Summary
Ambiguities in the nuclear electromagnetic current operator within the nuclear medium are used to examine the significance of the off-shell form of the current operator for the case of40Ca. The standard form of the electromagnetic current operator and two alternate forms, one of which is the popular de Forest prescription, are used to study current operator ambiguities in the context of the quasi-elastic (e, e′) and (e, e′p) reactions in the presence of realistic final-state interactions. Nucleons may themselves be modified in the nuclear medium and the associated modification of the current operator, which has been modelled through the use of density-dependent form factors, is studied here in the (e, e′p) reaction. For the quasi-elastic inclusive reaction we find large current-operator-dependent effects in both the longitudinal and transverse response. For the transverse response these effects are clearly linked to the nature of the final-state interactions and are traced to virtual pair processes present in the relativistic case. In particular, the de Forest current yields a greatly enhanced transverse response and a large high-energy tail in the relativistic case. Current operator ambiguities do not seriously affect Coulomb Sum Rule saturation trends and produce less dramatic effects for the exclusive (e, e′p) reaction. Our results suggest that present knowledge of the nucleon electromagnetic current operator is insufficient to allow firm predictions of the electronuclear reactions to be made to the precision required to resolve other physical issues.
Similar content being viewed by others
References
C. R. Chinn, A. Picklesimer andJ. W. Van Orden:Phys. Rev. C,40, 790 (1989).
T. de Forest:Nucl. Phys. A,392, 232 (1983).
A. M. Bincer:Phys. Rev.,118, 855 (1960).
X. Song, J. P. Chen, P. K. Kabir andJ. S. McCarthy:J. Phys. G,17, L-75 (1991).
H. W. L. Naus andJ. H. Koch:Phys. Rev. C,36, 2459 (1987).
P. C. Tiemeijer andJ. A. Tjon:Phys. Rev. C,42, 599 (1990).
H. W. L. Naus, S. J. Pollock, J. H. Koch andU. Oelfke:Nucl. Phys. A,509, 717 (1990).
C. Itzykson andJ.-B. Zuber:Quantum Field Theory (McGraw-Hill Book Company, San Francisco, Cal., 1980).
C. R. Chinn, A. Picklesimer andJ. W. Van Orden:Phys. Rev. C,40, 1159 (1989).
G. Do Dang andNguyen Van Giai:Phys. Rev. C,30, 731 (1984).
Y. Horikawa, F. Lenz andN. C. Mukhopadhyay:Phys. Rev. C,22, 1680 (1980).
A. Dellafiore, F. Lenz andF. A. Brieva:Phys. Rev. C,31, 1088 (1985).
H. Kurasawa andT. Suzuki:Phys. Lett. B,173, 377 (1986).
K. Wehrberger andF. Beck:Phys. Rev. C,35, 298 (1987).
K. Wehrberger andF. Beck:Phys. Rev. C,37, 1148 (1988).
J. R. Shepard, E. Rost andJ. A. McNeil:Phys. Rev. C,40, 2320 (1989).
C. J. Horowitz andJ. Piekarewicz:Nucl. Phys. A,511, 461 (1990).
H. Kurasawa andT. Suzuki:Nucl. Phys. A,490, 571 (1988).
X. Ji:Phys. Rev. C,39, 1668 (1989).
W. M. Alberico, M. Ericson andA. Molinari:Ann. Phys.,154, 356 (1984).
G. Co′, K. Quader, R. D. Smith andJ. Wambach:Nucl. Phys. A,485, 61 (1988).
G. Co′, K. Quader andJ. Wambach:II Workshop on Problems of Theoretical Nuclear Physics, Cortona, Italy, October 5–7, 1987.
S. Drozdz, G. Co′, J. Wambach andJ. Speth:Phys. Lett. B,185, 287 (1987).
S. Fantoni andV. R. Pandharipande:Nucl. Phys. A,473, 234 (1987).
J. Jaenicke, P. Schuck andR. W. Hasse:Phys. Lett. B,214, 1 (1988).
R. W. Lourie et al.:Phys. Rev. Lett.,56, 2364 (1986);57, 653e (1986).
P. E. Ulmer et al.:Phys. Rev. Lett.,59, 2259 (1987).
T. Takaki:Phys. Rev. C,39, 359 (1989);Phys. Rev. Lett.,62, 395 (1989).
P. M. Boucher andJ. W. Van Orden:Phys. Rev. C,43, 582 (1991);H. Sagawa, P. M. Boucher, B. Castel andY. Okuhara:Phys. Lett. B,219, 10 (1989).
A. Picklesimer andJ. W. Van Orden:Phys. Rev. C,35, 266 (1987).
A. Picklesimer andJ. W. Van Orden:Phys. Rev. C,40, 290 (1989).
A. Picklesimer, J. W. Van Orden andS. J. Wallace:Phys. Rev. C,32, 1312 (1985).
L. S. Celenza, A. Rosenthal andC. M. Shakin:Phys. Rev. C,31, 232 (1985).
L. S. Celenza, A. Harindranath andC. M. Shakin:Phys. Rev. C,33, 1012 (1986).
P. J. Mulders:Nucl. Phys. A,459, 525 (1986).
I. Sick:Phys. Lett. B,157, 13 (1985).
G. van der Steenhoven et al.:Phys. Rev. Lett.,57, 182 (1986).
J. V. Noble:Phys. Rev. Lett.,46, 412 (1981).
M. Traini:Phys. Lett. B,171, 266 (1986).
T. D. Cohen, J. W. Van Orden andA. Picklesimer:Phys. Rev. Lett.,59, 1267 (1987).
J. W. Van Orden andT. W. Donnelly:Ann. Phys.,131, 451 (1981).
G. Blunden andM. N. Butler:Phys. Lett. B,219, 151 (1989).
G. Höhler, E. Pietarinen, I. Sabba-Stefanescu, F. Borkowski, G. G. Simon, V. H. Walther andR. D. Wendling:Nucl. Phys. B,114, 505 (1976).
M. Gari andW. Krumpelmann:Phys. Lett. B,173, 10 (1986).
M. V. Hynes, A. Picklesimer, P. C. Tandy andR. M. Thaler:Phys. Rev. C,31, 1438 (1985).
J. C. Ward:Phys. Rev.,78, 182 (1950);Y. Takahashi:Nuovo Cimento,6, 371 (1957).
H. W. L. Naus andJ. H. Koch:Phys. Rev. C,39, 1907 (1989).
C. J. Horowitz andB. D. Serot:Nucl. Phys. A,368, 503 (1981).
R. H. McCamis et al.:Phys. Rev. C,33, 1624 (1986).
E. D. Cooper, B. C. Clark, S. Hama andR. L. Mercer:Phys. Lett. B,206, 588 (1988); Erratum:Phys. Lett. B,220, 658e (1989).
M. A. Franey andW. G. Love:Phys. Rev. C,31, 488 (1985).
J. L. Friar: private communication.
T. de Forest:Nucl. Phys. A,414, 347 (1984).
J. L. Friar:Ann. Phys.,81, 332 (1973).
A. Picklesimer, P. C. Tandy, R. M. Thaler andD. H. Wolfe:Phys. Rev. C,29, 1582 (1984);30, 1861 (1984).
R. Altemus, A. Cafolla, D. Day, J. S. McCarthy, R. R. Whitney andJ. E. Wise:Phys. Rev. Lett.,44, 965 (1980).
P. Barreau et al.: Nucl. Phys. A,358, 287c (1981).
P. Barreau et al.:Nucl. Phys. A,402, 515 (1983).
C. C. Blatchley, J. J. LeRose, O. E. Pruet, P. D. Zimmerman, C. F. Williamson andM. Deady:Phys. Rev. C,34, 1243 (1986).
M. Deady et al.:Phys Rev. C,28, 631 (1983).
M. Deady, C. F. Williamson, P. D. Zimmerman, R. Altemus andR. R. Whitney:Phys. Rev. C,33, 1897 (1986).
B. Frois:Nucl. Phys. A,434, 57c (1985).
A. Hotta, P. J. Ryan, H. Ogino, B. Parker, G. A. Peterson andR. P. Singhal:Phys. Rev. C,30, 87 (1984).
Z. E. Meziani et al.:Phys. Rev. Lett.,52, 2130 (1984).
Z. E. Meziani et al.:Phys. Rev. Lett.,54, 1233 (1985);Nucl. Phys. A,446, 113c (1985).
Author information
Authors and Affiliations
Additional information
This work is performed under the auspices of the U. S. Department of Energy and by the Lawrence Livermore National Laboratory under contract number W-7405-ENG-48.
Rights and permissions
About this article
Cite this article
Chinn, C.R., Picklesimer, A. Off-shell and medium effects on the electromagnetic nucleon current. Nuov Cim A 105, 1149–1177 (1992). https://doi.org/10.1007/BF02730873
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02730873