Speaker
Prof.
Paul Hoyer
(University of Helsinki)
Description
I discuss an analytic, first principles approach to QCD bound states based on an expansion in $\alpha_s$. As for QED atoms, the main features (including confinement) appear already at Born level (lowest order in $\hbar$, no loops). The classical gluon field is determined by Gauss’ law using as boundary condition a non-vanishing field strength at spatial infinity. In an equal-time, Hamiltonian formulation this implies a linear potential for mesons and a similar confinement for baryons. Poincaré invariance is preserved only for color singlet states. Hence the $O(\alpha_s^0)$ bound states (rather than single quarks and gluons) can serve as *in* and *out* states of the perturbative expansion.
The Born states are fully relativistic and have interesting properties under boosts. Quark-hadron duality is observed and the OZI rule is qualitatively understood. Pair production by the confining field leads to string breaking and calculable hadron loop corrections, as required for unitarity at $O(\alpha_s^0)$.
Author
Prof.
Paul Hoyer
(University of Helsinki)
