K. Abe, J. Adam, H. Aihara, 23 C. Andreopoulos, 27 S. Aoki, A. Ariga, S. Assylbekov, D. Autiero, M. Barbi, G.J. Barker, G. Barr, P. Bartet-Friburg, M. Bass, M. Batkiewicz, F. Bay, V. Berardi, B.E. Berger, 23 S. Berkman, S. Bhadra, F.d.M. Blaszczyk, A. Blondel, S. Bolognesi, S. Bordoni, S.B. Boyd, D. Brailsford, A. Bravar, C. Bronner, N. Buchanan, R.G. Calland, J. Caravaca Rodŕıguez, S.L. Cartwright, R. Castillo, M.G. Catanesi, A. Cervera, D. Cherdack, N. Chikuma, G. Christodoulou, A. Clifton, J. Coleman, S.J. Coleman, G. Collazuol, K. Connolly, L. Cremonesi, A. Dabrowska, I. Danko, R. Das, S. Davis, P. de Perio, G. De Rosa, T. Dealtry, 36 S.R. Dennis, 45 C. Densham, D. Dewhurst, F. Di Lodovico, S. Di Luise, S. Dolan, O. Drapier, K. Duffy, J. Dumarchez, S. Dytman, M. Dziewiecki, S. Emery-Schrenk, A. Ereditato, L. Escudero, C. Ferchichi, T. Feusels, A.J. Finch, G.A. Fiorentini, M. Friend, ∗ Y. Fujii, ∗ Y. Fukuda, A.P. Furmanski, V. Galymov, A. Garcia, S. Giffin, C. Giganti, K. Gilje, D. Goeldi, T. Golan, M. Gonin, N. Grant, D. Gudin, D.R. Hadley, L. Haegel, A. Haesler, M.D. Haigh, P. Hamilton, D. Hansen, T. Hara, M. Hartz, 51 T. Hasegawa, ∗ N.C. Hastings, T. Hayashino, Y. Hayato, 23 C. Hearty, † R.L. Helmer, M. Hierholzer, J. Hignight, A. Hillairet, A. Himmel, T. Hiraki, S. Hirota, J. Holeczek, S. Horikawa, F. Hosomi, K. Huang, A.K. Ichikawa, K. Ieki, M. Ieva, M. Ikeda, J. Imber, J. Insler, T.J. Irvine, T. Ishida, ∗ T. Ishii, ∗ E. Iwai, K. Iwamoto, K. Iyogi, A. Izmaylov, 22 A. Jacob, B. Jamieson, M. Jiang, S. Johnson, J.H. Jo, P. Jonsson, C.K. Jung, ‡ M. Kabirnezhad, A.C. Kaboth, T. Kajita, ‡ H. Kakuno, J. Kameda, Y. Kanazawa, D. Karlen, 51 I. Karpikov, T. Katori, E. Kearns, 23, ‡ M. Khabibullin, A. Khotjantsev, D. Kielczewska, T. Kikawa, A. Kilinski, J. Kim, S. King, J. Kisiel, P. Kitching, T. Kobayashi, ∗ L. Koch, T. Koga, A. Kolaceke, A. Konaka, A. Kopylov, L.L. Kormos, A. Korzenev, Y. Koshio, ‡ W. Kropp, H. Kubo, Y. Kudenko, § R. Kurjata, T. Kutter, J. Lagoda, I. Lamont, E. Larkin, M. Laveder, M. Lawe, M. Lazos, T. Lindner, C. Lister, R.P. Litchfield, A. Longhin, J.P. Lopez, L. Ludovici, L. Magaletti, K. Mahn, M. Malek, S. Manly, A.D. Marino, J. Marteau, J.F. Martin, P. Martins, S. Martynenko, T. Maruyama, ∗ V. Matveev, K. Mavrokoridis, E. Mazzucato, M. McCarthy, N. McCauley, K.S. McFarland, C. McGrew, A. Mefodiev, C. Metelko, M. Mezzetto, P. Mijakowski, C.A. Miller, A. Minamino, O. Mineev, A. Missert, M. Miura, ‡ S. Moriyama, ‡ Th.A. Mueller, A. Murakami, M. Murdoch, S. Murphy, J. Myslik, T. Nakadaira, ∗ M. Nakahata, 23 K.G. Nakamura, K. Nakamura, 14, ∗ S. Nakayama, ‡ T. Nakaya, 23 K. Nakayoshi, ∗ C. Nantais, C. Nielsen, M. Nirkko, K. Nishikawa, ∗ Y. Nishimura, J. Nowak, H.M. O’Keeffe, R. Ohta, ∗ K. Okumura, 23 T. Okusawa, W. Oryszczak, S.M. Oser, T. Ovsyannikova, R.A. Owen, Y. Oyama, ∗ V. Palladino, J.L. Palomino, V. Paolone, D. Payne, O. Perevozchikov, J.D. Perkin, Y. Petrov, L. Pickard, E.S. Pinzon Guerra, C. Pistillo, P. Plonski, E. Poplawska, B. Popov, ¶ M. Posiadala-Zezula, J.-M. Poutissou, R. Poutissou, P. Przewlocki, B. Quilain, E. Radicioni, P.N. Ratoff, M. Ravonel, M.A.M. Rayner, A. Redij, M. Reeves, E. Reinherz-Aronis, C. Riccio, P.A. Rodrigues, P. Rojas, E. Rondio, S. Roth, A. Rubbia, D. Ruterbories, A. Rychter, R. Sacco, K. Sakashita, ∗ F. Sánchez, F. Sato, E. Scantamburlo, K. Scholberg, ‡ S. Schoppmann, J. Schwehr, M. Scott, Y. Seiya, T. Sekiguchi, ∗ H. Sekiya, 23, ‡ D. Sgalaberna, R. Shah, 36 F. Shaker, D. Shaw, M. Shiozawa, 23 S. Short, Y. Shustrov, P. Sinclair, B. Smith, M. Smy, J.T. Sobczyk, H. Sobel, 23 M. Sorel, L. Southwell, P. Stamoulis, J. Steinmann, B. Still, Y. Suda, A. Suzuki, K. Suzuki, S.Y. Suzuki, ∗ Y. Suzuki, 23 R. Tacik, 51 M. Tada, ∗ S. Takahashi, A. Takeda, Y. Takeuchi, 23 H.K. Tanaka, ‡ H.A. Tanaka, † M.M. Tanaka, ∗ D. Terhorst, R. Terri, L.F. Thompson, A. Thorley, S. Tobayama, W. Toki, T. Tomura, Y. Totsuka,∗∗ C. Touramanis, T. Tsukamoto, ∗ M. Tzanov, Y. Uchida, A. Vacheret, M. Vagins, 5 G. Vasseur, T. Wachala, K. Wakamatsu, C.W. Walter, ‡ D. Wark, 36 W. Warzycha, M.O. Wascko, A. Weber, 36 R. Wendell, ‡ R.J. Wilkes, M.J. Wilking, C. Wilkinson, Z. Williamson, J.R. Wilson, R.J. Wilson, T. Wongjirad, Y. Yamada, ∗ K. Yamamoto, C. Yanagisawa, †† T. Yano, S. Yen, N. Yershov, M. Yokoyama, ‡ J. Yoo, K. Yoshida, T. Yuan, M. Yu, A. Zalewska, J. Zalipska, L. Zambelli, ∗ K. Zaremba, M. Ziembicki, E.D. Zimmerman, M. Zito, and J. Żmuda

The T2K off-axis near detector, ND280, is used to make the first differential cross section measurements of muon neutrino charged current single positive pion production on a water target at energies similar to 0.8 GeV. The differential measurements are presented as a function of the muon and pion kinematics, in the restricted phase space defined by p(pi+) > 200 MeV/c, p(mu) > 200 MeV/c, cos(theta(pi+)) > 0.3 and cos(theta(mu)) > 0.3. The total flux integrated nu(mu) charged current single positive pion production cross section on water in the restricted phase space is measured to be (phi) = 4.25 +/- 0.48(stat) +/- 1.56(syst) x 10(-40) cm(2)/nucleon. The total cross section is consistent with the NEUT prediction (5.03 x 10(-40) cm(2)/nucleon) and 2 sigma lower than the GENIE prediction (7.68 x 10(-40) cm(2)/nucleon). The differential cross sections are in good agreement with the NEUT generator. The GENIE simulation reproduces well the shapes of the distributions, but overestimates the overall cross section normalization.

We report a measurement of the nu(mu)-nucleus inclusive charged-current cross section (= sigma(cc)) on iron using data from the INGRID detector exposed to the J-PARC neutrino beam. The detector consists of 14 modules in total, which are spread over a range of off-axis angles from 0 degrees to 1.1 degrees. The variation in the neutrino energy spectrum as a function of the off-axis angle, combined with event topology information, is used to calculate this cross section as a function of neutrino energy. The cross section is measured to be sigma(cc) (1.1 GeV) = 1.10 +/- 0.15 (10(-38) cm(2)/nucleon), sigma(cc) (2.0 GeV) = 2.07 +/- 0.27 (10(-38) cm(2)/nucleon), and sigma(cc) (3.3 GeV) = 2.29 +/- 0.45 (10(-38) cm(2)/nucleon), at energies of 1.1, 2.0, and 3.3 GeV, respectively. These results are consistent with the cross section calculated by the neutrino interaction generators currently used by T2K. More importantly, the method described here opens up a new way to determine the energy dependence of neutrino-nucleus cross sections.

We thank the J-PARC staff for superb accelerator performance and the CERN NA61 collaboration for providing valuable particle production data. We acknowledge the support of MEXT, Japan; NSERC, NRC and CFI, Canada; CEA and CNRS/IN2P3, France; DFG, Germany; INFN, Italy; National Science Centre (NCN), Poland; RSF, RFBR and MES, Russia; MINECO and ERDF funds, Spain; SNSF and SER, Switzerland; STFC, UK; and DOE, USA. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET4, the WestGrid and SciNet consortia in Compute Canada, GridPP, UK. In addition participation of individual researchers and institutions has been further supported by funds from: ERC (FP7), EU; JSPS, Japan; Royal Society, UK; DOE Early Career program, USA.

The T2K experiment has performed a search for $\nu_e$ disappearance due to sterile neutrinos using $5.9 \times 10^{20}$ protons on target for a baseline of $280 m$ in a neutrino beam peaked at about $500 MeV$. A sample of \nu_e CC interactions in the off-axis near detector has been selected with a purity of 63\% and an efficiency of 26\%. The p-value for the null hypothesis is 0.085 and the excluded region at 95\% CL is approximately $sin^2 2 \theta_{ee}>0.3$ for $\Delta m^2_{eff}>7 eV^2 / c^4$.

We report a measurement of the $\nu_\mu$ charged current quasi-elastic cross-sections on carbon in the T2K on-axis neutrino beam. The measured charged current quasi-elastic cross-sections on carbon at mean neutrino energies of 1.94 GeV and 0.93 GeV are $(11.95\pm 0.19(stat.)_{-1.47}^{+1.82} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$ and $(10.64\pm 0.37(stat.)_{-1.65}^{+2.03} (syst.))\times 10^{-39}\mathrm{cm}^2/\mathrm{neutron}$, respectively. These results agree well with the predictions of neutrino interaction models. In addition, we investigated the effects of the nuclear model and the multi-nucleon interaction.

This paper reports a measurement by the T2K experiment of the nu(mu) charged current quasielastic (CCQE) cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum (rho(mu)) and angle with respect to the incident neutrino beam (theta(mu)). The flux-integrated CCQE cross section was measured to be = (0.83 +/- 0.12) x 10(-38) cm(2). The energy dependence of the CCQE cross section is also reported. The axial mass, M-A(QE), of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) rho(mu)-cos theta(mu) distribution, the effective M-A(QE) parameter was measured to be 1.26(-0.18)(+0.21) GeV/c(2) (1.43(-0.22)(+0.28) GeV/c(2)).

We report on measurements of neutrino oscillation using data from the T2K long-baseline neutrino experiment collected between 2010 and 2013. In an analysis of muon neutrino disappearance alone, we find the following estimates and 68% confidence intervals for the two possible mass hierarchies: Normal Hierarchy: $\sin^2\theta_{23}=0.514^{+0.055}_{-0.056}$ and $\Delta m^2_{32}=(2.51\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ Inverted Hierarchy: $\sin^2\theta_{23}=0.511\pm0.055$ and $\Delta m^2_{13}=(2.48\pm0.10)\times 10^{-3}$ eV$^2$/c$^4$ The analysis accounts for multi-nucleon mechanisms in neutrino interactions which were found to introduce negligible bias. We describe our first analyses that combine measurements of muon neutrino disappearance and electron neutrino appearance to estimate four oscillation parameters and the mass hierarchy. Frequentist and Bayesian intervals are presented for combinations of these parameters, with and without including recent reactor measurements. At 90% confidence level and including reactor measurements, we exclude the region: $\delta_{CP}=[0.15,0.83]\pi$ for normal hierarchy and $\delta_{CP}=[-0.08,1.09]\pi$ for inverted hierarchy. The T2K and reactor data weakly favor the normal hierarchy with a Bayes Factor of 2.2. The most probable values and 68% 1D credible intervals for the other oscillation parameters, when reactor data are included, are: $\sin^2\theta_{23}=0.528^{+0.055}_{-0.038}$ and $|\Delta m^2_{32}|=(2.51\pm0.11)\times 10^{-3}$ eV$^2$/c$^4$.

The observation of the recent electron neutrino appearance in a muon neutrino beam and the high-precision measurement of the mixing angle theta(13) have led to a re-evaluation of the physics potential of the T2K long-baseline neutrino oscillation experiment. Sensitivities are explored for CP violation in neutrinos, non-maximal sin(2) 2 theta(23), the octant of theta(23), and the mass hierarchy, in addition to the measurements of delta CP, sin(2) theta(23), and Delta m(32)(2), for various combinations of nu-mode and (nu) over bar -mode data-taking.With an exposure of 7.8 x 10(21) protons-on-target, T2K can achieve 1 sigma resolution of 0.050 (0.054) on sin(2) theta(23) and 0.040 (0.045) x 10(-3) eV(2) on Delta m(32)(2) for 100% (50%) neutrino beam mode running assuming sin(2) theta(23) = 0.5 and Delta m(32)(2) = 2.4 x 10(-3) eV(2). T2K will have sensitivity to the CP-violating phase delta(CP) at 90% C.L. or better over a significant range. For example, if sin(2) 2 theta(23) is maximal (i.e.theta(23) = 45 degrees) the range is -115 degrees < delta(CP) < -60 degrees for normal hierarchy and +50 degrees < delta(CP) < + 130 degrees for inverted hierarchy. When T2K data is combined with data from the NO nu A experiment, the region of oscillation parameter space where there is sensitivity to observe a non-zero delta CP is substantially increased compared to if each experiment is analyzed alone.

This paper presents a measurement of the charged current interaction rate of the electron neutrino beam component of the beam above $1.5$~GeV using the large fiducial mass of the T2K $\pi^0$ detector. The predominant poriton of the $\nu_e$ flux ($\sim$85 %) at these energies comes from kaon decays. The measured ratio of the observed beam interaction rate to the predicted rate in the detector with water targets filled is 0.89 $\pm$ 0.08 (stat.) $\pm$ 0.11 (sys.), and with the water targets emptied is 0.90 $\pm$ 0.09 (stat.) $\pm$ 0.13 (sys.). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 $\pm$ 0.33 (stat.) $\pm$ 0.21 (sys.). This is the first measurement of the interaction rate of electron neutrinos on water, which is particularly of interest to experiments with water Cherenkov detectors.

The T2K Collaboration K. Abe1, J. Adam2, H. Aihara3,4, T. Akiri5, C. Andreopoulos6, S. Aoki7, A. Ariga8, S. Assylbekov9, D. Autiero10, M. Barbi11, G.J. Barker12, G. Barr13, P. Bartet-Friburg14, M. Bass9, M. Batkiewicz15, F. Bay16, V. Berardi17, B.E. Berger4,9, S. Berkman18, S. Bhadra19, F.d.M. Blaszczyk20, A. Blondel21, C. Bojechko22, S. Bordoni23, S.B. Boyd12, D. Brailsford24, A. Bravar21, C. Bronner4, N. Buchanan9, R.G. Calland25, J. Caravaca Rodrı́guez23, S.L. Cartwright26, R. Castillo23, M.G. Catanesi17, A. Cervera27, D. Cherdack9, G. Christodoulou25, A. Clifton9, J. Coleman25, S.J. Coleman28, G. Collazuol29, K. Connolly30, L. Cremonesi31, A. Dabrowska15, I. Danko32, R. Das9, S. Davis30, P. de Perio33, G. De Rosa34, T. Dealtry6,13, S.R. Dennis6,12, C. Densham6, D. Dewhurst13, F. Di Lodovico31, S. Di Luise16,

The Charged-Current Quasi-Elastic (CCQE) interaction, ν_l + n → l^- + p, is the dominant CC process at E_ν∼ 1 GeV and contributes to the signal in accelerator-based long-baseline neutrino oscillation experiments operating at intermediate neutrino energies. This paper reports a measurement by the T2K experiment of the ν_μ CCQE cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum (p_μ) and angle with respect to the incident neutrino beam (θ_μ). The flux-integrated CCQE cross section was measured to be (0.83 ± 0.12) × 10^-38 cm^2 in good agreement with NEUT MC value of 0.88 × 10^-38 cm^2. The energy dependence of the CCQE cross section is also reported. The axial mass, M_A^QE, of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shape-only) p_μcosθ_μ distribution, the effective M_A^QE parameter was measured to be 1.26^+0.21_-0.18 GeV/c^2 (1.43^+0.28_-0.22 GeV/c^2).

The Charged-Current Quasi-Elastic (CCQE) interaction, νl + n → l − + p, is the dominant CC process at Eν ∼ 1 GeV and contributes to the signal in accelerator-based long-baseline neutrino oscillation experiments operating at intermediate neutrino energies. This paper reports a measurement by the T2K experiment of the νμ CCQE cross section on a carbon target with the off-axis detector based on the observed distribution of muon momentum (pμ) and angle with respect to the incident neutrino beam (θμ). The flux-integrated CCQE cross section was measured to be 〈σ〉 = (0.83 ± 0.12) × 10−38 cm2. The energy dependence of the CCQE cross section is also reported. The axial mass, M A , of the dipole axial form factor was extracted assuming the Smith-Moniz CCQE model with a relativistic Fermi gas nuclear model. Using the absolute (shapeonly) pμ-cosθμ distribution, the effective M QE A parameter was measured to be 1.26 +0.21 −0.18 GeV/c 2 (1.43 −0.22 GeV/c 2). PACS numbers: 13.15.+g ∗ also at J-PARC, Tokai, Japan † also at Institute of Particle Physics, Canada ‡ affiliated member at Kavli IPMU (WPI), the University of Tokyo, Japan § also at Moscow Institute of Physics and Technology and National Research Nuclear University ”MEPhI”, Moscow, Russia ¶ also at JINR, Dubna, Russia ∗∗ deceased †† also at BMCC/CUNY, Science Department, New York, New York, U.S.A.

New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta_23. Using an off-axis neutrino beam with a peak energy of 0.6 GeV and a data set corresponding to 6.57 x 10^20 protons on target, T2K has fit the energy-dependent nu_mu oscillation probability to determine oscillation parameters. Marginalizing over the values of other oscillation parameters yields sin^2 (theta_23) = 0.514 +0.055/-0.056 (0.511 +- 0.055), assuming normal (inverted) mass hierarchy. The best-fit mass-squared splitting for normal hierarchy is Delta m^2_32 = (2.51 +- 0.10) x 10^-3 eV^2/c^4 (inverted hierarchy: Delta m^2_13 = (2.48 +- 0.10) x 10^-3 eV^2/c^4). Adding a model of multinucleon interactions that affect neutrino energy reconstruction is found to produce only small biases in neutrino oscillation parameter extraction at current levels of statistical uncertainty.

The beam-helicity asymmetry in associated electroproduction of real photons, ep → eγπN , in the Δ(1232)-resonance region is measured using the longitudinally polarized Hera positron beam and an unpolarized hydrogen target. Azimuthal Fourier amplitudes of this asymmetry are extracted separately for two channels, ep → eγπ0 p and ep → eγπ+ n, from a data set collected with a recoil detector. All asymmetry amplitudes are found to be consistent with zero.

Single-spin asymmetries were investigated in inclusive electroproduction of charged pions and kaons from transversely polarized protons at the HERMES experiment. The asymmetries were studied as a function of the azimuthal angle psi about the beam direction between the target-spin direction and the hadron production plane, the transverse hadron momentum P-T relative to the direction of the incident beam, and the Feynman variable x(F). The sin psi* amplitudes are positive for pi(+) and K+ slightly negative for pi(-) and consistent with zero for K-, with particular P-T but weak x(F) dependences. Especially large asymmetries are observed for two small subsamples of events, where also the scattered electron was recorded by the spectrometer. (C) 2013 The Authors. Published by Elsevier B.V. All rights reserved.

The transverse polarization of $\Lambda$ hyperons was measured in inclusive quasireal photoproduction for various target nuclei ranging from hydrogen to xenon. The data were obtained by the HERMES experiment at HERA using the 27.6 GeV lepton beam and nuclear gas targets internal to the lepton storage ring. The polarization observed is positive for light target nuclei and is compatible with zero for krypton and xenon.

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 Δm(32)(2) and a CP violating phase δ(CP). In this neutrino oscillation scenario, assuming |Δm(32)(2)|=2.4×10(-3)  eV(2), sin(2)θ(23)=0.5, and Δm322>0 (Δm(32)(2)<0), a best-fit value of sin(2)2θ(13)=0.140(-0.032)(+0.038) (0.170(-0.037)(+0.045)) is obtained at δ(CP)=0. When combining the result with the current best knowledge of oscillation parameters including the world average value of θ(13) from reactor experiments, some values of δ(CP) are disfavored at the 90% C.L.

The T2K off-axis near detector, ND280, is used to make the first differential cross-section measurements of electron neutrino charged current interactions at energies ~1 GeV as a function of electron momentum, electron scattering angle and four-momentum transfer of the interaction. The total flux-averaged $\nu_e$ charged current cross-section on carbon is measured to be $1.11\pm0.09~(stat)\pm0.18~(syst)\times10^{-38} cm^2/nucleon$. The differential and total cross-section measurements agree with the predictions of two leading neutrino interaction generators, NEUT and GENIE. The NEUT prediction is $1.23\times10^{-38} cm^2/nucleon$ and the GENIE prediction is $1.08\times10^{-38} cm^2/nucleon$. The total $\nu_e$ charged current cross-section result is also in agreement with data from the Gargamelle experiment.

We report a measurement of the nu(mu) inclusive charged current cross sections on iron and hydrocarbon in the Tokai-to-Kamioka (T2K) on-axis neutrino beam. The measured inclusive charged current cross sections on iron and hydrocarbon averaged over the T2K on-axis flux with a mean neutrino energy of 1.51 GeVare (1.444 +/- 0.002(stat)(-0.157)(+0.189)- (syst)) x 10(-38) cm(2)/ nucleon and (1.379 +/- 0.009(stat)(-0.147)(+0.178) (syst)) x 10(-38) 38 cm(2)/ nucleon, respectively, and their cross-section ratio is 1.047 +/- 0.007(stat) +/- 0.035(syst). These results agree well with the predictions of the neutrino interaction model, and thus we checked the correct treatment of the nuclear effect for iron and hydrocarbon targets in the model within the measurement precisions.