M. Tada

University of Electro-Communications

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T. Hasegawa

High Energy Accelerator Research Organization

M. Nakahata

The University of Tokyo

A. Konaka

TRIUMF

Y. Takeuchi

The University of Tokyo

M. Yokoyama

The University of Tokyo

E. Kearns

The University of Tokyo

L. Ludovici

Istituto Nazionale di Fisica Nucleare, Sezione di Roma I

C. McGrew

Stony Brook University

M. Khabibullin

Institute for Nuclear Research

Y. Hayato

The University of Tokyo

Cooperative Institutions

University of California, Irvine

486

Boston University

469

Duke University

380

The University of Tokyo

364

Universidad Autónoma de Madrid

293

Colorado State University

276

University of Bern

222

Albert Einstein College of Medicine

200

University of Alberta

194

Institute of Particle Physics

184

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Measurement of neutrino oscillation by the K2K experiment

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2006)

Myunggeun Ahn E. Aliu S. Andringa S. Aoki Yuya Aoyama

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 of 2.8 x 10^{-3} eV^2.

10.1103/physrevd.74.072003

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Citations (640)

Measurement of the muon neutrino charged-current single π+ production on hydrocarbon using the T2K off-axis near detector ND280

Physical review. D/Physical review. D. (2020)

K. Abe R. Akutsu A. Ali C. Alt J. L. Amey

We report the measurements of the single and double differential cross section of muon neutrino charged-current interactions on carbon with a single positively charged pion in the final state at the T2K off-axis near detector using $5.56\ifmmode\times\else\texttimes\fi{}{10}^{20}$ protons on target. The analysis uses data control samples for the background subtraction and the cross section signal, defined as a single negatively charged muon and a single positively charged pion exiting from the target nucleus, is extracted using an unfolding method. The model-dependent cross section, integrated over the T2K off-axis neutrino beam spectrum peaking at 0.6 GeV, is measured to be $\ensuremath{\sigma}=(11.76\ifmmode\pm\else\textpm\fi{}0.44(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}2.39(\mathrm{syst}))\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}40}\text{ }\text{ }{\mathrm{cm}}^{2}\text{ }{\text{nucleon}}^{\ensuremath{-}1}$. Various differential cross sections are measured, including the first measurement of the Adler angles for single charged pion production in neutrino interactions with heavy nuclei target.

Charged current

Muon neutrino

10.1103/physrevd.101.012007

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Citations (17)

Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample ofνeinteractions at the far detector

Physical review. D/Physical review. D. (2017)

K. Abe J. L. Amey C. Andreopoulos M. Antonova S. Aoki

The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearance and disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a pion decay has been tagged is added to the four single-ring samples used in previous T2K oscillation analyses. Through combined analyses of these five samples, simultaneous measurements of four oscillation parameters, $|\Delta m^2_{32}|$, $\sin^2(\theta_{23})$, $\sin^2(\theta_{13})$, and $\delta_{CP}$ and of the mass ordering are made. A set of studies of simulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interaction model uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals are presented for combinations of the oscillation parameters with and without the inclusion of reactor constraints on $\sin^2(\theta_{13})$. When combined with reactor measurements, the hypothesis of CP conservation ($\delta_{CP}$$=0$ or $\pi$) is excluded at 90% confidence level. The 90% confidence region for $\delta_{CP}$ is [-2.95,-0.44] ([-1.47, -1.27]) for normal (inverted) ordering. The central values and 68\% confidence intervals for the other oscillation parameters for normal (inverted) ordering are $\Delta m^{2}_{32}=2.54\pm0.08$ ($2.51\pm0.08$) $\times 10^{-3}$ eV$^2 / c^4$ and $\sin^2(\theta_{23}) = 0.55^{+0.05}_{-0.09}$ ($0.55^{+0.05}_{-0.08}$), compatible with maximal mixing. In the Bayesian analysis, the data weakly prefer normal ordering (Bayes factor 3.7) and the upper octant for $\sin^2(\theta_{23})$ (Bayes factor 2.4).

Oscillation (cell signaling)

10.1103/physrevd.96.092006

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Citations (148)

Evidence of electron neutrino appearance in a muon neutrino beam

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2013)

K. Abe N. Abgrall H. Aihara T. Akiri J. B. Albert

The T2K collaboration: reports evidence for electron neutrino appearance at the atmospheric mass splitting, |\Delta m_{32}^2|=2.4x10^{-3} eV^2. An excess of electron neutrino interactions over background is observed from a muon neutrino beam with a peak energy of 0.6 GeV at the Super-Kamiokande (SK) detector 295 km from the beam's origin. Signal and background predictions are constrained by data from near detectors located 280 m from the neutrino production target. We observe 11 electron neutrino candidate events at the SK detector when a background of 3.3\pm0.4(syst.) events is expected. The background-only hypothesis is rejected with a p-value of 0.0009 (3.1\sigma), and a fit assuming \nu_{\mu}->\nu_e oscillations with sin^2(2\theta_{23})=1, \delta_{CP}=0 and |\Delta m_{32}^2|=2.4x10^{-3} eV^2 yields sin^2(2\theta_{13})=0.088^{+0.049}_{-0.039}(stat.+syst.).

Muon neutrino

Electron neutrino

10.1103/physrevd.88.032002

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Citations (163)

Observation of Electron Neutrino Appearance in a Muon Neutrino Beam

Physical Review Letters (2014)

K. Abe J. Adam H. Aihara T. Akiri C. Andreopoulos

The T2K experiment has observed electron neutrino appearance in a muon neutrino beam produced 295 km from the Super-Kamiokande detector with a peak energy of 0.6 GeV. A total of 28 electron neutrino events were detected with an energy distribution consistent with an appearance signal, corresponding to a significance of 7.3σ when compared to 4.92±0.55 expected background events. In the Pontecorvo-Maki-Nakagawa-Sakata mixing model, the electron neutrino appearance signal depends on several parameters including three mixing angles θ12, θ23, θ13, a mass difference Δm232 and a CP violating phase δCP. In this neutrino oscillation scenario, assuming |Δm232|=2.4×10−3 eV2, sin2θ23=0.5, and Δm232>0 (Δm232<0), a best-fit value of sin22θ13=0.140+0.038−0.032 (0.170+0.045−0.037) is obtained at δCP=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ13 from reactor experiments, some values of δCP are disfavored at the 90% C.L.Received 19 November 2013DOI:https://doi.org/10.1103/PhysRevLett.112.061802© 2014 American Physical Society

Electron neutrino

Muon neutrino

Oscillation (cell signaling)

Charged current

10.1103/physrevlett.112.061802

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Citations (486)

T2K neutrino flux prediction

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2013)

K. Abe N. Abgrall H. Aihara T. Akiri J. B. Albert

The Tokai-to-Kamioka (T2K) experiment studies neutrino oscillations using an off-axis muon neutrino beam with a peak energy of about 0.6 GeV that originates at the J-PARC accelerator facility. Interactions of the neutrinos are observed at near detectors placed at 280 m from the production target and at the far detector -- Super-Kamiokande (SK) -- located 295 km away. The flux prediction is an essential part of the successful prediction of neutrino interaction rates at the T2K detectors and is an important input to T2K neutrino oscillation and cross section measurements. A FLUKA and GEANT3 based simulation models the physical processes involved in the neutrino production, from the interaction of primary beam protons in the T2K target, to the decay of hadrons and muons that produce neutrinos. The simulation uses proton beam monitor measurements as inputs. The modeling of hadronic interactions is re-weighted using thin target hadron production data, including recent charged pion and kaon measurements from the NA61/SHINE experiment. For the first T2K analyses the uncertainties on the flux prediction are evaluated to be below 15% near the flux peak. The uncertainty on the ratio of the flux predictions at the far and near detectors is less than 2% near the flux peak.

10.1103/physrevd.87.012001

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Citations (206)

Measurement of the neutrino-oxygen neutral-current interaction cross section by observing nuclear deexcitationγrays

Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology (2014)

K. Abe J. Adam H. Aihara T. Akiri C. Andreopoulos

We report the first measurement of the neutrino-oxygen neutral-current quasielastic (NCQE) cross section. It is obtained by observing nuclear deexcitation $\gamma$-rays which follow neutrino-oxygen interactions at the Super-Kamiokande water Cherenkov detector. We use T2K data corresponding to $3.01 \times 10^{20}$ protons on target. By selecting only events during the T2K beam window and with well-reconstructed vertices in the fiducial volume, the large background rate from natural radioactivity is dramatically reduced. We observe 43 events in the $4-30$ MeV reconstructed energy window, compared with an expectation of 51.0, which includes an estimated 16.2 background events. The background is primarily nonquasielastic neutral-current interactions and has only 1.2 events from natural radioactivity. The flux-averaged NCQE cross section we measure is $1.55 \times 10^{-38}$ cm$^2$ with a 68\% confidence interval of $(1.22, 2.20) \times 10^{-38}$ cm$^2$ at a median neutrino energy of 630 MeV, compared with the theoretical prediction of $2.01 \times 10^{-38}$ cm$^2$.

Neutral current

10.1103/physrevd.90.072012

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Citations (28)

Table 3 ; First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector

K. Abe C. Andreopoulos M. Antonova S. Aoki A. Ariga

Charged current

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Table 7 ; First Measurement of the Muon Neutrino Charged Current Single Pion Production Cross Section on Water with the T2K Near Detector

K. Abe C. Andreopoulos M. Antonova S. Aoki A. Ariga

Charged current

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A coupled microwave-cavity system in the Rydberg-atom cavity detector for dark matter axions

arXiv (Cornell University) (2001)

M. Tada Y. Kishimoto M. Shibata K. Kominato I. Ogawa

A coupled microwave-cavity system of cylindrical TM$_{010}$ single-mode has been developed to search for dark matter axions around 10 $μ{\rm eV}$(2.4 GHz) with the Rydberg-atom cavity detector at 10 mK range temperature. One component of the coupled cavity (conversion cavity) made of oxygen-free high-conductivity copper is used to convert an axion into a single photon with the Primakoff process in the strong magnetic field, while the other component (detection cavity) made of Nb is utilized to detect the converted photons with Rydberg atoms passed through it without magnetic field. Top of the detection cavity is attached to the bottom flange of the mixing chamber of a dilution refrigerator, thus the whole cavity is cooled down to 10 mK range to reduce the background thermal blackbody-photons in the cavity. The cavity resonant frequency is tunable over $\sim$ 15% by moving dielectric rods inserted independently into each part of the cavities along the cylindrical axis. In order to reduce the heat load from the higher temperature side to the most cooled dilution refrigerator part, the tuning rod at the conversion cavity is especially driven via the Kevlar strings with a stepping motor outside the cryostat at room temperature. The lowest temperature achieved up to now is 12 $\sim$ 15 mK for the long period operation and the loaded Q value at low temperature is 3.5 $\sim$ 4.5 $\times$ $10^4$ for the whole range of frequency tuning. Characteristics and the performance of the coupled-cavity system are presented and discussed with possible future improvements.

Microwave cavity

Rydberg atom

Resonant cavity

10.48550/arxiv.physics/0101028

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