HIGH GRANULARITY CALORIMETER ANALYSIS SARAH MARIE BRUNO CMS - CALTECH GROUP SUPERVISORS: ADOLF BORNHEIM, LINDSEY GRAY, MARIA SPIROPULU

OVERVIEW Endcap More sensitive to radiation Crystals degrade quickly and must be replaced – expensive! New design – replace with silicon sensors Barrel Crystal (shashlik) design Will not change Goal: We want to investigate the performance of the new endcap design and compare to performance in the barrel. 2

H  ɤɤ SAMPLE Simulation to test performance of HGCal Pile-up-free sample Extremely large sample: 8020 Events Data in Barrel and Endcap (previously only endcap) 3

TREE ORGANIZATION 4 Data SetEvent 1Event 2ROI1Cluster 1Cluster 2Hit 1Hit 2Hit 3Hit 4Hit 5Hit 6Hit (…)Cluster 3 Cluster (…) ROI2Event (..)

SCATTER PLOT - RECONSTRUCTED COLLISION (EVENT 1) 5 2 Regions of interest correspond to the two photons. ROI2 ROI1 Contains three clusters (endcap) Contains one cluster (barrel), hits at same depth Note: transition between barrel and endcap occurs near z ≃ 270 Mean position of ROI2: (91.163, , ) Mean position of ROI1: ( , , )

FOR COMPARISON: (EVENT 2 LOOKS SIMILAR) 6 Most events are in the endcap, with only one or two clusters in the barrel.

ETA-PHI VIEWS OF BARREL AND ENDCAP (EVENT 1) 7 EndcapBarrel Barrel – traditional CMS crystal calorimeter (already use to do precision timing measurements. Very high granularity calorimeter. Focus here—study the precision timing for this part.

ETA-PHI VIEW FOR ALL EVENTS 8 Endcap Barrel

NOTE ON ETA-PHI PLOTS – RELEVANT RELATIONSHIPS 9

ETA-PT PLOTS (ALL EVENTS) 10 Barrel Endcap Events with higher pt are shifted towards lower eta in the endcap and higher eta in the barrel. (As expected - samples are flat in energy)

HIT TIMING 11 Much more spread in the endcap – length of the shower. In barrel, only one sampling of the time, so we are always sampling the same depth. (Minimal spread other than one late hit.) BarrelEndcap

HIT TIMING FOR ALL EVENTS 12

ETA BIAS IN TOF 13 Late outliers are the result of low pT secondary particles. “Curl around” and make a few loops in detector before hit is registered.

CALCULATION FOR FINDING THE COLLISION TIME 14

HITS BY CLUSTER 15 C0: Low number of hits, but still substantial energy. C1: Highest energy and greatest number of hits. C2 C3: Lowest energy and lowest number of hits.

ENERGIES OF CLUSTERS (FIRST EVENT) 16 ( 4 Clusters total) C3: 7.17 C2: C0 (barrel): C1: (GeV)

ENERGY OF CLUSTERS 17 (Gev)

CLUSTER PT 18

CLUSTER ETA 19

ROI DATA (EVENT 1) 20 ROIPtEtaTrue Energy (GeV) Difference between sum of energies of clusters in ROI2 and true energy of ROI2: Sum of Cluster Energy = GeV Difference = GeV

HIGGS MASS AND ENERGY CALCULATION We know the mass of the Higgs is ~125GeV C0 and C1, the two highest energy clusters, correspond to the two photons. Their energies combined are GeV. The additional energy is due to forward boosting—energy is greater than Higgs mass. Remaining questions: What is the best way to measure the energy? Would counting the sensors be a reasonable method for determining the energy of the system, or must we add all of the energies in the sensors? What is the correlation between the sensor reading and energy deposited in the absorber in front of the sensors? What is the difference between the true energy and the reconstructed energy? 21

SIDE NOTE: TEST BEAM 22 Testing Shashlik detector Electron beam Detected muon signal Shashlik – yellow MCP - green

23 THANK YOU Questions?