Search fo New States Decaying into J/psipi+pi- With the Atlas Detector at the Large Hadron Collder

Using pp collision data collected at sqrt(s) = 7 TeV in 2010 and 2011 with 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 X_c(3872) signal has been evaluated, and the systematic errors have been identified. Both the Psi(2S) and the X_c(3872) signals are observed in the J/PsiPi+Pi- mass spectrum. The detection of the charmonium-like X, Y, Z states is feasible with the ATLAS detector at the Large Hadron Collider (LHC). Other than the Psi(2S) and the X_c(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 X_c(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.