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A Dual Quark Model with Spin


Ellis, Stephen Dean (1971) A Dual Quark Model with Spin. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/G3AD-N729.


A dual quark model is developed from the usual Veneziano model by explicitly including the Dirac spin of the quarks. Resonances appear without the parity doubling and new ghosts present in previous models with spin. This is accomplished by eliminating the contributions of the negative parity components (MacDowell-twins) of the spin quarks 1/2 through the introduction of fixed J-plane cuts. The resonances belong to an SU6 symmetric spectrum identical, on the leading trajectory, with that of the usual static symmetrical quark model. All resonances couple via SU6w x O2Lz symmetric vertices and the model factorizes with essentially the same degeneracy as the usual Veneziano model. As a consequence of requiring these two features the model acquires further new structure which is studied in detail in terms of the asymptotic behavior of the model. This new structure leads to unavoidable "background" contributions to the imaginary parts of the amplitudes not present in previous dual models. This situation is examined and interpreted in the language of Finite Energy Sum Rules.

In order to test the basic features of the model explicit calculations are made for the case of pion-nucleon scattering in the Regge limit. To make the numerical work easier a somewhat simplified version of the model is used. Although the results of the calculations are suggestive of reasonable J-plane structure for the various amplitudes, i.e., the location of Regge pole-fixed cut interference is reasonable from the standpoint of the data, the overall kinematic behavior of the amplitudes is definitely not compatible with what is measured. However, it is noted that this kinematic behavior depends strongly on those details of the model which were simplified in the present study. If such models are to be unambiguously and successfully tested against data, future studies must treat these details more completely and realistically, including both unitarity and symmetry breaking effects.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Physics
Degree Grantor:California Institute of Technology
Division:Physics, Mathematics and Astronomy
Major Option:Physics
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Frautschi, Steven C. (advisor)
  • Mathews, Jon (co-advisor)
Thesis Committee:
  • Unknown, Unknown
Defense Date:12 May 1971
Funding AgencyGrant Number
Record Number:CaltechTHESIS:04202018-125942170
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:10823
Deposited By: Benjamin Perez
Deposited On:20 Apr 2018 22:55
Last Modified:21 Dec 2019 02:50

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