First ideas of physics concepts for the LHC masterclass measurements Michael Kobel Konrad Jende q qq

ConceptsW-Path Structure of the Proton New Physics with the LHC Z-Path Lepton Universality New Physics with the LHC 1. Concepts of the Measurement 2 The aim: Developing concepts that reflect the true motivation for the LHC (New physics) and allow to get deep insights (fundamental measurements).

Michael Kobel Konrad Jende The W-Path Concept 1.Introduction of the W: β decay of the neutron (learning objective: missing energy  Neutrino) 2.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  lv lv reduce tt  Wb Wb  lv Jet lv Jet requiring 0 Jets (deduce insight about: rare processes, backgrounds, new physics) 1. The W-Path 3 W-Path Single W + Jets (Structure of the Proton) WW-Pairs (Search for the Higgs)

expectations for LHC in 2010 Michael Kobel Konrad Jende 4 number of expected events during the LHC physics run in 2010 (ATLAS; 100pb -1 ; 7TeV) Njets category I: one leptoncategory II: two leptons e + ν, µ + ν e - ν, µ - ν e + νe - ν, µ + νµ - ν e + νµ - ν, µ + νe - ν number of expected events in W → lν: tt→ lν+Jets: 2 W → lν: tt→ lν+Jets: 2 H → WW → lνlν: ~1? WW → lνlν : ~1 tt → lνlν + Jets: ~1 1 W → lν: tt→ lν+Jets: 30 W → lν: tt→ lν+Jets: 30 H → WW → lνlν: <1 WW +Jets→ lνlν + Jets: 1 tt → lνlν + Jets: 15 >= 2 W → lν: tt→ lν+Jets: 2500 W → lν: tt→ lν+Jets: 2500 H → WW → lνlν: ~1? WW +Jets→ lνlν + Jets: 1 tt → lνlν + Jets: 1000

Sample preparation for students Michael Kobel Konrad Jende 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 5 CERN COURIER, Apr

Deeper background info (mostly for us) (single W) Michael Kobel Konrad Jende 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: g u d W+W+ 6 CERN COURIER, Apr

Michael Kobel Konrad Jende Reducing the washout... Jana Schaarschmidt, TU Dresden 7 R+- as a function of the lepton transverse momentum R+- as a function of η Jana Schaarschmidt, TU Dresden Figure 1Figure 2 …possible by rejecting events with leptons above p t > 20 GeV in sample preparation

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

Possible after some years or now with simulated events Michael Kobel Konrad Jende Search for Higgs via excess over known Eweak process Compare observed number of lvlv with expectation from WW (Excess maybe Higgs?) Check additional information: angle  ℓℓ between leptons Higgs would have low values CERN-OPEN (ATLAS, Higgs Boson in Gluon Fusion Higgs Signal not to scale!) 9

Michael Kobel Konrad Jende 2. The Z-Path 10 Z-Path Lepton Universality Search for New Physics 1.Introduction of the Z: heaviest messenger particle (learning objective: couples to all fundamental particles, making it a tool to study their properties) 2.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  Wb Wb  lv l(Jet) lv l(Jet) requiring 0 Jets or no Emiss (deduce insight about: rare processes, backgrounds)

expectations for LHC in 2010 Michael Kobel Konrad Jende 11 number of expected events during the LHC physics run in 2010 (ATLAS; 100pb -1 ; 7TeV) Njets category I: two leptoncategory II: four leptons e + e - µ+µ- µ+µ- e + e - e + e -, µ + µ - µ + µ - e + e - µ + µ - number of expected events in Z → ll: tt→ ll +X: 1 H → ZZ → 4l: <1 ZZ → 4l: ~1 tt → lνlν + 2l from Jets: ~1(?) 1 Z → ll: 6000 tt→ ll +X: 4 >= 2 Z → ll: 2500 tt→ ll + X: 250

Sample preparation for students Michael Kobel Konrad Jende 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 ? 12 CERN COURIER, Apr

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