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Studying the acceleration and propagation mechanisms of Galactic cosmic rayscan provide information regarding astrophysical sources, the properties of ourGalaxy, and possible exotic sources such as dark matter. To understand cosmicray acceleration and propagation mechanisms, accurate measurements of differentcosmic ray elements over a wide energy range are needed. The PAMELA experimentis a satellite-borne apparatus which allows different cosmic ray species to beidentified over background. Measurements of the cosmic ray antiproton flux andthe antiproton-to-proton flux ratio from 1.5 GeV to 180 GeV are presented inthis thesis. Compared to previous experiments, PAMELA extends the energy rangeof antiproton measurements and provides significantly higher statistics. Thederived antiproton flux and antiproton-to-proton flux ratio are consistent withprevious measurements and generally considered to be produced as secondaryproducts when cosmic ray protons and helium nuclei interact with theinterstellar medium.  To constrain cosmic ray acceleration and propagation models, the antiprotondata measured by PAMELA were further used together with the proton spectrumreported by PAMELA, as well as the B/C data provided by other experiments.Statistical tools were interfaced with the cosmic ray propagation packageGALPROP to perform the constraining analyses. Diffusion models with a lineardiffusion coefficient and modified diffusion models with a low energydependence of the diffusion coefficient were studied in the $\chi^{2}$ study.Uncertainties on the parameters and the goodness of fit of each model weregiven. Some models are further studied using the Bayesian inference. Posteriormeans and errors of the parameters base on our prior knowledge on them wereobtained in the Bayesian framework. This method also allowed us to understandthe correlation between parameters and compare models.

Measurements of cosmic ray antiprotons with PAMELA and studies of propagation models