Search For New States Decaying Into J Psi Pi Pi With The Atlas Detector At The Large Hadron Collider

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Search for New States Decaying Into J/psi Pi+ Pi- with the ATLAS Detector at the Large Hadron Collider

Using pp collision data collected at sqrt(s ) = 7 TeV in 2010 and 2011with the ATLAS detector (A Toroidal LHC ApparatuS), corresponding to an integrated luminosity of 2.44 fb-1 , the J/PsiPi+Pi- combinations have been studied. The selection criteria have been developed, the detection efficiency of the Xc (3872) signal has been evaluated, and the systematic errors have been identified. Both the Psi(2S ) and the Xc (3872) signals are observed in the J/PsiPi+Pi- mass spectrum. The detection of the charmonium-like X, Y, Zstates is feasible with the ATLAS detector at the Large Hadron Collider (LHC). Other than the Psi(2 S ) and the Xc (3872) signals, there is no evidence for any significant enhancement in the J/PsiPi+Pi- mass spectrum. This dissertation research establishes that ATLAS can detect Xc (3872) like new particles in the J/PsiPi+Pi- final state, and with current data sample, no new states have been observed in this study.
Search for Charmonium States Decaying to J/\psi\gamma \gamma $ Using Initial-State Radiation Events

We study the processes e{sup +}e{sup -} {yields} (J/{psi}{gamma}{gamma}){gamma} and e{sup +}e{sup -} {yields} (J/{psi}{pi}{sup -}{pi}{sup +}){gamma} where the hard photon radiated from an initial e{sup +}e{sup -} collision with center-of-mass (CM) energy near 10.58 GeV is detected. In the final state J/{psi}{gamma}{gamma} we consider J/{psi}{pi}{sup 0}, J/{psi}{eta}, {chi}{sub c1}{gamma}, and {chi}c{sub 2}{gamma} candidates. The invariant mass of the hadronic final state defines the effective e{sup +}e{sup -} CM energy in each event, so these data can be compared with direct e{sup +}e{sup -} measurements. We report 90% CL upper limits for the integrated cross section times branching fractions of the J/{psi}{gamma}{gamma} channels in the Y (4260) mass region.