Publications
152 results found
Abe K, Akutsu R, Ali A, et al., 2020, Search for electron antineutrino appearance in a long-baseline muon antineutrino beam, Physical Review Letters, Vol: 124, Pages: 161802-1-161802-8, ISSN: 0031-9007
Electron antineutrino appearance is measured by the T2K experiment in an accelerator-produced antineutrino beam, using additional neutrino beam operation to constrain parameters of the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix. T2K observes 15 candidate electron antineutrino events with a background expectation of 9.3 events. Including information from the kinematic distribution of observed events, the hypothesis of no electron antineutrino appearance is disfavored with a significance of 2.40σ and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows non-PMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.
Abe K, Akutsu R, Ali A, et al., 2020, Constraint on the matter-antimatter symmetry-violating phase in neutrino oscillations, Nature, Vol: 580, Pages: 339-344, ISSN: 0028-0836
The charge-conjugation and parity-reversal (CP) symmetry of fundamental particles is a symmetry between matter and antimatter. Violation of this CP symmetry was first observed in 19641, and CP violation in the weak interactions of quarks was soon established2. Sakharov proposed3 that CP violation is necessary to explain the observed imbalance of matter and antimatter abundance in the Universe. However, CP violation in quarks is too small to support this explanation. So far, CP violation has not been observed in non-quark elementary particle systems. It has been shown that CP violation in leptons could generate the matter–antimatter disparity through a process called leptogenesis4. Leptonic mixing, which appears in the standard model’s charged current interactions5,6, provides a potential source of CP violation through a complex phase δCP, which is required by some theoretical models of leptogenesis7,8,9. This CP violation can be measured in muon neutrino to electron neutrino oscillations and the corresponding antineutrino oscillations, which are experimentally accessible using accelerator-produced beams as established by the Tokai-to-Kamioka (T2K) and NOvA experiments10,11. Until now, the value of δCP has not been substantially constrained by neutrino oscillation experiments. Here we report a measurement using long-baseline neutrino and antineutrino oscillations observed by the T2K experiment that shows a large increase in the neutrino oscillation probability, excluding values of δCP that result in a large increase in the observed antineutrino oscillation probability at three standard deviations (3σ). The 3σ confidence interval for δCP, which is cyclic and repeats every 2π, is [−3.41, −0.03] for the so-called normal mass ordering and [−2.54, −0.32] for the inverted mass ordering. Our results indicate CP violation in leptons and our method enables sensitive searches for matter–antimatter
Abe K, Akutsu R, Ali A, et al., 2020, Measurement of the muon neutrino charged-current single pi(+) production on hydrocarbon using the T2K off-axis near detector ND280, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 101, ISSN: 1550-2368
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 5.56×1020 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 σ=(11.76±0.44(stat)±2.39(syst))×10−40 cm2 nucleon−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.
Abe K, Akutsu R, Ali A, et al., 2019, Measurement of neutrino and antineutrino neutral-current quasielasticlike interactions on oxygen by detecting nuclear deexcitation gamma rays, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, Pages: 1-19, ISSN: 1550-2368
Neutrino- and antineutrino-oxygen neutral-current quasielasticlike interactions are measured at Super-Kamiokande using nuclear deexcitation γ rays to identify signal-like interactions in data from a 14.94(16.35)×1020 protons-on-target exposure of the T2K neutrino (antineutrino) beam. The measured flux-averaged cross sections on oxygen nuclei are ⟨σν−NCQE⟩=1.70±0.17(stat.)+0.51−0.38(syst.)×10−38 cm2/oxygen with a flux-averaged energy of 0.82 GeV and ⟨σ¯ν−NCQE⟩=0.98±0.16(stat.)+0.26−0.19(syst.)×10−38 cm2/oxygen with a flux-averaged energy of 0.68 GeV, for neutrinos and antineutrinos, respectively. These results are the most precise to date, and the antineutrino result is the first cross section measurement of this channel. They are compared with various theoretical predictions. The impact on evaluation of backgrounds to searches for supernova relic neutrinos at present and future water Cherenkov detectors is also discussed.
Simpson C, Abe K, Bronner C, et al., 2019, Sensitivity of super-kamiokande with gadolinium to low energy antineutrinos from pre-supernova emission, The Astrophysical Journal: an international review of astronomy and astronomical physics, Vol: 885, Pages: 1-14, ISSN: 0004-637X
Supernova detection is a major objective of the Super-Kamiokande (SK) experiment. In the next stage of SK (SK-Gd), gadolinium (Gd) sulfate will be added to the detector, which will improve the ability of the detector to identify neutrons. A core-collapse supernova (CCSN) will be preceded by an increasing flux of neutrinos and antineutrinos, from thermal and weak nuclear processes in the star, over a timescale of hours; some of which may be detected at SK-Gd. This could provide an early warning of an imminent CCSN, hours earlier than the detection of the neutrinos from core collapse. Electron antineutrino detection will rely on inverse beta decay events below the usual analysis energy threshold of SK, so Gd loading is vital to reduce backgrounds while maximizing detection efficiency. Assuming normal neutrino mass ordering, more than 200 events could be detected in the final 12 hr before core collapse for a 15–25 solar mass star at around 200 pc, which is representative of the nearest red supergiant to Earth, α-Ori (Betelgeuse). At a statistical false alarm rate of 1 per century, detection could be up to 10 hr before core collapse, and a pre-supernova star could be detected by SK-Gd up to 600 pc away. A pre-supernova alert could be provided to the astrophysics community following gadolinium loading.
Abe K, Akutsu R, Ali A, et al., 2019, Search for heavy neutrinos with the T2K near detector ND280, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 100, ISSN: 1550-2368
This paper reports on the search for heavy neutrinos with masses in the range 140<MN<493 MeV/c2 using the off-axis near detector ND280 of the T2K experiment. These particles can be produced from kaon decays in the standard neutrino beam and then subsequently decay in ND280. The decay modes under consideration are N→ℓ±απ∓ and N→ℓ+αℓ−β(−)ν(α,β=e,μ). A search for such events has been made using the Time Projection Chambers of ND280, where the background has been reduced to less than two events in the current dataset in all channels. No excess has been observed in the signal region. A combined Bayesian statistical approach has been applied to extract upper limits on the mixing elements of heavy neutrinos to electron-, muon- and tau- flavored currents (U2e, U2μ, U2τ) as a function of the heavy neutrino mass, e.g., U2e<10−9 at 90% C.L. for a mass of 390 MeV/c2. These constraints are competitive with previous experiments.
Abe K, Akutsu R, Ali A, et al., 2019, Measurement of the muon neutrino charged-current cross sections on water, hydrocarbon and iron, and their ratios, with the T2K on-axis detectors, Progress of Theoretical and Experimental Physics, Vol: 2019, Pages: 1-30, ISSN: 0033-068X
We report a measurement of the flux-integrated νμ charged-current cross sections on water, hydrocarbon, and iron in the T2K on-axis neutrino beam with a mean neutrino energy of 1.5 GeV. The measured cross sections on water, hydrocarbon, and iron are σH2OCC=(0.840±0.010(stat.)+0.10−0.08(syst.))×10−38cm2/nucleon, σCHCC=(0.817±0.007(stat.)+0.11−0.08(syst.))×10−38cm2/nucleon, and σFeCC=(0.859±0.003(stat.)+0.12−0.10(syst.))×10−38cm2/nucleon, respectively, for a restricted phase space of induced muons: θμ<45∘ and pμ>0.4 GeV/c in the laboratory frame. The measured cross section ratios are σH2OCC/σCHCC=1.028±0.016(stat.)±0.053(syst.), σFeCC/σH2OCC=1.023±0.012(stat.)±0.058(syst.), and σFeCC/σCHCC=1.049±0.010(stat.)±0.043(syst.). These results, with an unprecedented precision for the measurements of neutrino cross sections on water in the studied energy region, show good agreement with the current neutrino interaction models used in the T2K oscillation analyses.
Abe K, Akutsu R, Ali A, et al., 2019, Search for neutral-current induced single photon production at the ND280 near detector in T2K, Journal of Physics G: Nuclear and Particle Physics, Vol: 46, ISSN: 0954-3899
Neutrino neutral-current (NC) induced single photon production is a sub-leading order process for accelerator-based neutrino beam experiments including T2K. It is, however, an important process to understand because it is a background for electron (anti)neutrino appearance oscillation experiments. Here, we performed the first search of this process below 1 GeV using the fine-grained detector at the T2K ND280 off-axis near detector. By reconstructing single photon kinematics from electron–positron pairs, we achieved 95% pure gamma ray sample from $5.738\times {10}^{20}$ protons-on-targets neutrino mode data. We do not find positive evidence of NC induced single photon production in this sample. We set the model-dependent upper limit on the cross-section for this process, at $0.114\times {10}^{-38}$ cm2 (90% C.L.) per nucleon, using the J-PARC off-axis neutrino beam with an average energy of $\left\langle {E}_{\nu }\right\rangle \sim 0.6$ GeV. This is the first limit on this process below 1 GeV which is important for current and future oscillation experiments looking for electron neutrino appearance oscillation signals.
Jiang M, Abe K, Bronner C, et al., 2019, Atmospheric neutrino oscillation analysis with improved event reconstruction in Super-Kamiokande IV, Progress of Theoretical and Experimental Physics, Vol: 2019, ISSN: 2050-3911
A new event reconstruction algorithm based on a maximum likelihood method has been developed for Super-Kamiokande. Its improved kinematic and particle identification capabilities enable the analysis of atmospheric neutrino data in a detector volume 32% larger than previous analyses and increase the sensitivity to the neutrino mass hierarchy. Analysis of a 253.9 kton⋅year exposure of the Super-Kamiokande IV atmospheric neutrino data has yielded a weak preference for the normal hierarchy, disfavoring the inverted hierarchy at 74% assuming oscillations at the best fit of the analysis.
Abe K, Akutsu R, Ali A, et al., 2019, Search for light sterile neutrinos with the T2K far detector Super-Kamiokande at a baseline of 295 km, Physical Review D: Particles, Fields, Gravitation and Cosmology, Vol: 99, ISSN: 1550-2368
We perform a search for light sterile neutrinos using the data from the T2K far detector at a baseline of 295 km, with an exposure of 14.7(7.6)×1020 protons on target in neutrino (antineutrino) mode. A selection of neutral-current interaction samples is also used to enhance the sensitivity to sterile mixing. No evidence of sterile neutrino mixing in the 3+1 model was found from a simultaneous fit to the charged-current muon, electron and neutral-current neutrino samples. We set the most stringent limit on the sterile oscillation amplitude sin2θ24 for the sterile neutrino mass splitting Δm241<3×10−3 eV2/c4.
Guerra ESP, Wilkinson C, Bhadra S, et al., 2019, Using world pi(+/-)-nucleus scattering data to constrain an intranuclear cascade model, Physical Review D, Vol: 99, ISSN: 2470-0010
The NEUT intranuclear cascade model is described and fit to a large body of π± -nucleus scattering data. Methods are developed to deal with deficiencies in the available historical data, and robust uncertainty estimates are produced. The results are compared to a variety of simulation packages and the data. This work provides a method for tuning final state interaction models, which are of particular interest to neutrino experiments that operate in the few-GeV energy region, and provides results which can be used directly by the T2K and Super-Kamiokande Collaborations, for whom NEUT is the primary simulation package.
Wan L, Abe K, Bronner C, et al., 2019, Measurement of the neutrino-oxygen neutral-current quasielastic cross section using atmospheric neutrinos at Super-Kamiokande, Physical Review D, Vol: 99, ISSN: 2470-0010
Neutral current (NC) interactions of atmospheric neutrinos on oxygen form one of the major backgrounds in the search for supernova relic neutrinos with water-based Cherenkov detectors. The NC channel is dominated by neutrino quasielastic (NCQE) scattering off nucleons inside 16O nuclei. In this paper we report the first measurement of NCQE cross section using atmospheric neutrinos at Super-Kamiokande (SK). The measurement used 2,778 live days of SK-IV data with a fiducial volume of 22.5 kiloton water. Within the visible energy window of 7.5–29.5 MeV, we observed 117 events compared to the expected 71.9 NCQE signal and 53.1 background events. Weighted by the atmospheric neutrino spectrum from 160 MeV to 10 GeV, the flux averaged NCQE cross section is measured to be (1.01±0.17(stat.)+0.78−0.30(sys.))×10−38 cm2.
Abe K, Akutsu R, Amey J, et al., 2018, Search for CP violation in neutrino and antineutrino oscillations by the T2K experiment with 2.2 x 10(21) protons on target, Physical Review Letters, Vol: 121, ISSN: 0031-9007
The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in accelerator-produced neutrino and antineutrino beams. With an exposure of 14.7(7.6)×1020 protons on target in the neutrino (antineutrino) mode, 89 νe candidates and seven anti-νe candidates are observed, while 67.5 and 9.0 are expected for δCP=0 and normal mass ordering. The obtained 2σconfidence interval for the CP-violating phase, δCP, does not include the CP-conserving cases (δCP=0, π). The best-fit values of other parameters are sin2θ23=0.526+0.032−0.036 and Δm232=2.463+0.071−0.070×10−3 eV2/c4.
Li Z, Abe K, Bronner C, et al., 2018, Measurement of the tau neutrino cross section in atmospheric neutrino oscillations with Super-Kamiokande, PHYSICAL REVIEW D, Vol: 98, ISSN: 2470-0010
Using 5326 days of atmospheric neutrino data, a search for atmospheric tau neutrino appearance has been performed in the Super-Kamiokande experiment. Super-Kamiokande measures the tau normalization to be 1.47±0.32 under the assumption of normal neutrino hierarchy, relative to the expectation of unity with neutrino oscillation. The result excludes the hypothesis of no-tau appearance with a significance level of 4.6σ. The inclusive charged-current tau neutrino cross section averaged by the tau neutrino flux at Super-Kamiokande is measured to be (0.94±0.20)×10−38 cm2. The measurement is consistent with the Standard Model prediction, agreeing to within 1.5σ.
Abe K, Amey J, Andreopoulos C, et al., 2018, Characterization of nuclear effects in muon-neutrino scattering on hydrocarbon with a measurement of final-state kinematics and correlations in charged-current pionless interactions at T2K, PHYSICAL REVIEW D, Vol: 98, ISSN: 2470-0010
This paper reports measurements of final-state proton multiplicity, muon and proton kinematics, and their correlations in charged-current pionless neutrino interactions, measured by the T2K ND280 near detector in its plastic scintillator (C8H8) target. The data were taken between years 2010 and 2013, corresponding to approximately 6×1020 protons on target. Thanks to their exploration of the proton kinematics and of imbalances between the proton and muon kinematics, the results offer a novel probe of the nuclear-medium effects most pertinent to the (sub-)GeV neutrino-nucleus interactions that are used in accelerator-based long-baseline neutrino oscillation measurements. These results are compared to many neutrino-nucleus interaction models which all fail to describe at least part of the observed phase space. In case of events without a proton above a detection threshold in the final state, a fully consistent implementation of the local Fermi gas model with multinucleon interactions gives the best description of the data. In the case of at least one proton in the final state, the spectral function model agrees well with the data, most notably when measuring the kinematic imbalance between the muon and the proton in the plane transverse to the incoming neutrino. Within the models considered, only the existence of multinucleon interactions are able to describe the extracted cross section within regions of high transverse kinematic imbalance. The effect of final-state interactions is also discussed.
Tanabashi M, Grp PD, Hagiwara K, et al., 2018, Review of Particle Physics, Physical Review D, Vol: 98, ISSN: 2470-0010
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,873new measurements from 758 papers, we list, evaluate, and average measured properties of gauge bosons and therecently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypotheticalparticles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and searchlimits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as HiggsBoson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology,Particle Detectors, Colliders, Probability and Statistics. Among the 118 reviews are many that are new or heavilyrevised, including a new review on Neutrinos in Cosmology.Starting with this edition, the Review is divided into two volumes. Volume 1 includes the Summary Tablesand all review articles. Volume 2 consists of the Particle Listings. Review articles that were previously part of theListings are now included in volume 1.The complete Review (both volumes) is published online on the website of the Particle Data Group(http://pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Bookletwith the Summary Tables and essential tables, figures, and equations from selected review articles is also available.
Abe K, Amey J, Andreopoulos C, et al., 2018, Measurement of inclusive double-differential nu(mu) charged-current cross section with improved acceptance in the T2K off-axis near detector, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 98, ISSN: 1550-2368
We report a measurement of the flux-integrated cross section for inclusive muon neutrino charged-current interactions on carbon. The double-differential measurements are given as a function of the muon momentum and angle. Relative to our previous publication on this topic, these results have an increased angular acceptance and higher statistics. The data sample presented here corresponds to 5.7×1020 protons on target. The total flux-integrated cross section is measured to be (6.950±0.662)×10−39 cm2 nucleon−1 and is consistent with our simulation.
Abe K, Abe K, Ahn SH, et al., 2018, Physics potentials with the second Hyper-Kamiokande detector in Korea, Progress of Theoretical and Experimental Physics, Vol: 2018, ISSN: 2050-3911
Hyper-Kamiokande consists of two identical water-Cherenkov detectors of total 520 kt, with the first one in Japan at 295 km from the J-PARC neutrino beam with 2.5∘ off-axis angles (OAAs), and the second one possibly in Korea at a later stage. Having the second detector in Korea would benefit almost all areas of neutrino oscillation physics, mainly due to longer baselines. There are several candidate sites in Korea with baselines of 1000–1300 km and OAAs of 1∘–3∘.We conducted sensitivity studies on neutrino oscillation physics for a second detector, either in Japan (JD ×2) or Korea (JD + KD), and compared the results with a single detector in Japan. Leptonic charge–parity (CP) symmetry violation sensitivity is improved, especially when the CP is non-maximally violated. The larger matter effect at Korean candidate sites significantly enhances sensitivities to non-standard interactions of neutrinos and mass ordering determination. Current studies indicate the best sensitivity is obtained at Mt. Bisul (1088 km baseline, 1.3∘ OAA). Thanks to a larger (1000 m) overburden than the first detector site, clear improvements to sensitivities for solar and supernova relic neutrino searches are expected.
Kachulis C, Abe K, Bronner C, et al., 2018, Search for boosted dark matter interacting with electrons in super-Kamiokande, Physical Review Letters, Vol: 120, ISSN: 0031-9007
A search for boosted dark matter using 161.9 kt yr of Super-Kamiokande IV data is presented. We search for an excess of elastically scattered electrons above the atmospheric neutrino background, with a visible energy between 100 MeV and 1 TeV, pointing back to the Galactic center or the Sun. No such excess is observed. Limits on boosted dark matter event rates in multiple angular cones around the Galactic center and Sun are calculated. Limits are also calculated for a baseline model of boosted dark matter produced from cold dark matter annihilation or decay. This is the first experimental search for boosted dark matter from the Galactic center or the Sun interacting in a terrestrial detector.
Abe K, Bronner C, Hayato Y, et al., 2018, Search for Neutrinos in Super-Kamiokande Associated with the GW170817 Neutron-star Merger, ASTROPHYSICAL JOURNAL LETTERS, Vol: 857, ISSN: 2041-8205
We report the results of a neutrino search in Super-Kamiokande (SK) for coincident signals with the first detected gravitational wave (GW) produced by a binary neutron-star merger, GW170817, which was followed by a short gamma-ray burst, GRB170817A, and a kilonova/macronova. We searched for coincident neutrino events in the range from 3.5 MeV to ~100 PeV, in a time window ±500 s around the gravitational wave detection time, as well as during a 14-day period after the detection. No significant neutrino signal was observed for either time window. We calculated 90% confidence level upper limits on the neutrino fluence for GW170817. From the upward-going-muon events in the energy region above 1.6 GeV, the neutrino fluence limit is ${16.0}_{-0.6}^{+0.7}$ (${21.3}_{-0.8}^{+1.1}$) cm−2 for muon neutrinos (muon antineutrinos), with an error range of ±5° around the zenith angle of NGC4993, and the energy spectrum is under the assumption of an index of −2. The fluence limit for neutrino energies less than 100 MeV, for which the emission mechanism would be different than for higher-energy neutrinos, is also calculated. It is 6.6 × 107 cm−2 for anti-electron neutrinos under the assumption of a Fermi–Dirac spectrum with average energy of 20 MeV.
Aguilar-Arevalo AA, Brown BC, Bugel L, et al., 2018, First Measurement of Monoenergetic Muon Neutrino Charged Current Interactions, PHYSICAL REVIEW LETTERS, Vol: 120, ISSN: 0031-9007
We report the first measurement of monoenergetic muon neutrino charged current interactions. MiniBooNE has isolated 236 MeV muon neutrino events originating from charged kaon decay at rest (K+→μ+νμ) at the NuMI beamline absorber. These signal νμ-carbon events are distinguished from primarily pion decay in flight νμ and ¯νμ backgrounds produced at the target station and decay pipe using their arrival time and reconstructed muon energy. The significance of the signal observation is at the 3.9σ level. The muon kinetic energy, neutrino-nucleus energy transfer (ω=Eν−Eμ), and total cross section for these events are extracted. This result is the first known-energy, weak-interaction-only probe of the nucleus to yield a measurement of ω using neutrinos, a quantity thus far only accessible through electron scattering.
Abe K, Bronner C, Haga Y, et al., 2018, Atmospheric neutrino oscillation analysis with external constraints in Super-Kamiokande I-IV, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 97, ISSN: 1550-2368
An analysis of atmospheric neutrino data from all four run periods of Super-Kamiokande optimized for sensitivity to the neutrino mass hierarchy is presented. Confidence intervals for Δm232, sin2θ23, sin2θ13and δCP are presented for normal neutrino mass hierarchy and inverted neutrino mass hierarchy hypotheses, based on atmospheric neutrino data alone. Additional constraints from reactor data on θ13and from published binned T2K data on muon neutrino disappearance and electron neutrino appearance are added to the atmospheric neutrino fit to give enhanced constraints on the above parameters. Over the range of parameters allowed at 90% confidence level, the normal mass hierarchy is favored by between 91.9% and 94.5% based on the combined Super-Kamiokande plus T2K result.
Abe K, Amey J, Andreopoulos C, et al., 2018, Measurement of the single pi(0) production rate in neutral current neutrino interactions on water, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 97, ISSN: 1550-2368
The single π0 production rate in neutral current neutrino interactions on water in a neutrino beam with a peak neutrino energy of 0.6 GeV has been measured using the PØD, one of the subdetectors of the T2K near detector. The production rate was measured for data taking periods when the PØD contained water (2.64 × 1020 protons-on-target) and also periods without water (3.49 × 1020 protons-on-target). A measurement of the neutral current single π0 production rate on water is made using appropriate subtraction of the production rate with water in from the rate with water out of the target region. The subtraction analysis yields 106 ± 41 ± 69 signal events where the uncertainties are statistical (stat.) and systematic (sys.) respectively. This is consistent with the prediction of 157 events from the nominal simulation. The measured to expected ratio is 0.68 ± 0.26 (stat) ± 0.44 (sys) ± 0.12 (flux). The nominal simulation uses a flux integrated cross section of 7.63 × 10−39cm2 per nucleon with an average neutrino interaction energy of 1.3 GeV.
Abe K, Amey J, Andreopoulos C, et al., 2018, First measurement of the nu(mu) charged-current cross section on a water target without pions in the final state, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 97, ISSN: 1550-2368
This paper reports the first differential measurement of the charged-current interaction cross section of νμ on water with no pions in the final state. This flux-averaged measurement has been made using the T2K experiment’s off-axis near detector, and is reported in doubly differential bins of muon momentum and angle. The flux-averaged total cross section in a restricted region of phase space was found to be σ = (0.95 ± 0.08 (stat) ± 0.06 (det syst) ± 0.04 (model syst) ± 0.08 (flux)) × 10 − 38cm2/n.
Abe K, Bronner C, Pronost G, et al., 2017, Search for an Excess of Events in the Super-Kamiokande Detector in the Directions of the Astrophysical Neutrinos Reported by the IceCube Collaboration, Astrophysical Journal, Vol: 850, ISSN: 0004-637X
We present the results of a search in the Super-Kamiokande (SK) detector for excesses of neutrinos with energies above a few GeV that are in the direction of the track events reported in IceCube. Data from all SK phases (SK-I through SK-IV) were used, spanning a period from 1996 April to 2016 April and corresponding to an exposure of 225 kiloton-years. We considered the 14 IceCube track events from a data set with 1347 livetime days taken from 2010 to 2014. We use Poisson counting to determine if there is an excess of neutrinos detected in SK in a 10° search cone (5° for the highest energy data set) around the reconstructed direction of the IceCube event. No significant excess was found in any of the search directions we examined. We also looked for coincidences with a recently reported IceCube multiplet event. No events were detected within a ±500 s time window around the first detected event, and no significant excess was seen from that direction over the lifetime of SK.
Abe K, Amey J, Andreopoulos C, et al., 2017, Measurement of neutrino and antineutrino oscillations by the T2K experiment including a new additional sample of nu(e) interactions at the far detector, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 96, ISSN: 1550-2368
The T2K experiment reports an updated analysis of neutrino and antineutrino oscillations in appearanceand disappearance channels. A sample of electron neutrino candidates at Super-Kamiokande in which a piondecay 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 oscillationparameters, jΔm232j, sin2 θ23, sin2 θ13, and δCP and of the mass ordering are made. A set of studies ofsimulated data indicates that the sensitivity to the oscillation parameters is not limited by neutrino interactionmodel uncertainty. Multiple oscillation analyses are performed, and frequentist and Bayesian intervals arepresented for combinations of the oscillation parameters with and without the inclusion of reactor constraintson sin2 θ13. When combined with reactor measurements, the hypothesis of CP conservation (δCP ¼ 0 or π) isexcluded at 90% confidence level. The 90% confidence region for δCP is½−2.95;−0.44 (½−1.47;−1.27) fornormal (inverted) ordering. The central values and 68% confidence intervals for the other oscillationparameters for normal (inverted) ordering are Δm232 ¼ 2.54 0.08ð2.51 0.08Þ × 10−3 eV2=c4 andsin2θ23 ¼ 0.55þ0.05 −0.09 (0.55þ0.05 −0.08 ), compatible with maximal mixing. In the Bayesian analysis, the dataweakly prefer normal ordering (Bayes factor 3.7) and the upper octant for sin2 θ23 (Bayes factor 2.4).
Abe K, Amey J, Andreopoulos C, et al., 2017, Measurement of (nu)over-bar(mu) and nu(mu) charged current inclusive cross sections and their ratio with the T2K off-axis near detector, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 96, ISSN: 1550-2368
We report a measurement of cross section σðνμ þ nucleus → μ− þ XÞ and the first measurements of thecross section σðν¯μ þ nucleus → μþ þ XÞ and their ratio Rðσðν¯ÞσðνÞÞ at (anti) neutrino energies below 1.5 GeV.We determine the single momentum bin cross section measurements, averaged over the T2K ν¯=ν-flux, forthe detector target material (mainly carbon, oxygen, hydrogen and copper) with phase space restrictedlaboratory frame kinematics of θμ < 32° and pμ > 500 MeV=c. The results are σðν¯Þ ¼ð0.900 0.029ðstatÞ 0.088ðsystÞÞ × 10−39 and σðνÞ¼ð2.41 0.022ðstatÞ 0.231ðsystÞÞ × 10−39 inunits of cm2=nucleon and Rðσðν¯ÞσðνÞÞ ¼ 0.373 0.012ðstatÞ 0.015ðsystÞ.
Abe K, Amey J, Andreopoulos C, et al., 2017, Updated T2K measurements of muon neutrino and antineutrino disappearance using 1.5 x 10(21) protons on target, PHYSICAL REVIEW D, Vol: 96, ISSN: 2470-0010
We report measurements by the T2K experiment of the parameters θ23 and Δm232 governing the disappearance of muon neutrinos and antineutrinos in the three-flavor neutrino oscillation model. Utilizing the ability of the experiment to run with either a mainly neutrino or a mainly antineutrino beam, the parameters are measured separately for neutrinos and antineutrinos. Using 7.482×1020 POT in neutrino running mode and 7.471×1020 POT in antineutrino mode, T2K obtained sin2(θ23)=0.51+0.08−0.07and Δm232=2.53+0.15−0.13×10−3 eV2/c4 for neutrinos, and sin2(¯θ23)=0.42+0.25−0.07 and Δ¯m232=2.55+0.33−0.27×10−3 eV2/c4 for antineutrinos (assuming normal mass ordering). No significant differences between the values of the parameters describing the disappearance of muon neutrinos and antineutrinos were observed.
Abe K, Bronner C, Pronost G, et al., 2017, Search for nucleon decay into charged antilepton plus meson in 0.316 megaton . years exposure of the Super-Kamiokande water Cherenkov detector, Physical Review D - Particles, Fields, Gravitation and Cosmology, Vol: 96, ISSN: 1550-2368
We have searched for proton decays into a charged antilepton (e+, μ+) plus a meson (η, ρ0, ω) and for neutron decays into a charged antilepton (e+, μ+) plus a meson (π−, ρ−) using Super-Kamiokande I-IV data, corresponding to 0.316 megaton⋅years of exposure. This measurement updates the previous published result by using 2.26 times more data and improved analysis methods. No significant evidence for nucleon decay is observed and lower limits on the partial lifetime of the nucleon are obtained. The limits range from 3×1031 to 1×1034 years at 90% confidence level, depending on the decay mode.
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