Phenomenological Study Of The Space- And Time-like Electromagnetic Form Factors Of The Pion And Kaon

The electromagnetic form factors of hadrons are important physical observables for the de-scription of exclusive reaction mechanisms. The study of them not only provide useful informa-tion concerning the internal structures of the hadrons, but also play a key role in understanding the transition from the perturbative to the non-perturbative behavior at intermediate energies, providing useful grounds to check the rightness of the perturbative QCD (PQCD) theory. Since the electromagnetic form factors of hadrons are such a popular topic that there have been exten-sive experimental and theoretical studies of them based on various different approaches during the past few decades. This thesis is devoted to give a phenomenological study of the space-and time-like electromagnetic form factors of the two lightest pseudoscalar mesons (πand K) in the intermediate energy region within the framework of PQCD factorization by a combination of model and PQCD calculations.We first give a brief review on the both experimental and theoretical study methods of the meson electromagnetic form factors and the light-cone (LC) distribution amplitudes (DAs) of the pseudoscalar meson. Then, motivated by the recent CLEO data, we present a combined analysis of the space-and time-like pion and kaon electromagnetic form factors in factorized PQCD by employing an analytic model for as(Q2) and an infrared (IR) finite gluon propagator and compare our results with the presently available experimental data. Our analysis shows that at low and moderate momentum transfers, compared with the standard LO twist-2 perturbative contribution, the contributions from the non-perturbative effects and the twist-3 meson LC DAs are important and should be took into account, in addition, the existing experimental data at moderate energies, including the CLEO data and J/ψresult can be reasonably well described by our results. To this end, we should point out that although the recent CLEO data provide the first precision measurements of the pion and kaon electromagnetic form factors for time-like momentum transfer ofQ2= 13.48 GeV, there is still lack of the accurate experimental data in the relative high energy region. Hopefully, with the availability of better quality experimental data in the future, there could be a better testing ground for theoretical predictions.