Universitat Autonoma` de Barcelona Doctoral Thesis Measurement of the Muon Neutrino Charged Current Interactions and the Muon Neutrino Single Pion Cross Section on CH Using the T2K Near Detector Supervisor: Dr. Federico Sanchez´ Nieto Author: Tutor: Raquel Castillo Fernandez´ Dr. Enrique Fernandez´ Sanchez´ A thesis submitted in fulfilment of the requirements for the degree of PhD on Physics in the Neutrino Group Institut de F´ısicad'Altes Energies (IFAE) June 2015 \No es sabio el que sabe donde est´ael tesoro, sino el que trabaja y lo saca." Francisco de Quevedo y Villegas UNIVERSITAT AUTONOMA` DE BARCELONA Abstract Facultat de Ci´encies Institut de F´ısicad'Altes Energies (IFAE) PhD on Physics Measurement of the Muon Neutrino Charged Current Interactions and the Muon Neutrino Single Pion Cross Section on CH Using the T2K Near Detector by Raquel Castillo Fernandez´ The T2K experiment is a long baseline neutrino experiment which utilizes an almost pure muon neutrino beam. The main goal of the experiment is the measurement of the oscillation parameters of the muon neutrinos. In order to achieve this goal, T2K requires an accurate prediction of the interaction rates in the far detector, Super{KamiokaNDE. The near detector of T2K, ND280, measures the interaction rates and estimates the number of events at the far detector. The muon neutrino charged current interactions in the near detector (ND280) are used to predict the rate at the far detector (Super{KamiokaNDE). To a better constrain of the cross section parameters, which are dominant in the analysis together with the flux uncertainty, we categorize the selected events in three different samples according to the number of pions in the final state. These categories allow for a better constrain of the oscillation signal channel (Charged Current Quasielastic) and the main oscillation background (Charged Current 1 Charged Pion). Current and future neutrino experiments are limited by neutrino cross section uncertain- ties. The actual cross section models are in tension with the experimental data in some energy ranges. It is still critical to study neutrino{nucleus cross sections on all possible interaction channels. The muon neutrino charged current single pion production is one of the main channels in tension with the model. As a second contribution, we present the measurement of the Charged Current single positive pion production cross section using a model independent approach exploring the full capability of the ND280 detector to determine the kinematical distributions of the event. The improved knowledge of the interactions, and in concrete for the single pion channel, will allow the reduction of the the systematical uncertainties in the oscillation analysis. Medida de las Interacciones de Neutrino Mu´onicode Corriente Cargada y Secci´onEficaz de Producci´onde un S´oloPi´onen Interacci´onde Neutrino Mu´onicode Corriente Cargada en CH usando el Detector Cercano de T2K por Raquel Castillo Fernandez´ El experimento T2K es un experimento de neutrinos de largo recorrido que utiliza un haz casi puro the neutrinos mu´onicos.El objetivo principal del experimento es a medida de los par´ametrosde oscilaci´ondel neutrino mu´onicos.Para conseguir ´esteobjetivo, T2K necesita una rigurosa predicci´ondel ´ındicede interacciones en el detector lejano, Super{ KamiokaNDE. El detector cercano de T2K, ND280, calcula el ´ındice de interacciones y estima el n´umerode eventos en el detector lejano. Las interacciones de neutrino mu´onicode corriente cargada en el detector cercano (ND280) son usadas para predecir el ´ındicede eventos en el detector lejano (Super{ KamiokaNDE). Para una mejor restricci´onde los par´ametrosde secci´oneficaz, los cuales dominan el an´alisisjunto con las incertezas de la prediccion del flujo, categorizamos los eventos seleccionados en tres grupos de acuerdo con el n´umerode piones en el estado final. Estas tres categor´ıaspermiten un mejor ajuste de la se~naldel canal de oscilaci´on (Corriente Cargada Quasiel´astica)y el principal ru´ıdoen ocilaciones (Corriente Cargada de 1 Pi´onCargado). Actuales y futuros experimentos de neutrinos est´anlimitados por las incertezas en las secciones eficaces de neutrinos. Los modelos actuales de secci´oneficaz est´anen tension con los datos experimentales en algunos rangos energ´eticos. Esto hace que sea critico estudiar secciones eficaces de neutrino{nucleo en todos los canales de interacci´onposibles. La producci´onthe un solo pi´onen interacciones de neutrino mu´onicode corriente cargada es uno de los principales canales en tensi´oncon los modelos. Como segunda contribuci´on, presentamos el c´alculode producci´onthe un solo pi´onen interacciones de neutrino mu´onicode corriente cargada usando un enfoque indepenediente del modelo explorando la capacidad total del detector ND280 para establecer las distribuciones cinem´aticasdel evento. La mejore del conocimiento de las interacciones, y en concreto del canal de producci´onde un s´olopi´on,permitir´ala reducci´onde las incertidumbres sistem´aticas en el an´alisisde oscilaciones. Acknowledgements First, I would like to thanks to Federico for the opportunity he gave me and all the disccussions we had during these four years. Each single discussion was important. I want to thanks as well Matteo and Ramon, previous and current IFAE's directors, thanks to take care of everybody! I would like to thanks the people who provide me support during my first years of research, Michela and Mike, thanks for your patiente! Thanks a lot to my convener among all the analysis, Francesca, for the patiente and all the support. I would like to thanks as well the rest of Cross Section Group conveners and specially to Kendall for her enthusiasm and motivation. Thanks to Martin, A.K.A \in potato", who was always providing support and very nice discussions during the cross section analysis. I would like to thanks specially to Alfons, who proposed to me to do the CC1π analysis during one of our jet{lag{discussions in that nice ryokan in Tokai. Thanks to the NIWG conveners and to the questioning sense of Kevin which make the analysis stronger. Thanks a lot to Michel and Sara which helped on the improvement of the work. And thanks to Stefania who read very carefully this thesis and make it easier to digest. Haig d'agrair molt especialment a Xavier Vinyas qui em va donar la primera oportunitat de treballar en recerca. Moltes gracies per la motivaci´o,pel carisma i per fer{me estimar la f´ısicanuclear. I want to thanks to all the T2K collaborators for all the nice time in this great experi- ment. And specially I would like to thanks to Jiae, Leila, Javi, Callum, Matt, Thomas, Sasha, Panos, Teppei, Denis, Lorena, Anselmo, Melody, Tianlu and Minoo, thanks a lot for the very nice time! Thanks to the IFAE people and especially to Gerard, Gianluca, J¨oern,Iv´anand Em- manuelle. Welcome to the new neutrino's IFAE members, Alfonso, Bruno and John! And specially thanks to Alfonso, it was so funny to work with you. Quiero agradecer a Irene, Sandrinha, Marta, Jose, Rafael, Miguel Angel, Roberto, Miguel, Roger y Carlos todos los buenos momentos en la UAB. Gracias por el gran sentido del humor. Me gustar´ıadedicar tambien esta tesis a Ana, nuestra mexicana loca y fuerte que siempre recordaremos. Vull agrair tot el suport i sentit del humor a l'Anna, Fran, Agnese, Noa, Nuri y Ana. Molt´ıssimesgr´acies!!! iv Pero sobretodo, quiero dar las las gracias a mi familia, mi madre, mi hermana Sara y Joaqu´ın.Sin vosotros esto no hubiera sido posible. Contents Abstract ii Acknowledgements iv List of Figures xi List of Tables xxi 1 Outline 1 2 Neutrino Physics 3 2.1 Historical Introduction ............................. 3 2.2 Neutrino Interactions .............................. 7 2.2.1 Neutrino-Nucleon scattering ...................... 7 2.2.1.1 Neutrino Charged Current Quasi-Elastic Interactions . 8 2.2.1.2 Neutrino Charged Current Single Pion production . 9 2.2.1.3 Nuclear Effects ........................ 16 2.2.1.4 When the Single Pion is Breaking Bad . 17 2.2.2 The neutrino Monte Carlo generator: NEUT . 18 2.2.2.1 Some other neutrino event Monte Carlo generator . 19 GENIE ............................. 19 NuWro .............................. 19 GiBUU ............................. 20 Some other neutrino interaction models . 20 3 T2K Long{Baseline Neutrino Oscillation Experiment 21 3.1 The T2K Neutrino Beam ........................... 22 3.1.1 The Proton Beam Accelerator Complex . 23 3.1.1.1 Primary Neutrino Beamline . 24 3.1.1.2 Secondary Neutrino Beamline . 25 3.1.2 The Off–Axis Configuration ...................... 27 3.1.3 The Neutrino Beam Composition ................... 29 3.1.3.1 The Neutrino Flux Prediction . 30 3.1.3.2 The NA61/SHINE Experiment . 31 3.2 The Near Detector Complex .......................... 32 vi Contents vii 3.2.1 The Off–Axis Detector: ND280 .................... 34 3.2.2 The UA1/NOMAD magnet ...................... 36 3.2.3 The Side Muon Range Detector (SMRD) . 36 3.2.4 The Electromagnetic Calorimeter (ECal) . 37 The ECal particle identification . 38 3.2.5 The π0 detector (P;D) ......................... 38 3.2.6 The Time Projection Chambers (TPCs) . 40 The TPC particle identification . 42 3.2.7 The Fine Grain Detectors (FGDs) . 44 3.2.7.1 The FGD PID ........................ 45 3.3 The far detector: SuperKamiaokaNDE .................... 46 4 Detector Systematical Uncertainties and Propagation 49 4.1 ND280 Detector Systematics ......................... 49 4.1.1 TPC Particle ID ............................ 50 4.1.2 TPC cluster efficiency ......................... 51 4.1.3 TPC single and double track–finding efficiency . 52 4.1.4 TPC momentum resolution ...................... 52 4.1.5 TPC charge confusion ......................... 52 4.1.6 Track \Ubermerging"¨ ........................ 53 4.1.7 TPC field distortions .......................... 53 4.1.8 TPC Momentum Scale ......................... 53 4.1.9 FGD-only track efficiency ....................... 54 4.1.10 FGD-only track PID .........................