HIGH GRANULARITY

CALORIMETER ANALYS

IS

SARAH MAR I E

BRUNO

C M S - C A LT E C H G

R O U P

S U P E RV I SO R S : A

D O L F BO R N H E I M

,

L I ND S E Y G

RAY , MA R I A

SP I R

O P U LU

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.

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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)

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TREE ORGANIZATION

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Data Set

Event 1

Event 2ROI1

Cluster 1

Cluster 2

Hit 1

Hit 2

Hit 3

Hit 4

Hit 5

Hit 6

Hit (…)

Cluster 3

Cluster (…)

ROI2Event (..)

SCATTER PLOT - RECONSTRUCTED COLLISION (EVENT 1)

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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, 33.747, 332.354)

Mean position of ROI1: (-65.907, -112.385, 158.059)

FOR COMPARISON: (EVENT 2 LOOKS SIMILAR)

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Most events are in the endcap, with only one or two clusters in the barrel.

ETA-PHI VIEWS OF BARREL AND ENDCAP (EVENT 1)

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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

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Endcap

Barrel

NOTE ON ETA-PHI PLOTS – RELEVANT RELATIONSHIPS

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ETA-PT PLOTS (ALL EVENTS)

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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

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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.)

Barrel Endcap

HIT TIMING FOR ALL EVENTS

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ETA BIAS IN TOF

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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

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HITS BY CLUSTER

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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)

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(4 Clusters total)

C3: 7.17

C2: 37.97

C0 (barrel): 111.76

C1: 133.1

(GeV)

ENERGY OF CLUSTERS

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CLUSTER PT

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CLUSTER ETA

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ROI DATA (EVENT 1)

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ROI Pt Eta True Energy (GeV)

1 71.20262146 1.02222347 111.75827484

2 48.65100098 1.9407146 172.88928036

Difference between sum of energies of clusters in ROI2 and true energy of ROI2:

Sum of Cluster Energy = 178.24288416215455 GeV

Difference = 5.3536038021545664 GeV

HIGGS MASS AND ENERGY CALCULATIONWe know the mass of the Higgs is ~125GeVC0 and C1, the two highest energy clusters, correspond to the

two photons. Their energies combined are 244.86GeV. 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?

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SIDE NOTE: TEST BEAM

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• Testing Shashlik detector

• Electron beam

•Detected muon signal•Shashlik – yellow•MCP - green

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THANK YOUQuestions?