Study Of The Moun Telescope Detector At RHIC And The Upsilon?nS? Production In Gold-Gold Collisions At ?S_NN=200 GeV

Data taken over the last decade demonstrated that a hot,dense medium with partonic degrees of freedom,called the Quark-Gluon Plasma(QGP),has been created in heavy ion collisions at RHIC and LHC.The suppression of quarkonia in the medium due to Debye screening was proposed as a direct signature of the QGP formation.Compared to charmonia,bottomonia suffer much less from both the regeneration contribution due to coalescence of deconfined charm-anticharm pairs and the co-mover absorption.Furthermore,different bottomonium states may dissociate at different temperatures,known as "sequential melting",which can be used to constrain the temperature of the QGP.Quarkonia decay into dileptons with a considerable branching ratio.Quarkonium measurements have been previously performed with the dielectron channel at RHIC.Compared to the dielectron channel,the dimuon channel suffers much less from Bremsstrahlung radiation,and thus has better invariant mass resolution which makes it possible to separate excited ? states from the ground one.This thesis conducts the research and development of the moun telescope detector(MTD)system at the STAR experiment,which allows for measuring the heavy quarkonia via the dimuon decay channel by providing muon triggering and identification capabilities at RHIC for the first time.The thesis performed full calibrations of MTD prototype and the fully installed MTD system with cosmic ray data,and obtained a timing resolution similar to 100 ps and a spatial resolution similar to 1-2 cm,fulfilling the physics requirement.With the MTD triggered data samples corresponding to an integrated luminosity of 14.2 nb-1 for Au+Au collisions at(?)= 200 GeV taken in 2014,the Y signal was reconstructed via the dimoun channel for the first time at RHIC.Different Y states were separated and their differential production yield at different transverse momentum(pT)and centrality bins were obtained.The pT dependence of the nuclear modification factor(RAA)for ? were obtained for the first time at RHIC and a hint of less suppression at high pT for excited Y states was observed.The RAA for ground and excited Y states as a function of centrality are presented and compared to theoretical calculations.The excited? states were found to be more suppressed than the ground state in central collisions.The calculations from strongly bound scenario models are favored by data,especially in central collisions.The RAA for Y ground state is consistent at the RHIC and the LHC,indicating that the temperate of the QGP created at RHIC and LHC is lower than the melt temperature of Y ground state.