One of the biggest quests in nuclear and particle physics in the last three decades is to unravel the spin structure of hadrons like protons and neutrons. Spin not only plays a central role in the strong force connecting the elementary constituents of matter, but is also responsible for many of its fundamental properties including the magnetic moment which defines the magnetic properties, the different phases in low temperature physics, and the stability of the universe in general. The origin of the spin of particles like protons and neutrons, which make up to 99.9% of the visible universe, has been the focus of experimental and theoretical efforts. Experiments at European Muon Collaboration (EMC) found that our knowledge of how the spin of the nucleon is derived from its elementary constituents is naive, and our interpretations are not valid. This was termed the spin crisis, an outstanding puzzle for more than three decades and is still not solved. Deciphering the spin puzzle requires knowing the spin of elementary constituents of these particles, quarks and gluons. One of the major objectives of the Relativistic Heavy Ion Collider (RHIC) spin program at Brookhaven National Laboratory is the measurement of the gluon helicity contribution to the proton spin via measuring the double helicity asymmetry (ALL) in various channels. In Pioneering High Energy Nuclear Interaction eXperiment (PHENIX) we measure ALL in π0 meson production. The π0 meson is reconstructed through its di-photon decay channel. The photons are detected by the PHENIX Electromagnetic Calorimeter, which consists of lead glass and lead scintillator detectors and covers a rapidity of |η|< 0.35 and azimuthal angle of 180°. In this dissertation, the results of ALLin π0 production from the data collected in 2013 at center of mass energy = 510 GeV are presented. In 2013, the total integrated luminosity is 150 pb-1 which is almost ten times the total luminosity recorded in 2009 at center of mass energy = 200 GeV. Due to the increase in the center of mass energy and integrated luminosity, these measurements cover the Bjorken x range down to ~0.01. A non-zero ALL result is observed that is consistent with positive gluon polarization in the probed kinematics.

abstract: The nucleon resonance spectrum consists of many overlapping excitations. Polarization observables are an important tool for understanding and clarifying these spectra. While there is a large data base of differential cross sections for the process, very few data exist for polarization observables. A program of double polarization experiments has been conducted at Jefferson Lab using a tagged polarized photon beam and a frozen spin polarized target (FROST). The results presented here were taken during the first running period of FROST using the CLAS detector at Jefferson Lab with photon energies ranging from 329 MeV to 2.35 GeV. Data are presented for the E polarization observable for eta meson photoproduction on the proton from threshold (W=1500 MeV) to W=1900 MeV. Comparisons to the partial wave analyses of SAID and Bonn-Gatchina along with the isobar analysis of eta-MAID are made. These results will help distinguish between current theoretical predictions and refine future theories. / Dissertation/Thesis / Ph.D. Physics 2011

The first-time measurement of the angular dependence of the beam-helicity asymmetry for $\gamma p \rightarrow pK^{+}K^{-}$ is shown and compared to $\gamma p \rightarrow p\pi^{+}\pi^{-}$. The data obtained were from the CLAS g12 experiment at Jefferson Lab. The experiment utilized a beam of circularly polarized photons with energies between 1.1 and 5.4 GeV incident on an unpolarized liquid hydrogen target, which produced an unprecedented number of strange hadrons in photoproduction. The production mechanism for strange hadrons is not well understood. The beam-helicity asymmetry is a polarization observable that provides information on interfering production mechanisms in the reaction. It is shown that the asymmetry is sensitive to several kinematic variables that are key in modeling the reaction dynamics. Furthermore, the comparison of the beam-helicity asymmetry between the kaon and pion channels serves as a platform for the investigation of flavor dependence. A partial wave analysis on the $pK^{-}$ system is also performed in a search for missing hyperon excitations.