1. A brief Update on secondary vertex tagged jets
MC-based Efficiency/Purity studies
12/4/2019
Eugene Galyaev

2. Central region jets, |y| < 0.5
12/4/2019
Added variable bins:
Central region jets, |y| < 0.5
12/4/2019
Eugene Galyaev

3. “Raw” X-section by trigger
Central region jets, |y| < 0.5
12/4/2019
Eugene Galyaev

4. Work is being done on MC efficiencies
Defined 5 cathegories:
b-parent, b in the Jet
No b-parent, but b in the Jet
c-parent, c in the Jet
No c-parent, but c in the Jet
No parton showers
This info will allow to estimate efficiencies/purities in MC
12/4/2019
Eugene Galyaev

5. What was done… Content study based on inclusive QCD MC
Various mean Pt ranges were used, approximately 1.5M events total
Central jets only
| y | < 0.5
Have divided MC into 9 P regions:
[0-40], [40-80], [80-120], [ ], [ ], [ ],
[ ], [ ], [ ] GeV
Observed shapes for the tagging variable distributions for b, c, and udsg MC contents
Template shapes shown to be universal at jet P > 40 GeV
Results on the b-content extraction by fitting was overlaid with the MC – derived purity curve, no cut on Log(2DdLSig)
Provides data-driven cross-check to the MC results
Included the possibility to vary the Log(2DdLSig) cut to be able to see the effect on Efficiency/Purity results
Will help to understand and optimize the cut
12/4/2019
Eugene Galyaev

6. Efficiency and Purity
Sample plots for Efficiency and Purity vs. cut in Log(2-D Decay Length Significance) in a couple of Pt regions:
[40-80] GeV
[0-40] GeV
12/4/2019
Eugene Galyaev

7. Efficiency and Purity dependence on Pt (no cut applied):
MC Efficiency, Purity vs. P (b-vtx, no cut)
Efficiency and Purity dependence on Pt (no cut applied):
b – vertex finding efficiency in MC is slowly decreasing with Pt
b – content in data seems to be in disagreement with the MC at low Pt
- The fitting procedure is
inefficient at low Pt?…
12/4/2019
Eugene Galyaev

8. Check the fitting procedure (recent…)
Try to fit the templates to the inclusive QCD MC
Good “Simulation”
Yield >>perfect<< fits EVERY TIME!!!
Fitting is NICE with Monte Carlo!
So the DATA must be different……….
c2 = 0.75
At 100 GeV Pt bin !
37% Vs. 34%
MC ‘Truth’ purity
12/4/2019
Eugene Galyaev

9. MC Efficiency/Purity curves, b-vtx, 2DdLSig > 32 cut
A cut:
Decay Length Significance > 32
Cut was picked from 2D Decay length distribution shapes a while ago:
Exists historically
From this plot this may not be the best value?
Let’s see corresponding Efficiency and Purity dependence on Pt!…
cut position values
Since Early 2VTX p13 studies…
12/4/2019
Eugene Galyaev

10. MC Efficiency, Purity vs. P, b-vtx, 2DdLSig > 32 cut
Efficiency and Purity dependence on Pt (2DdLSig > 32):
100 Gev
Efficiency drop by ~30%
Purity increase by the factor of x2
100 Gev
12/4/2019
Eugene Galyaev

11. MC Efficiency/Purity curves, b-vtx, 2DdLSig > 12 cut
A new experimental cut:
Decay Length Significance > 12
This point seem to have less efficiency loss with considerable gain in purity at the same time
Let’s see Efficiency and Purity dependence on Pt for this cut value!
cut position values
cut position values
12/4/2019
Eugene Galyaev

12. MC Efficiency, Purity vs. P, b-vtx, 2DdLSig > 12 cut
100 Gev
Efficiency drop by ~7%
It seems like this choice of cut would work better!
Purity increase by the factor of x1.6
100 Gev
12/4/2019
Eugene Galyaev

13. Work in progress…! Status and plans…
Need to think of some other cross-checks between MC and the data
Overall fairly good results so far – this is just the first steps…
Add a muon requirement?
Suggestions welcome!!!
Try to re-fit the low P data region
Maybe make some special templates for that region?
Come up with the ‘justified’ cut selection criteria
Need to intelligently pick the Decay Length Significance cut value, based on all known information.
Proceed with the 2VTX-tagged b-jet cross section results
Figure out and apply all the efficiencies…
Do the unsmearing…
Work in progress…!
12/4/2019
Eugene Galyaev

14. Efficiency and Purity (continued)
Efficiency and Purity vs. cut in Log(2-D Decay Length Significance) averaged per entire MC sample (all Pt)
Corresponding Log(2-D Decay Length Significance) shapes
12/4/2019
Eugene Galyaev

15. MC Efficiency/Purity curves (b-vtx, no cut)
No cut in
Log(2DdLSig) applied…
These curves reflect the Efficiency/Purity
values for the possible cut position…
Can be used to optimize the cut!
12/4/2019
Eugene Galyaev