical Society
The strong coupling αs(M2Z) has been measured using hadronic decays of Z0 bosons collected by the SLD experiment at SLAC. data were compared with QCD predictions both fixed order O(α2s) and including resummed analytic formulas based on next-to-leading logarithm approximation. In this comprehensive analysis we studied event shapes, jet rates, particle correlations, angular energy flow, checked consistency between values extracted from these different measures. Combining all results obtain...
We present a search for point sources of high energy neutrinos using 3.8 yr data recorded by AMANDA-II during 2000–2006. After reconstructing muon tracks and applying selection criteria designed to optimally retain neutrino-induced events originating in the northern sky, we arrive at sample 6595 candidate events, predominantly from atmospheric with primary 100 GeV 8 TeV. Our this reveals no indications neutrino source. place most stringent limits date on E−2 fluxes points an average upper...
We present measurements of ${\mathit{R}}_{\mathit{b}}$ using the SLD at SLC. The analyses use 2D and 3D impact parameter tags a displaced vertex tag which all exploit small size stability ${\mathit{e}}^{+}$${\mathit{e}}^{\mathrm{\ensuremath{-}}}$ interaction point precision CCD pixel detector to achieve high bb\ifmmode\bar\else\textasciimacron\fi{}-tagging efficiencies purities. combined measurement yields ${\mathit{R}}_{\mathit{b}}$=0.229\ifmmode\pm\else\textpm\fi{}0.011 is consistent with...
On 13 December 2006 the IceTop air shower array at South Pole detected a major solar particle event. By numerically simulating response of tanks, which are thick Cherenkov detectors with multiple thresholds deployed high altitude no geomagnetic cut-off, we determined energy spectrum in range 0.6 to 7.6 GeV. This is first such spectral measurement using single instrument well defined viewing direction. We compare and its time evolution previously published results outline plans for improved...
We present new results of searches for neutrino point sources in the northern sky, using data recorded 2007–2008 with 22 strings IceCube detector (approximately one-fourth planned total) and 275.7 days live time. The final sample 5114 candidate events agrees well expected background atmospheric muon neutrinos a small component muons. No evidence source is found, most significant excess sky at 2.2σ after accounting all trials. average upper limit over muon–neutrinos E−2 spectrum , energy...
We present the results of analysis neutrino observations by Antarctic Muon and Neutrino Detector Array (AMANDA) correlated with photon more than 400 gamma-ray bursts (GRBs) in Northern Hemisphere from 1997 to 2003. During this time period, AMANDA's effective collection area for muon neutrinos was larger that any other existing detector. Based on our zero during immediately prior GRBs dataset, we set most stringent upper limit emission bursts. Assuming a Waxman-Bahcall spectrum incorporating...
Point source searches with the IceCube neutrino telescope have been restricted to one hemisphere, due exclusive selection of upward going events as a way rejecting atmospheric muon background. We show that region above horizon can be included by suppressing background through energy-sensitive cuts. This improves sensitivity PeV energies, previously not accessible for declinations more than few degrees below absorption neutrinos in Earth. present results based on data collected 22 strings...
We present a study of ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$, ${\ensuremath{\tau}}^{\ensuremath{-}}\ensuremath{\rightarrow}{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\nu}}_{\ensuremath{\tau}}$,...
We present a new measurement of the left-right cross section asymmetry $({A}_{\mathrm{LR}})$ for $Z$ boson production by ${e}^{+}{e}^{\ensuremath{-}}$ collisions. The was performed at center-of-mass energy 91.28 GeV with SLD detector SLAC Linear Collider (SLC). luminosity-weighted average polarization SLC electron beam $(77.23\ifmmode\pm\else\textpm\fi{}0.52)%$. Using sample 93 644 decays, we measure pole value asymmetry, ${A}_{\mathrm{LR}}^{0}$, to be...