Measurement of Differential Cross Sections and Spin Density matrix elements along with a Partial Wave Analysis for γp → pω Using CLAS at JLab

Thesis/Dissertation · Thu Nov 29 00:00:00 EST 2007

DOI:https://doi.org/10.2172/955709· OSTI ID:955709

Williams, Michael ^[1]

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1. Carnegie Mellon Univ., Pittsburgh, PA (United States)

This work presents measurements of differential cross sections, dσ/dcosθ$$ω\atop{CW}$$, and spin density matrix elements, P$$0\atop{MM'}$$, for the reaction γp → pω in the energy range 1.72 GeV< √s <2.84 GeV. The data were collected at Jefferson Lab, using the CLAS detector, as part of the g11a run period in 2004. Our P$$0\atop{MM'}$$ measurements vastly increase the precision of the world s data and extend the large angle measurements by over 400 MeV in √s. Our data confirms that for √s < 2.1 GeV, the forward angle (small |t|) production amplitude is dominated by t-channel π⁰ exchange. At higher energies, existing non-resonant models do a poor job of describing our data. In particular, u-channel models fail to reproduce our highest energy backwards P$$0\atop{MM'}$$ measurements. A mass-independent partial wave analysis has also been performed. Near threshold, the dominant resonance contributions extracted are the **** F₁₅(1680) and *** D₁₃(1700). Together with the t-channel π⁰ exchange, these three waves provide a remarkably good description of our differential cross section and spin density matrix element measurements for √s < 2 GeV. Strong, but not conclusive, evidence for the **** G₁₇(2190) has also been extracted. Improved non-resonant models may be necessary to irrefutably show whether this state contributes to ω photoproduction. Evidence for missing resonances is suggestive, but inconclusive without theoretical input.

• Research Organization: Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-060R23177
• OSTI ID: 955709
• Report Number(s): JLAB-PHY-07-802; TRN: US201014%%1349
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ACCURACY
AMPLITUDES
DENSITY MATRIX
DIFFERENTIAL CROSS SECTIONS
ENERGY RANGE
PARTIAL WAVES
PRODUCTION
RESONANCE
SPIN
T CHANNEL
U CHANNEL
SPECTROMETERS