Measuring the Neutron Spin Asymmetry A1n in the Valence Quark Region in Hall C at Jefferson Lab
Genre
Thesis/DissertationDate
2023Author
Cardona, Melanie LeighAdvisor
Sparveris, NikosCommittee member
Meziani, ZeinEddineMetz, Andreas
Sawatzky, Brad
Department
PhysicsSubject
PhysicsParticle physics
Nuclear physics and radiation
Hadronic physics
Medium energy nuclear physics
Spin asymmetry
Spin structure
Valence quarks
Permanent link to this record
http://hdl.handle.net/20.500.12613/8584
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http://dx.doi.org/10.34944/dspace/8548Abstract
The quest to understand how the nucleon spin is decomposed into its constituent quark and gluon spin and orbital angular momentum (OAM) components has been at the forefront of nuclear physics for decades. Due to the nonperturbative nature of Quantum Chromodynamics (QCD)  the theory describing how quarks and gluons bind together to form protons and neutrons  making absolute predictions of nucleon spin structure is generally difficult, especially as a function of its quark and gluon longitudinal momentum fraction x. Measurements involving nucleon spin structure serve as a sensitive test for QCD, including abinitio lattice QCD calculations due to the advent of the quasiPDF formalism, and various predictions that diverge at largex. The neutron spin asymmetry A1n at highx is a key observable for probing nucleon spin structure. In the valence domain (x > 0.5), sea effects are expected to be negligible, and so the total nucleon spin is considered to be carried by the valence quarks. The valence region can therefore enable us to study the role of quark OAM and other nonperturbative effects of the strong force. A1^n was measured in the deep inelastic scattering region of 0.40 < x < 0.75 and 6 < Q^2 < 10 GeV^2 in Hall C at Jefferson Lab using a 10.4 GeV longitudinally polarized electron beam, upgraded polarized He3 target, and the High Momentum Spectrometer (HMS) and Super High Momentum Spectrometer (SHMS). E1206110 provides the first precision data in the valence quark region above x = 0.60, and its preliminary results proved consistent with earlier data disqualifying a pQCD model that excluded quark OAM. Combined with previous world proton data, the ratio of the polarizedtounpolarized up quark momentum distribution (∆u + ∆antiu)/(u + antiu) remained positive at largex, and the down quark (∆d + ∆antid)/(d + antid) remained negative.ADA compliance
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