Single top cross-section : context

1
Single top cross-section context motivation

• Single-top in the SM
• 3 production mechanisms
• W-g (t-channel) Wt (Associated) W
  (s-channel)
• ? Two of them could be seen at theTeVatron
  (W,Wg)
• ? All will be measured precisely at the LHC
• Motivations
• Properties of the Wtb vertex
• Determination of s(pp?tX), ?(t?Wb)
• Direct determination of Vtb
• W, Top polarization
• Precision measurements ? probe to new physics
• Anomalous couplings, FCNC

t-channel,Wt
s-channel
2
Status of the s-channel measurements
A. Lucotte, F. Chevallier (IN2P3 LPSC)

• S-channel xsection measurements
• Splitted Selection tb vs tbb to reduce top pair
  bckgd
• ? Single-top production is charge asymmetric
• W tbarb is favoured wrt tbarb
• Wg tqbarb is favoured wrt tbarqb
• ? Top pair production is charge symmetric
• ? Measurements of asymmetries, or
• ? Measurements of ?(W) ?tbbar , ?(W)
  ?tbarb
• assuming theoretical ratio (MCFM NLO)
• Analysis made for 2-jet 3-jet final states
• New background estimates
• ? Added top pair in di-tau, taujets
  (TDR-neglected)
• ? New estimates of top pair di-lepton (2nd
  lepton veto)
• ? Wbb and Wjets using MCFM predictions
• ? Need single-top MC_at_NLO samples
• ? Need high statistics Wjets Alpgen samples
• New estimates on charged Higgs sensitivity
• ? Sensitivity in plane (mH,tan?) using TopRex
• ? Need NLO generator for xsections
  cross-checks

3
s-channel selection reminder (Rome)

• S-channel x-section measurements
• Standard Selection
• 1 high pT lepton 2ndary (high-pT) lepton veto
• Exactly two high pT jets identified as two b-jet
• Window on reconstructed top mass (leptonic)
• Window on reconstructed HT
• New selection
• Splitted selection for two final states

4
Status of s-channel measurements
A. Lucotte, F. Chevallier (IN2P3 LPSC)

• S-channel xsection measurements
• New selection
• Splitted selection for two final states
• Skipped recoed top mass
• Relaxed window on HT
• ? Higher efficiency / higher statistical
  sensitivity
• (lower S/B, reduced systematics due to pTmiss)

W? tbbar
W? tbarb
5
S-channel xsection sensitivity update
A. Lucotte, F. Chevallier (IN2P3 LPSC)

• Xsection measurements
• Splitted analysis
• Analysis for final states 2jets 3 jets
  (2b1light)
• Sensitivity to final states 2b0j
• Likelihood under progress

 2b0j 

• Interpretation in terms of charged Higgs
• Sensitivity to H
• Replace W by H in the graph (same final state)
• Applied same anbalysis as for s-channel
• Used TopRex (LO) Generator need to check with
  NLO
• ? Results depend on tan? and mH

Yet to use a more specific selection to H?tbbar