Louisiana Tech University Louisiana Tech Digital Commons Doctoral Dissertations Graduate School Spring 5-2020 The Parity-Violating Asymmetry in the N→Δ Transition at Low Q2 Thamraa A. Alshayeb Follow this and additional works at: https://digitalcommons.latech.edu/dissertations Part of the Engineering Physics Commons THE PARITY-VIOLATING ASYMMETRY IN THE N→Δ TRANSITION AT LOW Q2 by Thamraa A. Alshayeb, B.S., M.S. A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy COLLEGE OF ENGINEERING AND SCIENCE LOUISIANA TECH UNIVERSITY March 2020 ABSTRACT Qweak has used the parity violating asymmetry to test the Standard Model (SM) by constantly flipping helicity states of a longitudinally polarized electron beam that scatters in the unpolarized LH2 target. The main focus of the Qweak experiment at Jefferson Lab was the recently published determination of the proton’s weak charge. In order to make corrections to the measured asymmetry at low 푄2 due to inelastically scattered electrons, dedicated measurements were made of the parity violating asymmetry in the N→∆ transition at two different beam energies. The measured inelastic asymmetries are used to extract the low energy constant dΔ, which is an additional physics result. The low energy constant dΔ results in a non-zero asymmetry at photon point (푄2 = 0) and is recognized as the parity violating hadronic excitation in the N→∆ transition. This has been known to be relevant to some puzzles in radiative hyperon decays. Theoretical analyses indicate potential values of 푑∆ much greater than its natural scale. By using the 2 Qweak apparatus, the parity violating asymmetry in the N→∆ transition at 푄 = 2 0.02 GeV was extracted to be Ainel,total = − 3.91 ± 0.80 (푠푡푎푡) ± 1.27 (푠푦푠푡) 푝푝푚, which constrains the low energy constant to be 푑∆ = ( 26 ± 18 (푠푡푎푡) ± 29 (푠푦푠푡) ± 3 (푡ℎ푒표푟푦)) 푔휋 . Inelastic measurement motivations, iii iv further analysis, and preliminary results for these measurements will be presented in this dissertation. APPROVAL FOR SCHOLARLY DISSEMINATION The author grants to the Prescott Memorial Library of Louisiana Tech University the right to reproduce, by appropriate methods, upon request, any or all portions of this Dissertation. It is understood that “proper request” consists of the agreement, on the part of the requesting party, that said reproduction is for his personal use and that subsequent reproduction will not occur without written approval of the author of this Dissertation. Further, any portions of the Dissertation used in books, papers, and other works must be appropriately referenced to this Dissertation. Finally, the author of this Dissertation reserves the right to publish freely, in the literature, at any time, any or all portions of this Dissertation. Author____________________________ Date _____________________________ GS Form 14 (5/03) DEDICATION This dissertation is dedicated to my precious mother for her endless love, measureless support, encouragement, and sustainment throughout my life. To my dear father’s soul. May Allah have mercy on him. To my beloved husband and children! vi TABLE OF CONTENTS ABSTRACT ....................................................................................................................... iii DEDICATION ................................................................................................................... vi LIST OF TABLES ............................................................................................................ xii LIST OF FIGURES ......................................................................................................... xiv ACKNOWLEDGMENTS ............................................................................................... xix CHAPTER 1 INTRODUCTION .........................................................................................1 1.1 Preview ....................................................................................................................1 1.1.1 Qweak Experiment Introduction ........................................................................3 CHAPTER 2 THEORY .......................................................................................................6 2.1 Physics Motivation...................................................................................................6 2.2 Electroweak Interaction and Parity Violation ..........................................................8 2.3 Inelastic Parity Violating Asymmetry .............................................................................. 11 2.3.1 The ∆ Resonance...........................................................................................12 2.3.2 푑∆ Extraction .................................................................................................14 2.3.2.1 Inelastic parity-violating asymmetry measurement .............................14 2.3.3 Implications for Other Measurements ..........................................................22 vii viii CHAPTER 3 EXPERIMENT AND Qweak APPARATUS ................................................24 3.1 Introduction ............................................................................................................24 3.2 Beamline ................................................................................................................26 3.2.1 Accelerator ....................................................................................................26 3.2.2 Beam Monitors..............................................................................................29 3.2.2.1 Beam position monitor (BPM) and beam charge monitor (BCM) ......29 3.3 Liquid Hydrogen Target ........................................................................................31 3.4 Qweak Luminosity Monitors ....................................................................................32 3.5 Qweak Toroidal Magnetic Spectrometer (QTOR) ...................................................33 3.6 Triple Collimators ..................................................................................................34 3.7 Beam Collimator ....................................................................................................35 3.8 Detectors ................................................................................................................36 3.8.1 The Main C̆erenkov Detectors ......................................................................36 3.9 Event Mode Detectors (Tracking System) .............................................................37 3.9.1 Drift Chambers..............................................................................................38 3.9.2 Trigger Scintillator ........................................................................................39 3.10 Beam Polarization ................................................................................................39 3.10.1 Møller polarimeter (Intrusive) ....................................................................39 3.10.2 Compton polarimeter (Non- intrusive) .......................................................40 CHAPTER 4 DATA QUALITY CHECKS .......................................................................41 4.1 Introduction ............................................................................................................41 4.2 Run 1 ......................................................................................................................42 4.2.1 Beam Charge Monitor, BCMs ......................................................................42 ix 4.2.1.1 BCM-1 for run 1 ..................................................................................43 4.2.1.2 BCM-2 for run 1 ..................................................................................44 4.3 Beam Charge Monitor Double Difference, BCM-DDs .........................................45 4.3.1 BCM-DD 12 for Run 1 .................................................................................45 4.4 Target .....................................................................................................................46 4.4.1 Target X for Run 1 ........................................................................................46 4.4.2 Target Y for Run 1 ........................................................................................48 4.4.3 Target X Slope for Run 1 ..............................................................................49 4.4.4 Target Y Slope for Run 1 ..............................................................................50 4.4.5 Upstream Luminosity (uslumisum) for Run 1 ................................................51 4.5 Run 2 ......................................................................................................................52 4.5.1 Beam Charge Monitor, BCMs ......................................................................52 4.5.1.1 BCM-1 for run 2 ..................................................................................52 4.5.1.2 BCM-2 for run 2 ..................................................................................53 4.5.2 Beam Charge Monitor Double Difference, BCMs .......................................54 4.5.2.1 BCM-DD 56 for run 2..........................................................................54 4.5.2.2 BCM-DD 58 for run 2..........................................................................55 4.5.2.3 BCM-DD 68 for run 2..........................................................................56