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Cosmic Rays Data Analysiswith CMS-ECAL
Mattia Fumagalli
(Università di Milano Bicocca)
CIAO!
Mattia Fumagalli - Summer Student Session 2008 2
Brief Review of CMS-ECAL.
BARRELL:36 supermodules
ENDCAPS: 2 dees each
ECAL BARREL:
61200 PbWO4 scintillating
crystals equipped with APD
Crystals point to the
Interaction Vertex
Mattia Fumagalli - Summer Student Session 2008 3
CMS-ECAL Calibration Strategy
• PRECALIBRATION:
• 120 GeV electron TEST BEAM (2006): 1/4 of the ECAL barrel. 0.3% in reproducibility
• Cosmic Muons at Point H4: precision 1.3% to 2% depending of η.
To have…
•FINAL CALIBRATION! PHYSICS EVENTS @ LHC:
• Phi-Symmetry and Calibration with Pions
• Z ee and W e processes: intercalibration of different regions
•absolute Energy scale setting.
2.7% 1500.5%
MeV
E EE
we need
Mattia Fumagalli - Summer Student Session 2008 4
In Situ Calibration with CosmicsCRUZET RUNS: no magnetic fieldalmost every part of CMS working ~70M events taken in 3 sessions
(5-7 days each) (4th CRUZET coming!)
INTERCALIBRATION:Independent check of the previous Calibrationswith the detector alreadyIn-Situ!
TrackerECALHCALMuons Drift Tubes
Mattia Fumagalli - Summer Student Session 2008 5
Muon Events at ECAL
BEST EVENTS !Cluster made of just one Crystal
(GOLDEN MUONS)
SEED CRYSTAL
Cosmic Muons are Minimum Ionizing Particles_ No Electromagnetic Shower_ Energy deposited just in the hit Crystals_ Energy proportional to Path Lenght
Mattia Fumagalli - Summer Student Session 2008 6
• Two Cluster Events
• Delta between clusters > 90°
• Impact Parameter < 10 cm
• Cosmic Muons that point to the Interaction Vertex
• Muon Path almost parallel to the Crystal Axis
InteractionVertex
Impact Parameter
NOT IN SCALE!
Selecting the Events
Mattia Fumagalli - Summer Student Session 2008 7
Energy and PathsGOAL! Cross Check of the ECAL Pre-Calibration
According to the Behaviour of a MIP
Peak at 0.012 GeV/cm
Comparison between the Energy deposited and the Path Length
(Inter)Calibrationcoefficients
i i iCLUSTER CLUSTER
dEL E c AdX
Inverse Matrix Tecnique
ECAL
Mattia Fumagalli - Summer Student Session 2008 8
OccupancyStatistics on each Crystals
Energy Distribution on the ECAL
SHAFT
Mattia Fumagalli - Summer Student Session 2008 9
What’s good… and what’s bad!
Low Statistics, depending on eta.Calibration not possilbe everywhere
Data from other parts of CMSPossibility of Track Reconstruction
Mattia Fumagalli - Summer Student Session 2008 10
Future Work• Fully Exploit the Statistics
• Implementation of a Calibration Algorithm
• Coefficients to cross check previous Calibrations
…and Thanks!GRAZIE!
