The Influence of the NN* Channel on Elastic NN Scattering

Author: Shepard, Harvey Kenneth

Year: 1966

Degree: Dissertation (Ph.D.)

Advisor: Frautschi, Steven C.

Committee Member: Unknown, Unknown

Option: Physics

DOI: 10.7907/5HRF-4A20

Abstract

The problem of two channels NN and NN*, coupled through unitarity, is studied to see whether sizable peaks can be produced in elastic nucleon-nucleon scattering due to the opening of a strongly coupled inelastic channel. One-pion-exchange (OPE) interactions are calculated to estimate the NN*→NN* and NN→NN* amplitudes. The OPE production amplitudes are used as the sole dynamical input to drive the multichannel ND-1 equations in the determinental approximation, and the effect on the J = 2+ (1D2) elastic NN scattering amplitude is studied as the width of the unstable N* and strength of coupling to the inelastic channel are varied. A cusp-type enhancement appears in the NN channel near the NN* threshold but for the known value of the N* width the cusp is so “wooly” that any resulting elastic peak is likely to be too broad and diminished in height to be experimentally prominent. A brief survey of current experimental knowledge of the real part of the 1D2 NN phase shift near the NN* threshold is given, and the values are found to be much smaller than the nearly “resonant” phase shifts predicted by the coupled channel model.

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