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D ATA ANALYSIS FROM THE CERN TEST EXPERIMENT ABOUT THE HADES ELECTROMAGNETIC CALORIMETER By : Tazio Torrieri Supervisor : Vladimir Wagner
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PLAN HADES experiment The HADES electromagnetic calorimeter The CERN test experiment Data analysis and results
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HADES High Acceptance Di-Electron Spectrometer
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HADES Study of nuclear matter properties at high density : Modification of hadron properties
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HADES Detection of electron-positron pair Extract the invariant mass of light vector mesons (ω, ρ, Φ)
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HADES ELECTROMAGNETIC CALORIMETER
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Aim : Improvement of the signal from light vector mesons by removing the background. Two main sources of background : π 0 → γ + e − + e + η → γ + e − + e + Dalitz decay ≈ 1.2 % Charged pions
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HADES ELECTROMAGNETIC CALORIMETER Detection of gamma pair : π 0 → γ + γ η → γ + γ Better π − / e − supression for large momenta
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HADES ELECTROMAGNETIC CALORIMETER Replace the HADES pre-shower detector Placed at 2.40 m from the target 8m² required Angle covering : 18° < θ < 45° ≈ 840 lead glass modules from OPAL experiment Module dimensions : 42 x 9.2 x 9.2 cm
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CERN TEST EXPERIMENT
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D ATA ANALYSIS AND RESULTS
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Distribution of the energy deposited in the first detector
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Electron peak fitting for the first detector
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Energy calibration Energy resolution Expected resolution : 5% / √E (GeV)
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Gaussian + Exponential fitting Gaussian + Parabole fitting
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Distribution of the energy deposited in the first detector after energy calibration
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Q UESTIONS ?
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