First application of CsI(Tl) pulse shape discrimination at an e^+ e^- collider to improve particle identification at the Belle II experiment

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dc.contributor.authorLongo, Savino
dc.contributor.supervisorRoney, John Michael
dc.date.accessioned2019-11-01T00:12:42Z
dc.date.available2019-11-01T00:12:42Z
dc.date.copyright2019en_US
dc.date.issued2019-10-31
dc.degree.departmentDepartment of Physics and Astronomyen_US
dc.degree.levelDoctor of Philosophy Ph.D.en_US
dc.description.abstractThis dissertation investigates CsI(Tl) pulse shape discrimination (PSD) as a novel experimental technique to improve challenging areas of particle identification at high energy $e^+ e^-$ colliders using CsI(Tl) calorimeters. In this work CsI(Tl) PSD is implemented and studied at the Belle II experiment operating at the SuperKEKB $e^+ e^-$ collider, representing the first application of CsI(Tl) PSD at a $B$ factory experiment. Results are presented from Belle II as well as a testbeam completed at the TRIUMF proton and neutron irradiation facility. From the analysis of the testbeam data, energy deposits from highly ionizing particles are shown to produce a CsI(Tl) scintillation component with decay time of $630\pm10$ ns, referred to as the hadron scintillation component, and not present in energy deposits from electromagnetic showers or minimum ionizing particles. By measuring the fraction of hadron scintillation emission relative to the total scintillation emission, a new method for CsI(Tl) pulse shape characterization is developed and implemented at the Belle II experiment's electromagnetic calorimeter, constructed from 8736 CsI(Tl) crystals. A theoretical model is formulated to allow for simulations of the particle dependent CsI(Tl) scintillation response. This model is incorporated into GEANT4 simulations of the testbeam apparatus and the Belle II detector, allowing for accurate simulations of the observed particle dependent scintillation response of CsI(Tl). With $e^\pm$, $\mu^\pm$, $\pi^\pm$, $K^\pm$ and $p/\bar{p}$ control samples selected from Belle II collision data the performance of this new simulation technique is evaluated. In addition the performance of hadronic interaction modelling by GEANT4 particle interactions in matter simulation libraries is studied and using PSD potential sources of data vs. simulation disagreement are identified. A PSD-based multivariate classifier trained for $K_L^0$ vs. photon identification is also presented. With $K_L^0$ and photon control samples selected from Belle II collision data, pulse shape discrimination is shown to allow for high efficiency $K_L^0$ identification with low photon backgrounds as well as improved $\pi^0$ identification compared to shower-shape based methods.en_US
dc.description.scholarlevelGraduateen_US
dc.identifier.bibliographicCitationS. Longo and J. M. Roney 2018 JINST 13 P03018en_US
dc.identifier.bibliographicCitationS. Longo and J. M. Roney. "Hadronic vs Electromagnetic Pulse Shape Discrimination in CsI(Tl) for High Energy Physics Experiments". In ArXiv e-prints (Jan 2018). arXiv:1801.07774v1 [physics.ins-det].en_US
dc.identifier.bibliographicCitationS. Longo and J. M. Roney. "Hadronic vs Electromagnetic Pulse Shape Discrimination in CsI(Tl) for High Energy Physics Experiments". In ArXiv e-prints (Mar 2018). arXiv:1801.07774v2 [physics.ins-det].en_US
dc.identifier.urihttp://hdl.handle.net/1828/11301
dc.languageEnglisheng
dc.language.isoenen_US
dc.rightsAvailable to the World Wide Weben_US
dc.subjectHigh Energy Physicsen_US
dc.subjectCalorimetersen_US
dc.subjectCsI(Tl)en_US
dc.subjectBelle IIen_US
dc.subjectPulse Shape Discriminationen_US
dc.subjectParticle Identificationen_US
dc.subjectPhotonsen_US
dc.subjectNeutral Kaonen_US
dc.subjectHadronic Showeren_US
dc.subjectGEANT4en_US
dc.subjectScintillatorsen_US
dc.subjectDetector Developmenten_US
dc.titleFirst application of CsI(Tl) pulse shape discrimination at an e^+ e^- collider to improve particle identification at the Belle II experimenten_US
dc.typeThesisen_US

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