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Martina Schäfer

Z’ studies at LHC Martina Schäfer. Exotics meeting @ CERN. 25 f ebruary 2004. Martina Schäfer. 1. Z ’ models Data used DY and interf e rence Total decay width Leptonic cross section FB studies A_FB Background Full sim and outlook. Martina Schäfer. 2. Z’ models. SSM

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Martina Schäfer

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  1. Z’ studies at LHC Martina Schäfer Exotics meeting @ CERN 25 february 2004 Martina Schäfer 1

  2. Z’ models • Data used • DY and interference • Total decay width • Leptonic cross section • FB studies • A_FB • Background • Full sim and outlook Martina Schäfer 2

  3. Z’ models • SSM • Z’ with same coupling constants as the usual Z • E6 models • Z’=sinß Z + cosß Z • Z, Z and Z • LR symetrique models •  =1 • Z’(KK) not yet done goal: discriminating between models Martina Schäfer

  4. data used • Simulationwith Pythia (within Athena) • Z’ at 1.5TeV with complete interference structure (DY) • usual Z boson • DY only • without ISR/FSR • cut CKIN(1)=1000 • first step: analysis at generation level • channel Z’ e+e- Martina Schäfer

  5. DY and interference (1) fit exp Martina Schäfer

  6. DY and interference (2) Interference (SSM) Zoom at peak Mll(GeV) DY+Z’ destructive narrower Mll(GeV) with int. broader Mll(GeV) with int. Mll(GeV) DY+Z’ Martina Schäfer

  7. total decay width (1) ±4 peak Fit for total decay width parton luminosity BW BW*exp+exp exp (DY) DY Martina Schäfer

  8. total decay width (2) DY Martina Schäfer

  9. cross section • calculated with • luminosity (cross section of Pythia) • number of events in the peak without DY • in 4  • theoretical predictions? • * (exotics) (n )/(15 )  LR Martina Schäfer n

  10. FB studies • in pp collisions no “natural” forward -backward definition  q direction “forward” • q direction approximated byZ’ boost direction • in 25% of the events wrong • cut in Y(Z’) at 0.8 wrong in only 10% * = (e-,q) in Z’ rest frame * = (e-,Z’) in Z’ rest frame * = (e-,z-axis) in Z’ rest frame Martina Schäfer

  11. A_FB (1) A_FB(M)=(N+-N-)/N N+: cos>0, at « fixed » M or fit fit (q<->\bar q) counting counting (q <-> \bar q)  counting (without y cut) counting (q <-> \bar q, without y cut) 0 counting fit at cos distribution at « fixed » M 3/8(1+ cos2) + A_FB cos Martina Schäfer Mll(GeV)

  12. A_FB (2) A_FB(Y)=(N+-N-)/N N+: cos>0, at « fixed » Y A_FB(-Y)= - A_FB(Y) • results on-peak A_FBfit, with y cut, * = (e-,q) Martina Schäfer

  13. background • Photon and jet rejection (ET>50GeV): • nomber of tracks • zvertex • E(calo)/p(tracking) • E237/E277 • , (track, cluster) • Efficency: • 85% for electrons • less then 0.1% for jets • 4.5% for photons bb bb  6X pT() << 50GeV Martina Schäfer

  14. full sim and outlook  model 1000events • first look at full sim • work in progress • Photon and jet rejection • Background studies • Full sim without interference/ISR/FSR Martina Schäfer

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