1. CMS-Bijing weekly meeting
Pi0 reconstruction with the Minimum Bias Data --The first step of intercalibration of crystals
J.Tao
IHEP-Beijing
CMS-Bijing weekly meeting
Dec. 18, 2009

2. Introduction
Data sample: /MinimumBias/BeamCommissioning09-PromptReco-v2/RECO
with a total number of events 89,695,020, and analysze 28,176,263 events events with CMSSW_3_3_4.
MC data samples, as a reference: /MinBias/Summer09-STARTUP3X_V8I_900GeV-v2/GEN-SIM-RECO
with a total number of events 9,991,360, and analysze 5,894,927 events with CMSSW_3_3_4.
Results of some Jobs can’t be returned to T2 with Crab.
Pi0 candidates can be reconstructed from
1) SuperClusters: hybridSuperClusters in Barrel & multi5x5SuperClusters in Endcap;
2) BasicClusters: hybridBasicClusters in Barrel & multi5x5BasicClusters in Endcap;
(These two objects can be obtained from the Reco. Data directly)
3) Clusters from 3x3 clustering algorithom.

3. RecHits in Ecal Barrel IPhi Run ID of Data Data
Readout of the crystals
IEta
Barre: IEta: -85~-1, IPhi: 1-360
Data:
27,362,534 evets have no EBHits
MC:
All events have EBHits

4. RecHits in Ecal Barrel
Eta E
Phi

5. RecHits in Ecal Endcap
1 supercrystal in z+ and 1 supercrystals in z- have no response. IX: 1~100, IY: 1-100
Data:
27,410,719 evets have no EEHits
MC:
All events have EEHits

6. RecHits in Ecal Endcap
Eta E
EE+ & EE- together
Phi

7. Pi0 candidates from SuperCluters in BarrelMC
Data
Invariant mass of 2 SuperClusters
Energy

8. Pi0 candidates from SuperCluters in Endcap
MC:
No pi0 candidates in Endcaps
Data
EE-
EE+

9. Pi0 candidates from BasicCluters
MC: Barrel
Data: Barrel
△R<0.3
0.04~0.23GeV
△R<0.3
Data: Endcap
MC: Endcap
△R<0.3

10. Clusters from 3x3 clustering algorithom
Seed crystal searching: threshold E>0.5GeV in Barrel & 1.0GeV in Endcap.
Seeds are then sorted according to their energy.
Starting from the seed with highest energy, a 3x3 cluster centered around the seed is formed, excluding the crystals with non-positive energy.
Require each crystal to belong to only one cluster. Hence, crystals surrounding the seed with energy greater than 0.5 GeV/1.0GeV are removed from the list of seeds. E
Max(△η, △)
in unit of crystals
from QCD MC samples

11. 3x3 Clusters in Barrel MC: Barrel Data: Barrel Energy Energy
Eta
Phi

12. Pi0 candidates from 3x3 Clusters in Barrel
Data: Barrel
MC: Barrel
All pair
Data: Barrel
MC: Barrel
△R<0.3
Data: Barrel
MC: Barrel
△R<0.3 &&
Nhits>2

13. 3x3 Clusters in Endcap
Data: Endcap
Energy
Energy, Eta & Phi

14. MC: Endcap
Energy, Eta & Phi

15. Pi0 candidates from 3x3 Clusters in Endcap
Data: Endcap
MC: Endcap
All pair
△R<0.3 &&
Nhits>2

16. Summary
Pi0 candidates were searched from the MinimuBias events of Real data and MC samples .
With the analyzed events, no shape peak of Pi0 candidates can be found from the real data, with the objects Super Clusters, Basic Clusters and 3x3 Clusters, with less statistics.
For the MC samples, a lot of Pi0 candidates can be obtained from 3x3 Clusters, especially a sharpe peak in ECAL Barrrel.
Try to run as more real data events as possible, to searching for the Pi0 peak. At the same time , should to analyze with the MC samples to select the Pi0 events with optimized selections.

17. Reco Track: Data
Data:
28,094,481 events no track PT
Eta
Phi

18. Reco Track: MC
MC:
815,396 events no track PT
Phi
Eta

19. 3x3 Clusters in Barrel Data: Barrel Delta R of pair clusters
MC: Barrel
Delta R of pair clusters
|PairMass-Pi0|<0.035GeV
|PairMass-Pi0|<0.035GeV

20. 3x3 Clusters in Barrel Data: Barrel NHits with E>0.
MC: Barrel
MC: Barrel
NHits with E>0.
|PairMass-Pi0|<0.035GeV