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

study

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

studyLorenzo Centioni1, Elena Eramo2,

Azzurra Giordani1

1Lic. Sc. B. Touschek, Grottaferrata (RM)

2 Lic. Sc. E. Amaldi, Roma

Tutor: Pasquale Di NezzaTechnician: Aldo Orlandi

Aim of the experimentAim 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).

Calorimeter and DAQ layout

Calorimeter and DAQ layout

The particle 0 The particle 0

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

dduu 2

1

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.

Decay of the 0 mesonDecay of the 0 meson

0

10-17s

222 mpE

0 spectrum0 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

invariant mass distributions

invariant mass distributions

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

0 M as a function of 0

minimum E0 M as a function of 0

minimum EThe 0 mass does not

depends on the energy of the particle

The results coincide with the expected value (0.135 GeV)

Signal and backgroundSignal and background

We can observe two different areas:

The signal (real decay of the 0)

The background (uncorrelated photons)

Ratio sign/back as a function of 0 minimum E

Ratio sign/back as a function of 0 minimum E

Sign/bg ratio of different spectra with different 0

minimum EWe obtained a second

order polynomialUncorrelated photon pairs

mainly at low energy

ConclusionsConclusions

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