Goldberger, M. L. and Treiman, S. B. (1958) Form factors in β decay and μ capture. Physical Review, 111 (1). pp. 354361. ISSN 0031899X. http://resolver.caltech.edu/CaltechAUTHORS:GOLpr58c

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Abstract
We suppose that β decay and μ capture are described by a universal vector and axial vector Lagrangian and we consider, via dispersion relation techniques, the properties of the corresponding Smatrix elements. Owing to the strong interactions of the nucleons, the structure of the S matrix is expected to be more complicated than that of the Lagrangian. In the former, vector and axial vector terms appear, but with coefficients which in general depend on the invariant nucleon momentum transfer; they can be thought of as Fermi interaction form factors. Moreover, two additional kinds of terms can appear in the Smatrix elements: one which simulates a direct pseudoscalar coupling and one which simulates a direct coupling involving derivatives of the nucleon wave functions. The latter is probably too small to have any experimental significance. The former, though negligible in β decay, may be appreciable in μ capture. We estimate the effective pseudoscalar coupling coefficient there to be about eight times as large as the axial vector coefficient. More generally, we investigate the structure of the various form factors; and we also reconsider, in further refinement, a recent quantitative discussion which we have given of π→μ+ν decay.
Item Type:  Article 

Additional Information:  ©1958 The American Physical Society. Received 7 March 1958. 
Record Number:  CaltechAUTHORS:GOLpr58c 
Persistent URL:  http://resolver.caltech.edu/CaltechAUTHORS:GOLpr58c 
Alternative URL:  http://dx.doi.org/10.1103/PhysRev.111.354 
Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided. 
ID Code:  7467 
Collection:  CaltechAUTHORS 
Deposited By:  Tony Diaz 
Deposited On:  22 Feb 2007 
Last Modified:  26 Dec 2012 09:32 
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