Advertisement

Electromagnetic form factors in the hypercentral CQM

  • M. De Sanctis
  • M.M. Giannini
  • E. Santopinto
  • A. Vassallo
Hadronic resonances

Abstract.

We report on the recent results of the hypercentral Constituent Quark Model (hCQM). The model contains a spin independent three-quark interaction which is inspired by Lattice QCD calculations and reproduces the average energy values of the SU(6) multiplets. The splittings are obtained with a SU(6)-breaking interaction, which can include also an isospin dependent term. Concerning Constituent Quark models, we have shown for the first time that the decreasing of the ratio of the elastic form factors of the proton is due to relativistic effects using relativistic corrections to the e.m. current and boosts. Now the elastic nucleon form factors have been recalculated, using a relativistic version of the hCQM and a relativistic quark current showing a very detailed reproduction of all the four form factor existing data over the complete range of 0-4 GeV 2. Futhermore, the model has been used for predictions concerning the electromagnetic transverse and longitudinal transition form factors giving a good description of the medium Q 2 behaviour. We show that the discrepancies in the reproduction of the helicity amplitudes at low Q 2 are due to pion loops. We have calculated the helicity amplitudes for all the 3 and 4 star resonances opening the possibility of application to the evaluation of cross sections.

PACS codes.

13.40.Gp - Electromagnetic form factors 12.39.Jh - Nonrelativistic quark model 14.20.Gk - Baryon resonances and helicity amplitudes 12.39.Ki - Relativistic quark model 12.39.Pn - Potential Models 13.40.Gp - Electromagnetic Form Factors 14.30.Gk - Baryon Resonances with S=0 25.20.Lj - Photoproduction reactions 25.30.Rw - Electroproduction reactions 

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. 1. N. Isgur and G. Karl: Phys. Rev. D 18, 4187 (1978); D 19, 2653 (1979); D 20, 1191 (1979); S. Godfrey and N. Isgur: Phys. Rev. D 32, 189 (1985)Google Scholar
  2. 2. S. Capstick and N. Isgur: Phys. Rev. D 34, 2809 (1986)Google Scholar
  3. 3. M. Ferraris, M.M. Giannini, M. Pizzo, E. Santopinto, and L. Tiator: Phys. Lett. B 364, 231 (1995); E. Santopinto: PhD Thesis, Universitá di Genova (1995)CrossRefGoogle Scholar
  4. 4. L. Ya. Glozman and D.O. Riska: Phys. Rep. C 268, 263 (1996)Google Scholar
  5. 5. L. Ya. Glozman, Z. Papp, W. Plessas, K. Varga, and R.F. Wagenbrunn: Phys. Rev. C 57, 3406 (1998); L. Ya. Glozman, W. Plessas, K. Varga, and R. F. Wagenbrunn, Phys. Rev. D 58, 094030 (1998)CrossRefGoogle Scholar
  6. 6. M. Ripani: to be published on Eur. Phys. J. (2004)Google Scholar
  7. 7. L.Tiator, D. Drechsel, S. Kamalov, E. Santopinto, M.M. Giannini, and A. Vassallo: to be published on Eur. Phys. J. (2004)Google Scholar
  8. 8. G. Bali et al.: Phys. Rev. D 51, 5165 (1995); G. Bali: Phys. Rept. 343, 1 (2001)Google Scholar
  9. 9. P. Hasenfratz, R.R. Horgan, J. Kuti, and J.M. Richard: Phys. Lett. B 94, 401 (1980)CrossRefGoogle Scholar
  10. 10. J.-M. Richard: Phys. Rep. C 212, 1 (1992)Google Scholar
  11. 11. M. Fabre de la Ripelle and J. Navarro: Ann. Phys. (N.Y.) 123, 185 (1979)Google Scholar
  12. 12. E. Santopinto, F. Iachello, and M.M. Giannini: Nucl. Phys. A 623, 100c (1997); Eur. Phys. J. A 1, 307 (1998)CrossRefGoogle Scholar
  13. 13. Particle Data Group: Eur. Phys. J. C 15, 1 (2000)Google Scholar
  14. 14. M. Aiello, M. Ferraris, M.M. Giannini, M. Pizzo, and E. Santopinto: Phys. Lett. B 387, 215 (1996)CrossRefGoogle Scholar
  15. 15. M. Aiello, M.M. Giannini, and E. Santopinto: J. Phys. G: Nucl. Part. Phys. 24, 753 (1998)CrossRefGoogle Scholar
  16. 16. M. De Sanctis, E. Santopinto, and M.M. Giannini: Eur. Phys. J. A 1, 187 (1998)Google Scholar
  17. 17. M. De Sanctis, M.M. Giannini, L. Repetto, and E. Santopinto: Phys. Rev. C 62, 025208 (2000)Google Scholar
  18. 18. L.A. Copley, G. Karl, and E. Obryk: Phys. Lett. 29, 117 (1969)CrossRefGoogle Scholar
  19. 19. R. Koniuk and N. Isgur: Phys. Rev. D 21, 1868 (1980)Google Scholar
  20. 20. F.E. Close and Z. Li: Phys. Rev. D 42, 2194 (1990); Z. Li and F.E. Close: Phys. Rev. D bf 42, 2207 (1990)Google Scholar
  21. 21. V.D. Burkert: private communicationGoogle Scholar
  22. 22. R.A. Thompson et al.: Phys. Rev. Lett. 86, 1702 (2001)Google Scholar
  23. 23. M.M. Giannini, E. Santopinto, and A. Vassallo: to be publishedGoogle Scholar
  24. 24. S. Capstick and B.D. Keister: Phys. Rev. D 51, 3598 (1995)Google Scholar
  25. 25. V.D. Burkert: arXiv:hep-ph/0207149Google Scholar
  26. 26. M. De Sanctis, E. Santopinto, and M.M. Giannini: Eur. Phys. J. A 2, 403 (1998)Google Scholar
  27. 27. M.M. Giannini, E. Santopinto, and A. Vassallo: Eur. Phys. J. A 12, 447 (2001)CrossRefGoogle Scholar
  28. 28. M.K. Jones et al.: Phys. Rev. Lett. B 84, 1398 (2000)Google Scholar
  29. 29. M. De Sanctis, M.M. Giannini, E. Santopinto, and A. Vassallo: to be publishedGoogle Scholar
  30. 30. O. Gayon et al.: Phys. Rev. Lett. 88, 092301 (2002)Google Scholar
  31. 31. M.M. Giannini, E. Santopinto, A. Vassallo, and M. De Sanctis: to be published on Eur. Phys. J. (2004)Google Scholar

Copyright information

© Società Italiana di Fisica, Springer-Verlag 2004

Authors and Affiliations

  • M. De Sanctis
    • 1
  • M.M. Giannini
    • 2
  • E. Santopinto
    • 1
  • A. Vassallo
    • 1
  1. 1.Universit a di Genova e INFN, Sezione di Genova, via Dodecaneso 33, 16142 Genova, Italy
  2. 2.INFN,Sezione di Roma1, Piazzale Aldo Moro, Roma, Italy

Personalised recommendations