1. 1 Studies of W’  tb  Wbb  lvbb

2. 2 Why W' important? Many beyond-the-standard model theories have predicted W' Extra-dimension model Theories that have an extra SU(2) gauge group Right-handed W boson Technicolor theory Little higgs theory Main decay channels: W' -> e/mu + neutrino W' -> tb

3. 3 Current limits of W' Standard model couplings assumed W' -> lnu CDF: 1.12TeV ATLAS: 1.49TeV (a soon-published result pushes the limit to 2.15TeV) CMS: 1.58TeV W' -> tb CDF (right-handed coupling) mass(W') > mass(right-handed neutrino): 800GeV mass(W') < mass(right-handed neutrino): 825GeV D0 mass(W') > mass(right-handed neutrino) left-handed coupling: 863GeV right-handed coupling: 885GeV both couplings: 916GeV mass(W') < mass(right-handed neutrino) right-handed coupling: 890GeV LHC experiments: no results yet

4. 4 Why W' -> tb important? Mass limit of W'->lnu greater than 1.5TeV, but standard model coupling is assumed In reality, W' may weakly coupled to leptonic channel There are models that W' is leptophobic It is possible that we find something in hadronic channel for W' < 1.5TeV W'->tb channel provides information about the chirality of W' but not the leptonic channel Question: Given that the current limit of W'->tb is at least 800GeV Should we optimize cuts for W' mass ~800GeV?

5. 5 Matrix method: finding QCD in muon channel for W’  tb  Wbb  lvbb

6. 6 Introduction to matrix method Measuring QCD with the help of two control regions Region 1 gives the probability of loose real muons being tight real muons Region 2 gives the probability of loose fake muons being tight loose muons N(loose) = N(loose,real) + N(loose, fake) N(tight) = N(tight,real) + N(tight, fake) N(tight) = r*N(loose,real) + f*N(loose, fake) Where: N(loose): number of events that have a loose muon, selected MET, at least two jets, and a b-tag N(loose,real/fake): number of events that have a loose real/fake muon, selected MET, at least two jets, and a b-tag N(tight): number of events that have a tight muon, selected MET, at least two jets, and a b-tag N(tight,real/fake): number of events that have a tight real/fake muon, selected MET, at least two jets, and a b-tag r: efficiency of loose real muons being tight = N(tight,real)/N(loose,real) f: efficiency of loose fake muons being tight = N(tight,fake)/N(tight,fake)

7. 7 Introduction to matrix method Loose muons: pass through all cuts except isolation cut Tight muons: pass through all cuts (including isolation cut) Region 1: Tag-and-probe events: 80GeV < mass of Zmumu < 100GeV muons with opposite charges Tag muon is tight, probe muon satisfies the loose requirement Probe muons give N(loose,real) and N(tight,real) Give r (with assumptions) Region 2: QCD region: transverse mass of W < 20 GeV transverse mass of W + MET < 60 GeV Give N(loose,fake) and N(tight,fake) Give f (with assumptions)

8. 8 full selection (b-tag included) QCD shape obtained from matrix method QCD scale factor found by template fit N(loose) = N(loose,real) + N(loose, fake) N(tight) = r*N(loose,real) + f*N(loose, fake)

9. 9 Z->mumu mass distribution exactly two opposite charge muons no constraint on number of jets Z->mumu mass distribution exactly two same charge muons no constraint on number of jets Cross-check that “real muon region” really gives real muons

10. 10 80GeV < Zmass < 100GeV exactly two opposite charge muons no constraint on number of jets 80GeV < Zmass < 100GeV exactly two opposite charge muons number of jets = 1 80GeV < Zmass < 100GeV exactly two opposite charge muons at least 2 jets efficiency of probe muon passing through isolation cut 80GeV < Zmass < 100GeV exactly two opposite charge muons number of jets = 0

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