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

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.

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

RecHits in Ecal Barrel Eta E Phi

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

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

Pi0 candidates from SuperCluters in Barrel MC Data Invariant mass of 2 SuperClusters Energy

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

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

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

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

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

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

MC: Endcap Energy, Eta & Phi

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

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.

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

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

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

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