The Physics of Generations

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The PhysicsofGenerations (Update) 11-Dec-03 Don
Lincoln f
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Motivation
Fact The multi-generational structure of the
quark doublets requires explanation and could
herald compositeness.

• Under hypothesis of compositeness, deviation from
  point-like behavior would likely manifest in
  third generation.
• Conclusion g ? bb may exhibit desired deviant
  behavior.
• Explore b quark dijet mass as a possible
  signature.
• Problem
• 1001 QCDbb
• Solutions
• m tagging
• 2nd VTX tagging
• Impact parameter

CDF PRL 82 (1999) 2038
Fit to CDF qQCD calculation
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Strict Cut Summary

• Reject multiply analyzed runs (p13.05.00
  r13.06.01)
• 169514 - 170150 ( others)
• Reject bad runs
• JET, MET, Muon, CFT, SMT, CAL
• Skim QCD to reduce data set (pt of high pt jet,
  in order to have lt 40 deviation from lower
  trigger)
• Pt(25) gt 40 GeV (Guess)
• Pt(45) gt 70 GeV
• Pt(65) gt 95 GeV
• Pt(95) gt 130 GeV

• NP 1mutrk skim
• 1 MuonCandidate (medium)
• Nseg 1
• Nwhits(A) 2
• Nwhits(BC) 3
• Nshits(A) 1
• Nshits(BC) 1
• 1 Track (Pt gt 6 GeV)
• Df (track/m cand) lt 0.2
• QCD Trigger
• JT_25TT_NG, JT_45TT, JT_65TT, JT_95TT, JT_125TT,
  JT_8TT, CJT5, min_bias, min_bias_NCU

2 data reduction
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D0JetInfo Building

• CalJet (baseline)
• Standard quality cuts
• Trackjet
• At least 2 tracks
• Pt(1) gt 1.0 GeV
• Pt(others) gt 0.5 GeV
• DR lt 0.5
• MuonCandidate (tight)
• Pt gt 4 GeV
• Associated track
• Nseg 3
• Nwhits(A) 2
• Nwhits(BC) 3
• Nshits(A) 1
• Nshits(BC) 1

• Match to CalJet
• TrackJet
• DR lt 0.7
• DZ lt 1.5 cm
• 2VTX
• Attached to TrackJet
• Complex requirements
• Muon
• DR lt 0.5
• DZ lt 1.5 cm
• MC information
• 2VTX
• DR lt 0.5
• DZ lt 3 cm
• Parent parton (Leading Order)
• DR lt 1.0
• DZ lt 100 cm

Ariel Schwartzman based code.
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Data Skim Result (All JT Trig) Entire Skim
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Luminosity pb-1 (good runs)
With bad run removal.
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MC Status
Requested 20,000 of each
MC Production foundered for many months.
Statistics only available in the last month
Big thanks to Drew Meyer of UTA for very helpful
MC assistance
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Long Term Goal Use bb to Search for Exotics

• Dijet bb mass might signal
  new physics
• Tags
• m
• Pros Skim based on this, much work done
• Cons Poor efficiency, ptrel similar sig/bkd at
  high Pt, hm lt 2.0, avoid ICD for Jet
• 2VTX
• Pros Very high efficiency, some work done, 2D
  Decay Length Significance tag promising
• Cons No skim available, hVTX lt 1.4, avoid ICD
  for Jet
• First approach jet m inclusive, hjet lt 0.5

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MC Predictions (single jet)

• Technique
• Use QCD MC (Ptmin 100 GeV)
• Identify Leading Order associated parton
• Apply cuts in RECO variables
• Identify efficiency and purity for each type
• Note light includes up, down, strange and
  gluons.

Note this is for all h. Reducing to h lt 0.5
will reduce cross section numbers by 1/3, but
slightly increase efficiency.
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MC Predictions (two jet or double tag)
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ds/dpt Cross-Section h lt 0.5
JT_25TT_NG JT_45TT JT_65TT JT_95TT JT_125TT
All jets with m Jet kinematics only
Obviously needs rebinning Normalized to
luminosity and bin width Full luminosity good
runs Uses standard JES No efficiency
corrections No b-enhancing muon cuts
All jets with m Jet m kinematics
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Pt Dependence of Cut Loss (m Data)
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Pt Dependence of Cut Loss (QCD Data)
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Efficiencies
eT Trigger Eff ePV Primary Vertex Eff ej
Jet Eff em m Eff fb?m Frac b ? m (Pt gt 4
GeV) fB?m Frac B ? m (Pt gt 4 GeV) L
Luminosity Dpt Pt bin width sb b
cross-section sB BKD cross-section
Correlated
Jet m (Pt gt 4 GeV)
b Jet m (Pt gt 4 GeV)
b Jet
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Primary Vertex Cut Event Retention
Respectable fit to a gaussian. Simply count
events outside z gt 50 cm to find loss rate.
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Primary Vertex Cut Event Retention
50
-50
ePV 0.935 0.050 Independent of Pt
100
300
700
Z(PV)
Error bars RMS
Pt
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Effect of Jet QC
Algorithm same as QCD analysis Find ratio (QC
applied)/(QC not applied) Correction ½
difference Error ½ difference eJ 0.99 0.01
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Pt Dependence of log(2D DL Sig)
Essentially Pt independent in MC
3.65
2.75
2.5
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Effect of Jet Pt on log(2D DL sig)
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Pt Dependence of log(2D DL Sig)
Essentially Pt independent in Data (Pt gt 100)
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Effect of Including m-only Jets in log(2D DL sig)
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Effect of m existence on log(2D DL sig)
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Compare templates of log(2D DL sig)
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Compare templates of log(2D DL sig)
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Fractions of b using Templates
For jets with both a good 2VTX and a muon, use
log(2D dl sig) and fit for b fraction. Result
15 ? 2 and 22.6 ? 2 MC 24.4 ? 1.5
w/o 2VTX requirement MC 10.5 ? 0.4
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Fit to smoothed templates
4 gaussian
Bump in c template probably Unphysical. Under
investigation.
3 gaussian
2 gaussian
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Fit to Smoothed Templates
For jets with a good 2VTX use log(2D dl sig) and
fit for b fraction. No muon requirement. Result
16.7 ? 1.2 MC 26.2 ? 0.8 Note doesnt
have the same selection of events as
data. (Even though no muon
requirement, was a muon skim.)
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Fraction of b-generated Events with m Pt gt 4.0 GeV
Generate bb MC Calculate fraction of b ? m (Pt gt
4 GeV) Plot vs. Jet m RECO Pt Fit Sys. Error.
From adding parameter error.
Frac 0.045 0.000081 Pt
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Fraction of QCD-generated Events with m Pt gt 4.0
GeV
Generate QCD MC Calculate fraction of QCD ? m (Pt
gt 4 GeV) Plot vs. Jet m RECO Pt Fit Sys. Error.
From adding parameter error.
Frac 1.0E-5 3.1E-6 Pt
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Efficiency/Fraction Summary
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m RECO Efficiency

• Thoughts
• e m system shouldnt care if its in a jet? (High
  Pt punch through?)
• e m track should care if its in a jet. Low
  tracking efficiency in jet
• e match should care if its in a jet. Lots of
  potential fakes.

Not much information from m ID group on this
topic. (But tracking eff 82 gives total eff of
85.7?82 70.2.
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Heavy Flavor JES
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Heavy Flavor JES
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Still To Do

• Double check m efficiencies
• Double check fractions of b/c/light
• Smearing ? Resolution ? Unsmearing
• Rebin (How to deal with highest pt events?)
• Bottom Line
• Most required knowledge is grossly available

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ds/dmCross-Section h lt 0.5
Both jets with m Jet kinematics only
At least one jet with m Jet kinematics only
JT_25TT_NG JT_45TT JT_65TT JT_95TT JT_125TT
Obviously needs rebinning Normalized to
luminosity and bin width Full luminosity good
runs Uses standard JES No efficiency
corrections No b-enhancing muon cuts
At least one jet with m Jet m kinematics