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Using Event shape to discriminate gg and g jet

This study aims to discriminate between gg and g-jet events by analyzing the color structure and using event shape variables. Pythia 8.1 C++ is used to simulate QCD production, with specific processes enabled or disabled. Selection criteria are applied to isolate g-jet events. The results show differences between true gg and gj events, providing insights for counting the number of gg, gj, and jj events in the mass peak using real data. Simulated data will be used to test the effects.

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Using Event shape to discriminate gg and g jet

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  1. Using Event shape to discriminate gg and gjet Initial idea First information using Pythia Outcomes

  2. Initial idea : use the color structure of gg anf g-jet Study done using Pythia (Pythia 8.1 C++) : (ISR, FSR, UE on) gg case : QCD production only (no higgs) g-jet case : QCD production HardQCD:all = off ! switch off all QCD jet + jet processes PromptPhoton:all = off ! swich off gamma + jet and gamma + gamma PromptPhoton:gg2gammagamma = on ! swich on gamma gamma PromptPhoton:ffbar2gammagamma = on ! swich on gamma gamma PromptPhoton:qg2qgamma = off ! swich off gamma + jet PromptPhoton:qqbar2ggamma = off ! swich off gamma + jet PromptPhoton:gg2ggamma = off ! swich off gamma + jet PhaseSpace:pTHatMin = 25. ! minimal pT scale in process HardQCD:all = off ! switch off all QCD jet + jet processes PromptPhoton:all = off ! swich off gamma + jet and gamma + gamma PromptPhoton:qg2qgamma = on ! swich on gamma + jet PromptPhoton:qqbar2ggamma = on ! swich on gamma + jet PromptPhoton:gg2ggamma = on ! swich on gamma + jet PhaseSpace:pTHatMin = 25. ! minimal pT scale in process

  3. Selection Use events where the 2 output (5 and 6) hard process particles are in the EM Calo acceptance : Use tracks acceptance : Pt>1 GeV, |h|<2.5 In the g-jet case, find a p0 that carries more than 70% of the outgoing q or gluon in dR<1 around that parton Apply an isolation criteria to have background like g-jet events : Sum of Track Pt in dR=0.3 around each « photon candidate » below 4 GeV if(fabs(event[g1].eta())>3||fabs(event[g2].eta())>3) continue;

  4. Results • Energy vs dr around g candidates gj gg

  5. Results • Energy vs deta around g candidates gj gg

  6. Plan g1-g2 • Angle between tracks and g candidates gj gg

  7. Outcomes • Differences are expected between true g and gj events • This could allow to count in the mass peak the number of gg, gj and jj using the data • Check the effect on simulated data first…

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