Slides for EB3

Left Problems from EB2

• 1. Why muon triggers are not used in e channel?• 2. Add backgrounds estimation for signal search region • 3. Add expected limits for signal search: stau neutrino & Z’• 4. In the emu channel the main bkg is ttbar. Would applying a bjet

veto help?• 5. Validate Wjet background at high mass region(shape from MC)• 6. QCD bkg comes from OS/SS method, relying on results from h->tautau for validation of the technique (NOS_QCD=NSS_QCD). An

independent validation might be useful• 7. some adjustments of text or format

Status

• Update muon selection, use only high pT recommendation• We have formed a new version of supporting note including

all the issues listed in slide #2• https://cds.cern.ch/record/1622230• waiting for the EB3• some further consistent check for FAR, will update the note if

needed

Update 1. add muon trigger into e channel

• For emu channel(data & MC):EF e24vhi medium1||EF e60 medium1

EF e24vhi medium1||EF e60 medium1||EF mu24i tight||EF mu36 tight

Only ele trigger Ele+mu trigger

data 13088 13710

MC 12740 13224

For Validation region (M<200GeV)

~ 5% more events

Update 2. add backgrounds estimation for signal search region

emu etau

mutau

Update 2. add backgrounds estimation for signal search region

Update 2. add backgrounds estimation for signal search region

emu

etau

mutau

Update 3. Add expected limits for signal search

Bayesian method is used to set limits for search

Update 3. Add expected limits for signal searchSearch for signal in a mass window for mass M signal: [M-3, M+3 ]

Inputs: expected background number and systematics in each mass windowSignal efficiency * Luminosity and systematics for each mass point

e channel as an example

Update 3. Add expected limits for signal searchStau neutrino Z’

Update 4 use b tagging to veto ttbar bkgd

• Ttbar background is one of the dominant background in emu channel for both validation region and signal search region.

• use btagging to veto ttbar background use MV1 method use 70% efficiency work point require the bjet number in a event is 0

•

More than 80% ttbar events are vetoed

Update 4 use b tagging to veto ttbar bkgdSystematics with btagging

Signal efficiencies are almost not affected by the N-bjet=0 requirement ~ 1% decreased

We have no gain for high mass region(M>1000GeV)

Update 5 Validate W+jet bkgd at high mass region

Wjet bkgd is validated in a data control region

• invert the cut on the angle phi between the leptons (, )(use , for an example ) from dphi > 2.7 to 1 <dphi < 2.7

• all other cuts are kept the same as signal selection• The signal from a resonance has almost no contribution at this

region whereas backgrounds are much wider.• Statistics are not great but OK

Update 5 Validate W+jet bkgd at high mass region

W+jet Enhanced control sample

• Missing Et > 30 GeV (enhance W).• Remove opposite sign requirement• Njet < 2 (reduce t tbar).‐• Remove Pt cut (increases statistics).

Update 5 Validate W+jet bkgd at high mass region

MC says that about 90% of events are W+jet

Update 5 Validate W+jet bkgd at high mass region

• In QCD calculation, we assume NOS_QCD =NSS_QCD is this correct ?• Construct a data control sample and perform a validation: same requirements as signal selection expect: reverse muon isolation requirement add MET<10GeV use non-isolated EF_mu36_tight trigger

Update 6 QCD test

We quote an additional 10% uncertainty for QCD multi-jet background