Author
M. Kohama
Bio: M. Kohama is an academic researcher from Kobe University. The author has contributed to research in topics: Neutrino & Solar neutrino. The author has an hindex of 28, co-authored 29 publications receiving 11833 citations.
Papers
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University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University5, George Mason University6, Gifu University7, University of Hawaii at Manoa8, Kobe University9, Los Alamos National Laboratory10, Louisiana State University11, University of Maryland, College Park12, University of Chicago13, Stony Brook University14, Niigata University15, Osaka University16, Seoul National University17, Tohoku University18, Tokai University19, Tokyo Institute of Technology20, University of Warsaw21, University of Washington22, Stanford University23
Abstract: We present an analysis of atmospheric neutrino data from a 33.0 kton yr (535-day) exposure of the Super-Kamiokande detector. The data exhibit a zenith angle dependent deficit of muon neutrinos which is inconsistent with expectations based on calculations of the atmospheric neutrino flux. Experimental biases and uncertainties in the prediction of neutrino fluxes and cross sections are unable to explain our observation. The data are consistent, however, with two-flavor ${\ensuremath{
u}}_{\ensuremath{\mu}}\ensuremath{\leftrightarrow}{\ensuremath{
u}}_{\ensuremath{\tau}}$ oscillations with ${sin}^{2}2\ensuremath{\theta}g0.82$ and $5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}l\ensuremath{\Delta}{m}^{2}l6\ifmmode\times\else\texttimes\fi{}1{0}^{\ensuremath{-}3}\mathrm{eV}{}^{2}$ at 90% confidence level.
3,784 citations
University of Tokyo1, Boston University2, Massachusetts Institute of Technology3, Brookhaven National Laboratory4, University of California, Irvine5, California State University, Dominguez Hills6, George Mason University7, Gifu University8, Kobe University9, Kyoto University10, Louisiana State University11, University of Maryland, College Park12, University of Minnesota13, Stony Brook University14, University of Utah15, Niigata University16, Osaka University17, Seoul National University18, Shizuoka University19, Tohoku University20, Tokai University21, Tokyo Institute of Technology22, University of Warsaw23, University of Washington24
TL;DR: Solar neutrino measurements from 1258 days of data from the Super-Kamiokande detector are presented and the recoil electron energy spectrum is consistent with no spectral distortion.
Abstract: Solar neutrino measurements from 1258days of data from the Super-Kamiokande detector are presented. The measurements are based on recoil electrons in the energy range 5.0{endash}20.0MeV. The measured solar neutrino flux is 2.32{+-}0.03(stat){sup +0.08}{sub {minus}0.07}(syst){times}10{sup 6} cm{sup {minus}2}s{sup {minus}1} , which is 45.1{+-}0.5(stat ){sup +1.6}{sub {minus}1.4}(syst) % of that predicted by the BP2000 SSM. The day vs night flux asymmetry ({Phi}{sub n}{minus}{Phi}{sub d})/ {Phi}{sub average} is 0.033{+-}0.022(stat){sup +0.013}{sub {minus}0.012}(syst) . The recoil electron energy spectrum is consistent with no spectral distortion. For the hep neutrino flux, we set a 90% C.L.upper limit of 40{times}10{sup 3} cm{sup {minus}2}s{sup {minus}1} , which is 4.3times the BP2000 SSM prediction.
878 citations
01 Apr 2003-Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment
TL;DR: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons as discussed by the authors, which collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency.
Abstract: Super-Kamiokande is the world's largest water Cherenkov detector, with net mass 50,000 tons. During the period April, 1996 to July, 2001, Super-Kamiokande I collected 1678 live-days of data, observing neutrinos from the Sun, Earth's atmosphere, and the K2K long-baseline neutrino beam with high efficiency. These data provided crucial information for our current understanding of neutrino oscillations, as well as setting stringent limits on nucleon decay. In this paper, we describe the detector in detail, including its site, configuration, data acquisition equipment, online and offline software, and calibration systems which were used during Super-Kamiokande I.
708 citations
Seoul National University1, Kobe University2, University of Washington3, University of California, Irvine4, Chonnam National University5, University of Tokyo6, Kyoto University7, Tohoku University8, Stony Brook University9, Okayama University10, Boston University11, University of Warsaw12, Korea University13, Niigata University14, Dongshin University15, Massachusetts Institute of Technology16, Tokyo University of Science17
TL;DR: The K2K experiment observed indications of neutrino oscillation after 250 km flight of υμ. as mentioned in this paper The observed number of events in the data corresponding to 4.8 x 1019 protons on target is 56, while 80.1 5.4 + 6.2 is expected.
Abstract: The K2K experiment observed indications of neutrino oscillation after 250 km flight of υμ. The observed number of events in the data corresponding to 4.8 x 1019 protons on target is 56, while 80.1 5.4 +6.2 is expected. Both the decrease of the events and observed spectrum shape distortion are consistent with neutrino oscillation. The probability that the observations are statistical fluctuation of non oscillation is less than 1%. The allowed region of oscillation parameters is consistent with the one obtained from the atmospheric neutrino observation. After the accident of Super-Kamiokande (SK) detector, the reconstruction of SK has finished in 2002 and the K2K experiment resumed in December 2002.
702 citations
University of Tokyo1, Boston University2, Brookhaven National Laboratory3, University of California, Irvine4, California State University, Dominguez Hills5, George Mason University6, Gifu University7, University of Hawaii8, KEK9, Kobe University10, Kyoto University11, Los Alamos National Laboratory12, Louisiana State University13, University of Maryland, College Park14, Massachusetts Institute of Technology15, University of Minnesota16, State University of New York System17, Nagoya University18, Niigata University19, Osaka University20, Seoul National University21, Shizuoka University22, Tohoku University23, Tokai University24, Tokyo Institute of Technology25, University of Warsaw26, University of Washington27
TL;DR: In this paper, a number of different fits to solar neutrino mixing and mass square difference were performed using 1496 days of Super-Kamiokande-I's solar NE data.
680 citations
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TL;DR: In this article, the Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data were used to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature.
Abstract: The Wilkinson Microwave Anisotropy Probe (WMAP) 5-year data provide stringent limits on deviations from the minimal, six-parameter Λ cold dark matter model. We report these limits and use them to constrain the physics of cosmic inflation via Gaussianity, adiabaticity, the power spectrum of primordial fluctuations, gravitational waves, and spatial curvature. We also constrain models of dark energy via its equation of state, parity-violating interaction, and neutrino properties, such as mass and the number of species. We detect no convincing deviations from the minimal model. The six parameters and the corresponding 68% uncertainties, derived from the WMAP data combined with the distance measurements from the Type Ia supernovae (SN) and the Baryon Acoustic Oscillations (BAO) in the distribution of galaxies, are: Ω b h 2 = 0.02267+0.00058 –0.00059, Ω c h 2 = 0.1131 ± 0.0034, ΩΛ = 0.726 ± 0.015, ns = 0.960 ± 0.013, τ = 0.084 ± 0.016, and at k = 0.002 Mpc-1. From these, we derive σ8 = 0.812 ± 0.026, H 0 = 70.5 ± 1.3 km s-1 Mpc–1, Ω b = 0.0456 ± 0.0015, Ω c = 0.228 ± 0.013, Ω m h 2 = 0.1358+0.0037 –0.0036, z reion = 10.9 ± 1.4, and t 0 = 13.72 ± 0.12 Gyr. With the WMAP data combined with BAO and SN, we find the limit on the tensor-to-scalar ratio of r 1 is disfavored even when gravitational waves are included, which constrains the models of inflation that can produce significant gravitational waves, such as chaotic or power-law inflation models, or a blue spectrum, such as hybrid inflation models. We obtain tight, simultaneous limits on the (constant) equation of state of dark energy and the spatial curvature of the universe: –0.14 < 1 + w < 0.12(95%CL) and –0.0179 < Ω k < 0.0081(95%CL). We provide a set of WMAP distance priors, to test a variety of dark energy models with spatial curvature. We test a time-dependent w with a present value constrained as –0.33 < 1 + w 0 < 0.21 (95% CL). Temperature and dark matter fluctuations are found to obey the adiabatic relation to within 8.9% and 2.1% for the axion-type and curvaton-type dark matter, respectively. The power spectra of TB and EB correlations constrain a parity-violating interaction, which rotates the polarization angle and converts E to B. The polarization angle could not be rotated more than –59 < Δα < 24 (95% CL) between the decoupling and the present epoch. We find the limit on the total mass of massive neutrinos of ∑m ν < 0.67 eV(95%CL), which is free from the uncertainty in the normalization of the large-scale structure data. The number of relativistic degrees of freedom (dof), expressed in units of the effective number of neutrino species, is constrained as N eff = 4.4 ± 1.5 (68%), consistent with the standard value of 3.04. Finally, quantitative limits on physically-motivated primordial non-Gaussianity parameters are –9 < f local NL < 111 (95% CL) and –151 < f equil NL < 253 (95% CL) for the local and equilateral models, respectively.
5,904 citations
TL;DR: In this article, the authors investigate the sequence of assumptions and corrections that together affect the cosmic star formation history (SFH) normalization to test their accuracy, both in this redshift range and beyond.
Abstract: Strong constraints on the cosmic star formation history (SFH) have recently been established using ultraviolet and far-infrared measurements, refining the results of numerous measurements over the past decade. The data show a compellingly consistent picture of the SFH out to redshift z ≈ 6, with especially tight constraints for z 1. We fit these data with simple analytical forms and derive conservative uncertainties. Since the z 1 SFH data are quite precise, we investigate the sequence of assumptions and corrections that together affect the SFH normalization to test their accuracy, both in this redshift range and beyond. As lower limits on this normalization, we consider the evolution in stellar and metal mass densities, and supernova rate density, finding it unlikely that the SFH normalization is much lower than indicated by our direct fit. As a corresponding upper limit on the SFH normalization, we consider the Super-Kamiokande limit on the electron antineutrino (e) flux from past core-collapse supernovae, which applies primarily to z 1. We find consistency with the SFH only if the neutrino temperatures from supernova events are relatively modest. Constraints on the assumed initial mass function (IMF) also become apparent. The traditional Salpeter IMF, assumed for convenience by many authors, is known to be a poor representation at low stellar masses (1 M☉), and we show that recently favored IMFs are also constrained. In particular, somewhat shallow, or top-heavy, IMFs may be preferred, although they cannot be too top-heavy. To resolve the outstanding issues, improved data are called for on the supernova rate density evolution, the ranges of stellar masses leading to core-collapse and type Ia supernovae, and the antineutrino and neutrino backgrounds from core-collapse supernovae.
1,901 citations
TL;DR: In this article, the neutralino is proposed as the lightest superpartner in many supersymmetric theories, and it is shown how to calculate the cosmological abundance of neutralino and event rates for both direct and indirect detection schemes.
1,670 citations
TL;DR: In this article, the authors give simple mass-matrices leading to tri-bimaximal mixing, and discuss its relation to the Fritzsch-Xing democratic ansatz.
1,347 citations
Heidelberg University1, Korea Institute for Advanced Study2, University of Nottingham3, Institute of Cosmology and Gravitation, University of Portsmouth4, University of Oxford5, Istituto Nazionale di Fisica Nucleare6, INAF7, University of Bologna8, University of Padua9, University of Toulouse10, University of Geneva11, University of Trieste12, Roma Tre University13, University of Milan14, University of Oslo15, Federal University of Rio Grande do Norte16, University College London17, Imperial College London18, Ludwig Maximilian University of Munich19, Autonomous University of Madrid20, ETH Zurich21, University of Edinburgh22, Leiden University23, Sun Yat-sen University24, Max Planck Society25, Royal Institute of Technology26, University of Milano-Bicocca27, University of California, Berkeley28, University of Pennsylvania29, Universidade Federal do Espírito Santo30, University of Porto31, University of Portsmouth32, King's College London33, Durham University34, Institut d'Astrophysique de Paris35, Helsinki Institute of Physics36, University of Lisbon37, Paris Diderot University38, Université Paris-Saclay39, University of Surrey40, University of Trento41, University of Chile42, Academy of Sciences of the Czech Republic43, University of Cyprus44, University of Barcelona45, California Institute of Technology46, Perimeter Institute for Theoretical Physics47
TL;DR: Euclid is a European Space Agency medium-class mission selected for launch in 2020 within the cosmic vision 2015-2025 program as discussed by the authors, which will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shift of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky.
Abstract: Euclid is a European Space Agency medium-class mission selected for launch in 2020 within the cosmic vision 2015–2025 program. The main goal of Euclid is to understand the origin of the accelerated expansion of the universe. Euclid will explore the expansion history of the universe and the evolution of cosmic structures by measuring shapes and red-shifts of galaxies as well as the distribution of clusters of galaxies over a large fraction of the sky. Although the main driver for Euclid is the nature of dark energy, Euclid science covers a vast range of topics, from cosmology to galaxy evolution to planetary research. In this review we focus on cosmology and fundamental physics, with a strong emphasis on science beyond the current standard models. We discuss five broad topics: dark energy and modified gravity, dark matter, initial conditions, basic assumptions and questions of methodology in the data analysis. This review has been planned and carried out within Euclid’s Theory Working Group and is meant to provide a guide to the scientific themes that will underlie the activity of the group during the preparation of the Euclid mission.
1,211 citations