Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance

Blomberg, Adam

doi:10.2172/1351258

Title: Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance

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Abstract

Non-spherical components of the nucleon wave function are measured through p(e,e'p)π⁰ experiment at the Δ⁺(1232) resonance for Q² = 0.04, 0.09, and 0.13 (GeV=c)² utilizing the Jefferson National Accelerator Facility (JLab) pulsed beam and Hall A spectrometers. The new data extend the measurements of the Coulomb quadrupole amplitude to the lowest momentum transfer ever reached. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations that include pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements indicate that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The Coulomb to magnetic multipole ratio (CMR) and generalized polarizability (GP) of the nucleon are also measured through virtual Compton scattering (VCS) for Q² = 0.2(GeV=c)² utilizing the Mainz Microtron (MAMI) continuous beam and A1 spectrometers. This data represents the first low Q² GP measurement at the Δ⁺(1232) resonance. The GP measurement explores a region where previous data and theoretical calculations disagree. The CMR measurement will be the first VCS extraction to compare with world data generated through pion electroproduction. The Dispersion Relation (DR) model used for the VCS extraction provides a new theoretical frameworkmore »« less

Authors:

Blomberg, Adam ^[1]

Temple Univ., Philadelphia, PA (United States)

Publication Date:: Thu Dec 01 00:00:00 EST 2016

Research Org.:: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)

Sponsoring Org.:: USDOE Office of Science (SC), Nuclear Physics (NP)

OSTI Identifier:: 1351258

Report Number(s):: JLAB-PHY-16-2442; DOE/OR/23177-4116

DOE Contract Number:: AC05-06OR23177

Resource Type:: Thesis/Dissertation

Country of Publication:: United States

Language:: English

Subject:: 72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Citation Formats


                    Blomberg, Adam. Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance.  United States: N. p., 2016. 
        Web.  doi:10.2172/1351258.

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                    Blomberg, Adam. Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance.  United States.  https://doi.org/10.2172/1351258

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                    Blomberg, Adam. 2016.  
        "Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance".  United States.  https://doi.org/10.2172/1351258.  https://www.osti.gov/servlets/purl/1351258.

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@article{osti_1351258,

  title        = {Low momentum transfer measurements of pion electroproduction and virtual Compton scattering at the Delta resonance},

  author       = {Blomberg, Adam},

  abstractNote = {Non-spherical components of the nucleon wave function are measured through p(e,e'p)π0 experiment at the Δ+(1232) resonance for Q2 = 0.04, 0.09, and 0.13 (GeV=c)2 utilizing the Jefferson National Accelerator Facility (JLab) pulsed beam and Hall A spectrometers. The new data extend the measurements of the Coulomb quadrupole amplitude to the lowest momentum transfer ever reached. The results disagree with predictions of constituent quark models and are in reasonable agreement with dynamical calculations that include pion cloud effects, chiral effective field theory and lattice calculations. The reported measurements indicate that improvement is required to the theoretical calculations and provide valuable input that will allow their refinements. The Coulomb to magnetic multipole ratio (CMR) and generalized polarizability (GP) of the nucleon are also measured through virtual Compton scattering (VCS) for Q2 = 0.2(GeV=c)2 utilizing the Mainz Microtron (MAMI) continuous beam and A1 spectrometers. This data represents the first low Q2 GP measurement at the Δ+(1232) resonance. The GP measurement explores a region where previous data and theoretical calculations disagree. The CMR measurement will be the first VCS extraction to compare with world data generated through pion electroproduction. The Dispersion Relation (DR) model used for the VCS extraction provides a new theoretical framework for the data signal and backgrounds that is largely independent from the pion electroproduction models. The independence of the DR from the traditional models provides a strong crosscheck on the ability of the models to isolate the data signal.},

  doi          = {10.2172/1351258},

  url          = {https://www.osti.gov/biblio/1351258},
  journal      = {},
number       = ,

  volume       = ,

  place        = {United States},

  year         = {Thu Dec 01 00:00:00 EST 2016},

  month        = {Thu Dec 01 00:00:00 EST 2016}

}

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