Search for chargino and neutralino High pT channel

1
Search for chargino and neutralino High pT ??
channel

• Study of control regions in 131 pb-1
• use Good Run List v6 cmup cmx electron
• control region I 2 leptons invariant mass in
  Z mass window 76-106 GeV
• control region II 2 leptons Met lt 10 GeV
• Study of control region in 325 pb-1
• use Good Run List v7 cmup cmx electron
• control region III 3 leptons, invariant mass
  in Z mass window 76-106 GeV
• Kinematic cuts
• Setting the limit assuming scale factor 1 and
  trigger efficiency 100

2
Implementation of fake rate

• Fake rate evaluated by Liverpool group
• Fake rate is the probability that a fakeable
  object (jet or track) be a fake lepton (electron
  or muon)
• Per jet or track, as function of jet Et or track
  pt (the jet Et is smeared to be assigned to the
  fake lepton)
• Measured in Jet20/50/70/100 samples and averaged

• Fake rate implementation in the analysis
• Check whether there is fakeable obj in the event
  (either e or mu)
• the fakeable obj is any third lepton in the event
  which does NOT come from primary interact.
• the fakeable obj must be ??R gt 0.4 from the
  primary leptons
• As for now select the highest pt fakeable obj
  (the fakeable obj must be ?R gt 0.4 from the
  primary leptons) --- reasonable assumption
• Assign the event a weight which is the
  probability the fakeable object has to fake the
  lepton
• The fake lepton is dealt with as a real third
  lepton goes through the analysis cuts

3
Control regions

• Control region I and II the main background is
• Drell Yan
• One real lepton fake lepton --- DATA estimated
• each event with 1 fully ID muon is checked for a
  fake muon if the fake muon is found, the event
  goes trough the analysis cut weighted accordingly
• Control region III, main background is classified
  as
• HF with 3 real leptons (NO constraint on the
  leptons do not necessarily come from hard
  scattering) --- this contribution is NOT included
  in the fake rate
• WZ/ZZ with 3 real leptons (leptons MUST be the
  decay product of the W or Z)
• WW and DY give 2 real leptons (leptons MUST be
  the decay product of the W or Z) and contribute
  to the 3 lepton scenario if
• any lepton radiates a ? which converts into a
  lepton pair (the event is checked if there is a
  photon radiated from any of the primary leptons)
  --- MC estimated
• a fake lepton is found in the event --- DATA
  estimated

4
Z window control region (I)

• The event is selected if the lepton invariant
  mass is in 76-106 GeV
• The following contributions are included
• Heavy flavor (tt bb/cc direct production)
• WZ and ZZ
• DY
• Fake contribution from data
• Check if the smearing affects
• the mass window

5
Z window control region (I)

• Met and SumEt corrected for tight muons
• Open question
• How to correct the MEt to take into account the
  fake muon

Good agreement data and MC for MEt gt 2 GeV
6
Z window control region (I)

• Very good agreement data and MC in both the ??
  between the muons and the Et of the leading jet

??? 249 pb
7
Low MEt - control region (II)

• The event is selected if MEtlt10 GeV
• No agreement between data and MC
• Some background contributions are still missing
  (more heavy flavor W?BB/CC)

cosmics ?
Low pt physics ?
b-bbar/c-cbar ?
8
Z window 3 leptons - control region (III)

• The event is accepted if ANY pair of leptons has
  invariant mass in 76-106 GeV
• Very good agreement between data and MC
• Further investigation needed for the contribution
  from conversions (gamma radiated from a primary
  lepton which then converts into lepton pair). In
  the ee channel, less conversion
• Might be due to ratio 902 between electron and
  muon event when asking for the third object in
  Z?? MC

9
Analysis cuts

• Selection of 2 tight muon events
• Leading muon high pt
• Non leading muon either high or low pt
• Selection of the third object (tight central
  electon or tight muon or CMIO muon)
• Invariant mass cut
• M?? gt 11 GeV
• M?? ?76106GeV
• Jet constraint
• Event is rejected if more than 2 jets with Et gt
  20 GeV
• MEt cut
• MEt gt 15 GeV

Remove low mass region because of W? background
we WILL add
Tighten up since last presentation because of
contribution from ? conversion
10
W? contribution

• Beate is now producing sample for all channels in
  Madgraph
• This process is not included in Pythia
• From hep9907505, comes out it is the largest
  contribution
• It is NOT included in this study yet
• Low mass cut to anticipate a possible choice

Need to investigate how much it contributes when
asking for 3 leptons
11
Muon invariant mass

• Invariant mass distribution of events with 3
  leptons at reconstruction level

Before any analysis cut applied, 4 events from
DY conversion
12
MEt content

• Reject events with MEt gt 15 GeV helps mainly
  removing fake contribution and conversion

Conversion in Z?? events (not scaled)
Fakes (not scaled)
13
Sensitivity for 325 pb-1

• Signal points under investigation
• anadi point m0100 GeV, m1/2180 GeV,
  tan?5,A00,?gt0
• D0 point m074 GeV, m1/2168 GeV, tan?3,A00,?gt0

14
Summary

• Number of expected signal events
• anadi point 0.560.03
• D0 point 0.960.04
• Number of expected SM events
• 0.0400.003 genuine leptons
• 0.0500.05 leptons from conversion
• 0.0260.026 fake leptons
• TOTAL BACKGROUND 0.12 0.06
• Acceptance
• anadi point 1.0
• D0 point 0.7
• As for now, SM processes which yields
• 0 expected events are NOT taken into
  account

Limit on ?BR
Combined limit (high pt only) ?BR 0.5
Signal ?BR
15
Next

• Next,
• Include the new background and optimize again the
  selection
• Further investigate conversion from primary
  leptons and fake contribution
• Remove gamma conversion with new function
  compatible with fake rate
• Improve the acceptance
• Include plug electron (gain 11-14 in acceptance)
• Accept CMIO as second muon (?)
• Further investigation of the control regions
• Evaluation of systematics (RunI, 16)
• Scheduled preblessing at the end of January