Abstract.
The exclusive ω electroproduction off the proton was studied in a large kinematical domain above the nucleon resonance region and for the highest possible photon virtuality (Q2) with the 5.75 GeV beam at CEBAF and the CLAS spectrometer. Cross-sections were measured up to large values of the four-momentum transfer (- t < 2.7 GeV2) to the proton. The contributions of the interference terms σ{TT} and σ{TL} to the cross-sections, as well as an analysis of the ω spin density matrix, indicate that helicity is not conserved in this process. The t-channel π0 exchange, or more generally the exchange of the associated Regge trajectory, seems to dominate the reaction γ*p↦ωp, even for Q2 as large as 5 GeV2. Contributions of handbag diagrams, related to Generalized Parton Distributions in the nucleon, are therefore difficult to extract for this process. Remarkably, the high-t behaviour of the cross-sections is nearly Q2-independent, which may be interpreted as a coupling of the photon to a point-like object in this kinematical limit.
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References
T.H. Bauer , Rev. Mod. Phys. 50, 261 (1978).
L.L. Frankfurt, G.A. Miller, M.I. Strikman, Annu. Rev. Nucl. Sci. 44, 501 (1994).
M. Vanderhaeghen, P.A.M. Guichon, M. Guidal, Phys. Rev. D 56, 2982 (1997).
F. Cano, J.-M. Laget, Phys. Rev. D 65, 074022 (2002).
S. Donnachie, G. Dosch, P. Landshoff, O. Nachtmann, Pomeron Physics and QCD (Cambridge University Press, New York, 2002).
J.-M. Laget, Phys. Lett. B 489, 313 (2000).
M. Battaglieri , Phys. Rev. Lett. 90, 022002 (2003).
X. Ji, Phys. Rev. Lett. 78, 610 (1997)
A.V. Belitsky, A.V. Radyushkin, Report JLAB-THY-04-34 (2004), hep-ph/0504030.
J.C. Collins, L. Frankfurt, M. Strikman, Phys. Rev. D 56, 2982 (1997).
A. Airapetian , Eur. Phys. J. C 17, 389 (2000).
C. Hadjidakis , Phys. Lett. B 605, 256 (2005).
M. Diehl, Phys. Rep. 388, 41 (2003).
J. Ballam , Phys. Rev. D 10, 765 (1974).
C. del Papa , Phys. Rev. D 19, 1303 (1979).
P. Joos , Nucl. Phys. B 122, 365 (1977).
D.G. Cassel , Phys. Rev. D 24, 2787 (1981).
J. Breitweig , Phys. Lett. B 487, 273 (2000).
M. Tytgat, DESY-THESIS-2001-018 (2001).
A.H. Rosenfeld, P. Söding, Properties of the fundamental interactions, in Proceedings of the 1971 International School of Subnuclear Physics, Erice, edited by A. Zichichi, Vol. 9C (Editrice Compositori, Bologna, 1973) p. 883.
L. Morand, Thèse de doctorat, Université Denis Diderot-Paris 7 (2003)
M.L. Stevenson , Phys. Rev. 125, 687 (1962).
B.A. Mecking , Nucl. Instrum. Methods A 503, 513 (2003).
A separate CLAS experiment, under analysis, addresses the low $W$ and low $Q^2$ $\omega$ electroproduction
P. Corvisiero , Nucl. Instrum. Methods A 346, 433 (1994)
L.W. Mo, Y.S. Tsai, Rev. Mod. Phys. 41, 205 (1969).
L.N. Hand, Phys. Rev. 129, 1834 (1963).
Particle Data Group (S. Eidelman ), Phys. Lett B 592, 1 (2004).
J.-M. Laget, Phys. Rev. D 70, 054023 (2004).
K. Schilling, G. Wolf, Nucl. Phys. B 61, 381 (1973).
A. Sibirtsev, K. Tsushima, S. Krewald, Phys. Rev. C 67, 055201 (2003).
M.N. Sergeenko, Z. Phys. C 64, 315 (1994).
K. Goeke, M.V. Polyakov, M. Vanderhaeghen, Prog. Part. Nucl. Phys. 47, 401 (2001).
Pre-conceptual design report for the science and experimental equipment for the 12 GeV upgrade of CEBAF, http:/ /www.jlab.org/ div\_dept/ physics\_division/pCDR\_ public/pCDR\_final.
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Th. Walcher
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The CLAS Collaboration., Morand, L., Doré, D. et al. Deeply virtual and exclusive electroproduction of ω-mesons. Eur. Phys. J. A 24, 445–458 (2005). https://doi.org/10.1140/epja/i2005-10032-4
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DOI: https://doi.org/10.1140/epja/i2005-10032-4