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IntMasterclasses@LHC

IntMasterclasses@LHC. First ideas of p hysics concepts for the LHC masterclass measurements. q. ` q. Michael Kobel Konrad Jende. 1. Concepts of the Measurement.

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IntMasterclasses@LHC

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  1. IntMasterclasses@LHC First ideas of physics conceptsfor the LHC masterclass measurements q `q Michael Kobel Konrad Jende

  2. 1. Concepts of the Measurement The aim: Developing conceptsthat reflectthe truemotivation for the LHC (New physics) and allow to get deep insights (fundamental measurements). 2 Michael Kobel Konrad Jende

  3. 1. The W-Path • The W-Path Concept • Introduction of the W: βdecay of the neutron (learning objective: missing energy  Neutrino) • Measurement on preselected events with missing energy:Identify and count #leptons (e or mu) and #jets • Determine for single W (+Jets)the ratio (deduce insight about: structure of the proton) • Search for double W candidates via WW  lvlvreduce tt WbWb  lv Jet lv Jet requiring 0 Jets(deduce insight about: rare processes, backgrounds, new physics) 3 Michael Kobel Konrad Jende

  4. expectations for LHC in 2010 4 Michael Kobel Konrad Jende

  5. Sample preparation (by us!) using missing energy cut eliminate Z+Jets  1(+1 missed) leptons + Jets  reduce QCD (minimum bias), but not completely • Tasks for students: • identify and count isolated leptons (electrons and myons) • reject events w/o leptons (QCD background, leptons in Jets etc.) • be aware of electric charges • 1 lepton: count charges separately • 2 leptons: reject same-sign (here SUSY extension possible) • >3 leptons: reject (here SUSY extension possible) • count number of jets • enhance new physics (Higgs) for 2 leptons requiring 0 Jets Sample preparation for students • CERN COURIER, Apr 1 2003 5 Michael Kobel Konrad Jende

  6. g d • Charge ratio in events with 1 Lepton & missing Energy Compton-Process: • Drell-Yan-Process: • Result from processes above, if only valence quarks u,d • would be involved: 2:1 (2 u- and 1 d-quark in proton) • Washed out - by above processes with see quarks u, d- by gluon fusion: u W+ Deeper background info (mostly for us)(single W) • CERN COURIER, Apr 1 2003 6 Michael Kobel Konrad Jende

  7. Reducing the washout... …possiblebyrejectingeventswithleptonsabovept> 20 GeVin sample preparation • R+- as a function of the lepton transverse momentum • R+- as a function of η • Jana Schaarschmidt, TU Dresden • Jana Schaarschmidt, TU Dresden • Figure 1 • Figure 2 7 Michael Kobel Konrad Jende

  8. Deeper background info (WW pairs) Distribution of Njets„QCD+EWeak WW“ „ttbar“ • Jana Schaarschmidt, TU Dresden • Jan Schumacher, TU Dresden • Figure 4 • Figure 3 8 Michael Kobel Konrad Jende

  9. Search for Higgs via excess over known Eweakprocess • Compare observednumber of lvlvwith expectation from WW (Excess maybe Higgs?) • Check additional information: angle Dfℓℓ between leptons Higgs would have low values Possible after some years or now with simulated events • CERN-OPEN-2008-020 (ATLAS, Higgs Boson in Gluon Fusion Higgs Signal not to scale!) 9 Michael Kobel Konrad Jende

  10. 2. The Z-Path • Introduction of the Z: heaviestmessengerparticle(learning objective: couples to all fundamental particles,making it a tool to study their properties) • Measurement on preselected events with at least 1 lepton:Identify and count #lepton pairs (ee or mumu) and #jets(?) • Determine for single Z (+Jets)the ratio (deduce insight about: lepton universality) • Search for double Z candidates via ZZ  4l reduce tt WbWb  lv l(Jet) lv l(Jet) requiring 0 Jets or no Emiss(deduce insight about: rare processes, backgrounds) 10 Michael Kobel Konrad Jende

  11. expectations for LHC in 2010 11 Michael Kobel Konrad Jende

  12. Sample preparation (by us!) using 1 identified lepton  reduce QCD (minimum bias), but not completely  still a lot of W + Jets background • Tasks for students: • identify and find lepton pairs with opposite charge • reject events w 1 lepton (W background) or same-sign pairs • be aware of lepton flavor (check universality) • 1 lepton pair: count flavors separately • 2 lepton pairs: count number of jets? Require no Emiss? for rejecting ttbar and enhancing new physics (Higgs) • undecided • build 2-lepton mass  Z mass? • maybe build 4-lepton mass  Higgs mass ? Sample preparation for students • CERN COURIER, Apr 1 2003 12 Michael Kobel Konrad Jende

  13. Invariant masses Tasks (how?): • Determine the invariant mass of each di-lepton system • Determine the invariant mass of the 4-lepton system • CERN-OPEN-2008-020 (Di-muon invariant massdistribution in the Z->μμ channel) 13 Michael Kobel Konrad Jende

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