Studies of W’  tb  Wbb  lvbb

1. Studies of W’tbWbblvbb

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

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

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

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