B-(*())(B)over-bar(()*()) intermediate states contribution to Gamma(4S, 5S) -> eta(b) + gamma radiative decay

In this work, we investigate the rescattering effects in the radiative decay Gamma(5S) -> eta(b) + gamma , which were suggested to be crucially important for understanding the anomalous largeness of the branching ratios B(Gamma(5S) -> Gamma(1S) + pi pi) and B(Gamma(5S) -> Gamma(1S) + eta). Our calculations show that the rescattering effects may enhance Gamma(Gamma(10860) -> eta(b) +gamma) by four orders, but the tetraquark structure does not. Recently the BABAR and CLEO collaborations have measured the mass of eta(b) and the branching ratios B(Gamma(2S) -> eta(b) +gamma), B(Gamma(3S) -> eta(b) +gamma). We hope that very soon, Gamma(10860) -> eta(b) + gamma) will be measured and it would be an ideal opportunity for testing whether the rescattering or the tetraquark structure is responsible for the anomaly of B(Gamma(5S) -> Gamma(nS) pi(+) pi(-))(n = 1, 2, 3)), i. e., the future measurements on the radiative decays of Gamma(5S) might be a touchstone of the two mechanisms.

eta production off the proton in a Regge-plus-chiral quark approach

A chiral constituent quark model approach, embodying s- and u-channel exchanges, complemented with a Reggeized treatment for the t channel is presented. A model is obtained allowing data for pi(-)p ->eta n and gamma p ->eta p to be described satisfactorily. For the latter reaction, recently released data by the CLAS and CBELSA/TAPS Collaborations in the system total energy range 1.6 less than or similar to W less than or similar to 2.8 GeV are well reproduced by the inclusion of Reggeized trajectories instead of simple. and. poles. The contribution from "missing" resonances, with masses below 2 GeV, is found to be negligible in the considered processes.

State-to-state dynamics of elementary chemical reactions using Rydberg H-atom translational spectroscopy

In this review, a few examples of state-to-state dynamics studies of both unimolecular and bimolecular reactions using the H-atom Rydberg tagging TOF technique were presented. From the H2O photodissociation at 157 nm, a direction dissociation example is provided, while photodissociation of H2O at 121.6 has provided an excellent dynamical case of complicated, yet direct dissociation process through conical intersections. The studies of the O(D-1) + H-2 --> OH+H reaction has also been reviewed here. A prototype example of state-to-state dynamics of pure insertion chemical reaction is provided. Effect of the reagent rotational excitation and the isotope effect on the dynamics of this reaction have also been investigated. The detailed mechanism for abstraction channel in this reaction has also been closely studied. The experimental investigations of the simplest chemical reaction, the H-3 system, have also been described here. Through extensive collaborations between theory and experiment, the mechanism for forward scattering product at high collision energies for the H+HD reaction was clarified, which is attributed to a slow down mechanism on the top of a quantized barrier transition state. Oscillations in the product quantum state resolved different cross sections have also been observed in the H+D-2 reaction, and were attributed to the interference of adiabatic transition state pathways from detailed theoretical analysis. The results reviewed here clearly show the significant advances we have made in the studies of the state-to-state molecular reaction dynamics.