
T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Escudero, L., Izmaylov, A., Sorel, M., & Stamoulis, P. (2014). Measurement of the Inclusive Electron Neutrino Charged Current Cross Section on Carbon with the T2K Near Detector. Phys. Rev. Lett., 113(24), 241803–7pp.
Abstract: The T2K offaxis near detector ND280 is used to make the first differential crosssection measurements of electron neutrino charged current interactions at energies similar to 1 GeV as a function of electron momentum, electron scattering angle, and fourmomentum transfer of the interaction. The total fluxaveraged nu(e) charged current cross section on carbon is measured to be <sigma >(phi) = 1.11 +/ 0.10(stat) +/ 0.18(syst) x 10(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 x 10(38) cm(2)/nucleon and the GENIE prediction is 1.08 x 10(38) cm(2)/nucleon. The total nu(e) charged current crosssection result is also in agreement with data from the Gargamelle experiment.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Escudero, L., GomezCadenas, J. J., Izmaylov, A., Monfregola, L., et al. (2013). Measurement of Neutrino Oscillation Parameters from Muon Neutrino Disappearance with an OffAxis Beam. Phys. Rev. Lett., 111(21), 211803–7pp.
Abstract: The T2K Collaboration reports a precision measurement of muon neutrino disappearance with an offaxis neutrino beam with a peak energy of 0.6 GeV. Near detector measurements are used to constrain the neutrino flux and cross section parameters. The SuperKamiokande far detector, which is 295 km downstream of the neutrino production target, collected data corresponding to 3.01 x 10(20) protons on target. In the absence of neutrino oscillations, 205 +/ 17 (syst) events are expected to be detected while only 58 muon neutrino event candidates are observed. A fit to the neutrino rate and energy spectrum, assuming three neutrino flavors and normal mass hierarchy yields a bestfit mixing angle sin(2) (theta(23)) = 0.514 +/ 0.082 and mass splitting vertical bar Delta m(32)(2)vertical bar = 2.44(0.15)(+0.17) x 10(3) eV(2)/c(4). Our result corresponds to the maximal oscillation disappearance probability.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Novella, P., Izmaylov, A., Sorel, M., & Stamoulis, P. (2016). Measurement of Coherent pi(+) Production in Low Energy NeutrinoCarbon Scattering. Phys. Rev. Lett., 117(9), 192501–7pp.
Abstract: We report the first measurement of the fluxaveraged cross section for charged current coherent pi(+) production on carbon for neutrino energies less than 1.5 GeV, and with a restriction on the final state phase space volume in the T2K near detector, ND280. Comparisons are made with predictions from the ReinSehgal coherent production model and the model by AlvarezRuso et al., the latter representing the first implementation of an instance of the new class of microscopic coherent models in a neutrino interaction Monte Carlo event generator. We observe a clear event excess above background, disagreeing with the null results reported by K2K and SciBooNE in a similar neutrino energy region. The measured fluxaveraged cross sections are below those predicted by both the ReinSehgal and AlvarezRuso et al. models.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Escudero, L., Izmaylov, A., Monfregola, L., Sorel, M., et al. (2014). Precise Measurement of the Neutrino Mixing Parameter theta(23) from Muon Neutrino Disappearance in an OffAxis Beam. Phys. Rev. Lett., 112(18), 181801–8pp.
Abstract: New data from the T2K neutrino oscillation experiment produce the most precise measurement of the neutrino mixing parameter theta(23). Using an offaxis 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 energydependent nu(mu) oscillation probability to determine oscillation parameters. The 68% confidence limit on sin(2)(theta(23)) is 0.514(0.056)(+0.055) (0.511 +/ 0.055), assuming normal (inverted) mass hierarchy. The bestfit masssquared splitting for normal hierarchy is Delta m(32)(2) = (2.51 +/ 0.10) x 10(3) eV(2)/c(4) (inverted hierarchy: Delta m(13)(2) = (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.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Izmaylov, A., Sorel, M., & Stamoulis, P. (2016). Measurement of Muon Antineutrino Oscillations with an AcceleratorProduced OffAxis Beam. Phys. Rev. Lett., 116(18), 181801–8pp.
Abstract: T2K reports its first measurements of the parameters governing the disappearance of (nu) over bar μin an offaxis beam due to flavor change induced by neutrino oscillations. The quasimonochromatic (nu) over bar μbeam, produced with a peak energy of 0.6 GeVat JPARC, is observed at the far detector SuperKamiokande, 295 km away, where the (nu) over bar μsurvival probability is expected to be minimal. Using a data set corresponding to 4.01 x 10(20) protons on target, 34 fully contained mulike events were observed. The bestfit oscillation parameters are sin(2) ((theta) over bar (23)) = 0.45 and vertical bar Delta(m) over bar (2)(32)vertical bar = 2.51 x 10(3) eV(2) with 68% confidence intervals of 0.380.64 and 2.262.80 x 10(3) eV(2), respectively. These results are in agreement with existing antineutrino parameter measurements and also with the nu(mu) disappearance parameters measured by T2K.



T2K Collaboration(Abe, K. et al), Antonova, M., CerveraVillanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2018). Search for CP Violation in Neutrino and Antineutrino Oscillations by the T2K Experiment with 2.2 x 10(21) Protons on Target. Phys. Rev. Lett., 121(17), 171802–9pp.
Abstract: The T2K experiment measures muon neutrino disappearance and electron neutrino appearance in acceleratorproduced neutrino and antineutrino beams. With an exposure of 14.7(7.6) x 10(20) protons on target in the neutrino (antineutrino) mode, 89 nu(e) candidates and seven antinu(e) candidates are observed, while 67.5 and 9.0 are expected for delta(CP) = 0 and normal mass ordering. The obtained 2 sigma confidence interval for the CPviolating phase, delta(CP), does not include the CPconserving cases (delta(CP) = 0, pi). The bestfit values of other parameters are sin(2) theta(23) = 0.526(0.036)(+0.032) and Delta m(32)(2) = 2.463(0.070)(+0.071) x 10(3) eV(2)/c(4).



T2K Collaboration(Abe, K. et al), Antonova, M., CerveraVillanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2020). Search for Electron Antineutrino Appearance in a LongBaseline Muon Antineutrino Beam. Phys. Rev. Lett., 124(16), 161802–8pp.
Abstract: Electron antineutrino appearance is measured by the T2K experiment in an acceleratorproduced antineutrino beam, using additional neutrino beam operation to constrain parameters of the PontecorvoMakiNakagawaSakata (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 2.40s and no discrepancy between data and PMNS predictions is found. A complementary analysis that introduces an additional free parameter which allows nonPMNS values of electron neutrino and antineutrino appearance also finds no discrepancy between data and PMNS predictions.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Izmaylov, A., Novella, P., & Sorel, M. (2017). Combined Analysis of Neutrino and Antineutrino Oscillations at T2K. Phys. Rev. Lett., 118(15), 151801–9pp.
Abstract: T2K reports its first results in the search for CP violation in neutrino oscillations using appearance and disappearance channels for neutrinoand antineutrinomode beams. The data include all runs from January 2010 to May 2016 and comprise 7.482 x 10(20) protons on target in neutrino mode, which yielded in the far detector 32 elike and 135 mulike events, and 7.471 x 10(20) protons on target in antineutrino mode, which yielded 4 elike and 66 mulike events. Reactor measurements of sin(2) 2 theta(13) have been used as an additional constraint. The onedimensional confidence interval at 90% for the phase delta(CP) spans the range (3.13,0.39) for normal mass ordering. The CP conservation hypothesis (delta(CP) = 0, pi) is excluded at 90% C.L.



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Izmaylov, A., Sorel, M., & Stamoulis, P. (2016). Measurement of doubledifferential muon neutrino chargedcurrent interactions on C8H8 without pions in the final state using the T2K offaxis beam. Phys. Rev. D, 93(11), 112012–25pp.
Abstract: We report the measurement of muon neutrino chargedcurrent interactions on carbon without pions in the final state at the T2K beam energy using 5.734 x 10(20) protons on target. For the first time the measurement is reported as a fluxintegrated, doubledifferential cross section in muon kinematic variables (cos theta(mu), p(mu)), without correcting for events where a pion is produced and then absorbed by final state interactions. Two analyses are performed with different selections, background evaluations and crosssection extraction methods to demonstrate the robustness of the results against biases due to modeldependent assumptions. The measurements compare favorably with recent models which include nucleonnucleon correlations but, given the present precision, the measurement does not distinguish among the available models. The data also agree with Monte Carlo simulations which use effective parameters that are tuned to external data to describe the nuclear effects. The total cross section in the full phase space is sigma = (0.417 +/ 0.047(syst) +/ 0.005(stat)) x 10(38) cm(2) nucleon(1) and the cross section integrated in the region of phase space with largest efficiency and best signaloverbackground ratio (cos theta(mu) > 0.6 and p(mu) > 200 MeV) is sigma = (0.202 +/ 0.036(syst) +/ 0.003(stat)) x 10(38) cm(2) nucleon(1).



T2K Collaboration(Abe, K. et al), CerveraVillanueva, A., Escudero, L., Izmaylov, A., Sorel, M., & Stamoulis, P. (2015). Measurement of the electron neutrino chargedcurrent interaction rate on water with the T2K ND280 pi(0) detector. Phys. Rev. D, 91(11), 112010–11pp.
Abstract: 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 portion of the v(e) flux (similar to 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 +/ 0.08(stat) +/ 0.11(sys), and with the water targets emptied is 0.90 +/ 0.09(stat) +/ 0.13 (sys). The ratio obtained for the interactions on water only from an event subtraction method is 0.87 +/ 0.33(stat) +/ 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.

