Exclusive processes of charmonium production and charmonium wave functions

Results obtained by studying the properties of the leading-twist wave functions for the S- and P-wave states of charmonia are presented. Wave-function models that can be used to calculate various processes involving the production of these mesons were constructed on the basis of these investigations. Calculations for some exclusive processes of charmonium production were performed within the models in question.     

Radiative transitions of layered semiconductor GaS doped with P

Photoluminescence (PL) measurement has been made on P-doped p-GaS. The 2.35 and 2.12 eV emission bands are observed in the PL spectrum of P-doped sample at 77 K. The temperature dependence of full-width at half-maximum and the shape of the PL spectrum of the 2.12 eV emission band are characterized by the recombination mechanism of the configurational coordinate model. It is found that the 2.12 eV emission band is related to the complex center of vacancy and acceptor due to P atoms. It is found from the presence of the complex center that the P-doped samples include a high concentration of defects or defect complexes.     

Examining coupled-channel effects in radiative charmonium transitions

Coupled-channel effects due to coupling of charmonia to the charmed and anticharmed mesons are of current interest in heavy quarkonium physics. However, the effects have not been unambiguously established. In this Letter, a clean method is proposed in order to examine the coupled-channel effects in charmonium transitions. We show that the hindered M1 radiative transitions from the 2P to 1P charmonia are suitable for this purpose. We suggest to measure one or more of the ratios Γ(h(c)'→χ(cJ)γ)/Γ(χ(cJ)'→χ(cJ)π(0)) and Γ(χ(cJ)'→h(c)γ)/Γ(χ(cJ)'→χ(cJ)π(0)), for which highly nontrivial and parameter-free predictions are given. The picture can also be tested using both unquenched and quenched lattice calculations.     

Radiative E1 decay of the1P1 level of charmonium in the sum rules of quantum chromodynamics

An analysis of the radiative decay¹P₁ ¹S₀ + of charmonium is performed by using the sum rules of quantum chromodynamics (QCD). A sum rule that allows for luon power corrections is obtained, and the decay width _c + is computed.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 80–84, November, 1991.Finally, the author express thanks to professor R. N. Faustov for valuable advice and useful discussion of the resulting work.     

On ηc line shape in charmonium transitions

The line shapes to observe ηc in charmonium transitions, I.e.,ψ(2S), J/ψ→γηc, are investigated. The ηc line shapes in exclusive decays or by observing the inclusive photon spectrum are given. The sensitivities to measure the ηc resonance parameters are also evaluated. With more than two thousand ηc events observed, the precision of the ηc decay width measurement will be improved by better than 3%. However, the uncertainties associated with the ηc modified line shapes will dominate the systematic errors and this will prohibit precision mass and width measurements.     

On the order of levels in charmonium

We prove a theorem concerning the energies of the 2S and 3D states in a potential $\text{V(r) =}\text{?g}{}^2\text{r}\text{+ V}{}_{\mathrm{<mtext>c</mtext>}}\text{(r)}$, where V_c is a non-singular confining potential. If $\text{(}\text{d}\text{d}\text{r)}{}^3\text{(r}{}^2\text{V}{}_{\mathrm{<mtext>c</mtext>}}\text{)}$ is positive, then the 3D state lies above the 2S state, provided

$\text{d}\text{d}\text{r}\text{1}\text{r}\text{d}\text{d}\text{r}\text{2V}{}_{\mathrm{<mtext>c</mtext>}}\text{+r}\text{d}\text{V}{}_{\mathrm{<mtext>c</mtext>}}\text{d}\text{r}\text{< 0, ?}{}_{\mathrm{r}}\text{>0.}$

For V_c = r^α, this corresponds to 0 < α < 2.     

Radiative collisions and two-photon transitions

We explore the heuristic connections between laser-induced energy transfer in radiative collisions and a simple two photon transition involving two near-resonant fields.     

Radiative transitions involving impurities

A many-electron development of effective-mass theory is given, based on a Hartree-Fock viewpoint. The procedure provides a basis for the calculation of polarization effects other than those produced by single point charges. An exact effective-mass differential equation is obtained, taking into account non-parabolicities of the band and gradients of the perturbation. Results are obtained for the matrix-element for dipole emission between two impurity-states in a semiconductor. When applied to the problem of donor-acceptor transfer, the results offer an explanation as to why the no-phonon process is considerably stronger in Ge than in Si, even though dielectric constant and effective-mass magnitude effects predict the opposite. The highly non-parabolic conduction band of Ge is responsible.     

Radiative and nonradiative transitions in atomic systems

In the nonrelativistic limit, radiationless (Auger) transitions are mediated by the Coulomb interaction between two charged particles. It is shown that the standard relativistic generalization or the nonrelativistic Auger interaction yields matrix elements which include both radiationless and radiative transitions. The separation of terms responsible for radiationless transitios is presented.     

Radiative transitions in the system of autoionizing levels of cesium atoms excited by electron impact

We study the energy dependences of electron excitation cross sections of the autoionizing levels (5p ⁵6s ²)² P _3/2 and (5p ⁵5d(³ P)6s)² P _3/2, as well as the autoionization cross sections of cesium atoms in the impact energy range from the excitation threshold to 600 eV. It is established that an increase in the excitation cross section of the ² P _3/2 levels (to 60% of the maximum value) and the deep minimum in the autoionization cross section observed in the energy region of 17–27 eV are caused by the predominance of the radiative decay channel for autoionizing levels with excitation thresholds above 17 eV. The high efficiency of the process is mainly related to the resonance excitation of these levels in the near-threshold energy region.     

Radiative transitions of baryons in the MIT bag

Resonance photoproduction is studied via the MIT bag model and comparison is made with a single quark transition SU(6)_θ analysis. Correspondence is found between the two pictures. The bag model predictions are shown to be in good qualitative agreement with experiment; however, specific numerical results are rather model dependent and in general less successful.     

The effect of colored glue in the charmonium wave function

Using an adiabatic approximation and the MIT bag model, we examine the effect of including a term in the charmonium wave function which contains one quantum of the lowest mode of the transverse gluon field in addition to the quark and antiquark. The amplitude of this term is calculated in perturbation theory, and its presence leads to a significant reduction in magnetic dipole transition rates with no corresponding reduction in electric dipole transitions. Although going in the right direction, the effect is not large enough to explain the discrepancy with the experimental M1 rates.     

Radiative transitions in highly ionised silicon-like ions

Transition energies, oscillator strengths and transition probability values for radiative transitions have been calculated for the highly ionised atoms of Si isoelectronic sequence from Mn¹¹⁺ to Kr²²⁺ for the singly excited states up to principal quantum number n = 7. Time-dependent coupled Hartree-Fock (TDCHF) theory has been used to estimate such transition properties. Most of the results for the oscillator strengths and transition probabilities are new. Transition energies agree reasonably well with available spectroscopic values. Received 25 January 2000 and Received in final form 24 October 2000     

Radiative transitions from singly ionized oxygen

 Fully relativistic calculations have been performed on the states of configurations of singly ionized oxygen. The calculations have been carried out using multi-configuration Dirac-Fock wavefunctions with the inclusion of Breit interaction and quantum electrodynamic contributions. A substantial amount of correlation has also been included in our calculations. The numerical results for more than 150 electric dipole lines in the spectrum of O⁺ are compared with other theoretical and experimental values.