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The Relativistic String in the Caltech-II Model of Hadronization and Electron-Positron Annihilation


Morris, Duncan Andrew (1987) The Relativistic String in the Caltech-II Model of Hadronization and Electron-Positron Annihilation. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/gbwt-0788.


This study uses the full equations of motion of the massless relativistic string as a phenomenological model of color flux tubes in the process of hadronization in electron-positron annihilation. Perturbatively generated sets of partons are mapped onto color singlet strings, which fragment according to a generalization of the covariant decay law for point relativistic particles. String evolution is terminated when string masses are a few GeV above particle production threshold. Low-mass strings are decayed into primary hadrons using a parameterization of low-mass data. The complete model, which factorizes event evolution into three stages including perturbative QCD, string fragmentation and parameterized low-mass decays, is implemented as a Monte Carlo program known as the Caltech-II model of hadronization. An exact formalism is presented for the fragmentation function of heavy quarks within the string model.

The main results are, in their order of appearance: (1) The kinematics of the evolution and decay of arbitrarily complex massless relativistic strings is most conveniently expressed in terms of momentum currents. (2) The Caltech-II model, which uses the momentum current formalism to describe relativistic strings, provides a good description of electron-positron annihilation data over a wide range of center-of-mass energies. (3) Introducing transverse momentum at the sites of string breaks is conceptually necessary and may be required to further improve agreement between the Caltech-II model and data. (4) Fragmentation functions are predictions, not assumptions, of the string model in Caltech-II. The fragmentation function of heavy quarks in the Caltech-II string model is shown to exhibit the behavior expected from model-independent arguments. The discovery of the top quark or additional generations of heavy quarks will be a testing ground for future studies of hadronization.

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):
  • Fox, Geoffrey C.
Thesis Committee:
  • Fox, Geoffrey C. (chair)
  • Feynman, Richard Phillips
  • Filippone, Bradley W.
  • Newman, Harvey B.
  • Gottshalk, Thomas D.
Defense Date:4 May 1987
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Record Number:CaltechTHESIS:02222019-100949837
Persistent URL:
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:11407
Deposited On:22 Feb 2019 18:44
Last Modified:16 Apr 2021 22:11

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