# Presentation: 928869

## Electron and Photon Identification

- Drew Alton, University of Michigan
- Harald Fox, Northwestern
- Yurii Maravin, Fermilab
- _Jan Stark_, Grenoble

- Winter Physics Workshop, February 22nd, 2004

## Electron-ID: Performance and documentation

- The performance of our p14 electron identification machinery is documented in great detail
- in the “Z  e+ e- and W  e  cross section” note by Chapin, Fox, Gardner, Illingworth, Lyon,
- Steinbrück, Verzocchi and Zhu:
-    - Cluster reconstruction efficiency
-    - Preselection efficiency
-    - H-matrix efficiency,
-    - Track-matching efficiency,
-    - Fake-rates,
-    - ...
- This analysis note also serves as a standard reference on EM-ID performance.
- For this session of the workshop, we will follow the same logic: standard performance plots
- will be shown by John in the first analysis talk this afternoon (right after Patrice on missing ET).
- The present talk will focus on more general issues.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## p14: improved geometry and scale corrections

- Geometry corrections:
- (Magnan, Crepe)

- EM scale corrections:
- (Kermiche, Mendes)
- Based on Z. Also studying J/Psi now.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## p14: all new electron likelihood

- For p14, a new electron likelihood was implemented by Kozminski, Park, Gardner, Jabeen, Kehoe, Quadt and Weerts.
- A draft D0 note is available. It is used with loose precuts and exploits “all the remaining information” (HMx8, E/p,
- track-matching, track-isolation, ...). It comes in two flavours: one without CPS and one with CPS information.

- For p13, we were on this curve.
- Now we are on this curve.

- Unfortunately, some CPS information was lost during the first pass of TMB fixing.
- The upcoming second pass (from the original TMBs) will recover this information. Looking forward to using
- the CPS in physics analysis !

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## New for p14: H-matrix 7

- Greg L.
- HF

- HMx8    CC

- HMx7    CC

- HMx8    EC

- HMx7    EC

- Blue: Monte Carlo
- Red:  data

- HMx8: data/MC agreement lets something
- to be desired, especially in CC.
- One of the worst offenders: shower shape
- in z. Removed one of the corresponding
- input variables from the H-matrix
-      HMx7.

- Rejection power of HMx7 and HMx8 in the CC
- for different cuts.
- HMx7 does not only have better data/MC agreement,
- it also gives better rejection.
- HMx7 will be included in electron likelihood.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Energy resolution

- Blue: Monte Carlo
- Red:  data

- Z  e+ e-

- Di-EM mass (GeV)

- Z  e+ e-

- Di-EM mass (GeV)

- At the conferences our
- Z  e+ e- peak will look like this.

- But we to keep in mind that, before
- energy smearing (S. Jain) it looks
- like this.
- We have a task-force working on
- this problem, your contribution is
- welcome.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Track matching

- E/p

- centered around 1.05
-      ~ 0.15

- The cluster-track matching (R. Zitoun  M. Titov) comes in two flavours: spatial only, and spatial + E/p.

- efficiency

- fake rate

- With E/p, the efficiency is somewhat low.
- But keep in mind:  computing a 2 probability with
- non-gaussian distribution does not make sense.
- Recommended solution: use electron likelihood.
- Another issue: spatial track-matching efficiency
- drops pretty badly at high |detector |.
- This is mostly a tracking problem, not a matching problem.
- More on next slide.

- Spatial track-matching efficiency
- as a function of detector 

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Track matching at high ||

- Z  e+ e- candidate, right at the centre
- of the mass peak.

- Track !

- Track ?

- Cannot conclude anything from one event. But we have a whole load of such events.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## A reminder: DST repro vs. reco from RAW

- This is the crappiest t-tbar candidate
- from the e+jets/soft-muon-tag
- analysis. The default analysis uses
- run 165777 reprocessed from a
- p13 DST. On the right,
- the kinematics of the candidate event.

- When the candidate event is processed from RAW
- (p14.06.00, event display on the right), it fails the
- electron likelihood cut.
- The likelihood includes a track isolation.
- Most likely, that suspicious track close to the
- electron candidate is not found in DST reprocessing.
- Such subtle differences are expected. This is just
- a reminder that such oddities can occur.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## EM objects and data quality

- J. Gardner

- High-pT EM objects are a great tool
- to find electronics problems in the
- calorimeter precision readout.
- Unfortunately that means that
- analyses using objects are very
- sensitive to the electronics problems.
- / distribution of all candidate EM objects:
-   pT > 25 GeV
-   EM fraction > 0.9
-   isolation < 0.15
-   HMx8 < 20
- pink boxes: tower two problem
- blue boxes: energy sharing problem
- Green boxes: cable swaps
-    These three problems are taken
-    care of by the TMB fixing.
-    But keep in mind that we cannot
-    fix events that were rejected at L3.
- red boxes: other stuff ...

- Checkerboard

- The calorimeter hard- and software experts are working hard to get a checkerboard fix ready for the
- Second pass of TMB fixing.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Photon ID

- First-order photon identification: “a photon is an electron candidate without track-match”.
- Sophisticated tools for next-order photon ID are in the final stages of development:
-     Cal-CPS-TRK (not-trk) matching (YM + Askew)
- Trying to choose best method
- Line from Vertex-EM3 choose closest
- Fit CPS+EM1-4 find best fit
- Line from 0,0-EM3 choose highest energy
- Prefer not to use vertex
-     Hits on the Road(Atraventov + YM)
- Separate electrons, photons, fakes
- Recover/remove electrons without track match
- Separate photons from EM-jets
- Information
-  2 for both roads
- Number of hits on each road from each detector

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Photon ID

- For electron-ID, it is relatively easy to get a control sample of real electrons
- (di-EM resonances). Trying to get a control sample of real photon (DA et al.):
-         **W********, QCD-********, ********0****, ********c****, D*, etc**
- Other projects pursued by the photon ID subgroup:
-        - Implement standard track isolation
- - Test/study other cuts and construct likelihood
- - MC studies comparing e and 
- - Efficiency measurements in data (system 8?)

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark

## Conclusions

- Electron and photon ID are in a reasonably good shape: during this afternoon, we will see that nice
- analyses can be done based on these objects.
- Powerful new developments have been introduced in p14:
-   - TMB fixing
-   - improved geometry and scale corrections
-   - HMx7
-   - new track-matching
-   - new electron likelihood
-   - ...
- Many parts of this particular talk had sort of a negative note. This is because the speaker believes that
- he can leave the excitement for the analysis talks and that it is his role to point out areas with room
- for improvement.
- Over the past months, a lot of effort has shifted from ID work towards analysis. We are seeing
- The fruits of this analysis effort (and also our past detector and ID work !) today, and we hope
- For a large-scale re-involvement in ID-work after Moriond.

- Winter Physics Workshop, Feb. 2004

- Alton, Fox, Maravin, Stark