# Presentation: 049608

## Status Report of electron response in φ crack 

- Universiry of Rochester
- Yeonsei Chung, Geumbong Yu

## For study

- 1 million MC(Z→ee) used
-     →Zewkae: Pythia MC with min bias events
- Data set of bhel0d (high pt electron):                            454 files read(~48G)
- Eta towers, 19~32, used for both of electron and track.
- For electron, tight central electron cut used except Et cut.
- Cut strategy is to have clean Z sample by every possile tight cut.

## Track selection 

- Track pt > 20 GeV
- Opposite charge to electron’s
- E/p<2.0
- Had/Em<0.05
- No other track within 0.4 cone of track.
- All energy used in cut is 2x2 Cal energy.
- To make similar condition of track with electron, raise track pt cut to 20 GeV.

- Footnote: we found the electron Et>25 GeV cut make bias in comparing
- E/p distribution of track and electron(higher E/p of electron than track).
-  Therefore we tried to apply pt>20GeV to both of el and track.

## Z mass

- Monte Carlo
- Data

- 2x2 Cal E

- Track Mom

- To reconstruct Z we used 2x2 Cal data
-  and track momentum for 4-vector of track.
- Emobject used for electron 4-vector.

## Zmass

- 2x2 Cal E

- Track Mom. used

- trk |rphi|<0.9

- trk |rphi|>=0.9
- Crack region

- In the case of Cal data, Z mass are
- strongly affected by hit position of
- phi since we lost energy in crack.
- But if we use track momentum for
- 4-vector of track, the shape is not
- changed by Relative phi position.

- Selected Zmass
- 80< MZ < 100

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>=0.9
- Data in dot

## Zmass 

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>=0.9
- Data in dot

- Compare events in |rphi|>=0.9 of track with |rphi|<0.9.
- Obviously there’s mismatch in Zmass with Cal E.

## Selected Zmass with Cal Eafter 80<M(Z,trk)<100 cut

- In addition to the M(Ztrk) mass cut,
- we require |rphi|<0.8 of electron
- to reduce possible background on electron leg.

- Monte Carlo
- Data

- overall dist.

- Trk |rphi|<0.9

- Trk |rphi|>=0.9

## E/p 

- Single Tower Cal energy
- Track Momentum

- Electron

- Track

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>=0.9
- Data in dot

- We have seen the E/p dist. of
- crack region (either electron of track)
-  is different from non-crack area.

## E/p

- Electron

- Track

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>0.9

- Data in dot

- Does the high E/p distribution
- mean background on electron leg?

## Zmass in el crack

- Blue : |rphi|<0.9
- Green : |rphi|>0.9
- Data in dot

**Combined**

## Had/Em(track)

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>=0.9
- Data in dot

- Tight central electron cut
- including sliding Had/Em cut
- already was applied to electron leg.
- To have track cut,
- we plotted normalized Had/Em dist.
- Had/Em on track less than 0.05
- selected to have clean Z sample.

- 2x2 Had Cal Energy
- 2x2 EM Cal Energy

## Had/Em

- Black : overall dist.
- Blue : |rphi|<0.9
- Green : |rphi|>=0.9
- Data in dot

- Data shows sharper Had/Em in low
- but more fluctuation in high region.

## Events in rel. position

- Track

- Electron

- Rel. phi

- Rel. eta

- We have flat relative phi distribution
- of track without requiring em object

- Monte Carlo
- Data

## E/p vs rel. phi & rel. eta

- Rel. phi

- Rel. eta

- Electron

- Track

- Monte Carlo
- Data

## E/p vs rel. phi & rel. eta

- Rel. phi

- Rel. eta

- Electron

- Track

- Monte Carlo
- Data

- Just blowup of
- Previous page

- Have correction on Cal Data?

## E/p vs. rel. phi & rel. eta

- Rel. phi

- Rel. eta

- Emobject E/p variable shows flat distribution after correction
- but we don’t have no way to see how track response change.

## Cal energy distribution in phi

- Track

- Monte Carlo
- Data

- Electron

## Cal energy distribution in eta

- Track

- Monte Carlo
- Data

- Electron

## Summary

- To study crack response properly, we had to use track momentum instead of Cal energy for clean Z sample.
- We used pt>20 cut for both of electron and track to make a fair comparision of E/p profile.
- There’s a discrepancy between MC and data in phi, electron and track in eta. It needs to be understood.