1. Efficiency of Muon Reconstruction
July 23,2007 Jongseok Lee, Suyong Choi
(Sungkyunkwan University)

2. Introduction
For more details about analysis see Suyong's talk in Muon POG of June 19:
Based on Drell-Yan muon sample from CMSSW131: CMSSW_1_3_1-Spring /GEN-SIM-DIGI-RECO
No backgrounds (yet)
Question: how does efficiency obtained with tag-and-probe compare to efficiency from MC Truth?

3. decay mode : Z -> μ+μ- (mc data)
stand alone muon : reconstructed muon by muon detectors
track : reconstructed muon by tracker
global muon : reconstructed muon by tracker + muon detectors

4. Steps for tag-and-probe
1.Choose a high momentum
global muon (pt>10GeV)
2.Look for another high momentum
track from the global muon
(typically ΔΦ>1.5)
3.Form invariant mass of
global muon + track (red)
4.Form invariant mass of
global muon + matched track
with opposite global muon
(green, matching cut ΔR<0.01)

5. Efficiencies from tag-and-probe method
pt(μ)>15, ΔΦ(μ μ)>1.5, 70<mass(μμ)< pt(μ)>15, ΔΦ(μ μ)>0.5, no masscut

6. Steps for mc-truth 1.Choose a mc muon (|η|<2.4)
2.Look for a matched track
with the mc muon
(matching cut ΔR<0.01)
3.Repeat 1~2 for the opposite mc
muon
3.Form invariant mass of
mc muon + opposite mc muon (red)
4.Form invariant mass of
mc muon + matched track
with opposite global muon
(green, matching cut ΔR<0.01)

7. Efficiencies from mc-truth method
cut for mc truth μ
|η|<2.4
cut for matching
ΔR<0.01
(ΔR = sqrt(Δθ2+ΔΦ2))

8. Isolation ΔR = sqrt(Δθ2+ΔΦ2) : isolation angle
isolation energy = sum energy of particles near the μ
 cut for jet (1GeV) μ
ΔR<0.5
jet μ a2 a4 a3 a1
GeV
isolated

9. Efficiencies from tag-and-probe method
ΔR< ΔR< ΔR< ΔR< ΔR<0.5
Cut :
pt(μ)>10GeV
no masscut
ΔΦ(μ μ)>0.5
isolationE 1GeV

10. Distribution of mass(μμ), pt and η
tag-and-probe method(ΔR<0.5)
mc-truth method(|η|<2.4)

11. Efficiencies overlay of tag&probe and mc-truth
Cut of tag-and-probe method:
pt(μ)>10GeV
no masscut
ΔΦ(μ μ)>0.5
ΔR<0.5 (isolation)
isolationE 1GeV
Cut of mc-truth method:
|η|<2.4
ΔR<0.01 (matching)
average efficiency of pt:
0.975± (tag-and-probe)
0.971± (mc-truth)
average efficiency of η:
0.975± (tag-and-probe)
0.971± (mc-truth)

12. Efficiencies with Fits
tag&probe method(ΔR<0.5) mc-truth method

13. Conclusion Average Tag-and-probe and MC Truth agree better than 1%
More study needed to understand sub-1% differences, and dependence vs eta and pT
Next steps: look at other components of the efficiency (e.g. trigger) - add realistic background - develop a complete analysis strategy

14. Back up

15. Entries comparison # of all mc-truth muon(no cut ) = 7000
# of all global muon (no cut) = 8069
isolation energy of global muon
isolation energy of track muon
ΔR<0.5
ΔR<0.5
GeV
GeV