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Hydrodynamic Flow Fluctuations in √sNN = 5.02 TeV PbPb Collisions
dc.contributor.advisor | Sanders, Stephen J | |
dc.contributor.author | Castle, James Robert | |
dc.date.accessioned | 2018-02-18T20:20:55Z | |
dc.date.available | 2018-02-18T20:20:55Z | |
dc.date.issued | 2017-08-31 | |
dc.date.submitted | 2017 | |
dc.identifier.other | http://dissertations.umi.com/ku:15513 | |
dc.identifier.uri | http://hdl.handle.net/1808/26000 | |
dc.description.abstract | The collective, anisotropic expansion of the medium created in ultrarelativistic heavy-ion collisions, known as flow, is characterized through a Fourier expansion of the final-state azimuthal particle density. In the Fourier expansion, flow harmonic coefficients $v_n$ correspond to shape components in the final-state particle density, which are a consequence of similar spatial anisotropies in the initial-state transverse energy density of a collision. Flow harmonic fluctuations are studied for PbPb collisions at $\sqrt{s_{\rm NN}} = 5.02$ TeV using the CMS detector at the CERN LHC. Flow harmonic probability distributions $p(v_n)$ are obtained using particles with $0.3 < p_{\rm T} < 3.0$ GeV/$c$ and $\lvert \eta \rvert < 1.0$ by removing finite-multiplicity resolution effects from the observed azimuthal particle density through an unfolding procedure. Cumulant elliptic flow harmonics ($n=2$) are determined from the moments of the unfolded $p(v_2)$ distributions and used to construct observables in $5\%$ wide centrality bins up to $60\%$ that relate to the initial-state spatial anisotropy. Hydrodynamic models predict that fluctuations in the initial-state transverse energy density will lead to a non-Gaussian component in the elliptic flow probability distributions that manifests as a negative skewness. A statistically significant negative skewness is observed for all centrality bins as evidenced by a splitting between the higher-order cumulant elliptic flow harmonics. The unfolded $p(v_2)$ distributions are transformed assuming a linear relationship between the initial-state spatial anisotropy and final-state flow and are fitted with elliptic power law and Bessel Gaussian parametrizations to infer information on the nature of initial-state fluctuations. The elliptic power law parametrization is found to provide a more accurate description of the fluctuations than the Bessel-Gaussian parametrization. In addition, the event-shape engineering technique, where events are further divided into classes based on an observed ellipticity, is used to study fluctuation-driven differences in the initial-state spatial anisotropy for a given collision centrality that would otherwise be destroyed by event-averaging techniques. Correlations between the first and second moments of $p(v_n)$ distributions and event ellipticity are measured for harmonic orders $n=2-4$ by coupling event-shape engineering to the unfolding technique. | |
dc.format.extent | 220 pages | |
dc.language.iso | en | |
dc.publisher | University of Kansas | |
dc.rights | Copyright held by the author. | |
dc.subject | Physics | |
dc.subject | Event-shape engineering | |
dc.subject | Heavy ions | |
dc.subject | High-density QCD | |
dc.subject | Hydrodynamic flow | |
dc.subject | Unfolding/deconvolution | |
dc.title | Hydrodynamic Flow Fluctuations in √sNN = 5.02 TeV PbPb Collisions | |
dc.type | Dissertation | |
dc.contributor.cmtemember | Takaki, Daniel | |
dc.contributor.cmtemember | Bean, Alice L | |
dc.contributor.cmtemember | Lewis, Ian | |
dc.contributor.cmtemember | Elles, Christopher G | |
dc.thesis.degreeDiscipline | Physics & Astronomy | |
dc.thesis.degreeLevel | Ph.D. | |
dc.identifier.orcid | https://orcid.org/0000-0002-2177-617X | |
dc.rights.accessrights | openAccess |