A new potential for quarkonium

We suggest a new potential for bound states of a heavy quark-antiquark pair. This potential has a logarithmic piece interpolating between a confining linear part at large distances and an asymptotically free Coulombic part at short distances. We show that the logarithmic piece of our potential considerably influences the $\text{ψ}\text{J}$-family spectrum, and dominates the ?-family. An excellent fit to the $\text{psi;}\text{J}$ data below the DD? threshold and the correct ?′?? mass splitting is obtained in a natural way. We suggest a possible test for this new potential through the leptonic widths of the ?-family.     

A comment on the potential in heavy quarkonium quantum-mechanical systems

I discuss the characteristics of the non-relativistic potential responsible for the ψ and ? systems. In particular a comparison is made between the recently advocated flavour independent power behaved potential and the QCD inspired Coulomb + linear potential. The ratios $\text{ΔM}{}_{\mathrm{?}}\text{ΔM}{}_{\mathrm{\psi }}$ of radical excitation energy level differences are used as sensitive tests to the r dependence of V(r). Deviations of these ratios from a constant value may indicate a gradual increase in the effective power of the potentials as r increases (in agreement with the Coulomb + linear potential). Decisive tests have to come from the not yet discovered toponium family where the ratios $\text{ΔM}{}_{\mathrm{T}}\text{ΔM?}$ should start to become greater than 1 if a singularity of the potential exists at r → 0.     

Effective field theories for the heavy quarkonium

We briefly review how nonrelativistic effective field theories give us a definition of the QCD potentials and a coherent field-theory-derived quantum-mechanical scheme to calculate the properties of bound states made by two or more heavy quarks. In this framework heavy quarkonium properties depend only on the QCD parameters (quark masses and α _s ) and nonpotential corrections are systematically accounted for. The relation between the form of the nonperturbative potentials and the low-energy QCD dynamics is also discussed.     

A phenomenological woods-saxon potential for p-shell nuclei

The parameters of a Woods-Saxon potential well have been determined for ten p-shell nuclei by fitting the electron scattering form factors and single-particle binding energies. The resulting radius shows, for all but very light nuclei, a regular $\text{A}\text{1}\text{3}$ dependence while the depth smoothly decreases with the increasing proton energy. The observed energy dependence may be ascribed to the non-locality of the HF potential. An energy-independent non-local potential, compatible with elastic electron and proton scattering, is proposed in the energy range ?50 to +50 MeV.     

A new polarization potential for heavy ion fusion spin distribution

The real part of the polarization potential which depends on both energy and angular momentum is calculated in a simple way using dispersion relation. A barrier penetration model (BPM) has been used to explain the fusion cross-section and compound nucleus spin distribution for³²S+⁶⁴Ni system in the energy range 50–75 MeV. It is also shown that the polarization potential which only depends on energy, is not adequate to give rise to correct spin distribution even after including any radial dependence. The proposed polarization potential with implicitE andl dependences is able to explain both fusion cross-section and average spin values.     

Bag like potential and quarkonium

We discuss the properties of charmonium in the frame work of a bag like potential and show that the upsilon and charmonium spectra can be fitted by a common potential.     

Analysis of the QCD sum rules for the heavy quarkonium

We study phenomenologically the QCD sum rules given by Shifman et al. for the heavy quarkonium. In the charmonium sum rules, we find that the contribution of the physical continuum to the moment ?_n is consistent with that of the effective one. As for the bottonium, the sum rules corrected by the Coulomb-like interaction are saturated very well by the four resonances observed at CESR. It is predicted that the³S₁ ground state of the toponium must exist in the range of \(M_{t\bar t} \) =30–44GeV, if the sum rules for the top quark are assumed.     

Search for promptly produced heavy quarkonium states in hadronic Z decays

A search has been made for direct production of heavy quarkonium states in more than 3 million hadronic Z ⁰ decays in the 1991–1994 DELPHI data. Prompt J/ψ, ψ(2S) and Υ candidates have been searched for through their leptonic decay modes using criteria based on the kinematics and decay vertex positions. New upperlimits are set at the 90% confidence level for Br(Z⁰ → (QQ) X)/Br (Z⁰ → hadrons) for various strong production mechanisms of J/ψ and Υ these range down to 0.9 × 10^?4. The limits are set in the presence of a small excess (～ 1% statistical probability of a background fluctuation) in the sum of candidates from prompt J/ψ, ψ(2S), Υ(1S),Υ(2S) and Υ(3S) relative to the estimated background.     

A new representation of the heavy ion Coulomb potential

The Coulomb potential between two heavy ions at their interpretation condition has been represented in terms of two point charges with reduced effective charge, dependent on overlap volume. This representation enables visualization of the dynamic development of the deformations of the colliding nuclei as a function of the degree of overlap. The potential has been compared with well known potentials for heavy-ion collisions. This Coulomb potential gave good agreement in reproducing excitation functions for fusion for a large number of heavy-ion systems.     

Influence of hadronic channels on heavy quarkonium systems

Using theP-matrix formalism the influence of hadronic channels on states of the J/ψ andY family is estimated. The influence is small for states below open charm respectively beauty threshold (shifts ?5 MeV) and moderate (shifts ?50 MeV) for those above threshold.     

A phenomenological approch to α-clustering in heavy nuclei

We suggest that α-clustering may play an important role in the structure of heavy nuclei and propose a phenomenological model for treating it. We discuss the structure of spectra in two simple limits of this model.