Theory Of Quantum Chromodynamics Research Articles

Applications of QCD to the Production of Mesons and Jets in Hadron-Hadron Collisions

Applications of the theory of quantum chromodynamics (QCD) with asymptotic freedom to processes involving large momentum transfers are examined. The theory describes correctly many features of the lepton initiated processes eN, μN, vN, vN as well as large-mass muon-pair production and the production of mesons and jets at large p⊥ in hadron-hadron collisons. Some predictions are made for future large p⊥ meson and jet experiments. The preliminary conclusion is that QCD might well be the correct theory behind all these phenomena, although a definitive test has not yet been made.

Electron-positron annihilation energy pattern in quantum chromodynamics: Asymptotically free perturbation theory

High-energy cross sections of quantum chromodynamics can be computed entirely in terms of the renormalization-group running coupling constant if these cross sections have no infrared mass singularities. Since the theory is asymptotically free, at high energies the running coupling constant vanishes and such cross sections can be computed perturbatively. Thus the theory of quantum chromodynamics may be rigorously tested. We compute the angular distribution of the hadronic energy produced in high-energy electron-positron annihilation to second order and find no mass singularities. Our result can be interpreted in terms of a jet opening angle which vanishes logarithmically as the energy increases. We compute phenomenologically the corrections to the energy pattern resulting from nonperturbative confinement effects. They become small at the energies of the colliding-beam machines now under construction.

Non-Abelian gauge theories of Fermi systems: Quantum-chromodynamic theory of highly condensed matter

A systematic perturbation theory for high-density quark gas is developed. The ground-state thermodynamic potential is evaluated up to the second order in the Gell-Mann-Low coupling ${\ensuremath{\alpha}}_{s}(M)$. Phenomenological analysis of the resulting equation of state suggests that the neutron-quark matter phase transition occurs at neutron matter densities ${n}_{B}l2$ baryon/${\mathrm{fm}}^{3}$ provided $0.2l{\ensuremath{\alpha}}_{s}(3 \mathrm{GeV})l0.3$. The result supports the conjecture that superheavy stellar objects may exist in the quark rather than in the neutron phase. The production of quark matter in heavy-ion collisions is also discussed briefly.

On the effective quark potential in baryons

We analyse the splitting of the non-strange memebers of the first excited level [70,1 −] 1 of baryon resonances. The spin-dependent forces (spin-spin, spin-orbit, tensor) are supposed to arise from the Coulomb term due to one-gluon exchange, from the long-range linearly rising part of the potential, and from additional “hard-core” spin-spin terms which may be generated by higher-order graphs contributing to the qq kernel. For the long range part we either assume that it comes from a superposition of a vector and a scalar kernel of the form ϵ( γ μ ⊗ γ μ ⊗ 1 + (1 − ϵ)(1 ⊗ 1 ⊗ 1) (+ permutations), or, alternatively, that it arises from a vector exchange with an anomalous moment κ in the quark-gluon vertex. Values of ϵ ≈ 0 or κ ≈ −1 turn out to be favoured. The strong coupling constant and the slope of the linear potential come out in the correct order of magnitude. Very large hard-core spin-spin terms are needed. This fact makes the determination of the effective potential from the underlying theory of quantum chromodynamics as well as the phenomenological analysis of the observed spectra rather problematic.