Screening in the bremsstrahlung reactions and determination of the magnetic moment of the {delta} resonance

Journal Article · Sun Aug 31 04:00:00 EDT 2008 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.2973489· OSTI ID:21149157

Machavariani, A I ^[1]

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1. Joint Institute for Nuclear Research, Dubna, Moscow region 141980 (Russian Federation)

The new form of current conservation is used for the analytical determination of the dipole magnetic moments of the {delta} resonances in the pion-nucleon bremsstrahlung reaction {pi}+N{yields}{gamma}'+{pi}'+N'. This current conservation condition presents a modified Ward-Takahashi identity for the on shell {pi}N bremsstrahlung amplitude. According to this identity the internal and external particle radiation parts of the {pi}N bremsstrahlung amplitude have an opposite sign i.e. they contain terms which cancel each other. Therefore a screening of the internal and external particle radiation in the {pi}N bremsstrahlung is generated. In particular it is shown, that the internal double A exchange diagram with the {delta}-{gamma}'{delta}' vertex cancel with the appropriate longitudinal part of the external particle radiation diagrams. This enables to obtain a model independent estimation of the dipole magnetic moment of {delta}{sup +} and {delta}{sup ++} resonances {mu}{sub {delta}} through the anomalous magnetic moment of the proton {mu}{sub p} as {mu}{sub {delta}}{sub +} = (M{sub {delta}}/m{sub p}){mu}{sub p} and {mu}{sub {delta}}{sub ++} = (3/2){mu}{sub {delta}}{sub +} in agreement with the values obtained from the fit of the experimental cross section of the {pi}{sup +}P{yields}{gamma}'{pi}{sup +}P reaction.Considering pions and nucleons as bound (cluster) states of quarks in the usual quantum field theory [5,6,7,8] a generalization of the suggested approach is suggested [2]. The resulting equations for the external and internal particle radiation amplitudes of the {pi}N bremsstrahlung reaction have the same form as in formulation without quark degrees of freedom [1]. Therefore the model independent estimation of the dipole magnetic moment of {delta}{sup +} and {delta}{sup ++} resonances {mu}{sub {delta}}{sub +}/{mu}{sub p} = M{sub {delta}}/m{sub p} and {mu}{sub {delta}}{sub ++}/{mu}{sub {delta}}{sub +} (3/2) in the usual local quantum field theory is preserved in the general quantum field formulation with the quark degrees of freedom.

• OSTI ID: 21149157
• Journal Information: AIP Conference Proceedings, Journal Name: AIP Conference Proceedings Journal Issue: 1 Vol. 1030; ISSN APCPCS; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
BREMSSTRAHLUNG
CHIRAL SYMMETRY
COMPTON EFFECT
CROSS SECTIONS
DEGREES OF FREEDOM
DELTA BARYONS
DIPOLES
FEYNMAN DIAGRAM
MAGNETIC MOMENTS
PION-NUCLEON INTERACTIONS
PIONS PLUS
PROTONS
QUANTUM FIELD THEORY
QUARKS
SCATTERING AMPLITUDES
WARD IDENTITY