K. S. Ganezer

Loyola Marymount University, Los Ángeles, California, United States

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Publications (210)

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    [Show abstract] [Hide abstract] ABSTRACT: For 17 days in August and September 2002, the LIGO and GEO interferometer gravitational wave detectors were operated in coincidence to produce their first data for scientific analysis. Although the detectors were still far from their design sensitivity levels, the data can be used to place better upper limits on the flux of gravitational waves incident on the earth than previous direct measurements. This paper describes the instruments and the data in some detail, as a companion to analysis papers based on the first data.
    Full-text Article · May 2016
  • Article · Feb 2016 · Physics Reports
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    K. Abe · Y. Haga · Y. Hayato · [...] · R. J. Wilkes
    [Show abstract] [Hide abstract] ABSTRACT: We present a real-time supernova neutrino burst monitor at Super-Kamiokande (SK). Detecting supernova explosions by neutrinos in real time is crucial for giving a clear picture of the explosion mechanism. Since the neutrinos are expected to come earlier than light, a fast broadcasting of the detection may give astronomers a chance to make electromagnetic radiation observations of the explosions right at the onset. The role of the monitor includes a fast announcement of the neutrino burst detection to the world and a determination of the supernova direction. We present the online neutrino burst detection system and studies of the direction determination accuracy based on simulations at SK.
    Full-text Article · Jan 2016 · Astroparticle Physics
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    [Show abstract] [Hide abstract] ABSTRACT: A comprehensive study on the atmospheric neutrino flux in the energy region from sub-GeV up to several TeV using the Super-Kamiokande water Cherenkov detector is presented in this paper. The energy and azimuthal spectra of the atmospheric ${\nu}_e+{\bar{\nu}}_e$ and ${\nu}_{\mu}+{\bar{\nu}}_{\mu}$ fluxes are measured. The energy spectra are obtained using an iterative unfolding method by combining various event topologies with differing energy responses. The azimuthal spectra depending on energy and zenith angle, and their modulation by geomagnetic effects, are also studied. A predicted east-west asymmetry is observed in both the ${\nu}_e$ and ${\nu}_{\mu}$ samples at 8.0 {\sigma} and 6.0 {\sigma} significance, respectively, and an indication that the asymmetry dipole angle changes depending on the zenith angle was seen at the 2.2 {\sigma} level. The measured energy and azimuthal spectra are consistent with the current flux models within the estimated systematic uncertainties. A study of the long-term correlation between the atmospheric neutrino flux and the solar magnetic activity cycle is also performed, and a weak indication of a correlation was seen at the 1.1 {\sigma} level, using SK I-IV data spanning a 20 year period. For particularly strong solar activity periods known as Forbush decreases, no theoretical prediction is available, but a deviation below the typical neutrino event rate is seen at the 2.4 {\sigma} level.
    Full-text Article · Oct 2015
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    [Show abstract] [Hide abstract] ABSTRACT: Search results for nucleon decays $p \rightarrow e^+X$, $p \rightarrow \mu^+X$, $n \rightarrow \nu\gamma$ (where $X$ is an invisible, massless particle) as well as di-nucleon decays $np \rightarrow e^+\nu$, $np \rightarrow \mu^+\nu$ and $np \rightarrow \tau^+\nu$ in the Super-Kamiokande experiment are presented. Using single-ring data from an exposure of 273.4 kton $\cdot$ years, a search for these decays yields a result consistent with no signal. Accordingly, lower limits on the partial lifetimes of $\tau_{p \rightarrow e^+X} > 7.9 \times 10^{32}$ years, $\tau_{p \rightarrow \mu^+X} > 4.1 \times 10^{32}$ years, $\tau_{n \rightarrow \nu\gamma} > 5.5 \times 10^{32}$ years, $\tau_{np \rightarrow e^+\nu} > 2.6 \times 10^{32}$ years, $\tau_{np \rightarrow \mu^+\nu} > 2.2 \times 10^{32}$ years and $\tau_{np \rightarrow \tau^+\nu} > 2.9 \times 10^{31}$ years at a $90 \% $ confidence level are obtained. Some of these searches are novel.
    Full-text Article · Aug 2015 · Physical Review Letters
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    B Abbott · R Abbott · R. Adhikari · [...] · S. Hild
    Full-text Dataset · Jul 2015
  • K Ganezer · M Krmar · Z Cvejic · [...] · B Pajic
    [Show abstract] [Hide abstract] ABSTRACT: The angular distribution of x-radiation scattered at small angles (up to 16 degrees) from several different animal soft tissue (skin, fat, muscle, retina, etc) were measured using standard equipment devoted to study of crystal structure which provides excellent geometry conditions of measurements. showed measurable differences for different tissues. In the simplest possible case when measured samples do not differ in structure (different concentration solutions) it can be seen that intensity of scattered radiation is decreasing function of the concentration and the peak of the maximum of scattering distribution depends on the concentration as well. An x-ray scattering profile usually consists of sharp diffraction peak; however some properties of the spatial profiles of scattered radiation as intensity, the peak position, height, area, FWHM, the ratio of peak heights, etc. The data contained measurable differences for different tissues. In the simplest possible case when measured samples do not differ in structure (different concentration solutions) it can be seen that intensity of scattered radiation is decreasing function of the concentration and the peak of the maximum of scattering distribution depends on the concentration as well. Measurements of different samples in the very preliminary phase showed that simple biological material used in study showed slightly different scattering pattern, especially at higher angles (around 10degrees). Intensity of radiation scattered from same tissue type is very dependent on water content and several more parameters. This preliminary study using animal soft tissues on the angular distributions of scattered x-rays suggests that angular distributions of X-rays scattered off of soft tissues might be useful in distinguishing healthy tissue from malignant soft tissue.
    Article · Jun 2015 · Medical Physics
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    K Ganezer · M Krmar · I Josipovic
    [Show abstract] [Hide abstract] ABSTRACT: The development in the last few years of photon-counting pixel detectors creates an important and significant opportunity for x-ray spectroscopy to be applied in diagnostics. The energy weighting technique was originally developed to obtain the maximum benefit from the spectroscopic information. In all previous published papers the concept of an energy weighting function was tested on relatively simple test objects having only two materials with different absorption coefficients. In this study the shape of the energy weighting function was investigated with a set of ten trabecular bone test objects each with a similar geometry and structure but with different attenuation properties. In previous publications it was determined that the function E-3 was a very good choice for the weighting function (wi). The most important Result from this study was the discovery that a single function of the form E-b was not sufficient to explain the energy dependence of the different types of materials that might be used to describe common bodily tissues such as trabecular bone. It was also determined from the data contained in this paper that the exponent b is often significantly dependent upon the attenuation properties of the materials that were used to make the test objects. Studies of the attenuation properties will be useful in further studies involving energy weighting.
    Full-text Article · Jun 2015 · Medical Physics
  • K Ganezer · J Bulman · P Halcrow · I Neeson
    [Show abstract] [Hide abstract] ABSTRACT: In this study we update our studies presented in a talk in the ultrasound symposium in 2014 on the topic of noncontact ultrasound spectroscopy applied to cortical bone phantoms in which we found we found a high correlation between the BUA parameter and the Bone Mineral densities of the phantoms that was provided a linear regression with a r^₂as high as 0.96. The purpose of our current study was to have two separate ultrasound analyzers one at CSUDH in Carson California and a second analyzer at VN and associates in Elizabethtown, Ontario, Canada, in which the two analyzers only had minor differences in the transducers, pulse generators, and other hardware and software. Our goal was to compare the BUA parameters, speed of sound(SOS), attenuation, and spectra. We also considered changes in speed of sound, and attenuation taken 4 years ago with similar measurements made recently. We used Matlab shell files to compute SOS for 2 different methods, BUA, and attenuation for 15 or 16 phantoms that ranged in BMD from 150-1700 gm/m^3. Linear regressions were calculated for sets of two parameters. Some of the phantoms were scanned using a pixelized grid. The two systems behaved similarly. There seemed to be only small changes in SOS with larger changes in BUA, that might be attributed to oxidation and loss of water. There was a high degree of reproducibility in most of our measurements.
    Article · Jun 2015 · Medical Physics
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    [Show abstract] [Hide abstract] ABSTRACT: A search for dinucleon decay into pions with the Super-Kamiokande detector has been performed with an exposure of 282.1 kiloton-years. Dinucleon decay is a process that violates baryon number by two units. We present the first search for dinucleon decay to pions in a large water Cherenkov detector. The modes $^{16}$O$(pp) \rightarrow$ $^{14}$C$\pi^{+}\pi^{+}$, $^{16}$O$(pn) \rightarrow$ $^{14}$N$\pi^{+}\pi^{0}$, and $^{16}$O$(nn) \rightarrow$ $^{14}$O$\pi^{0}\pi^{0}$ are investigated. No significant excess in the Super-Kamiokande data has been found, so a lower limit on the lifetime of the process per oxygen nucleus is determined. These limits are: $\tau_{pp\rightarrow\pi^{+}\pi^{+}} > 7.22 \times 10^{31}$ years, $\tau_{pn\rightarrow\pi^{+}\pi^{0}} > 1.70 \times 10^{32}$ years, and $\tau_{nn\rightarrow\pi^{0}\pi^{0}} > 4.04 \times 10^{32}$ years. The lower limits on each mode are about two orders of magnitude better than previous limits from searches for dinucleon decay in iron.
    Full-text Article · Apr 2015 · Physical Review D
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    [Show abstract] [Hide abstract] ABSTRACT: Super-Kamiokande (SK) can search for weakly interacting massive particles (WIMPs) by detecting neutrinos produced from WIMP annihilations occurring inside the Sun. In this analysis, we include neutrino events with interaction vertices in the detector in addition to upward-going muons produced in the surrounding rock. Compared to the previous result, which used the upward-going muons only, the signal acceptances for light (few-GeV/$c^2$ $\sim$ 200-GeV/$c^2$) WIMPs are significantly increased. We fit 3903 days of SK data to search for the contribution of neutrinos from WIMP annihilation in the Sun. We found no significant excess over expected atmospheric-neutrino background and the result is interpreted in terms of upper limits on WIMP-nucleon elastic scattering cross sections under different assumptions about the annihilation channel. We set the current best limits on the spin-dependent (SD) WIMP-proton cross section for WIMP masses below 200 GeV/$c^2$ (at 10 GeV/$c^2$, 1.49$\times 10^{-39}$ cm$^2$ for $\chi\chi\rightarrow b \bar{b}$ and 1.31$\times 10^{-40}$ cm$^2$ for $\chi\chi\rightarrow\tau^+\tau^-$ annihilation channels), also ruling out some fraction of WIMP candidates with spin-independent (SI) coupling in the few-GeV/$c^2$ mass range.
    Full-text Article · Mar 2015 · Physical Review Letters
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    [Show abstract] [Hide abstract] ABSTRACT: Hyper-Kamiokande will be a next generation underground water Cherenkov detector with a total (fiducial) mass of 0.99 (0.56) million metric tons, approximately 20 (25) times larger than that of Super-Kamiokande. One of the main goals of Hyper-Kamiokande is the study of $CP$ asymmetry in the lepton sector using accelerator neutrino and anti-neutrino beams. In this document, the physics potential of a long baseline neutrino experiment using the Hyper-Kamiokande detector and a neutrino beam from the J-PARC proton synchrotron is presented. The analysis has been updated from the previous Letter of Intent [K. Abe et al., arXiv:1109.3262 [hep-ex]], based on the experience gained from the ongoing T2K experiment. With a total exposure of 7.5 MW $\times$ 10$^7$ sec integrated proton beam power (corresponding to $1.56\times10^{22}$ protons on target with a 30 GeV proton beam) to a $2.5$-degree off-axis neutrino beam produced by the J-PARC proton synchrotron, it is expected that the $CP$ phase $\delta_{CP}$ can be determined to better than 19 degrees for all possible values of $\delta_{CP}$, and $CP$ violation can be established with a statistical significance of more than $3\,\sigma$ ($5\,\sigma$) for $76%$ ($58%$) of the $\delta_{CP}$ parameter space.
    Full-text Article · Dec 2014 · Progress of Theoretical and Experimental Physics
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    [Show abstract] [Hide abstract] ABSTRACT: A search for neutrino oscillations induced by Lorentz violation has been performed using 4,438 live-days of Super-Kamiokande atmospheric neutrino data. The Lorentz violation is included in addition to standard three-flavor oscillations using the non-perturbative Standard Model Extension (SME), allowing the use of the full range of neutrino path lengths, ranging from 15 to 12,800 km, and energies ranging from 100 MeV to more than 100 TeV in the search. No evidence of Lorentz violation was observed, so limits are set on the renormalizable isotropic SME coefficients in the $e\mu$, $\mu\tau$, and $e\tau$ sectors, improving the existing limits by up to seven orders of magnitude and setting limits for the first time in the neutrino $\mu\tau$ sector of the SME.
    Full-text Article · Oct 2014 · Physical Review D
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    [Show abstract] [Hide abstract] ABSTRACT: We present limits on sterile neutrino mixing using 4,438 live-days of atmospheric neutrino data from the Super-Kamiokande experiment. We search for fast oscillations driven by an eV$^2$-scale mass splitting and for oscillations into sterile neutrinos instead of tau neutrinos at the atmospheric mass splitting. When performing both these searches we assume that the sterile mass splitting is large, allowing $\sin^2(\Delta m^2 L/4E)$ to be approximated as $0.5$, and we assume that there is no mixing between electron neutrinos and sterile neutrinos ($|U_{e4}|^2 = 0$). No evidence of sterile oscillations is seen and we limit $|U_{\mu4}|^2$ to less than 0.041 and $|U_{\tau4}|^2$ to less than 0.18 for $\Delta m^2 > 0.8$ eV$^2$ at the 90% C.L. in a 3+1 framework. The approximations that can be made with atmospheric neutrinos allow these limits to be easily applied to 3+N models, and we provide our results in a generic format to allow comparisons with other sterile neutrino models.
    Full-text Article · Oct 2014 · Physical Review D
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    [Show abstract] [Hide abstract] ABSTRACT: The observation of neutrons turning into antineutrons would constitute a discovery of fundamental importance for particle physics and cosmology. Observing the transition would show that baryon number ( ) is violated by two units and that matter containing neutrons is unstable. It would provide a clue to how the matter in our universe might have evolved from the early universe. If seen at rates observable in foreseeable next-generation experiments, it might well help us understand the observed baryon asymmetry of the universe. A demonstration of the violation of by 2 units would have a profound impact on our understanding of phenomena beyond the Standard Model of particle physics.
    Full-text Article · Oct 2014
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    Dataset: parafin
    M. Krmar · D. Nikolic · A. Kuzmanovic · [...] · K. Ganezer
    Full-text Dataset · Sep 2014
  • K Abe · Y Hayato · T Iida · [...] · R J Wilkes
    [Show abstract] [Hide abstract] ABSTRACT: We present the results of searches for nucleon decay via n→ν[over ¯]π^{0} and p→ν[over ¯]π^{+} using data from a combined 172.8 kt·yr exposure of Super-Kamiokande-I,-II, and-III. We set lower limits on the partial lifetime for each of these modes: τ_{n→ν[over ¯]π^{0}}>1.1×10^{33} years and τ_{p→ν[over ¯]π^{+}}>3.9×10^{32} years at a 90% confidence level.
    Article · Sep 2014 · Physical Review Letters
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    [Show abstract] [Hide abstract] ABSTRACT: The trilepton nucleon decay modes $p \rightarrow e^+ \nu \nu$ and $p \rightarrow \mu^+ \nu \nu$ violate $|\Delta (B - L)|$ by two units. Using data from a 273.4 kiloton year exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of $\tau_{p \rightarrow e^+ \nu \nu} > 1.7 \times 10^{32}$ years and $\tau_{p \rightarrow \mu^+ \nu \nu} > 2.2 \times 10^{32}$ years at a $90 \% $ confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.
    Full-text Article · Sep 2014 · Physical Review Letters
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    V Takhistov · K Abe · Y Haga · [...] · R J Wilkes
    [Show abstract] [Hide abstract] ABSTRACT: The trilepton nucleon decay modes p→e^{+}νν and p→μ^{+}νν violate |Δ(B-L)| by two units. Using data from a 273.4 kt yr exposure of Super-Kamiokande a search for these decays yields a fit consistent with no signal. Accordingly, lower limits on the partial lifetimes of τ_{p→e^{+}νν}>1.7×10^{32} years and τ_{p→μ^{+}νν}>2.2×10^{32} years at a 90% confidence level are obtained. These limits can constrain Grand Unified Theories which allow for such processes.
    Full-text Article · Sep 2014 · Physical Review Letters
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    [Show abstract] [Hide abstract] ABSTRACT: We have searched for proton decay via $p \rightarrow \nu K^{+}$ using Super-Kamiokande data from April 1996 to February 2013, 260 kiloton$\cdot$year exposure in total. No evidence for this proton decay mode is found. A lower limit of the proton lifetime is set to $5.9 \times 10^{33}$ years at 90% confidence level.
    Full-text Article · Aug 2014 · Physical Review D

Publication Stats

13k Citations

Institutions

  • 2015
    • Loyola Marymount University
      Los Ángeles, California, United States
    • University of Novi Sad
      Varadinum Petri, Vojvodina, Serbia
  • 1994-2014
    • California State University
      Long Beach, California, United States
  • 1995-2012
    • California State University, Dominguez Hills
      • Department of Physics
      Carson, California, United States
  • 2004-2009
    • The University of Tokyo
      • Institute for Cosmic Ray Research
      Tokyo, Tokyo-to, Japan
    • Carleton College
      نورثفیلد، مینه‌سوتا, Minnesota, United States
    • University of Birmingham
      • School of Physics and Astronomy
      Birmingham, England, United Kingdom
  • 2007
    • Nagoya University
      Nagoya, Aichi, Japan
  • 2005
    • California Institute of Technology
      • Department of Physics
      Pasadena, California, United States
  • 1988-2004
    • Boston University
      • Department of Physics
      Boston, Massachusetts, United States
  • 1998-1999
    • CSU Mentor
      Long Beach, California, United States
  • 1985-1995
    • University of California, Irvine
      • Department of Physics and Astronomy
      Irvine, California, United States
  • 1993
    • University of Adelaide
      Tarndarnya, South Australia, Australia
  • 1984
    • Cleveland State University
      Cleveland, Ohio, United States