PhD Thesis defense Joey Butterworth
April 11, 2017
Congratulations to Joey Butterworth for his successfull defense on April 11 of his PhD thesis on "Electron-positron pair production in Au+Au collisions at √sNN= 27 GeV as part of the Beam Energy Scan Program at STAR"
From the official announcement:
This thesis reports the e+e- pair production in the top 80% most central Au on Au collisions at √sNN = 27 GeV from the STAR experiment. The production exhibits an excess yield, in the low invariant mass region (M(e+e-) ≤1.2 GeV/c2), when compared to a hadronic cocktail without ρ-meson contributions. This excess yield is shown to be successfully described by model calculations that include a broadening of the ρ-meson spectral function in a hot, dense medium, and similar agreement to the excess yield, after applying an acceptance-correction, is also exhibited. These results are a part of a systematic study of the e+e- pair production in Relativistic Heavy Ion Collider Beam Energy Scan Program and are presented with data from Au on Au collisions at √sNN = 19.6, 39, 62.4, and 200 GeV. Each collision energy e+e- pair measurement has an excess with respect to a hadronic model without ρ-meson contributions, and each excess yield is described by model calculations that include a broadening of the ρ-meson spectral function in a hot, dense medium. This suggests that the ρ meson is modified by the hot, dense medium. The acceptance-corrected excess yields are also reported as a function √sNN, charged particle multiplicity, and predicted lifetimes. Given uncertainties, no statistically significant excess yield dependence on √sNN, charged particle multiplicity, and predicted lifetimes are observed for Au on Au collisions with a 0-80% centrality.
From the official announcement:
This thesis reports the e+e- pair production in the top 80% most central Au on Au collisions at √sNN = 27 GeV from the STAR experiment. The production exhibits an excess yield, in the low invariant mass region (M(e+e-) ≤1.2 GeV/c2), when compared to a hadronic cocktail without ρ-meson contributions. This excess yield is shown to be successfully described by model calculations that include a broadening of the ρ-meson spectral function in a hot, dense medium, and similar agreement to the excess yield, after applying an acceptance-correction, is also exhibited. These results are a part of a systematic study of the e+e- pair production in Relativistic Heavy Ion Collider Beam Energy Scan Program and are presented with data from Au on Au collisions at √sNN = 19.6, 39, 62.4, and 200 GeV. Each collision energy e+e- pair measurement has an excess with respect to a hadronic model without ρ-meson contributions, and each excess yield is described by model calculations that include a broadening of the ρ-meson spectral function in a hot, dense medium. This suggests that the ρ meson is modified by the hot, dense medium. The acceptance-corrected excess yields are also reported as a function √sNN, charged particle multiplicity, and predicted lifetimes. Given uncertainties, no statistically significant excess yield dependence on √sNN, charged particle multiplicity, and predicted lifetimes are observed for Au on Au collisions with a 0-80% centrality.