Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1997. / Includes bibliographical references (leaves 124-127). / by Scott P. Palmtag. / Ph.D.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1970. Sc.D. / Errata leaf inserted between leaves 4 and 5. Vita. / Bibliography: leaves 168-174. / Sc.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1991. / Includes bibliographical references (leaf 101). / by Chan Yoo. / M.S.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1970. Ph.D. / Bibliography: leaves 192-197. / Ph.D.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Nuclear Engineering, 1996. / Includes bibliographical references (p. 119-120). / by Jon R. Lunghofer. / M.S.

Massachusetts Institute of Technology. Dept. of Nuclear Engineering. Thesis. 1973. M.S. / Lacking leaf 172. / Bibliography: leaves 86-87. / M.S.

This dissertation presents the first measurement of electron-muon azimuthal correlations at the PHENIX experiment at RHIC in 200 GeV proton-proton and deuteron-gold collisions. Electron-muon pairs result from the semileptonic decay of D mesons, which come from correlated charm pairs. The pairs are measured at forward rapidity, with η < 0.5 for the electron and 1.4 < η < 2.1 for the muon. Electron-muon pairs exhibit a characteristic peak at Δφ = π in the azimuthal distribution due to momentum conservation in the c\bar{c} decay, and this enables clear identification. The shape of the azimuthal pair distribution in p+p collisions helps us determine which hard scattering processes contribute to charm production, and it allows us to test NLO QCD predictions. The p+p result also serves as a baseline measurement for understanding heavy ion collisions. Pairs were also measured in d+Au collisions at forward rapidity in the deuteron-going direction, which is a kinematic region at which we expect suppression effects to be evident. The pair yield in d+Au was found to be suppressed relative to that in p+p. Also the peak in Δφ almost disappears in d+Au, indicating either a change in charm production mechanisms or interactions with the nuclear matter.

The study of strong interactions at very high energies has prompted a large interest in the small-x regime of quantum chromodynamics where partons carry a small fraction of the momentum of their parent hadrons. In this regime gluon occupation numbers are believed to be very high leading to saturation of the corresponding parton densities. This thesis is intended to explore the validity of factorization approaches in the small-x regime and establish a relation with partonic interpretations when possible. Two fundamental unintegrated (transverse momentum dependent) gluon distributions are proposed as fundamental building blocks to describe all processes sensitive to the small-x regime which admit a factorized description. Single-particle production processes and two-particle production processes are studied in asymmetric collisions of a dilute probe scattering from a dense target and it is shown that it is possible to recover factorized expression in a particular kinematical limit.

Collision of heavy nuclei at the Relativistic Heavy Ion Collider (RHIC) recreates the state of high temperature quark-gluon plasma that existed shortly after the Big Bang. Measurement using single particle spectra and two-particle correlation shows that this medium is largely opaque to the transit of a high energy quark or gluon. Reconstructing the kinematics of these quarks and gluons can provide additional constraints for the property of their interaction with the medium. While the direct reconstruction of quantum chromodynamics jets, the final state showers of quarks and gluons, has become an indispensable tool at hadron and electron accelerator experiments, the application of this technique to heavy ion collisions at the RHIC energy has been considered a hard problem. The relatively low yield of high transverse momentum jets would have to be detected within a large, fluctuating background that can give rise to a false jet signal. At the RHIC PHENIX experiment, jet reconstruction also has to cope with the limited aperture of the central arm spectrometers. To overcome both problems, which can distort the jet signal in the traditional reconstruction algorithms, this thesis develops an algorithm that reconstructs the jets as maxima of the Gaussian filtered event transverse momentum distribution. The Gaussian angular weighting causes the algorithm to become more sensitive to the jet core versus the jet periphery. It is then combined with a fake jet rejection discriminant to remove the background fluctuation from the jet signal. This algorithm is used to obtain the first jet measurement in heavy ion environment at PHENIX, using data from the 2004/2005 RHIC run. The result includes the proton-proton inclusive jet spectrum, the proton-proton fragmentation function, the copper-copper jet nuclear modification factor, the copper-copper jet central-to-peripheral modification factor, and the copper-copper dijet azimuthal correlation. The measured copper-copper jet nuclear modification factor shows that there is a significant initial state effect to the jet suppression. The observation of no broadening in the copper-copper dijet azimuthal correlation indicates that the traditional energy loss picture via multiple soft scattering may not be applicable to the quark-gluon plasma.

A new jet tomographic model and numerical code, CUJET, is developed in this thesis and applied to the phenomenological study of the Quark Gluon Plasma produced in Heavy Ion Collisions.