QCD phenomenology from effective field theories

In this thesis, we use effective field theories to study the phenomenology of Quantum Chromodynamics (QCD). We develop quenched Chiral Perturbation Theory for vector mesons and heavy baryons. In this framework we calculate the leading non-analytic dependence of their masses on the masses of the light quarks. By comparing with analogous quantities computed in ordinary chiral perturbation theory, we estimate the size of quenching effects. We find that in general errors introduced by quenching could be large. This estimate is relevant to lattice simulations. We use the heavy quark effective theory and ChPT to estimate the expected width of $X+c1JP=32+$ baryon. We discuss the phenomenology of the excited csq and css states, and consider what additional charmed baryons might be observable in the future. We point out that the final state $Xc$K could be an interesting new channel to examine. We study the production of charmonium hybrids in B decays. We use the operator product expansion and nonrelativistic QCD to organize the various contributions to this process. We express the decay rate in terms of a few matrix elements which eventually will be fixed by experimental measurements or calculated on the lattice. While the Fock state expansion is problematic for hybrids, in that there is no perturbative large mass limit, the operator product expansion still provides a model independent framework for phenomenological calculations of hybrid production and decay. We then use a simple flux tube model to estimate the branching ratio B → $yg$ + X, where $yg$ is a JPC = 0+− hybrid, the large production of which could help resolve the low charm multiplicity and semileptonic branching ratio observed in B decays. We also investigate the possible contributions of tensor charmonium production. We observe that it is unlikely for either effect to be large enough to play a significant role in resolving these problems. We investigate the radiative leptonic decay B_c → γl$n$ within the framework of NRQCD, an effective field theory formulated for non-relativistic quarks. This process is an important background to the annihilation process B_c → l$n$ which will be used to extract the B_c decay constant.