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Abstract:

We present the first measurement of differential cross sections for charged-current muon neutrino interactions on argon with one muon, two protons, and no pions in the final state. These final states are dominated by two-nucleon knockout interactions, which are complicated to model and for which there is currently limited information about the characteristics of these interactions in existing neutrino-nucleus scattering data. Detailed investigations of two-nucleon knockout are vital to support upcoming experiments exploring the nature of the neutrino. Among the different kinematic quantities measured, the opening angle between the two protons, the angle between the total proton momentum and the muon, and the total transverse momentum of the final state system are most sensitive to the underlying physics processes as embodied in various theoretical models

Abstract:

Artículo escrito por un elevado número de autores. Solo se referencia el que aparece en primer lugar, el nombre del grupo de colaboración si hubiere y los autores pertenecientes a la UAMThe T2K experiment widely uses plastic scintillator as a target for neutrino interactions and an active medium for the measurement of charged particles produced in neutrino interactions at its near detector complex. Over 10 years of operation the measured light yield recorded by the scintillator based subsystems has been observed to degrade by 0.9–2.2% per year. Extrapolation of the degradation rate through to 2040 indicates the recorded light yield should remain above the lower threshold used by the current reconstruction algorithms for all subsystems. This will allow the near detectors to continue contributing to important physics measurements during the T2K-II and Hyper-Kamiokande eras. Additionally, work to disentangle the degradation of the plastic scintillator and wavelength shifting fibres shows that the reduction in light yield can be attributed to the ageing of the plastic scintillator. The long component of the attenuation length of the wavelength shifting fibres was observed to degrade by 1.3–5.4% per year, while the short component of the attenuation length did not show any conclusive degradationWe thank the J-PARC staff for superb accelerator performance. We thank the CERN NA61/SHINE Collaboration for providing valuable particle production data. We acknowledge the support of MEXT, JSPS KAKENHI (JP16H06288, JP18K03682, JP18H03701, JP18H05537, JP19J01119, JP19J22440, JP19J22258, JP20H00162, JP20H00149, JP20J20304) and bilateral programs (JPJSBP120204806, JPJSBP120209601), Japan; NSERC, the NRC, and CFI, Canada; the CEA and CNRS/IN2P3, France; the DFG (RO 3625/2), Germany; the INFN, Italy; the Ministry of Education and Science( DIR/WK/2017/05) and the National Science Centre (UMO-2018/30/E/ST2/00441), Poland; the RSF19-12-00325, RSF22-12-00358 and the Ministry of Science and Higher Education (075-15-2020- 778), Russia; MICINN (SEV-2016-0588, PID2019-107564GB-I00, PGC2018-099388-BI00) and ERDF funds and CERCA program, Spain; the SNSF and SERI (200021_185012, 200020_188533, 20FL21_186178I), Switzerland; the STFC, U.K.; and the DOE, U.S.A. We also thank CERN for the UA1/NOMAD magnet, DESY for the HERA-B magnet mover system, NII for SINET5, the WestGrid and SciNet consortia in Compute Canada, and GridPP in the United Kingdom. In addition, the participation of individual researchers and institutions has been further supported by funds from the ERC (FP7), “la Caixa” Foundation (ID 100010434, fellowship code LCF/BQ/IN17/11620050), the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Sklodowska-Curie grant agreement numbers 713673 and 754496, and H2020 grant numbers RISE-GA822070-JENNIFER2 2020 and RISE-GA872549-SK2HK; the JSPS, Japan; the Royal Society, U.K.; French ANR grant number ANR-19-CE31-0001; and the DOE Early Career programme, U.S.A

Abstract:

A simultaneous beam and atmospheric oscillation analysis that combines the T2K and SK experiments has been presented. The first sensitivities of the joint analysis are reported, with the intention for the two collaborations to publish a data analysis in the near-future. This analysis leverages the different energies and baselines of the two experiments and provides strong sensitivities on δCP, sin2(θ23) and ∆m232. To do this, a Bayesian Markov Chain Monte Carlo technique is utilised to generate parameter estimates and credible intervals. Constraints from the T2K near detector are also used to constrain the uncertainties of both beam and atmospheric predictions.

For a known set of oscillation parameters close to the preferred values from a T2K-only data fit, the sensitivity of the joint analysis to sin2(θ23) is increased compared to the beam-only analysis, illustrated by a 7% reduction in the width of the 1σ credible interval. Furthermore, the sensitivity of the joint analysis to select the correct mass hierarchy hypothesis is drastically improved compared to the beam-only analysis, culminating in a substantial preference as classified by Jeffrey’s scale. This statement is stronger than the sensitivity of the beam-only analysis, either with or without external constraints on sin2(θ13). The sensitivities of the beam-only and joint beam-atmospheric analyses have also been compared for a known set of oscillation parameters which are CP-conserving. The joint analysis displays an improved ability to select the correct phase of δCP and octant of sin2(θ23) compared to the beam-only analysis. This thesis illustrates the benefit of the combined beam and atmospheric analysis, which could also be extended for use in the next-generation Hyper-Kamiokande experiment.