# Presentation: 068514

## DØ collaboration Workshop

- BUSATO Emmanuel 	LPNHE		 18 june 2003
- VLIMANT Jean-Roch

- _T42 algorithm : noise suppresion_
- _Towards a better Data Quality _
- www-d0.fnal.gov/~vlimant/noise-suppdescr/Description.html

- Principle
- Effects on calorimeter objects
- Conclusions

## T42Inspired from an algorithm used in H1

- Principle
- Keep high signal cells (above 4 sigma) : noise less than 4 cells/event
- Keep their neighbours above 2 sigma : very likely to be signal rather than noisy cells
- 		Thresholds 2 is 2.5 at the moment due to current offline zero-suppression
- Reject negative energy cells : such signal cell less than 4 cells/event, very likely to be noise
- Equivalent neighbours as with NADA
- Complexity is linear with respect to the cell number (quick algorithm)
- Killing/Shadow mode available (modify/leave untouched the CalDataChunk)
- Dedicated Chunk with noisy cells : Calt42Chunk
- Full description is available in DØNote 4124, 4146

- I-Principle

## T42 How to

- T42 is set shadow mode in d0reco since p14 (included) : Calt42Chunk at DST level
- You are invited to have to look at it
- Processing
- At DST level : combine the chunks with Calt42Combine hook
- At TMB level : set killing mode in Calt42Reco hook
- Post-reconstruction of physical objects chunks is necessary : EMparticleChunk, JetChunk,... 	Clear exercised instructions are at
- _[www-d0.fnal.gov/~vlimant/noise-suppdescr/Description.html](http://www-d0.fnal.gov/~vlimant/noise-suppdescr/Description.html)_
- _[www-d0.](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[fnal](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[.](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[gov](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[/~](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[busato](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[/](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[HowTo](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)__[/D0_code/reconstruction_at_TMB_level.html](http://www-d0.fnal.gov/~busato/HowTo/D0_code/reconstruction_at_TMB_level.html)_

## Population reportunstreamed data

- Population reportunstreamed data

## Peaks and strange features are removed

- Smoothing effect

- Before

- After

- Rejected

## Rejection status

- Number of cells with negative energy and  positive energy are balanced : evidence of actual noise rejection
- 40% cells rejected
- 1 event = 3.3% of available cells in the calorimeter
- Rejection a bit too high in the region close to the beam due to base line subtraction in underlying event cells

## Samples

- Data sets
- EM studies
- DIEM15 stream of Wzskim, p13.05 p13.06
- Jpsi skim by Jan Stark,
- Jet studies
- Alljets stream from Top group, p13.06
- MET studies
- recoT file dated March, p13.06
- MC sets
- Jet studies
- QCD Pt20 from CTF, p13.08

- II- Effects on objects

## Effect on Electronsfrom calorimeter cluster

- 30% more EMid objects
- 18% more EMid+track match objects(electrons)
- Mostly at low energy

- Difference

## EMid efficiency 

- EMid efficiency

- no T42

- Method : use diem events, Probe is a track matched cluster and Tag is a tight electron back to back with the Probe

## Effect on Electrons

- T42

## J/Ψ mass with cluster electrons

-  T42

- no T42

- 48 tights events in the mass window 2.5-3.5

## Effect on Electrons from Road Method

- Tiny gain ( 8.10-2%) at low energy ( improvement limited by the number of isolated tracks )

- Difference

## Effect on Soft Electrons

-  T42

- no T42

## Effect on Soft Electrons

-  T42

- no T42

## Summary on  EM objects

- From calorimeter cells clustering

- EMiD was 90.02.8 % is 90.32.7 %

- Slightly more J/Psi
- Better Soft Electron Tag efficiency

- Slightly better efficiency in central region
- Fake rate not estimated yet
- Better mass
- Better mass resolution
- Less noise

- TighSoftEl was 887 % is 927 %

- From Road method

## Effect on calorimeter jets

## Data/MC comparison for jets (-1<<1)

## Quality cut efficiencies

- Data sample :
- 	  stripped thumbnails of jet-photon events from JES :
- 	 	  reco version : p13.06.01
- 	       	  triggers : all single electromagnetic triggers in CMT-9.50
- 		  At least one EM object with |id|=10,11 and pT > 4.0 GeV
- Additional cuts :
- 	 Photon candidate selection :
- 		  Hmx8<20
- 		  Isolation<0.15
- 		  EM fraction>0.9
- 		  in fiducial
- 		  no track match
- 	  (jet-photon)>3.0

- Method : use photonjet events, apply back to back requirement to maximize  real jets over fakes  apply quality cuts on these jets

## Jets properties

- CHF

- emf

- n90

- f90

## Quality cut efficiencies

- (Statistical error only)

**Total                  ****0.914 ******** 0.008****      ****0.929 ******** 0.008**** **

## Does T42 cuts real energy ?

-  **** Single top events – s channel production mode :
- 	 no calorimeter noise
- 	no minimum bias

- Without t42  :   Number of jets = 3568
- With t42  :   Number of jets = 3540
-  Reduction is 

**** In top group’s alljets skim : 0.9% of jets with pT > 25 GeV are not found
-      with T42. Two physical reasons explain this difference :
- 	 threshold effect : “very” noisy jets or low pT good jets surrounded
- 	   by  “very” hot cells and towers are suppressed
- 	 split/merge effect
- (cf http://www-d0.fnal.gov/~d0upgrad/d0_private/software/jetid/meetings2003/Apr24/busato.ppt)

## A particular event

## What else  

-    Jets reconstructed after t42 have lower energy, thus this cut may also be
-    reconsidered.
-  Of course, new JES corrections need to be applied to « t42 jets ».

- What else

- 735 MeV
- difference for
- the same jet

## Summary on jets

- jetID was 91.4  0.8% is 92.9  0.8 %

- Quality cuts may be reconsidered : particularly on emf and f90
- Maybe apply different pT threshold at reco level
- In MC without noise very few real jets are lost with T42.
- Almost all high pT good jets remain after T42.

## Effect on mEt

## Effect on mEtx

## Effect on mEty

## Effect on sEt

## Effect on missing energy

- Less missing energy
- Better resolution
- “Hot” region cleaned
- Event without any cells now

- x y decreases by 30%
- <SEt> decreases by 30%
- <mEt> decreases by 13%

## Summary 

- T42 algorithm removes 40% of cells and 30% of energy
- without modifying relevant physics
- smoothes the occupancy distributions
- Still beam pipe BLS over-occupancy
- Calt42Chunk in ThumbnailChunk to be implemented
- Calorimeter based objects within ||=2.5 identification is improved even though studied on biased (skimmed) samples
- Fake rate and efficiencies to be re-calculated on unskimmed data
- Quality cuts and energy scales should be reconsidered with T42
- T42 in killing mode would improve the data quality for analysis...