The treatment of radiative decays in the tensor formalism is subtle.On the example of radiative J/psi decays the procedure is developed,discussing several methods to construct the amplitudes.In the appendices,spin wave functions,different gauges and form factors for radiative dcays are adressed.
Taking the process antiproton proton to omega pi0,omega to pi0 gamma as example the rho matrix of the final state is derived in the helicity formalism taking into account P- and C-conservation.The differential cross section and the gamma polarization observables are calculated using Mathematica.A comparison with similar calculations for the decay omega to pi+ pi+ pi0 is performed.
Submitted by u.kurilla on Tue, 25/02/2014 - 14:41.
The analysis of pbar p reactions in flight has been started up to now from the JPC intermediate states(Standard Method).The problem with the Standard Method is,that additional Clebsch-Gordan Coefficients describing the coupling of the pbar p system with the JPC system are not taken correctly into account.The same is true for the kinematical factors(different for different beam-energies).They are important in the comparison of amplitudes at different p energies.Here,the whole reaction chain is described starting from the antiproton- and proton- helicity states, avoiding the above mentioned complications.That is done for the pbarp→ωπ0, ω→π0γ reaction, but can be easily expanded to more general cases. A comparison of the results with the Standard Method is performed showing that the Standard Method does not reproduce the correct sign of the amplitudes. Also the spin density matrix of the omega is discussed and the determination of its elemen ts using different methods is outlined.