UMD Theses and Dissertations

Permanent URI for this collectionhttp://hdl.handle.net/1903/3

New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a given thesis/dissertation in DRUM.

More information is available at Theses and Dissertations at University of Maryland Libraries.

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    Directed Flow In Heavy Ion Collisions at sqrt{s_NN}=2.76 TeV
    (2015) Gomez, Jaime Arturo; Mignerey, Alice L; Chemical Physics; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    The directed flow of charged particles at midrapidity is measured in Pb-Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV relative to the collision Event Plane, defined by the participant plane using various subdetectors. The rapidity-even directed flow component is measured for the first time using an Event Plane weighted by the transverse momentum of the emitted charged hadrons and found to be largely independent of pseudorapidity with a sign change at transverse momenta $p_{T}$ between 1.2 and $1.7$  GeV/c. These results are compared to measurements made by two other experiments at the LHC. Combined with the observation from ALICE of a vanishing rapidity-even $p_{T}$ shift along the spectator deflection plane is strong evidence for dipole like initial density fluctuations in the overlap zone of the nuclei. These observations open new possibilities for investigation of the initial conditions in heavy-ion collisions with spectator nucleons.
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    Nuclear Modification Factor of High Momentum Jets in PbPb Collisions
    (2013) Lu, Ying; Mignerey, Alice; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    According to quantum chromodynamics (QCD), the release of quarks and gluons creates a new form of matter, the quark gluon plasma (QGP), expected to occur in relativistic heavy-ion collisions at high energies. The structure and dynamics of the QGP can be studied using partonic interactions at large momentum transfers. This was studied at the Relativistic Heavy Ion Collider starting in 2002 utilizing AuAu collisions at 200 GeV center-of-mass. In this analysis, fully reconstructed jets in pp and PbPb collisions at 2.76 TeV center-of-mass energy are analyzed with the CMS detector at the Large Hadron Collider (LHC) in CERN. The ratio of inclusive reconstructed jet transverse momenta spectra of PbPb collisions to that of proton+proton (pp) collisions is defined as jets nuclear modification factor (RAA) and it is studied to quantify the medium modification within transverse momenta above 100GeV/c. Jet RAA results are compared for three different unfolding methods: Bayesian Unfolding, bin-by-bin Unfolding and Generalized Singular Value Decomposition (GSVD) Unfolding, as well as corrections performed with pp data smearing. A jet RAA of approximately 0.5 is observed in the most central collisions and close to unity in the most peripheral collisions without a strong indication of the transverse momenta (pT) dependence. A suppression of high pT jets is observed in central PbPb collisions in comparison to peripheral collisions. This is consistent with the observation of jet quenching.