MINISTRY OF EDUCATION VIETNAM ACADEMY OF SCIENCE AND TRAINING AND TECHNOLOGY GRADUATION UNIVERSITY OF SCIENCE AND TECHNOLOGY ———————o0o——————– Tran Van Ngoc TESTING CP AND CPT INVARIANCES WITH NEUTRINO OSCILLATION MEASUREMENTS IN T2K EXPERIMENT Doctor of Philosophy Dissertation in Physics Hanoi, 2023 MINISTRY OF EDUCATION VIETNAM ACADEMY OF SCIENCE AND TRAINING AND TECHNOLOGY GRADUATION UNIVERSITY OF SCIENCE AND TECHNOLOGY ———————o0o——————– Tran Van Ngoc TESTING CP AND CPT INVARIANCES WITH NEUTRINO OSCILLATION MEASUREMENTS IN T2K EXPERIMENT Major: Mathematical Physics and Theoretical Physics Code: 9440103 Doctor of Philosophy Dissertation in Physics Supervisor 1: Assoc. Nguyen Thi Hong Van Supervisor 2: Prof. Tsuyoshi Nakaya Hanoi, 2023 i Declaration of Authorship I hereby declare that the thesis titled “Testing CP and CPT invariances with neutrino oscillation measurements in T2K experiment” and the work presented in it are my own. I confirm that this work does not contain my previous work as well as other people’s work without being clearly stated.
The bibliography contains all the references that I used in writing the thesis. I declare that this is a true copy of my thesis, which is approved by my thesis supervisors, and that this thesis has not been submitted for a doctoral degree to any other university or institution. I certify that any republication of materials presented in this thesis has been approved by the relevant publishers and coauthors. Signature of the Author Tran Van Ngoc ii Acknowledgements This thesis is dedicated to my parents Tran Van Khanh and Nguyen Thi Lai, my wife Viet Ha and beloved son Khoi Nguyen.
Without their unconditional love and support, I could not finish this arduous journey. I would like to express the deepest appreciation to my advisors, Assoc. Nguyen Thi Hong Van and Prof. Hong Van is not just an advisor, she is like a dear sister.
We can discuss not only the research work but also issues in everyday life. Nakaya is a distinguished scientist and a gentleman. He is willing to help no matter what the problem is. I am deeply indebted to Dr.
Cao Van Son for his assistance. Without him this work could not be completed. His experiences and ideas profoundly opened my mind. He is a real talent scientist and a coworker whom I am very lucky to work with.
I could not have undertaken the PhD journey without the financial support of ICISE, Quy Nhon. This wonderful place was built with the heart and soul of Prof. Tran Thanh Van and Prof. Le Kim Ngoc.
I am really grateful to them. I also would like to extend my sincere thanks to Dr. Tran Thanh Son and his wife. You make me feel like ICISE is a family.
I had the pleasure of working with the neutrino group at IFIRSE on all parts of the thesis. I would like to express my cordial appreciation to Dr. Tatsuya Kikawa, Kenji Yasutome and Pintaudi Giogio for the works done in Chapter 2 and Appendix A. Kikawa inherited and developed the framework for the neutrino beam measurement at the INGRID near detector.
Kenji and Giogio helped me a lot on the work related to measurement at WAGASCI-BabyMIND. Ngoc was funded by Vingroup JSC and supported by the Master, PhD Scholarship Programme of Vingroup Innovation Foundation (VINIF), Institute of Big Data, code VINIF.069 in doing some parts of this thesis. I really appreciate its support. Finally, sincere thanks are given to ICISE and GUST staff for their support in administrative work.
Tran Van Ngoc IFIRSE, ICISE and GUST Quy Nhon, May 2023 iii Abstract CP and CPT are among the most fundamental symmetries of Nature. Test- ing CP and CPT invariances is of prime importance for fundamental physics. T2K is a long-baseline neutrino oscillation experiment. It uses an intense muon neutrino (antineutrino) beam to study neutrino oscillation phenomenon.
By operating in both neutrino mode and antineutrino mode, T2K is able to test CP symmetry in lepton sector. In addition, the disappearance channels of muon neutrino and antineutrino at long-baseline experiments such as T2K are the “golden channels” to test CPT invari- ance. The on-axis near detector INGRID provides information about neutrino event rate and beam profile. The measurements at INGRID are in good agreement with MC predictions.
The neutrino event rate and beam profile are stable within the physics requirements in T2K run 10. Testing CP and CPT symmetries with T2K and with a combined analysis of T2K-II, NOνA extension, and JUNO experiments are presented. T2K ruled out CP conserving values (δCP = 0; π) at more than 95% C. using data collected from run 1 to run 9 with a total exposure of 3.
The value of CP violating phase (δCP ) was measured to be −2.69 for normal mass ordering (NO) and −1.69 for inverted mass ordering (IO). With constraint from short baseline reactor experiments, the best fit values of δCP with ±1σ uncertainties are −1.58 for NO and −1. We also show that by 2028, the joint fit of T2K-II, NOνA extension, and JUNO will be able to exclude CP conservation at ∼ 5σ C. The analysis of the T2K data with 3.13 × 1021 POT exposure is consistent with CPT conservation hypothesis.
The joint analysis of T2K-II, NOνA extension, and JUNO will be able to exclude CPT conservation at 1. if the best-fit values of T2K (NOνA) in the mass squared splittings (∆m231 , ∆m231 ) and mixing angles (θ23 , θ23 ) are presumed to be true values. In addition, the synergy can improve the bound on |∆m231 −∆m231 | to the world’s best value ever made, 5., which is slightly better than DUNE and about one order of magnitude better than the value analysed by current neutrino oscillation experiments. iv Contents Declaration of Authorship.
v List of Abbreviations. vi List of Tables. viii List of Figures. 1 1 Neutrino oscillation phenomenon and experiments 3 1.2 Neutrino in Standard Model .3 Neutrino mass and seesaw mechanism .4 Neutrino oscillation in vacuum .5 Neutrino oscillation in matter .2 Introduction to some neutrino oscillation experiments .2 The NOvA experiment .3 The JUNO experiment.
28 2 Measurements at INGRID - the T2K on-axis near detector 29 2.1 Neutrino flux prediction .2 Event rate measurement .1 Simulation of neutrino interactions with NEUT .4 The event rate at INGRID .3 Beam profile measurement. 40 3 Testing CP and CPT invariances with neutrino oscillation measure- ments in T2K experiment 42 3.2 The CPT theorem .1 Proof of CPT theorem based on Lagrangian quantum field theory 46 v 3.2 Proof of CPT theorem based on axiomatic quantum field theory 47 3.3 Testing CP invariance with neutrino oscillation experiments .1 Testing CP invariance in neutrino oscillation .2 Testing CP invariance with T2K experiment .3 Sensitivity to CP violation with a joint fit of T2K-II, NOvA-II, and JUNO .4 Testing CPT invariance with neutrino oscillation experiments .1 Testing CPT invariance in neutrino oscillation .2 GLoBES setup for simulating T2K-II, NOvA-II, and JUNO ex- periments .3 Testing CPT invariance with T2K experiment .4 Sensitivity to CPT violation with a joint fit of T2K-II, NOvA-II, and JUNO. 75 List of Publications. 84 A Neutrino cross section measurements at WAGASCI BabyMIND i A.2 Neutrino-nucleus interaction cross section models .4 Monte Carlo simulation.
ix vi List of Abbreviations AEDL Abstract Experiment Definition Language AGS Alternating Gradient Synchrotron CC charged current DIS deep inelastic scattering DONUT Direct observation of the nu tau, E872 GeV giga-electron-volt INGRID Interactive Neutrino GRID J-PARC Japan Proton Accelerator Research Complex JUNO Jiangmen Underground Neutrino Observatory GLoBES General Long Baseline Experiment Simulator MPPC Multi-Pixel Photon Counter MSW Mikheyev–Smirnov–Wolfenstein MRD muon range detector NC neutral current NOvA NuMI Off-axis νe Appearance PCAC partially conserved axial vector current PMNS Pontecorvo–Maki–Nakagawa–Sakata PMT Photo-Multiplier Tube QED Quantum Electrodynamics QCD Quantum Chromodynamics SM Standard Model T2K Tokai to Kamioka WAGASCI BabyMIND WAter Grid SCIntillator Detector – prototype Magnetized Iron Neutrino Detector vii List of Tables 2.1 Systematic errors for total number of events in all modules for neutrino mode and anti-neutrino mode.2 Event rate comparison between FHC runs and MC with +250kA horn operation.3 Event rate comparison between RHC runs and MC with -250kA horn operation.4 Summary of INGRID MC beam center with 250 kA and 320 kA horn operations.5 Summary of INGRID MC beam width with 250 kA and 320 kA horn operations.1 Values of oscillation parameters used in calculating Jarlskog invariant.2 The predicted number of events for δCP = −π/2 and the measured number of events in the three electron-like samples at Super-K.3 The best fit and best fit ±1σ intervals of δCP for T2K only and T2K+reactor for normal (NH) and inverted (IH) hierarchies. The ±1σ interval corre- sponds to the values for which ∆χ2 ≤ 1.4 Nominal values of oscillation parameters used for study in Section 3. Normal mass hierarchy is assumed.5 Experimental specifications of T2K-II and NOνA-II in GLoBES.6 Detection efficiencies(%) of νe /ν̄e events in appearance samples. Normal hierarchy and δCP = 0 are assumed.7 Detection efficiencies(%) of νµ /ν̄µ events in disappearance samples.
Nor- mal hierarchy is assumed.8 JUNO simulated specifications in GLoBES.9 Fractional region of δCP , depending on sin2 θ23 , can be explored with 3σ or higher significance.10 Values of nominal parameters used for the study in Section 3.4, taken from Ref.11 The bounds on CPT violation with atmospheric mass-squared difference and mixing angle at 3σ C. for three analyses: T2K-II only, a joint of T2K-II and NOνA-II, a joint of T2K-II, NOνA-II, and JUNO.12 Lower limits for the true |δνν (∆m231 )| amplitude to exclude CPT at 3σ C. are computed at different true values of the involved parameters.13 Measurements of the (∆m231 , ∆m231 , θ23 , θ23 ) parameters, which govern the muon neutrino and muon antineutrino disappearances, from differ- ent experiments: MINOS(+) [3, 4], T2K [1], NOνA [5], Daya Bay [6]. Normal neutrino mass hierarchy is assumed.14 Lower limits for the true |δνν (sin2 θ23 )| amplitude to exclude CPT at 3σ C.
are computed at different true values of involved parameters.1 Summary of data taking at WAGASCI-BabyMIND.2 Threshold angles for matching tracks between detectors.3 Threshold distancs for matching tracks between detectors.4 Three dimensional track matching conditions. viii ix List of Figures 1.2 The ν e survival probability as a function of L/E.3 Feynman diagrams for CC and NC coherent forward scatterings of neu- trinos.4 The transition probabilities νµ → νe and ν̄µ → ν̄e for T2K baseline (left) and NOνA baseline (right).5 The relative CP asymmetry as a function of δCP , the solid band indicates the uncertainty of θ23. The plot is taken from Ref.6 Schematic diagram of the T2K experiment.1 The schematic view of INGRID detector.2 INGRID MC simulation programs, taken from Ref.3 Neutrino fluxes at INGRID without horn current applied.4 Neutrino fluxes at INGRID with -250 kA horn current applied.5 Neutrino fluxes at INGRID with +250 kA horn current applied.6 Neutrino fluxes at INGRID with -320 kA horn current applied.7 Neutrino fluxes at INGRID with +320 kA horn current applied.8 -320 kA (left) and +320 kA (right) fluxes at 2.9 Cellular automaton algorithm.10 The daily event rate at INGRID in T2K run 10 without correction.11 MC event distributions vs angle (left) and vertex x (right) of RHC mode (top) and FHC mode (bottom) for 320 kA horn operation.12 Reconstructed neutrino beam profiles for horizontal (left) and vertical (right) modules for T2K run 10. Each point represents the number of selected events in each module.13 The stability of neutrino beam profiles of INGRID horizontal (left) and vertical (right) modules for T2K run 10.14 The history of neutrino beam width for INGRID horizontal (left) and vertical (right) modules for T2K run 10.1 The Jarlskog invariant versus the baryon asymmetry varying δCP = [0, 2π] (cyan).
The red region denotes the 2σ range for the baryon asym- metry. The magenta and blue lines indicate values of Jarlskog invariant in the quark and lepton sectors. The plot is taken from Ref.
