2 research outputs found
Jets in Deep Inelastic Scattering and High Energy Photoproduction at HERA
Recent results on jet production in neutral current deep inelastic scattering
and high energy photoproduction at the HERA electron-proton-collider are
briefly reviewed. The results are compared to QCD expectations in NLO and
determinations using these data are summarized.Comment: 12 pages, 10 figures, talk given at the 9th Adriatic Meeting
"Particle Physics and the Universe" in Dubrovnik/Croatia, 4.-24.9.200
(In-)Consistencies in the relativistic description of excited states in the Bethe-Salpeter equation
The Bethe-Salpeter equation provides the most widely used technique to
extract bound states and resonances in a relativistic Quantum Field Theory.
Nevertheless a thorough discussion how to identify its solutions with physical
states is still missing. The occurrence of complex eigenvalues of the
homogeneous Bethe-Salpeter equation complicates this issue further. Using a
perturbative expansion in the mass difference of the constituents we
demonstrate for scalar fields bound by a scalar exchange that the underlying
mechanism which results in complex eigenvalues is the crossing of a normal (or
abnormal) with an abnormal state. Based on an investigation of the
renormalization of one-particle properties we argue that these crossings happen
beyond the applicability region of the ladder Bethe-Salpeter equation. The
implications for a fermion-antifermion bound state in QED are discussed, and a
consistent interpretation of the bound state spectrum of QED is proposed.Comment: 39 pages, 14 figures, LaTeX2e, uses amssymb, minor changes,
references added, to appear in Annals Phy