Download or read book Upsilon Production at Center of Mass Energy written by Rosi J. Reed and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Quarkonia suppression, caused by the Debye screening of the Quantum Chromo-Dynamic (QCD) potential between the two heavy quarks, was originally claimed to be an unambiguous signal of the formation of a Quark-Gluon Plasma (QGP). J/[psi] supression has been observed in heavy ion collisions at both SPS and RHIC, however, the magnitude of the suppression in both systems was similar despite the differing energy densities. This indicates that Quarkonia suppression isn't as unambiguous a signal as previously supposed because there are many competing processes that affect the yield of quarkonia in heavy ion collisions. Some of these effects enhance the quarkonia yield, such as the statistical recombination of the QQ̄ pairs, while others reduce it, such as co-mover absorption. These processes affect the Upsilon family less than the J/[psi] family at 200 GeV, and it is believed that color screening should be the dominant process that contributes to any observed supression of the [Upsilon]. A measurement of bottomonia spectra in heavy ion collisions with sufficient statistics and resolution should be able to constrain the various models of the QGP. In order to measure the suppression of the [Upsilon], it was necessary to measure the cross section of the bottomonia sates in p+p. This was measured to be 114 ± 38 (stat. + fit) +23/-24 (sys.) pb. The same trigger algorithm and experimental procecures developed for this measurement were applied to the Au+Au measurement, with the exception of a slight increase in trigger thresholds. This algorithm was applied to 4 Million triggered events taken during run 7 (2007) and combined with the p+p cross section, an R[subscript AA](0-60%) of 0.80 ± 0.34 (stat.) was calculated. The mass resolution was improved with the removal of the SVT and its support structure from the center of STAR. A modified trigger algorithm was applied to 50 Millions triggers taken during run 10 (2010) and this yield an R[subscript AA](0-60%) of 0.55 ± 0.23 (stat.) +0.07/-0.13 (sys.) when combined with the p+p cross section.