0000000000235222
AUTHOR
Tadayuki Takahashi
Evidence for Muon Neutrino Oscillation in an Accelerator-Based Experiment
We present results for muon neutrino oscillation in the KEK to Kamioka (K2K) long-baseline neutrino oscillation experiment. K2K uses an accelerator-produced muon neutrino beam with a mean energy of 1.3 GeV directed at the Super-Kamiokande detector. We observed the energy dependent disappearance of muon neutrino, which we presume have oscillated to tau neutrino. The probability that we would observe these results if there is no neutrino oscillation is 0.0050% (4.0 sigma).
Observation of a Be double-Lambda hypernucleus in the J-PARC E07 experiment
A double-$\Lambda$ hypernucleus, ${}_{\Lambda\Lambda}\mathrm{Be}$, was observed by the J-PARC E07 collaboration in nuclear emulsions tagged by the $(K^{-},K^{+})$ reaction. This event was interpreted as a production and decay of $ {}_{\Lambda\Lambda}^{\;10}\mathrm{Be}$, ${}_{\Lambda\Lambda}^{\;11}\mathrm{Be}$, or ${}_{\Lambda\Lambda}^{\;12}\mathrm{Be}^{*}$ via $\Xi^{-}$ capture in ${}^{16}\mathrm{O}$. By assuming the capture in the atomic 3D state, the binding energy of two $\Lambda$ hyperons$\,$($B_{\Lambda\Lambda}$) of these double-$\Lambda$ hypernuclei are obtained to be $15.05 \pm 0.11\,\mathrm{MeV}$, $19.07 \pm 0.11\,\mathrm{MeV}$, and $13.68 \pm 0.11\,\mathrm{MeV}$, respectively. Base…
Experimental validation of a novel compact focusing scheme for future energy-frontier linear lepton colliders.
A novel scheme for the focusing of high-energy leptons in future linear colliders was proposed in 2001 [ P. Raimondi and A. Seryi , Phys. Rev. Lett. 86 , 3779 ( 2001 ) ]. This scheme has many advantageous properties over previously studied focusing schemes, including being significantly shorter for a given energy and having a significantly better energy bandwidth. Experimental results from the ATF2 accelerator at KEK are presented that validate the operating principle of such a scheme by demonstrating the demagnification of a 1.3 GeV electron beam down to below 65 nm in height using an energy-scaled version of the compact focusing optics designed for the ILC collider.
Status of the J-PARC E07, Systematic Study of Double Strangeness Nuclei with the Hybrid Emulsion Method
The current status of the J-PARC E07 experiment and two typical events, a _ΛΛBe hypernuclear event named “MINO” and \(_{\Xi }^{15}\text{C}\) hypernuclear event named “IBUKI”, are presented. J-PARC E07 is the most complex emulsion experiment so far to investigate double hypernuclei. The physics run at the K1.8 beam line in the J-PARC hadron facility and photographic development of all emulsion sheets have been completed. The emulsion sheets are presently being analyzed with dedicated optical microscopes. Current statistics are estimated to be about twice that of KEK-PS E373. Quantitative data on ΔB_ΛΛ of double Λ hypernucleus and \(B_{\Xi ^{ - }}\) of Ξ hypernucleus are being accumulated suc…
Measurement of neutrino oscillation by the K2K experiment
We present measurements of nu_mu disappearance in K2K, the KEK to Kamioka long-baseline neutrino oscillation experiment. One hundred and twelve beam-originated neutrino events are observed in the fiducial volume of Super-Kamiokande with an expectation of 158.1^{+9.2}_{-8.6} events without oscillation. A distortion of the energy spectrum is also seen in 58 single-ring muon-like events with reconstructed energies. The probability that the observations are explained by the expectation for no neutrino oscillation is 0.0015% (4.3sigma). In a two flavor oscillation scenario, the allowed Delta m^2 region at sin^2(2theta) is between 1.9 and 3.5 x 10^{-3} eV^2 at the 90% C.L. with a best-fit value o…
The Large Observatory For x-ray Timing
The Large Observatory For x-ray Timing (LOFT) was studied within ESA M3 Cosmic Vision framework and participated in the final down-selection for a launch slot in 2022-2024. Thanks to the unprecedented combination of effective area and spectral resolution of its main instrument, LOFT will study the behaviour of matter under extreme conditions, such as the strong gravitational field in the innermost regions of accretion flows close to black holes and neutron stars, and the supra-nuclear densities in the interior of neutron stars. The science payload is based on a Large Area Detector (LAD, 10 m 2 effective area, 2-30 keV, 240 eV spectral resolution, 1 deg collimated field of view) and a WideFi…
Broadband Multi-wavelength Properties of M87 during the 2017 Event Horizon Telescope Campaign
Full list of authors: EHT MWL Science Working Group; Algaba, J. C.; Anczarski, J.; Asada, K.; Baloković, M.; Chandra, S.; Cui, Y. -Z.; Falcone, A. D.; Giroletti, M.; Goddi, C.; Hada, K.; Haggard, D.; Jorstad, S.; Kaur, A.; Kawashima, T.; Keating, G.; Kim, J. -Y.; Kino, M.; Komossa, S.; Kravchenko, E. V.; Krichbaum, T. P.; Lee, S. -S.; Lu, R. -S.; Lucchini, M.; Markoff, S.; Neilsen, J.; Nowak, M. A.; Park, J.; Principe, G.; Ramakrishnan, V.; Reynolds, M. T.; Sasada, M.; Savchenko, S. S.; Williamson, K. E.; Event Horizon Telescope Collaboration; Akiyama, Kazunori; Alberdi, Antxon; Alef, Walter; Anantua, Richard; Azulay, Rebecca; Baczko, Anne-Kathrin; Ball, David; Barrett, John; Bintley, Dan; …
Search for coherent charged pion production in neutrino-carbon interactions
We report the result from a search for charged-current coherent pion production induced by muon neutrinos with a mean energy of 1.3 GeV. The data are collected with a fully active scintillator detector in the K2K long-baseline neutrino oscillation experiment. No evidence for coherent pion production is observed and an upper limit of $0.60 \times 10^{-2}$ is set on the cross section ratio of coherent pion production to the total charged-current interaction at 90% confidence level. This is the first experimental limit for coherent charged pion production in the energy region of a few GeV.
Measurement of inclusive pi(0) production in the charged-current interactions of neutrinos in a 1.3-GeV wide band beam
In this paper we report on the measurement of the rate of inclusive $\pi^0$ production induced by charged-current neutrino interactions in a C$_8$H$_8$ target at a mean energy of 1.3 GeV in the K2K near detector. Out of a sample of 11,606 charged current neutrino interactions, we select 479 $\pi^0$ events with two reconstructed photons. We find that the cross section for the inclusive $\pi^0$ production relative to the charged-current quasi-elastic cross section is $$\frac{\sigma_{CC\pi^0}}{\sigma_{CCQE}}=0.426\pm0.032(stat.)\pm0.035(syst.)$$ The energy dependent cross section ratio is also measured. The results are consistent with previous experiments for exclusive channels on different ta…