arXiv subjects

Peter Kroll

Publications and source records attributed to Peter Kroll.

41 records · Page 3Linked to original sources

arXiv1997

Exclusive charmonium decays

The role of power corrections and higher Fock-state contributions to exclusive charmonium decays will be discussed. It will be argued that the J/Psi (Psi') decays into baryon-antibaryon pairs are dominated by the valence Fock-state contributions. P-wave charmonium decays, on the other hand, receive strong contributions from the c cbar g Fock states since the valence Fock-state contributions are suppressed in these reactions. Numerical results for J/Psi (Psi') --> B Bbar decay widths will be also presented and compared to data.

hep-ph↗

arXiv1997

A perturbative approach to the eta_c-gamma transition form factor

The eta_c-gamma transition form factor is calculated within a perturbative approach. For the eta_c-meson, a wave function of the Bauer-Stech-Wirbel type is used where the two free parameters, namely the decay constant f(eta_c) and the transverse size of the wave function, are related to the Fock state probability and the width for the two-photon decay Gamma[eta_c -> gamma gamma]. The Q^2 dependence of the eta_c-gamma transition form factor is well determined.

hep-ph↗

arXiv1997

Higher Fock states and power counting in exclusive P-wave quarkonium decays

Exclusive processes at large momentum transfer Q factor into perturbatively calculable short-distance parts and long-distance hadronic wave functions. Usually, only contributions from the leading Fock states have to be included to leading order in 1/Q. We show that for exclusive decays of P-wave quarkonia the contribution from the next-higher Fock state |Q Qbar g> contributes at the same order in 1/Q. We investigate how the constituent gluon attaches to the hard process in order to form colour-singlet final-state hadrons and argue that a single additional long-distance factor is sufficient to parametrize the size of its contribution. Incorporating transverse degrees of freedom and Sudakov factors, our results are perturbatively stable in the sense that soft phase-space contributions are largely suppressed. Explicit calculations yield good agreement with data on chi_{c J} decays into pairs of pions, kaons, and etas. We also comment on J/psi decays into two pions.

hep-ph↗

arXiv1997

Exclusive J/Psi and Psi'decays into baryon-antibaryon pairs

Within a perturbative approach we investigate decays of charmonium states into baryon-antibaryon pairs. Using a recently proposed wave function for the nucleon and suitable generalizations of it to the hyperons and decouplet baryons, we obtain the decay widths for the baryon-antibaryon channels in reasonable agreement with data. An important difference to previous work is the use of the c-quark mass in the perturbative calculation instead of the charmonium mass. As a consequence of this feature our approach possesses, the J/Psi and the Psi' decay widths do not scale with a high power of the ratio of their masses.

hep-ph↗

arXiv1997

The $πγ$ transition form factor and its impact on charmonium decays into two pions

The analysis of the $πγ$ transition form factor provides severe constraints on the pion's wave function. This information is used to examine charmonium decays into two pions critically. It will be argued that the standard perturbative QCD analysis of these reactions fails, i.e. the need for additional contributions can convincingly be demonstrated. Colour-octet admixtures to the charmonium states are proposed as a possible dynamical mechanisms to solve the puzzle. Consequences of the $πγ$ analysis for the electromagnetic form factor of the pion are also discussed.

hep-ph↗