# Presentation: 808729

## The Dijets Paper

## The Search

- Use lepton-triggered dijet data
- 8 GeV lepton
- Second jet ET>15
- Use SECVTX / JPBTAG to determine heavy flavor content
- Measured both on lepton trigger jet and away jets

- In away jets, measure
- SLT rate
- Supertag (SLT + SECVTX / JPBTAG)
- CDF 5833, 4795, 6409

## Trigger on 8 GeV Lepton

***Trigger on 8 GeV Lepton***

***What is SLT rate here?***

- Need to know
-  HF fraction of trigger jet
-  HF fraction of away jets when
-    Trigger IS HF
-    Trigger is NOT HF
-  SLT tag rate of away HF jets
-  SLT fake rate of away non-HF jets

*SECVTX, JPBTAG*

*Fake rates*

*MC+Fit*

*Fake rates*

*MC+Fit+ SF*

## Selection Requirements

- Electron ET > 8 GeV or muon pT>8 GeV
- Non-isolated
- I>0.1 (add’l energy within cone of 0.4)
- Includes 2 SVX tracks
- ET of jet > 15 GeV
- Lepton w/in DR of 0.4

- Second jet > 15 GeV
- SECVTX / JPBTAG evaluated above 15 GeV
- Select 65k e, 15k mu events

## Away Jet

- Look for SLT
- 2 GeV leptons
- CMU or CMX 2<pt<3
- CMU+CMP pt>3
- Calorimeter electrons

## SECVTX: Trigger Jet HF Fraction

- MC
- Pythia 2->2, QQ, QFL
- Implements SECVTX b-jet scale factor of 1.25+-0.08
- No JPBTAG, SECVTX c scale factors
- Measured consistent with one
- MC samples have ~same # of events as data
- Examine rate of SECVTX, JPBTAG in trigger jet data
- E: ~10k / 11k
- Mu: ~3.5/4 k
- SECVTX, JPBTAG eff’y in MC (considerably simplified)
- E: ~33%, 42%
- Mu: ~45%, 55%

- Use SECVTX, JPBTAG on lepton jets, away jets, and double tags, to determine
- B fraction
- C fraction
- Production mechanisms
- All with some light constraints
- Finds scale factors consistent with 1
- Finds extra gluon splitting
- E 45% hf, m 59% hf
- 3-5% diff’t from most naïve possible use of MC (mine)
- Kinematics distributions look good afterwards
- Mass, pT, lifetime

## SLT Tags

- Examine SLT tags in away jets
- Pf: “the rate of fake SLT tags”
- In jets? Per track?  In an event?
- P: the probability that a fiducial track produces an SLT tag
- Pf=0.74xP
- ?????
- “It follows that, in generic jet data, the probability that leptons arise from HF decay is 0.26xP”

- Calculate the rate of SLT tags due to heavy flavor in the away jet
- Also considering possibility that trigger jet is not HF
- 2.2% / hf jet
- Calculate rate of SLT fakes using # of fiducial tracks in jet
- Roughly 50% of SLT tags are fake
- SLT SF of 0.85+-0.05 used
- Correction from generic-jet data
- Use fit for fractions, now including SJ terms
- Results about 2% diff’t from naïve use of MC results
- ~2k SLT in e jets, 600 SLT in mu jets
- -> 1k, 300 after sutracting fakes

## SLT (Away jets) Fit results

- SLT only
- E/mu
- ?? Tables VI, VIII inconsistent
- No description how to go from raw counts to “data”
- Data: 865+-114 / 273+-35
- MC: 598+-70 / 149+-22
- Sum Data/MC:
- 1138 +- 119 / 747 +- 41
- Delta: 391 +-125
- 3.1

- SECVTX SJ
- E/mu
- Data: 323+-23 / 63+-10
- MC: 242+-23 / 54 +-9
- Sum Data / MC:
- 386 +- 25 / 296 +- 25
- Delta: 90 +- 35
- JPBTAG SJ
- E/mu
- Data: 350+-26/103+-12
- MC: 252+-22 / 65+-9
- 453+-29 / 317 +- 23
- Delta: 136+- 37
- Two SJ methods correlated, 2.4 & 3.5 

## Cross-Checks

- To saturate delta
- Fake SLT’s 60% higher than expected
- Estimate was +-10%
- SLT eff’y 50% higher than expected
- I.e. 3.3% instead of 2.2%
- In lepton-triggered data:
- SLT Fakes: 1286 +- 150 (+??? 1064–865 + 309- 273)= 1521 +-150
- SLT hf: 747 +- 41
- SLT sum pred: 2268+-135 (+- 45)
- SLT in data: 2659

- JET20+50+100
- SLT fake prediction: 15570
- SLT hf prediction: 3102
- SLT sum prediction: 18672 +- 1608 (+- 136)
- SLT in data: 18885
- JET20+JET50+JET100 + SECVTX
- SLT fake prediction: 508
- SLT hf prediction: 999
- SLT sum prediction: 1507+-78 (+- 39)
- SLT in data: 1451