T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Izmaylov, A., Sorel, M., & Stamoulis, P. (2016). Measurement of double-differential muon neutrino charged-current interactions on C8H8 without pions in the final state using the T2K off-axis beam. Phys. Rev. D, 93(11), 112012–25pp.
Abstract: We report the measurement of muon neutrino charged-current 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 flux-integrated, double-differential 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 cross-section extraction methods to demonstrate the robustness of the results against biases due to model-dependent assumptions. The measurements compare favorably with recent models which include nucleon-nucleon 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 signal-over-background 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).
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T2K Collaboration(Abe, K. et al), Cervera-Villanueva, A., Izmaylov, A., Novella, P., Sorel, M., & Stamoulis, P. (2017). Search for Lorentz and CPT violation using sidereal time dependence of neutrino flavor transitions over a short baseline. Phys. Rev. D, 95(11), 111101–9pp.
Abstract: A class of extensions of the Standard Model allows Lorentz and CPT violations, which can be identified by the observation of sidereal modulations in the neutrino interaction rate. A search for such modulations was performed using the T2K on-axis near detector. Two complementary methods were used in this study, both of which resulted in no evidence of a signal. Limits on associated Lorentz and CPT-violating terms from the Standard Model extension have been derived by taking into account their correlations in this model for the first time. These results imply such symmetry violations are suppressed by a factor of more than 10(20) at the GeV scale.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., Fernandez, P., Izmaylov, A., & Novella, P. (2020). First combined measurement of the muon neutrino and antineutrino charged-current cross section without pions in the final state at T2K. Phys. Rev. D, 101(11), 112001–44pp.
Abstract: This paper presents the first combined measurement of the double-differential muon neutrino and antineutrino charged-current cross sections with no pions in the final state on hydrocarbon at the off-axis near detector of the T2K experiment. The data analyzed in this work comprise 5.8 x 10(20) and 6.3 x 10(20) protons on target in neutrino and antineutrino mode respectively, at a beam energy peak of 0.6 GeV. Using the two measured cross sections, the sum, difference, and asymmetry were calculated with the aim of better understanding the nuclear effects involved in such interactions. The extracted measurements have been compared with the prediction from different Monte Carlo generators and theoretical models showing that the difference between the two cross sections have interesting sensitivity to nuclear effects.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., & Novella, P. (2020). Simultaneous measurement of the muon neutrino charged-current cross section on oxygen and carbon without pions in the final state at T2K. Phys. Rev. D, 101(11), 112004–32pp.
Abstract: This paper reports the first simultaneous measurement of the double differential muon neutrino chargedcurrent cross section on oxygen and carbon without pions in the final state as a function of the outgoing muon kinematics, made at the ND280 off-axis near detector of the T2K experiment. The ratio of the oxygen and carbon cross sections is also provided to help validate various models' ability to extrapolate between carbon and oxygen nuclear targets, as is required in T2K oscillation analyses. The data are taken using a neutrino beam with an energy spectrum peaked at 0.6 GeV. The extracted measurement is compared with the prediction from different Monte Carlo neutrino-nucleus interaction event generators, showing particular model separation for very forward-going muons. Overall, of the models tested, the result is best described using local Fermi gas descriptions of the nuclear ground state with RPA suppression.
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T2K Collaboration(Abe, K. et al), Antonova, M., Cervera-Villanueva, A., & Molina Bueno, L. (2021). Improved constraints on neutrino mixing from the T2K experiment with 3.13 x 10(21) protons on target. Phys. Rev. D, 103(11), 112008–59pp.
Abstract: 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) x 10(20) 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 sin(2)theta(13) from reactor data and assuming normal mass ordering T2K measures sin(2)theta(13) = 0.53(-0.04)(+0.03) and Delta m(32)(2) = (2.45 +/- 0.07) x 10(-3) eV(2) c(-4). The Bayesian analyses show a weak preference for normal mass ordering 89)% posterior probability) and the upper sin(2)theta(13) octant (80% posterior probability), with a uniform prior probability assumed in both cases. The T2K data exclude CP conservation in neutrino oscillations at the 2 sigma level.
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