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Upgrade of the Near Detector ND280 and its expected impact on the T2K sensitivity and on the study of neutrino-nucleus interactions

Sep 27, 2022
219 pages
Supervisor:
Thesis: PhD
  • Paris U., VI-VII
(2022)
  • Published: Sep 27, 2022
Report number:
  • tel-03935726,
  • 2022SORUS348
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Abstract: (TEL)
Neutrino physics has entered the precision era; apart from precise measurements of oscillation parameters, the long-baseline experiments also aim to identify the neutrino mass hierarchy and amount of CP violation observed in the neutrino sector. In order to achieve these goals, current and future long-baseline experiments need to reduce the systematic uncertainty to a few per cent. One of the key challenges in reaching such accuracy is our limited understanding of few-GeV neutrino-nucleus interactions. The uncertainties stem from neutrino-nucleus interaction are already the main systematic uncertainties on current neutrino oscillation analysis, such as the one of T2K, and will remain the primary restriction if a better comprehension of the nuclear effect is not attained. These interactions systematic can be improved by using the upgraded near detector ND280.The ND280 is under an upgrade project, and the newly upgraded sub-detectors will be installed at the beginning of 2023. With the new configuration, the target mass of the upgraded ND280 is significantly enhanced with a 2-ton fully-active SuperFGD. Moreover, the upgraded ND280 will become a great tracking device with SuperFGD and High Angle Time Projection Chambers (HA-TPC). These sub-detectors provided the upgraded ND280 with the 4π acceptance, which is equivalent to the far detector. This thesis contributed to the test beam results for HA-TPC, such as the gain uniformity, the drift velocity and especially the deposited energy resolution. The test beam at DESY II facility has proved that the spatial resolution is better than 600~µm, and the energy resolution is better than 9% for all incident angles. These results meet the requirements for upgrading the ND280 TPC.The main concentration of this thesis is on the importance of the upgraded near detector in the future constraints of the systematic uncertainties, especially the ones stemming from nuclear effects. This thesis described a method for studying nuclear effects in neutrino-nucleus interaction by measuring final state particles' kinematics in muon neutrino charged-current interactions with no pions but at least one proton in the final state - CC0π+Np interactions. With the upgraded ND280, the ability to reconstruct the hadronic part is significantly improved. Thanks to this future improvement, a likelihood fit was developed to evaluate the sensitivity of the upgrade to the flux and cross-section model by exploiting the new observables called single-transverse variables which are sensitive to several nuclear effects. The fitter has provided good quantitative sensitivities to key uncertainties. These results show promising constraints on cross-section and flux parameters obtained at the upgraded near detector for future oscillation analysis.With the use of nucleon kinematics in upgraded ND280, the demand for a well-described neutrino-nucleus interaction model is more than ever before.A fake data study for Martini et al. model for pion production channel was done in this thesis. This study aims to evaluate the robustness of the oscillation analysis to modelling in the neutrino-nucleus interaction model outside of the recommendation by T2K. This thesis has described a reweight technique to turn the current T2K prediction of neutrino cross-section to Martini et al. model's cross-section. The impact of Martini et al. fake data study on several oscillation parameters is quantified in this thesis. One of the main results is that the shift on δCP 1D δchi2 distribution caused by this fake data is not significant enough to cause a change in the T2K conclusion of δCP result. Overall, the result of oscillation fit with the Martini et al. one pion production shows consistent oscillation parameters' values with the published results of T2K.
  • Neutrino
  • T2K experiment
  • Neutrino oscillation
  • Expérience T2K
  • Oscillation de neutrinos
  • neutrino nucleus: interaction
  • interaction: model
  • neutrino: oscillation
  • neutrino: current
  • neutrino: interaction