Quark-antiquark Interactions Research Articles

On the universality of quark-antiquark interactions in the independent quark model

Parameters of the QCD-motivated static potential are evaluated on the basis of 1 −− meson mass spectra. Their values are found to be with high precision the same for different quark-antiquark interactions independently on the quark flavours. Using these universal parameters the renormalization group invariant masses of quarks are calculated. It is also shown that the masses of π-meson radial excitations in this model are compatible with experimental data.

Studying the quark-antiquark force with inelastic pion-electron scattering.

The concept of studying the internal structure of mesons is explored. Mesons, which are in principle two body quark-antiquark interactions, may be much easier to understand than the nucleon. Measurements of the inelastic form factors to specific final states may permit careful direct studies of various components of the strong force. For example, by looking at vector meson final states the spin flip amplitude can be isolated. Technical difficulties involved in a realistic experiment are examined. Experiments to some final states such as \ensuremath{\rho}, ${\mathit{K}}^{\mathrm{*}}$, and ${\mathit{a}}_{0}$ are practical today.

Quantum-chromodynamic potential model for light-heavy quarkonia and the heavy quark effective theory.

We have investigated the spectra of light-heavy quarkonia with the use of a quantum-chromodynamic potential model which is similar to that used earlier for the heavy quarkonia. An essential feature of our treatment is the inclusion of the one-loop radiative corrections to the quark-antiquark potential, which contribute significantly to the spin-splittings among the quarkonium energy levels. Unlike $c\bar{c}$ and $b\bar{b}$, the potential for a light-heavy system has a complicated dependence on the light and heavy quark masses $m$ and $M$, and it contains a spin-orbit mixing term. We have obtained excellent results for the observed energy levels of $D^0$, $D_s$, $B^0$, and $B_s$, and we are able to provide predicted results for many unobserved energy levels. Our potential parameters for different quarkonia satisfy the constraints of quantum chromodynamics. We have also used our investigation to test the accuracy of the heavy quark effective theory. We find that the heavy quark expansion yields generally good results for the $B^0$ and $B_s$ energy levels provided that $M^{-1}$ and $M^{-1}\ln M$ corrections are taken into account in the quark-antiquark interactions. It does not, however, provide equally good results for the energy levels of $D^0$ and $D_s$, which indicates that the effective theory can be applied more accurately to the $b$ quark than the $c$ quark.

Global Solutions of the Schrödinger Equation with Coulomb plus Linear Potential

Normalizable solutions of the Schrödinger equation with a potential of the type used to describe the quark-antiquark or quark-quark interactions are discussed. The eigenenergies are computed by connecting the series solutions near the origin with the formal asymptotic solutions. The Regge trajectories for the charm-anticharm and the bottom-antibottom systems are obtained in that way.

Composite structure of electrons and a proposed static potential for quark-antiquark interactions

A Yukawa-like model of an electron consisting of a source and a field quantum leads to a 70.028 MeV/ c 2 particle identified as a light quark. A generalization of the static potential energy V(r) = −( αℏc r )[1 − exp(−2μr)] , obtained with this model is suggested as an appropriate quark-antiquark potential energy and is applied to a structure calculation for the π 0, yielding a predicted mass of 134.90 MeV/ c 2.

Antibaryon-Baryon Scattering Problem

The implications of the failure of duality in $\overline{B}B$ scattering are discussed in the framework of a quark model in which all quarks of the target interact simultaneously with all quarks in the projectile through two-body quark-antiquark interactions. It is assumed that the peculiarity of $\overline{B}B$ interactions, which at the particle level manifests itself through annihilation channels, is due to the strong $q\overline{q}$ interaction at the quark level which inhibits the presence of non-active quarks (spectators) in the scattering process. This leads to the replacement of the additivity approach of quark amplitudes by factorization of quark amplitudes. Factorization of quark amplitudes implies, in general, nonfactorization of particle amplitudes and appearance of effects similar to cuts (dips versus peaks in the forward direction) due to the simultaneous exchange of natural and unnatural parity at the quark level. Exchange of exotic quantum numbers appears as a natural consequence of the model, without assuming the existence of exotic particles. It is, however, inhibited by the smallness of charge- and strangeness-exchange cross sections. This model should apply both for large- and small-angle scattering, the difference in these two regions manifesting itself only through different relations between the helicity amplitudes at the quark level. Predictions are made for quasielastic $\overline{B}B$ scattering at small and large momentum transfer. For the reactions where data exist, the agreement between the relations predicted by the model and experiment is satisfactory.