abstract

The mesons A\(_1\)(1270), Q\(_1\)(1280), D(1285), E(1400) are tentatively classified according to the \(J^{PC}=1^{++}\) nonet of SU(3) and the quark antiquark contents of the two isoscalars are estimated by the use of the usual SU(3) symmetry-breaking mechanism. Then the harmonic oscillator quark model for mesons is used to calculate the widths of the decays A\(_1\)(1270) \(\to \rho \pi \), Q\(_1\)(1280) \(\to \) K\(^*\pi \) and D(1285) \(\to \delta \)(980)\(\pi \). We get reasonable widths for these decays with the harmonic oscillator parameter \(\alpha ^2 \simeq 0.055\) GeV\(^2\) and the quark–pion coupling constant \(f^2_{\rm q}\simeq 0.371\). The main result is that a much smaller \(\alpha ^2\)-value (than the one used in the description of baryon decays) is needed to describe the mesonic processes. This conclusion is consistent with the model results obtained for the radiative widths of the “old” \(L = 0\) mesons, the decay \(\psi \to \gamma \pi ^0\) the radiative widths of the low-lying positive parity \(L = 1\) “old” mesons and the decays A\(_2\)(1310) \(\to \rho \pi \), A\(_2\)(1310) \(\to \eta \pi \); \(\psi \to \rho \pi \), D\(^* \to \) D\(\pi \); A\(_3\)(1660) \(\to \) f\(\pi \) and A\(_3\)(1660) \(\to \rho \pi \).

abstract

We perform a mass renormalization scheme invariant analysis of the ITEP heavy quarkonium sum rules in terms of the scale invariant mass \(\hat m\), thus relating in an unambiguous manner the quarkonium data to the basic QCD parameters \(\hat m\) and \({\mit \Lambda }_{\overline MS}\). Satisfactory predictions are obtained for all low-lying charmonium states, except the scalar and pseudoscalar ones, for 150 MeV \(\lt {\mit \Lambda }_{\overline MS}\lt \) 250 MeV. The gluon condensate comes out in average a factor of 3 smaller than the ITEP value. Both expanded and unexpanded ratios are used, yielding similar results. Bottonium sum rules in the vector channel are shown to be consistent with the results of the charmonium sector.

abstract

We review some recent work on quarkonium and discuss in particular how naive models can be improved to include nonperturbative quark loops phenomenologically using the unitarized quark model. We argue that such nonperturbative loops which are required by unitarity and finite widths play an important role in shifting hadron masses by up to 100’s of MeV, generating considerable resonance mixings and higher Fock space (multi-quark) components in hadron wave functions. Many effects currently often ascribed to gluon exchange alone can also be described by quark loops. Allowing for a smaller \(\alpha _{rm s}\) in bound states nonperturbative quark loops could e.g., resolve the puzzle of absence of the \(\vec {L}\cdot \vec {S}\) term in baryon spectroscopy. Even for the heavy upsilon states the mass shifts axe as large as up to 80 MeV — and in particular the 5S mass, being above the B\(\bar {\rm B}\) threshold provides a sensitive test to these ideas.

abstract

The review of QCD determination of static and dynamical properties of hadrons is given. Hadron masses, their transition constants into quark currents, meson formfactors at intermediate momentum transfers, mesonic partial widths and structure functions at small \(x\) arc considered. A special attention is paid to calculation of static parameters of hadrons in external fields (nucleon and hyperon magnetic moments, interaction constants with axial currents).

abstract

General kinetic formulae taking into account an arbitrary number of \(\mu \)-atomic and \(\mu \)-molecular transitions in the chain leading to the muon-catalyzed nuclear synthesis in a D\(_2\) or T\(_2\) target with possible \(Z \gt 1\) contaminations are derived. Application of the obtained formulae to the analysis of the experimental data is discussed.

abstract

A general framework is proposed for description of the cycle-by-cycle evolution in time of the processes forming the muon-catalysis chain leading to nuclear synthesis in mixtures of hydrogen isotopes. In the approximation of constant transition rates, practically any \(\mu \)-atomic and \(\mu \)-molecular processes can be taken into account and treated strictly. Energy-dependent rates can be also dealt with in an approximate manner. Formulae in which the experimental detection efficiency is taken into account are also presented.