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Validation of DC3 fully simulated W → e ν samples (NLO, reconstructed in 11.0.42)PowerPoint Presentation

Validation of DC3 fully simulated W → e ν samples (NLO, reconstructed in 11.0.42)

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### Validation of DC3 fully simulated W→eν samples (NLO, reconstructed in 11.0.42)

Laura Gilbert 01/08/06

W→eνfrom [email protected], full sim

- Original sample submitted for generation in December, some of the one million W→e-ν now fully simulated on the grid, in batches of 10k events.
- 47800 events available (using CBNTs)
- Lepton generator level filter efficiency (10Gev, |η|<2.7) was ~63.3%
- Generated cross section is 8.4nb (cf. 30nb for W→l-ν: TDR). Luminosity for 10k events is 1.9pb-1.
- Cuts applied at any stage are listed on top right of slide.
- ALL truth plots are normalised to weighting of simulated data EXCEPT multiplicity plots.

Electron Selection Cuts

- At least one electron with transverse energy > 25GeV. (Use ET rather than pT since brem recovery not properly implemented yet0
- Electron candidate has at least one associated track matched (exclude photons)
- η < 2.4. This cuts out dubious candidates at the end of the electromagnetic calorimeter.
- IsEM flag = 0, electron isolation cut. This should now be tuned correctly but I need to look into the bitwise cuts in more detail to check.

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Sanity plots: multiplicity of electrons that pass selection cuts

- truth

- full sim

Almost always only one electron candidate per event passes cuts.

ELECTRONS

Checking cuts with truth info:

Cuts:

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Initially tracks of candiadates entered into egamma container include kaons, pions, muons. After cuts only electrons remain.

- before cuts

- after cuts

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Sanity plots: phi

- truth

- full sim

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Sanity plots: eta

- truth

- full sim

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Identifying electrons with their partner in truth containers, matching (η,φ) space:

If (ΔR<0.1) match is found

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Sanity plots: ET

- truth

- full sim

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

Difference between simulated and truth ET distributions:

PROBLEM?

No overall difference between simulated and truth ET shapes!

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4
- ΔR<0.1 (matching sim to truth)

Electron ET resolution: (sim-truth)/truth for matched sim:truth electron pairs.

Resolution looks roughly ok though…

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

"Wrong sign" electrons found from associated track q/p, AFTER cuts:

Wrong sign

Correct sign

*PROBLEM*

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

ET distribution of "wrong sign" electron candidates:

- +ve charge electrons (from track q/p)

- all electron candidates (for shape comparison)

- ET (ele truth) > 25GeV

Consider truth information: just cut on ET > 25GeV

There are positrons present in egamma truth, but none pass ET cut.

- before cuts

- after cuts

ELECTRONS

- What are the wrong sign electrons?
- Not generated positrons
- Don't have high pT tracks, so probably not electrons mis-reconstructed.
- Possibly wrong track-cluster combinations. Needs further investigation.

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- η(ele) < 2.4

- Further investigation needed:

- E over p always 0! → needs to be fixed in future.
- Where do the "positrons" come from?
- Need to look into IsEM flags in detail.

ELECTRON JETS

W Transverse mass plots look fishy if I apply exclusions on events containing jets with ET>30GeV.

Therefore many jets come from electrons.

Identify and exclude these electron jets.

Can only be one on jets with η<2.5 to make electron matching possible.

(Jets reconstructed using cone algorithm with R<0.7, see later)

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- Jet η < 2.5

Matching electrons and jets in (η,φ) space:

- truth

- full sim

Log scale→

Identify jets with electrons if ΔR<0.7

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- Jet η < 2.4

Matching electrons and jets in energy:

Trying to match energy as well as (η,φ) distribution (no cut made):

Jets are corrected to have more energy than electron candidates so -ve values more likely to be a match.

- truth

- full sim

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- Jet η < 2.4

A closer look at electron-jet ΔR and energy distributions: simulation

Smattering of events here

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- Jet η < 2.4

A closer look at electron-jet ΔR and energy distributions: truth

no events here

- ET(ele) > 25GeV
- At least one track matched
- IsEM=0
- Jet η < 2.4

A closer look at electron-jet ΔR and energy distributions: (truth - simulation)

Truth - simulated

This is the normalised difference of the last two plots!

Energy difference (MeV)

ΔR

- ΔR (e-jet) > 0.7
- Jet η < 2.4

- Looking at all jets which have not been matched with electrons: ie. Jets which are isolated from electron candidates by at least 0.7 in (η,φ).
- Still looking at jets with η<2.4 for accurate electron matching.
- There are three available clustering algorithms:
- Kt alorithm: apparently unsuitable for low pT jets.
- Cone algorithm with R<0.4. Discounted as produces very low statistics (few jets reconstructed)
- Cone algorithm with R<0.7. Use this.

- ΔR (e-jet) > 0.7
- Jet η < 2.4

Sanity plots: multiplicity after electron/jet matches removed, jet η<2.4

- truth

- full sim

Log scale→

Multiplicity greatly reduced

- ΔR (e-jet) > 0.7
- Jet η < 2.4
- ΔR(jet-truth)<0.5

Matching jets with truth in (η,φ) space:

Log scale→

If (ΔR<0.5) match is found

- ΔR (e-jet) > 0.7
- Jet η < 2.4

Sanity plots: ET

- truth

- full sim

Jets not reconstructed < 10GeV

- ΔR (e-jet) > 0.7
- Jet η < 2.4

Sanity plots: ET

- truth

- full sim

Strange: data is shifted down from truth.

JET ISSUES

- Jets from electrons are easily identified and removed by an exclusion cut in (η,φ) space.
- Not certain this is the best algorithm, but other available algorithms have more problems.
- Jet statistics low after removal of electrons, therefore resolutions not well defined.
- Meaning of jet “mass” not well understood, left-shift of simulation w.r.t. truth unexpected.

- Ptele > 25GeV
- At least one track matched
- IsEM=0
- Electron η < 2.4
- Jet η < 2.4
- ΔR (e-jet) > 0.7
- MET>25GeV

Sanity plots: Missing ET

Probably not properly calibrated

- truth: calculated from non-interacting particles

- full sim: corrected, inc. muons

Cut on MET>25GeV

- Ptele > 25GeV
- At least one track matched
- IsEM=0
- Electron η < 2.4
- Jet η < 2.4
- ΔR (e-jet) > 0.7
- MET>25GeV

Missing ET Resolution:

Asymmetry reflecting right-shift of data w.r.t. truth

- Ptele > 25GeV
- At least one track matched
- IsEM=0
- Electron η < 2.4
- Jet η < 2.4
- ΔR (e-jet) > 0.7
- MET>25GeV

Missing ET φ distribution:

- truth

- full sim

- Ptele > 25GeV
- At least one track matched
- IsEM=0
- Electron η < 2.4
- Jet η < 2.4
- ΔR (e-jet) > 0.7
- MET>25GeV

W transverse mass reconstructed from Missing ET and highest ET electron:

- truth

- full sim

Conclusions:

- The W looks like TDR (right)!
- Electrons are well reconstructed.
- The e/p variable in the egamma container should probably be fixed.
- Electrons with mis-identified charge not yet understood.
- Missing energy doesn’t seem best corrected to match truth.
- Insufficient stats for decent jet resolution.
- Jet “mass” shift seems strange.

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