Observation of leading Phi-mesons in high pT jets with the ATLAS detector at sqrt(s)=7 TeV

This note describes the reconstruction of high pT Phi-mesons in the environment of energetic jets from √s = 7 TeV pp collisions, in the ATLAS tracking detector at the LHC. Results are presented using an integrated luminosity of 25 pb^{−1} recorded during the 2010 LHC running. A signal to background ratio of approximately 1 to 3 in the Phi mass region is achieved. The Phi peak parameters are obtained by fitting the M_{K+K−} distribution with a sum of lognormal distribution and a background shape function. The pT spectrum of the reconstructed Phi-mesons is derived using the side band technique and cross-checked using an explicit pT cut on the K+K− system. These distributions are compared with the PYTHIA 6.4.20 predictions. The resulting spectra are in reasonable agreement. The fact that 90 GeV leading Phi-mesons can still be well reconstructed in the dense environment of a high pT jet demonstrates the high quality of the ATLAS tracking system.