Tübingen 2003 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 38: Elektromagnetische und hadronische Proben VI
HK 38.3: Talk
Thursday, March 20, 2003, 14:00–14:15, B
Generalized parton distributions and the energy–momentum tensor in the nucleon — •C. Weiss3 and M.V. Polyakov1,2 — 1Institut für Theoretische Physik II, Ruhr–Universität Bochum — 2Petersburg Nuclear Physics Institute, Russia — 3Institut für Theoretische Physik, Universität Regensburg
The form factors associated with the matrix element of the QCD energy–momentum tensor (EMT) between nucleon states are an important ingredient in the parametrization of generalized parton distributions (GPD’s). They determine e.g. the normalization of the so–called “D–term”, which summarizes certain resonance–exchange contributions to the GPD’s absent in ordinary parton distributions [1]. We study the EMT form factors in the large–Nc limit, describing the nucleon as a topological soliton of the chiral Lagrangian (skyrmion). Extending the chiral Lagrangian to include couplings to vector mesons (ρ, ω) as well as to a scalar dilaton field, we are able to develop a qualitative picture of the role of the various resonances in the EMT form factors, in close analogy to the vector and axial form factors [2]. We also comment on the accuracy with which the EMT form factors can be extracted from model calculations.
[1] M. V. Polyakov and C. Weiss, Phys. Rev. D 60, 114017 (1999)
[2] M. V. Polyakov and C. Weiss, in preparation