A Data Acquisition system with an e'm' calorimeter for cosmic rays and 0 mesons study

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A Data Acquisition system with an e.m.
calorimeter for cosmic rays and ?0 mesons study

• Lorenzo Centioni1, Elena Eramo2,
• Azzurra Giordani1

1Lic. Sc. B. Touschek, Grottaferrata (RM) 2 Lic.
Sc. E. Amaldi, Roma
Tutor Pasquale Di Nezza Technician Aldo Orlandi
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Aim of the experiment

• Realize a DAQ to analyze cosmic rays signals
  reconstructed by an e.m. calorimeter
• In order to perform a study on a calorimeter
  working in a real experiment, we have
  reconstructed the ?0 particle invariant mass
  (data from the Hermes experiment).

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Calorimeter and DAQ layout
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The particle ?0

• The particle ?0 is a meson formed by a mix of u
  and d quarks

It decays by electromagnetic force in two
photons in the 98.8 of the time (Particle Data
Book). Its life time is about 10-17 seconds.
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Decay of the ?0 meson
10-17s
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?0 spectrum

• The spectrum fit is a superposition of a gaussian
  curve and a first order polynomial
• The mean value of the distribution is the ?0 mass

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?? invariant mass distributions

• Different spectra with different ?0 minimum E
• Less events
• Less uncorrelated photons
• Similar mass values

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?0 M as a function of ?0 minimum E

• The ?0 mass does not depends on the energy of the
  particle
• The results coincide with the expected value
  (0.135 GeV)

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Signal and background

• We can observe two different areas
• The signal (real decay of the ?0)
• The background (uncorrelated photons)

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Ratio sign/back as a function of ?0 minimum E

• Sign/bg ratio of different spectra with different
  ?0 minimum E
• We obtained a second order polynomial
• Uncorrelated photon pairs mainly at low energy

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Conclusions

• We have created a DAQ made by a sampling e.m.
  calorimeter
• Collected data analyzed within the Linux
  operating system (LabView, Paw)
• Studies on ?0 meson invariant mass
  reconstruction, energy dependence, sign/bg ratio