1. B Tagging studies with non prompt J/Ψ's
Alberto Escalante del Valle
Juan Pablo Fernández Ramos
CIEMAT
2/5/2013
BTV performance meeting

2. Introduction: Content:
Evaluate the b-tagging efficiencies and scale factors using a specific subsample of b-jets (those with Bhadrons→ J/ψ+X ) in 2012 data and Summer12 MC vs Jet-pt (standard for reference).
Using tag and probe technique
Content:
Selection
Method
Comparison of relevant variables
B-tag efficiency definition
Results
Systematics
Conclusions

3. Selection for b-tagging
● Muon cuts : #hits > 10 ; χ2 < 10 ; # μ-cham > 0
● Emulate Inclusive J/psi triggers in MC :
• DCA cut between the two muons of < 0.5 cm.
• Lxy-significance > 3
• ptμ1 + ptμ2 > 10 GeV
• cosα > 0.9
● |dz(PV)μ1|< 0.2 && |dz(PV)μ2|< 0.2 (PU cut)
● | DiMu invmass - m(J/ψ) | < 0.1 GeV, sidebands: [2.7,2.9] ∪ [3.3,3.5]
● Tag with Reco::PFJets with :
• ΔR (J/ψ, jet) < 0.5
• ptjet> 10 GeV && |ηjet |< 2.5
• Number of charged (charged+neutral) tracks in jet >= 1 (2)
• Pileup subtraction with FastJet & L2, L3 corrections
● Look for any other away-jet with:
• ΔR (J/ψ, jet) > 0.5
• Previous requirements in pt, n tracks, pileup subtraction &
L2,L3 corrections

4. Sample for b-tagging 18.7 fb-1
Run2012A,B,C,D : /MuOnia/Run2012A-22Jan2013-v1/AOD
/MuOnia/Run2012B-22Jan2013-v1/AOD
/MuOnia/Run2012C-22Jan2013-v1/AOD
/MuOnia/Run2012D-22Jan2013-v1/AOD
18.7 fb-1
Summer12 MC :
MC weights :
/BpToPsiMuMu_2MuPtEtaFilter_8TeV-pythia6-evtgen/
Summer12_DR53X-PU_S10_START53_V7A-v1/AODSIM
/B0ToPsiMuMu_2MuPtEtaFilter_8TeV-pythia6-evtgen/
/BsToPsiMuMu_2MuPtEtaFilter_8TeV-pythia6-evtgen/
/LambdaBToPsiMuMu_2MuPtEtaFilter_8TeV-pythia6-evtgen/
Summer12_DR53X-PU_S10_START53_V7A-v2/AODSIM
/JPsiToMuMu_2MuPtEtaFilter_tuneD6T_8TeV-pythia6-evtgen/
Weight B+=(2.11E-4 * E7)/ ;
B0=(1.97E-4 * E7)/ ;
Bs=(7.2E-5 * E7)/ ;
LambdaB=(3.6E-5 * E7)/ ;
prompt=( * E7)/ ;

5. Comparison of relevant variables
MC & data Pile up distribution :
MC was generated with the same Pile up

6. Comparison of relevant variables (II)
● | DiMu invmass - m(J/ψ) | < 0.1 GeV, sidebands: [2.7,2.9] ∪ [3.3,3.5]
DiMuinvMass
TCHP

7. Coparison of relevant variables (III)
CSV
Reasonable agreement on btag-discriminators.
Jet probability

8. Comparison of relevant variables (IV)
CSVr
Reasonable agreement on rCSV btag-discriminator and somewhat different CSV+SL (not affecting the analysis , see OP's)
CSV+SL
Operational points for CSVSL
CSVSLL
CSVSLM
CSVSLT

9. Method for b-tagging => Using tag and probe technique
● Tag : J/ψ – jet
● Probe : any other jet in the event
Divide the sample in bins of pt of the jet
For each pt-bin plot the lifetime discriminant variable for data and perform a fit.
The fit uses light, c and b templates from MC
Fit output: B-fraction (fb)
The fit is done for a sample before (tag) fbbefore tag and after (all) fbtag b-tagging
Apply independent tagger
sample before tag
=> Using tag and probe technique
● Tag : J/ψ – jet
● Probe : any other jet in the event
Divide the sample in bins of pt of the jet
For each pt-bin plot the lifetime discriminant variable for data and perform a fit.
The fit uses light, c and b templates from MC
Fit output: B-fraction (fb)
The fit is done for a sample before (tag) fbbefore tag and after (all) fbtag b-tagging
sample with (tag)
b-tagging

10. Results: B-tag efficiencies
The b-tag efficiency is taken from equation 4 of BTV
• Definition (for a given pt-bin)
Cb = Fraction of events with tag info.
All plots are sideband subtracted
Will show results for JPM, CVSM and CSV+SL M b-tagging algorithms

11. B-tagging efficiencies and SF (I)
JPM
Tagged jet
Probe jet

12. B-tagging efficiencies and SF (II)
CSVM
Tagged jet
Probe jet

13. B-Tagging efficiencies and SF (III)
CSV+SL M
Tagged jet
Probe jet

14. Systematics
● Analysis of the btagging efficiency as a function of the variation of the following selection cuts.
New values chosen for the evaluation of the systematic uncertainty:
●ΔR (J/ψ, jet) > [0.4]
●|ΔR(J/ψ, probejet) - π|< [0.15,0.25]
●Lxy-significance > [2,4]
●ptμ1 + ptμ2 > 10 GeV [8,12]
● cos α > [0.85,0.95]
●|dz(PV)μ1|< 0.2 && |dz(PV)μ2|< [0.15,0.25]
●| DiMu invmass - m(J/ψ) | < [0.075,0.125]
● In addition we study the pileup dependence .

15. Systematics ( |ΔR(J/ψ, probejet) - π|<0.2 )
ΔR jet
B fraction decreases (bef & after tagging) when increasing the deltaR probe window, for ptjet< 65 GeV. Despite this dependence, the SF do not change.
J/ψ jet
probe jet
B Fraction
fbtag
fbbefore tag

16. Systematics ( ptμ1 + ptμ2 > 10 GeV)
Despite the ptμ1 + ptμ2 Data /MC disagreement, btagging efficiency and SF do not present changes when including the low ptμ1 + ptμ2 region.
fbtag
fbbefore tag

17. Systematics ( Lxy-significance > 3 )
JPM
JPM
Tagged jet
Probe jet
CSVM
CSVM
Tagged jet
Probe jet

18. Pileup dependence (not taken as systematics)
B fraction
JPM
JPM
Probe jet
B fraction
But SF's do not change
B fraction changes at low pt
CSVM
Probe jet
CSVM

19. SF (JPM)

20. SF (CSVM)

21. SF (CSV+SL) M

22. Summary
SF (18.7 fb data/Summer12MC) using 22 Jan 2013 data obtained for the probe jet ( the SF are within 10 %)
SF's for the probe jet shown to be independent of any of the selection cuts, despite the variation of B fraction at low pt.
Included an analysis using different criteria for probe jet.
Links to the full study of systematics uncertainties and default plots in the backup.
To do:
Write the note of the analysis
Wait for approval, before providing SF's.

23. Backup
Default cuts :
Systematic studies :
Cosalpha :
Z0 :
ΔR :
Lxys :
Ptsum :
ΔR probe :
Pileup :
Mass :
η :