1. background studies for GMSB Andrea Bangert Santa Cruz Institute for Particle Physics May 6 th, 2010

2. object definitions all photons: pT > 20 GeV |eta| < 2.5 signal photons: “gammas” isEM::TightPhoton == 0 Control sample photons: “QCD” pass loose EM but not tight isEM criteria (isEM::LoosePhoton == 0) && (isEM::TightPhoton != 0) question: how effective is this criteria for selecting “control” photons?

3. samples two signal photons: “gamma-gamma” one signal photon, one “control” photon: “gamma-QCD” two “control” photons: “QCD” goal: collect a “QCD sample” which we can use to model the background due to events without true MET question: will “QCD” events be in the event stream?

4. estimates MC sampleinitial eventsgamma-gammagamma-QCDQCD GMSB110,0005,0001,200100 leptonic ttbar20,000000 SM diphoton100,00020,00010,0002,000 SM dijets (JF17)50,000000 need to require g20_loose or 2g10_loose trigger to fire. will this collect “QCD” events? need to know how cut on H T affects sample populations. need to use cross sections, scale to L = 1 pb -1 only cuts on photon objects have been made two photon objects were required no cuts were made on MET or H T