Pi 0 Eta reconstruction in ECAL Barrel with

Pi 0 & Eta reconstruction in ECAL Barrel with the Minimum Bias Data Events J. Tao IHEP-Beijing CMS-Bijing weekly meeting Dec. 25, 2009 1

Samples and π0 Selections ØData sample: /Minimum. Bias/Beam. Commissioning 09 -Prompt. Reco-v 2/RECO l A total number of events 89, 695, 020, with RUN ID from 121672 to 124371. l All events were analyzed @ccin 2 p 3 directly ØMC data samples, as a reference: /Min. Bias/Summer 09 -STARTUP 3 X_V 8 I_900 Ge. V -v 2/GEN-SIM-RECO /Min. Bias/Summer 09 -STARTUP 3 X_V 8 I_900 Ge. V-v 2/GEN-SIM-RECO l A total number of events 9, 991, 360 l All events were analyzed @cc. IHEP directly ØAll events skimmed on BSC (Beam Scintillator Counters) technical bits (“ 40 OR 41”) l Data: 1, 107, 589 events left l MC: 6, 800 events left l L 1 tenical trigger bits: https: //twiki. cern. ch/twiki/bin/view/CMS/L 1 Technical. Trigger. Bits ØPi 0 candidates selections l γ candidates in barrel: 3 x 3 clusters with seed threshold E>0. 1 Ge. V l ET(γ)>300 Me. V; l ET(π0)>900 Me. V; l S 4/S 9 > 0. 85 (shower shape) l All γγ combinations allowed, no constraint in opening angle Other data: 1) /Minimum. Bias/Beam. Commissioning 09 -Prompt. Reco-v 1/RECO 106, 550, 190 events with RUN ID seems 079022~097742 2 2) /Minimum. Bias/Beam. Commissioning 09 -Prompt. Reco-v 3/RECO 110, 296, 049 events with RUN ID seems 100303~102001 3) /Minimum. Bias/Beam. Commissioning 09 -Prompt. Reco-v 4/RECO 40, 179, 959 events with RUN ID seems 102013~102352

Pi 0 candidates in Ecal Barrel DATA MC ØRoo. Fit: Gaussian + 3 order Chebychev polynomial function Øm(γγ)<m(π0): due to uncorrected energies Ø Data-MC comparison: mass & width are compatible PDG: m(π0)=134. 9766± 0. 0006 Me. V 3

Results from ECAL group 900 Ge. V: 900 Ge. V All runs with nonnegligible stat. up to run 124120 4

η Selections η candidates selections l γ candidates in barrel: 3 x 3 clusters with seed threshold E>0. 1 Ge. V l No constraint in opening angle of γγpairs. l π0 veto: reject γif m(γγ) compatible with m(π0) (reject γif 0. 05<m(γγ)<0. 18 in my analysis) l ET(γ)>400 Me. V; l ET(η)>2. 0 Ge. V; l S 4/S 9 > 0. 85 (shower shape) 5

DATA η candidates in Ecal Barrel MC Roo. Fit: Gaussian + 3 order Chebychev polynomial function with fitting range (0. 2, 2. 0) Roo. Fit: Gaussian + 3 order Chebychev polynomial function with fitting range (0. 2, 1. 5) PDG: m(η)=547. 853± 0. 024 Me. V 6

Results from ECAL group 7

Seed energy in Ecal Barrel with ET(3 x 3 Cluster)>0. 3 Ge. V DATA 0. 1 Ge. V 8

Related to the Mass Calculation: Prim. Vertex MC Enlarged range: 0 -10 tracks Vertices from >=2 tracks “offline. Primary. Vertices. With. BS” If no more than 1 tracks, take the position of Beam. Spot 9

Related to the Mass Calculation: Prim. Vertex Data Enlarged range: 0 -10 tracks Vertices from >=2 tracks “offline. Primary. Vertices. With. BS” were used in my analysis! 10

3 x 3 clusters in Barrel with seed threshold E>0. 1 Ge. V Energy Hit Energy in Barrel PT Mass of all 3 x 3 cluster pair 11

Summary, plan and discussion Ø Pi 0 & Eta candidates were searched from the Minimu. Bias events of Real data and MC samples. Ø With 3 x 3 Clusters algorithm and seed threshold 0. 1 Ge. V, a lot of Pi 0 and Eta candidates can be obtained in ECAL Barrrel. Ø Try to optimized the selections to get more statistic of Pi 0 & Eta candidates in ECAL Barrel. Ø Try to see if Pi 0 & Eta candidates can be reconstructed in Endcap. Ø With the available statistics, the ECAL group will start commissioning π0 calibration. What we can contribute to the ECAL group with such a topic? 12

Backup slides 13

Pi 0 candidates in Ecal Barrel DATA MC Eseed > 0. 2 Ge. V 14

3 x 3 clusters in Endcap with seed threshold E>0. 1 Ge. V Hit Energy in Barrel Energy Mass of all 3 x 3 cluster pair 15