Bound states and asymptotic limits for quantum chromodynamics in two dimensions

For quantum chromodynamics in two dimensions in the limit of an increasing number of colors (N/sub C/ → infinity) with g2N/sub C//π equivalent m2 fixed, the meson bound-state problem requires the solution to 't Hooft's integral equation. For low masses, we express the 't Hooft equation as an explicit matrix problem, which enables us to calculate accurate masses m/sub n/2, (n = 0,1,...,50) and wave functions phi/sup a/b-bar/sub n/(x) for the quark (a) -antiquark (b-bar) bound states. In the large-mass (or WKB) limit, the 't Hooft equation is solved analytically. We obtain the spectrum m/sub n/2 = π2m2(n + 3/4) + (m/sub a/2 + m/sub b/2)lnn + C (m/sub a/2) + C (m/sub b/2) + O (1/n), where C (m/sub a/2) is explicitly calculated. The corresponding WKB wave function, phi/sup a/b-bar/sub n/(x) approx. = √2over-bar sin[(n + 1) πx + delta/sup a/b-bar/sub n/(x)], has a phase shift delta/sup a/b-bar/sub n/(x), which is crucial for obtaining the following new asymptotic results for meson bound-state amplitudes: (1) The normalization of the scaling term for e+e- → X and e-h → e-X is demonstrated to agree exactly with the parton model. (2) The inclusive cross section for e+e- → hX is given by the sum over quark fragmentation (a → h + b) functions D/sub h//a(x/sub F/) = vertical-barPhi/sub n//sup a/b-bar(1/x/sub F/) vertical-bar2, where the complex amplitude Phi/sup a/b-bar/sub n/(x) is the analytic continuation of the wave function phi/sup a/b/sub n/(x) to x > 1