Vector meson dominance: Difference between revisions
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Measurements of the interaction between energetic photon and hadrons show that the interaction is much more intense than expected by the interaction of photons with the hadron's electric charge. Furthermore, the interaction of energetic photon with proton is similar to the interaction of photon with neutron<ref>The hadronic properties of the photon in high-energy interactions, Rev. Mod. Phys. 50, 261–436 (1978), pages 292-293</ref> although the electric charge structures of proton and neutron are substantially different. |
Measurements of the interaction between energetic photon and hadrons show that the interaction is much more intense than expected by the interaction of photons with the hadron's electric charge. Furthermore, the interaction of energetic photon with proton is similar to the interaction of photon with neutron<ref>The hadronic properties of the photon in high-energy interactions, Rev. Mod. Phys. 50, 261–436 (1978), pages 292-293</ref> although the electric charge structures of proton and neutron are substantially different. |
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According to VMD, the photon is a superposition of the |
According to VMD, the photon is a superposition of the pure electromagnetic photon (which interacts only with electric charges) and vector meson. |
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Just after 1970, when more accurate data on the above processes became available, some discrepancies with the VMD predictions appeared and new extensions of the model were published.<ref> Generalized vector dominance and inelastic electron nucleon scattering—the small <math>\omega</math>′ region, Sakurai J. J. and Schildknecht D., Phys. Lett., 40B (1972) 121</ref> These theories are known as Generalized Vector Meson Dominance theories (GVMD). |
Just after 1970, when more accurate data on the above processes became available, some discrepancies with the VMD predictions appeared and new extensions of the model were published.<ref> Generalized vector dominance and inelastic electron nucleon scattering—the small <math>\omega</math>′ region, Sakurai J. J. and Schildknecht D., Phys. Lett., 40B (1972) 121</ref> These theories are known as Generalized Vector Meson Dominance theories (GVMD). |
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"...this eliminated the model [VMD] as a possible description of deep inelastic scattering... calculations of the generalized vector-dominance failed in general to describe the data over the full kinematic range..." |
"...this eliminated the model [VMD] as a possible description of deep inelastic scattering... calculations of the generalized vector-dominance failed in general to describe the data over the full kinematic range..." |
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The theoretical basis of VMD was also under attack. According to VMD |
The theoretical basis of VMD was also under attack. According to VMD a photon is superposition of pure electromagnetic photon which always moves in the speed of light and hadronic matter which always moves in lower speed. Therefore the VMD idea seems to contradict [[Special Relativity]].<ref>[[Eliyahu Comay|E. Comay]] Remarks on Photon-Hadron Interactions, Apeiron vol. 10, 87 (2003)</ref> |
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Today, VMD is not considered as part of the [[Standard Model]].<ref> H.B. O’Connell, B.C. Pearce, A.W. Thomas and A.G. Williams, Rho-omega mixing, vector meson dominance and the pion form-factor, Prog. Nucl. Part. Phys. 39 (1997) 201-252</ref> |
Today, VMD is not considered as part of the [[Standard Model]].<ref> H.B. O’Connell, B.C. Pearce, A.W. Thomas and A.G. Williams, Rho-omega mixing, vector meson dominance and the pion form-factor, Prog. Nucl. Part. Phys. 39 (1997) 201-252</ref> |
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Revision as of 21:04, 17 June 2012
In physics, vector meson dominance (VMD) was a model developed by J. J. Sakurai[1] in the 1960s before the advent of QCD in order to describe interactions between photons and hadronic matter.
In particular the hadronic components of the photon polarization tensor consist of the lightest vector mesons and . Therefore interactions between photons and hadronic matter occur by the exchange of a hadron between the dressed photon and the hadronic target.
Background
Measurements of the interaction between energetic photon and hadrons show that the interaction is much more intense than expected by the interaction of photons with the hadron's electric charge. Furthermore, the interaction of energetic photon with proton is similar to the interaction of photon with neutron[2] although the electric charge structures of proton and neutron are substantially different.
According to VMD, the photon is a superposition of the pure electromagnetic photon (which interacts only with electric charges) and vector meson.
Just after 1970, when more accurate data on the above processes became available, some discrepancies with the VMD predictions appeared and new extensions of the model were published.[3] These theories are known as Generalized Vector Meson Dominance theories (GVMD).
Attacks on VMD
Measurements of the photon-hadron interactions in higher energy levels show that VMD cannot predict the interaction in such levels. In his nobel lecture[4] J.I. Friedman summarizes the situation of VMD as follows: "...this eliminated the model [VMD] as a possible description of deep inelastic scattering... calculations of the generalized vector-dominance failed in general to describe the data over the full kinematic range..."
The theoretical basis of VMD was also under attack. According to VMD a photon is superposition of pure electromagnetic photon which always moves in the speed of light and hadronic matter which always moves in lower speed. Therefore the VMD idea seems to contradict Special Relativity.[5]
Today, VMD is not considered as part of the Standard Model.[6]
Notes
- ^ Theory of strong interactions, J. J. Sakurai, Ann. Phys., 11 (1960)
- ^ The hadronic properties of the photon in high-energy interactions, Rev. Mod. Phys. 50, 261–436 (1978), pages 292-293
- ^ Generalized vector dominance and inelastic electron nucleon scattering—the small ′ region, Sakurai J. J. and Schildknecht D., Phys. Lett., 40B (1972) 121
- ^ J.I. Friedman, Nobel Lecture, Deep Inelastic Scattering, Comparisons with the Quark Model, Rev. Mod. Phys. vol 63 3 1991
- ^ E. Comay Remarks on Photon-Hadron Interactions, Apeiron vol. 10, 87 (2003)
- ^ H.B. O’Connell, B.C. Pearce, A.W. Thomas and A.G. Williams, Rho-omega mixing, vector meson dominance and the pion form-factor, Prog. Nucl. Part. Phys. 39 (1997) 201-252
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