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Update in Forward Backward Asymmetry in Z ee

Update in Forward Backward Asymmetry in Z ee. Samir Ferrag. Introduction. Z ee Sample: Zee M>150 GeV: 45800 Evts (sample 5114) Incoming quark truth doesn’t exist in SpecialMC (AOD) Full Truth from ESDs dumped into AODs 10% events don’t have truth (quark, lepton, Z*)

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Update in Forward Backward Asymmetry in Z ee

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  1. Update in Forward BackwardAsymmetry in Zee Samir Ferrag

  2. Introduction • Zee Sample: • Zee M>150 GeV: 45800 Evts (sample 5114) • Incoming quark truth doesn’t exist in SpecialMC (AOD) • Full Truth from ESDs dumped into AODs • 10% events don’t have truth (quark, lepton, Z*) • Understand the acceptance effects • Evalute the dilution effect on the Cos(Theta*) distribution (effect on the AFB fit evaluated last time)

  3. electron In Z* center of Mass q* q qbar positron FB asymmetry in EW sector Asymmetric distribution

  4. Dilution at P-P collider No access to the incoming quark direction Assumption: The quark direction is the one of the Z boson (lep-lep pair) Fraction of the events with wrong q-direction Fraction of the events with wrong q-direction • Wrong quark direction assignment: Cos(Theta*)-Cos(Theta*) (dilution) • Built Likelihood function in ROOT: • L1D:  g=3/8(1+cos(theta)*cos(theta))+Afb*cos(theta). L2D:  g=3/8(1+cos(theta)*cos(theta))+Afb*(1-2*W(eta))*cos(theta)

  5. Reconstruction Efficiency

  6. Acceptance components • Simple pseudorapidity cut on leptons: electrons Positrons Cos(Theta*) Vs Pseudorapidity

  7. Acceptance function contributions • Cos(Theta*) distributions • Acceptance functions for eta<2.5 cut positrons Zee events electrons • The acceptance function is symmetric among Cos(Theta*) •  Atlas response is symmetric electronpositron

  8. Cos(Theta*) Distribution inside acceptance Reconstructed

  9. Wrong Quark Assignment (WQA) Fraction of event with wrong quark direction: -150 GeV < MZ < 350 GeV - 350 GeV < MZ < 550 GeV - 550 GeV < MZ Event with Quark and Z* in opposite directions Mass dependence of the wrong assignment distribution due to PDFs

  10. Dilution from the WQA Grey: Non diluted distributions Black: Contribution of the wrong assigned quark direction events Red: Diluted distribution (Observed)

  11. Observed distribution • White: Generator level without dilution • Gray: reconstruction level without dilution • Black: reconstruction level with dilution

  12. Mass dependence of dilution • Distributions shown for the invariant mass bins • at generator level: • -(M1): 150 GeV < MZ < 350 GeV • -(M2): 350 GeV < MZ < 550 GeV • -(M3): 550 GeV < MZ Cos(Theta*) distributions Fraction of events with wrong quark direction assignement  It better to go to high mass to measure AFB (to confirm with Likelihood fit)

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