Exact symmetries and the role of the pion cloud in deep-inelastic electron-nucleon scattering

Journal Article · Tue Sep 01 04:00:00 EDT 1992 · Physical Review, C (Nuclear Physics); (United States)

DOI:https://doi.org/10.1103/PhysRevC.46.1108· OSTI ID:7157091

Dmitrasinovic, V; Tegen, R ^[1]

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1. Nuclear and Particle Theory Group, Department of Physics, University of the Witwatersrand, P.O. Wits 2050, Johannesburg (South Africa)

A careful analysis of exact symmetries, such as the charge conjugation symmetry and the electromagnetic and baryon current conservation, shows that exactly two nontrivial Feynman diagrams contribute to deep-inelastic inclusive pion electroproduction from the nucleon to {ital O}({ital g}{sub {pi}{ital N}{ital N}}{sup 2}). The same analysis reveals certain relationships between the two graphs. The two graphs are expressed as convolutions of the pion ({ital g}{sub {pi}}({ital y})) and the nucleon ({ital g}{sub {ital N}}({ital y})) smearing functions and their respective deep-inelastic structure functions. The nucleon smearing functions are evaluated in three models of the nucleon off-shell dependence of the {pi}{ital NN} vertex function and they turn out to have remarkably similar shapes. It is shown that this universality of {ital g}{sub {ital N}}({ital y}) persists in a wide class of models. Such universal {ital g}{sub {ital N}}({ital y}) peaks at {ital y}{sub 0}=1{minus}{ital m}{sub {pi}}/{ital M}{sub {ital N}}=0.85 and allows a simple parton model interpretation. Furthermore, the normalized smearing functions approximately satisfy the Berger-Coester-Wiringa-Thomas ansatz {ital g}{sub {pi}}({ital y})={ital g}{sub {ital N}}(1{minus}{ital y}) for two of the three models examined. Strong constraints on the nucleon off-shell dependence of the {pi}{ital NN} vertex function ({ital g}{sub {pi}{ital N}{ital N}}({ital p}{sub {ital N}}{sup 2})) are obtained using the observed Gottfried sum rule violation as empirical input.

• OSTI ID: 7157091
• Journal Information: Physical Review, C (Nuclear Physics); (United States), Journal Name: Physical Review, C (Nuclear Physics); (United States) Vol. 46:3; ISSN 0556-2813; ISSN PRVCA
• Country of Publication: United States
• Language: English

Related Subjects

663300 -- Nuclear Reactions & Scattering
General-- (1992-)
663420* -- Lepton-Induced Reactions & Scattering-- (1992-)
73 NUCLEAR PHYSICS AND RADIATION PHYSICS
BASIC INTERACTIONS
BOSONS
CONSERVATION LAWS
DEEP INELASTIC SCATTERING
DIAGRAMS
ELECTROMAGNETIC INTERACTIONS
ELECTRON-NUCLEON INTERACTIONS
ELEMENTARY PARTICLES
EQUATIONS
FEYNMAN DIAGRAM
HADRONS
INELASTIC SCATTERING
INTERACTIONS
LEPTON-BARYON INTERACTIONS
LEPTON-HADRON INTERACTIONS
LEPTON-NUCLEON INTERACTIONS
LIE GROUPS
MESONS
PARTICLE INTERACTIONS
PIONS
PSEUDOSCALAR MESONS
SCATTERING
SU GROUPS
SU-2 GROUPS
SU-3 GROUPS
SUM RULES
SYMMETRY
SYMMETRY GROUPS