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Volumn 58, Issue 4, 1998, Pages 2478-2488

[Formula Presented] transition and Siegert’s theorem

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EID: 0345911569     PISSN: 05562813     EISSN: 1089490X     Source Type: Journal    
DOI: 10.1103/PhysRevC.58.2478     Document Type: Article
Times cited : (54)

References (55)
  • 4
    • 85035264283 scopus 로고    scopus 로고
    • C. N. Papanicolas and S. E. Williamson, Proceedings of the International Conference on Hadron Spectroscopy (Hadron ’91), College Park, 1991, p. 145
    • J. R. Comfort, Proceedings of the Seventh International Sym-posium on Meson-Nucleon Physics and the Structure of the Nucleon, Vancouver, 1997[πN Newsletter 13, 55 (1997)]; ZZZZZZC. N. Papanicolas and S. E. Williamson, Proceedings of the International Conference on Hadron Spectroscopy (Hadron ’91), College Park, 1991, p. 145.
    • (1997) , vol.13 , pp. 55
    • Comfort, J.R.1
  • 25
    • 85035262131 scopus 로고    scopus 로고
    • Instead of classifying the quark-quark interactions in terms of relativistic invariants, one can also classify them in terms of the five nonrelativistic invariants: spin-independent central, spin-dependent central, spin-orbit, tensor, quadratic spin-orbit. For each of these invariants and for each meson, the lowest nonvanishing contribution is kept. The leading-order potential of each diagram is considered to be of the same order as the nonrelativistic kinetic energy, which is of order (Formula presented)
    • Instead of classifying the quark-quark interactions in terms of relativistic invariants, one can also classify them in terms of the five nonrelativistic invariants: spin-independent central, spin-dependent central, spin-orbit, tensor, quadratic spin-orbit. For each of these invariants and for each meson, the lowest nonvanishing contribution is kept. The leading-order potential of each diagram is considered to be of the same order as the nonrelativistic kinetic energy, which is of order (Formula presented)
  • 40
    • 85035305552 scopus 로고    scopus 로고
    • The two-body pion and gluon exchange charge densities are of order (Formula presented) and (Formula presented) respectively, and the question concerning the convergence of such an expansion arises. However, we have repeatedly argued that it is more important to include the lowest nonvanishing exchange currents for each degree of freedom than to insist on formal consistency of all operators in a given relativistic order (Formula presented) Our approach of keeping for each degree of freedom the lowest nonvanishing order is phenomenologically successful. For example, the lowest nonvanishing order pion and gluon exchange terms in the charge operator contain a tensor in spin space (Formula presented) not present in the one-body charge operator. This leads to nonvanishing (Formula presented) and via Siegert’s theorem also to a nonvanishing (Formula presented) transition amplitude of the right sign and magnitude. Evidently, one should not discard these terms. We have pointed out a similar effect in connection with Eq. (1). The color-magnetic term in the one-gluon exchange potential of Eq. (4) is a relativistic correction of order (Formula presented) which is, however, the lowest nonvanishing (Formula presented) type term resulting from one-gluon exchange. This term is crucial for explaining the difference between (Formula presented) and (Formula presented) masses in the quark model
    • The two-body pion and gluon exchange charge densities are of order (Formula presented) and (Formula presented) respectively, and the question concerning the convergence of such an expansion arises. However, we have repeatedly argued that it is more important to include the lowest nonvanishing exchange currents for each degree of freedom than to insist on formal consistency of all operators in a given relativistic order (Formula presented) Our approach of keeping for each degree of freedom the lowest nonvanishing order is phenomenologically successful. For example, the lowest nonvanishing order pion and gluon exchange terms in the charge operator contain a tensor in spin space (Formula presented) not present in the one-body charge operator. This leads to nonvanishing (Formula presented) and via Siegert’s theorem also to a nonvanishing (Formula presented) transition amplitude of the right sign and magnitude. Evidently, one should not discard these terms. We have pointed out a similar effect in connection with Eq. (1). The color-magnetic term in the one-gluon exchange potential of Eq. (4) is a relativistic correction of order (Formula presented) which is, however, the lowest nonvanishing (Formula presented) type term resulting from one-gluon exchange. This term is crucial for explaining the difference between (Formula presented) and (Formula presented) masses in the quark model.


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