Atomic screening effects on electron-neutrino angular correlation and. beta. -decay asymmetry in allowed transitions

Journal Article · Fri Sep 01 00:00:00 EDT 1989 · Physical Review (Section) C: Nuclear Physics; (USA)

DOI:https://doi.org/10.1103/PhysRevC.40.1376· OSTI ID:5552283

Chen, Z ^[1]; Johnson, W R ^[2]; Spruch, L ^[3]

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1. Department of Physics, New York University, New York, New York 10003 (US)
2. Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556 Institute for Theoretical Physics, University of California, Santa Barbara, California 93106
3. Department of Physics, New York University, New York, New York 10003 Institute for Theoretical Physics, University of California, Santa Barbara, California 93106

Atomic screening effects on the electron-neutrino angular correlation coefficient {ital a}{sub 0} and the {beta} asymmetry coefficient {ital A}{sub 0}, in allowed transitions, are studied. It has long been known that the dominant screening effect on the spectrum is the replacement, in the factor which represents the phase space of the {beta} particle, of {ital W}, the energy with which the {beta} particle emerges, by {ital W}{minus}{ital V}{sub 0}, the energy with which it is born; {ital V}{sub 0} is the energy of interaction of the {beta} particle at the origin with the potential generated there by the atomic electrons. (One also replaces the momentum {ital p}={ital p}({ital W}) by {ital p}{prime}={ital p}({ital W}{minus}{ital V}{sub 0}).) One might well expect a similar result for screening effects on {ital a}{sub 0} and {ital A}{sub 0}, which include the influence of the nuclear Coulomb potential---and this intuitive expectation is shown to be the case. One need merely replace the velocity of emergence {ital v}={ital v}({ital W}) in the correlation functions by the velocity at birth, {ital v}{prime}={ital v}({ital W}{minus}{ital V}{sub 0}). As for the case of the spectrum, the effect can be obtained by using a static approximation, with the atomic electrons unaffected by the {beta} particle, and with the screening potential treated to second order; the effect of virtual or real excitation of the atomic electrons is negligible. The screening effect is of order 10{sup {minus}4} for most superallowed and mirror image transitions (presently, both theory and experiment for superallowed transitions---with implications for electro-weak theory and the standard model---give {ital ft} values accurate to about one part in 10{sup 3}); it can be as large as 20% for some pure Gamow-Teller transitions, for which the nuclear matrix element does not enter into the analysis of {ital a}{sub 0} and {ital A}{sub 0}.

• OSTI ID: 5552283
• Journal Information: Physical Review (Section) C: Nuclear Physics; (USA), Vol. 40:3; ISSN 0556-2813
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BETA DECAY
ASYMMETRY
ANGULAR CORRELATION
ATOMIC MODELS
BINDING ENERGY
CORRELATION FUNCTIONS
COUPLING CONSTANTS
ELECTRONS
ENERGY-LEVEL TRANSITIONS
FT VALUE
GAMOW-TELLER RULES
MATRIX ELEMENTS
NEUTRINOS
PHASE SPACE
SCREENING
SELECTION RULES
SHELL MODELS
CORRELATIONS
DECAY
ELEMENTARY PARTICLES
ENERGY
FERMIONS
FUNCTIONS
LEPTONS
MASSLESS PARTICLES
MATHEMATICAL MODELS
MATHEMATICAL SPACE
NUCLEAR DECAY
NUCLEAR MODELS
SPACE
653003* - Nuclear Theory- Nuclear Reactions & Scattering