A Probe of Colored Medium Effects on Quarkonia Polarization in √s = 7 TeV pp collisions at CMS

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dc.contributor.advisorMignerey, Alice Cen_US
dc.contributor.authorFerraioli, Charles Christopheren_US
dc.contributor.departmentChemistryen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2017-09-14T05:41:19Z
dc.date.available2017-09-14T05:41:19Z
dc.date.issued2017en_US
dc.description.abstractThe suppression of quarkonia mesons is one of the signature indications of the presence of a quark-gluon plasma, the colored, asymptotically free state of matter believed to have existed moments after the Big Bang, and recreated by colliding heavy-ions. Two S-wave charmonia states, the J/ψ and the ψ(2S), along with three S-wave bottomonia states, the Υ(1S), Υ(2S), and Υ(3S), have been studied in heavy-ion collisions at both the Relativistic Heavy Ion Collider and the Large Hadron Collider (LHC), showing clear sequential suppression patterns, with the most tightly bound states less suppressed than the others, relative to scaled proton-proton (pp) collisions. Yet, the results remain difficult to interpret, owing to a combination of complicated feed-down processes from P-wave χ states, as well as regeneration of quarkonia occurring well after the initial collision. Further, the basic production mechanism of quarkonia is still far from certain, leaving open the possibility that changing mechanisms could affect the scaling of pp yields. This thesis aims to be the first in a line of studies into the effects of a colored medium on the basic production mechanism of quarkonia by measuring quarkonia polarization. Polarization can be measured using the angular distributions of dimuons emanating from quarkonia decays, and the Compact Muon Solenoid detector is well suited for these measurements. The polarizations of the three Υ(nS) and two ψ(nS) states were measured versus event multiplicity using a dimuon data sample collected during the 2011 LHC run of √s = 7 TeV pp collisions, with a total integrated luminosity of 4.9 fb−1. The measurements were integrated over the available rapidity range, for transverse momentum up to 35 GeV/c. All quarkonia states showed small polarizations, which were cross checked across several reference frames, and are consistent with multiplicity-integrated analyses. In the states for which a precise measurement could be made, the J/ψ and the Υ(1S), there was no variation with multiplicity, but these states are strongly affected by feed-down, preventing any definitive conclusions. Ultimately, this study leads the way for a polarization measurement in heavy-ion collisions, which would provide a more decisive look into the affect of a colored medium on quarkonium production.en_US
dc.identifierhttps://doi.org/10.13016/M2TX3567P
dc.identifier.urihttp://hdl.handle.net/1903/19948
dc.language.isoenen_US
dc.subject.pqcontrolledNuclear chemistryen_US
dc.subject.pqcontrolledNuclear physics and radiationen_US
dc.subject.pquncontrolledPolarizationen_US
dc.subject.pquncontrolledPsien_US
dc.subject.pquncontrolledQuark-gluon plasmaen_US
dc.subject.pquncontrolledQuarkoniaen_US
dc.subject.pquncontrolledUltra-relativist nuclear physicsen_US
dc.subject.pquncontrolledUpsilonen_US
dc.titleA Probe of Colored Medium Effects on Quarkonia Polarization in √s = 7 TeV pp collisions at CMSen_US
dc.typeDissertationen_US

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