研究者詳細 - 西村　康宏

西村　康宏 (ニシムラ　ヤスヒロ)

NISHIMURA Yasuhiro

写真a

所属（所属キャンパス）: 理工学部物理学科理工学部物理学科（矢上）

職名: 准教授

HP

西村研究室

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Search for neutrinos in coincidence with gravitational wave events from the LIGO–Virgo O3a observing run with the Super-Kamiokande detector

Abe K., Bronner C., Hayato Y., Ikeda M., Imaizumi S., Kameda J., Kanemura Y., Kataoka Y., Miki S., Miura M., Moriyama S., Nagao Y., Nakahata M., Nakayama S., Okada T., Okamoto K., Orii A., Pronost G., Sekiya H., Shiozawa M., Sonoda Y., Suzuki Y., Takeda A., Takemoto Y., Takenaka A., Tanaka H., Watanabe S., Yano T., Han S., Kajita T., Okumura K., Tashiro T., Wang R., Xia J., Megias G.D., Bravo-Berguño D., Labarga L., Marti L., Zaldivar B., Pointon B.W., Blaszczyk F.D.M., Kearns E., Raaf J.L., Stone J.L., Wan L., Wester T., Bian J., Griskevich N.J., Kropp W.R., Locke S., Mine S., Smy M.B., Sobel H.W., Takhistov V., Weatherly P., Hill J., Kim J.Y., Lim I.T., Park R.G., Bodur B., Scholberg K., Walter C.W., Bernard L., Coffani A., Drapier O., El Hedri S., Giampaolo A., Gonin M., Mueller T.A., Paganini P., Quilain B., Ishizuka T., Nakamura T., Jang J.S., Learned J.G., Anthony L.H.V., Martin D.G.R., Sztuc A.A., Uchida Y., Berardi V., Catanesi M.G., Radicioni E., Calabria N.F., Machado L.N., de Rosa G., Collazuol G., Iacob F., Lamoureux M., Ospina N., Ludovici L., Maekawa Y., Nishimura Y., Cao S., Friend M., Hasegawa T., Ishida T., Jakkapu M., Kobayashi T., Matsubara T., Nakadaira T.

Astrophysical Journal （Astrophysical Journal) 918 （ 2 ） 2021年09月

ISSN 0004637X

　概要を見る

The Super-Kamiokande detector can be used to search for neutrinos in time coincidence with gravitational waves detected by the LIGO–Virgo Collaboration (LVC). Both low-energy (7–100 MeV) and high-energy (0.1–105 GeV) samples were analyzed in order to cover a very wide neutrino spectrum. Follow-ups of 36 (out of 39) gravitational waves reported in the GWTC-2 catalog were examined; no significant excess above the background was observed, with 10 (24) observed neutrinos compared with 4.8 (25.0) expected events in the high-energy (low-energy) samples. A statistical approach was used to compute the significance of potential coincidences. For each observation, p-values were estimated using neutrino direction and LVC sky map; the most significant event (GW190602_175927) is associated with a post-trial p-value of 7.8% (1.4σ). Additionally, flux limits were computed independently for each sample and by combining the samples. The energy emitted as neutrinos by the identified gravitational wave sources was constrained, both for given flavors and for all flavors assuming equipartition between the different flavors, independently for each trigger and by combining sources of the same nature.
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Supernova Model Discrimination with Hyper-Kamiokande

Abe K., Adrich P., Aihara H., Akutsu R., Alekseev I., Ali A., Ameli F., Anghel I., Anthony L.H.V., Antonova M., Araya A., Asaoka Y., Ashida Y., Aushev V., Ballester F., Bandac I., Barbi M., Barker G.J., Barr G., Batkiewicz-Kwasniak M., Bellato M., Berardi V., Bergevin M., Bernard L., Bernardini E., Berns L., Bhadra S., Bian J., Blanchet A., Blaszczyk F.D.M., Blondel A., Boiano A., Bolognesi S., Bonavera L., Booth N., Borjabad S., Boschi T., Bose D., Boyd S.B., Bozza C., Bravar A., Bravo-Berguo D., Bronner C., Brown L., Bubak A., Buchowicz A., Buizza Avanzini M., Cafagna F.S., Calabria N.F., Calvo-Mozota J.M., Cao S., Cartwright S.L., Carroll A., Catanesi M.G., Cebrian S., Chabera M., Chakraborty S., Checchia C., Choi J.H., Choubey S., Cicerchia M., Coleman J., Collazuol G., Cook L., Cowan G., Cuen-Rochin S., Danilov M., Díaz López G., De La Fuente E., De Perio P., De Rosa G., Dealtry T., Densham C.J., Dergacheva A., Deshmukh N., Devi M.M., Di Lodovico F., Di Meo P., Di Palma I., Doyle T.A., Drakopoulou E., Drapier O., Dumarchez J., Dunne P., Dziewiecki M., Eklund L., El Hedri S., Ellis J., Emery S., Esmaili A., Esteve R., Evangelisti A., Feely M., Fedotov S., Feng J., Fernandez P., Fernández-Martinez E., Ferrario P., Ferrazzi B., Feusels T.

Astrophysical Journal （Astrophysical Journal) 916 （ 1 ） 2021年07月

ISSN 0004637X

　概要を見る

Core-collapse supernovae are among the most magnificent events in the observable universe. They produce many of the chemical elements necessary for life to exist and their remnants - neutron stars and black holes - are interesting astrophysical objects in their own right. However, despite millennia of observations and almost a century of astrophysical study, the explosion mechanism of core-collapse supernovae is not yet well understood. Hyper-Kamiokande is a next-generation neutrino detector that will be able to observe the neutrino flux from the next galactic core-collapse supernova in unprecedented detail. We focus on the first 500 ms of the neutrino burst, corresponding to the accretion phase, and use a newly-developed, high-precision supernova event generator to simulate Hyper-Kamiokande's response to five different supernova models. We show that Hyper-Kamiokande will be able to distinguish between these models with high accuracy for a supernova at a distance of up to 100 kpc. Once the next galactic supernova happens, this ability will be a powerful tool for guiding simulations toward a precise reproduction of the explosion mechanism observed in nature.
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First T2K measurement of transverse kinematic imbalance in the muon-neutrino charged-current single- π+ production channel containing at least one proton

Abe K., Akhlaq N., Akutsu R., Ali A., Alt C., Andreopoulos C., Antonova M., Aoki S., Arihara T., Asada Y., Ashida Y., Atkin E.T., Awataguchi Y., Barker G.J., Barr G., Barrow D., Batkiewicz-Kwasniak M., Beloshapkin A., Bench F., Berardi V., Berns L., Bhadra S., Blanchet A., Blondel A., Bolognesi S., Bonus T., Bourguille B., Boyd S.B., Bravar A., Bravo Berguño D., Bronner C., Bron S., Bubak A., Buizza Avanzini M., Cao S., Cartwright S.L., Catanesi M.G., Cervera A., Chakrani J., Cherdack D., Christodoulou G., Cicerchia M., Coleman J., Collazuol G., Cook L., Coplowe D., Cudd A., De Rosa G., Dealtry T., Delogu C.C., Dennis S.R., Densham C., Dergacheva A., Di Lodovico F., Dolan S., Douqa D., Doyle T.A., Dumarchez J., Dunne P., Eguchi A., Eklund L., Emery-Schrenk S., Ereditato A., Finch A.J., Fiorillo G., Francois C., Friend M., Fujii Y., Fukuda R., Fukuda Y., Fusshoeller K., Giganti C., Gonin M., Goodman E.A.G., Gorin A., Grassi M., Guigue M., Hadley D.R., Hamacher-Baumann P., Harris D.A., Hartz M., Hasegawa T., Hassani S., Hastings N.C., Hayato Y., Hiramoto A., Hogan M., Holeczek J., Hong Van N.T., Honjo T., Iacob F., Ichikawa A.K., Ikeda M., Ishida T., Ishitsuka M., Iwamoto K., Izmaylov A., Izumi N., Jakkapu M., Jamieson B.

Physical Review D （Physical Review D) 103 （ 11 ） 2021年06月

ISSN 24700010

　概要を見る

This paper reports the first T2K measurement of the transverse kinematic imbalance in the single-π+ production channel of neutrino interactions. We measure the differential cross sections in the muon-neutrino charged-current interaction on hydrocarbon with a single π+ and at least one proton in the final state, at the ND280 off axis near detector of the T2K experiment. The extracted cross sections are compared to the predictions from different neutrino-nucleus interaction event generators. Overall, the results show a preference for models that have a more realistic treatment of nuclear medium effects including the initial nuclear state and final-state interactions.
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Improved constraints on neutrino mixing from the T2K experiment with 3.13×1021 protons on target

Abe K., Akhlaq N., Akutsu R., Ali A., Alt C., Andreopoulos C., Antonova M., Aoki S., Arihara T., Asada Y., Ashida Y., Atkin E.T., Awataguchi Y., Barker G.J., Barr G., Barrow D., Batkiewicz-Kwasniak M., Beloshapkin A., Bench F., Berardi V., Berns L., Bhadra S., Blanchet A., Blondel A., Bolognesi S., Bonus T., Bourguille B., Boyd S.B., Bravar A., Bravo Berguño D., Bronner C., Bron S., Bubak A., Buizza Avanzini M., Cao S., Cartwright S.L., Catanesi M.G., Cervera A., Chakrani J., Cherdack D., Christodoulou G., Cicerchia M., Coleman J., Collazuol G., Cook L., Coplowe D., Cudd A., De Rosa G., Dealtry T., Delogu C.C., Dennis S.R., Densham C., Dergacheva A., Di Lodovico F., Dolan S., Douqa D., Doyle T.A., Dumarchez J., Dunne P., Eguchi A., Eklund L., Emery-Schrenk S., Ereditato A., Finch A.J., Fiorillo G., Francois C., Friend M., Fujii Y., Fukuda R., Fukuda Y., Fusshoeller K., Giganti C., Gonin M., Goodman E.A.G., Gorin A., Grassi M., Guigue M., Hadley D.R., Hamacher-Baumann P., Harris D.A., Hartz M., Hasegawa T., Hassani S., Hastings N.C., Hayato Y., Hiramoto A., Hogan M., Holeczek J., Hong Van N.T., Honjo T., Iacob F., Ichikawa A.K., Ikeda M., Ishida T., Ishitsuka M., Iwamoto K., Izmaylov A., Izumi N., Jakkapu M., Jamieson B.

Physical Review D （Physical Review D) 103 （ 11 ） 2021年06月

ISSN 24700010

　概要を見る

The T2K experiment reports updated measurements of neutrino and antineutrino oscillations using both appearance and disappearance channels. This result comes from an exposure of 14.9(16.4)×1020 protons on target in neutrino (antineutrino) mode. Significant improvements have been made to the neutrino interaction model and far detector reconstruction. An extensive set of simulated data studies have also been performed to quantify the effect interaction model uncertainties have on the T2K oscillation parameter sensitivity. T2K performs multiple oscillation analyses that present both frequentist and Bayesian intervals for the Pontecorvo-Maki-Nakagawa-Sakata parameters. For fits including a constraint on sin2θ13 from reactor data and assuming normal mass ordering T2K measures sin2θ23=0.53-0.04+0.03 and Δm322=(2.45±0.07)×10-3 eV2 c-4. The Bayesian analyses show a weak preference for normal mass ordering (89% posterior probability) and the upper sin2θ23 octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the 2σ level.
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T2K measurements of muon neutrino and antineutrino disappearance using 3.13×1021 protons on target

Abe K., Akhlaq N., Akutsu R., Ali A., Alt C., Andreopoulos C., Antonova M., Aoki S., Arihara T., Asada Y., Ashida Y., Atkin E.T., Awataguchi Y., Barker G.J., Barr G., Barrow D., Batkiewicz-Kwasniak M., Beloshapkin A., Bench F., Berardi V., Berns L., Bhadra S., Blondel A., Bolognesi S., Bonus T., Bourguille B., Boyd S.B., Bravar A., Bravo Berguño D., Bronner C., Bron S., Bubak A., Buizza Avanzini M., Cao S., Cartwright S.L., Catanesi M.G., Cervera A., Cherdack D., Christodoulou G., Cicerchia M., Coleman J., Collazuol G., Cook L., Coplowe D., Cudd A., De Rosa G., Dealtry T., Delogu C.C., Dennis S.R., Densham C., Dergacheva A., Di Lodovico F., Dolan S., Doyle T.A., Dumarchez J., Dunne P., Eguchi A., Eklund L., Emery-Schrenk S., Ereditato A., Finch A.J., Fiorentini G.A., Francois C., Friend M., Fujii Y., Fukuda R., Fukuda Y., Fusshoeller K., Giganti C., Gonin M., Gorin A., Guigue M., Hadley D.R., Hamacher-Baumann P., Hartz M., Hasegawa T., Hassani S., Hastings N.C., Hayato Y., Hiramoto A., Hogan M., Holeczek J., Hong Van N.T., Honjo T., Iacob F., Ichikawa A.K., Ikeda M., Ishida T., Ishitsuka M., Iwamoto K., Izmaylov A., Izumi N., Jakkapu M., Jamieson B., Jenkins S.J., Jesús-Valls C., Jonsson P., Jung C.K., Jurj P.B., Kabirnezhad M.

Physical Review D （Physical Review D) 103 （ 1 ） 2021年01月

ISSN 24700010

　概要を見る

We report measurements by the T2K experiment of the parameters θ23 and Δm322, which govern the disappearance of muon neutrinos and antineutrinos in the three-flavor PMNS neutrino oscillation model at T2K's neutrino energy and propagation distance. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, muon-like events from each beam mode are used to measure these parameters separately for neutrino and antineutrino oscillations. Data taken from 1.49×1021 protons on target (POT) in neutrino mode and 1.64×1021 POT in antineutrino mode are used. The best-fit values obtained by T2K were sin2(θ23)=0.51-0.07+0.06(0.43-0.05+0.21) and Δm322=2.47-0.09+0.08(2.50-0.13+0.18)×10-3 eV2/c4 for neutrinos (antineutrinos). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed. An analysis using an effective two-flavor neutrino oscillation model where the sine of the mixing angle is allowed to take nonphysical values larger than 1 is also performed to check the consistency of our data with the three-flavor model. Our data were found to be consistent with a physical value for the mixing angle.
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