DATA ANALYSIS FROM THE CERN TEST EXPERIMENT ABOUT THE HADES ELECTROMAGNETIC CALORIMETER

By : Tazio TorrieriSupervisor : Vladimir Wagner

PLAN

HADES experiment

The HADES electromagnetic calorimeter

The CERN test experiment

Data analysis and results

HADESHigh Acceptance Di-Electron Spectrometer

HADES

Study of nuclear matter properties at high density : Modification of hadron properties

HADES Detection of electron-positron pair

Extract the invariant mass of light vector mesons (ω, ρ, Φ)

HADES ELECTROMAGNETIC CALORIMETER

HADES ELECTROMAGNETIC CALORIMETER

Aim : Improvement of the signal from light vector mesons by removing the background.

Two main sources of background :

π0 → γ + e− + e+ η → γ + e− + e+ Dalitz decay≈ 1.2

%Charged pions

HADES ELECTROMAGNETIC CALORIMETER Detection of gamma pair :

π0 → γ + γ η → γ + γ

Better π− / e− supression for large momenta

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

CERN TEST EXPERIMENT

CERN TEST EXPERIMENT

DATA ANALYSIS AND RESULTS

Distribution of the energy deposited in the first detector

Electron peakfitting for the first detector

Energy calibration

Energy resolution

Expected resolution :5% / √E (GeV)

Gaussian + Exponential fitting

Gaussian + Parabole fitting

Distribution of the energy deposited in the first detectorafter energy calibration

200 400 600 800 10001200140016001800200022000.700

0.750

0.800

0.850

0.900

0.950

1.000

1.050

e− / π− separation

Series1Series5Series9

Energy (MeV)

π−

sep

/ al

l π−

QUESTIONS ?