Absorber characteristics

Using the test beam data is also possible to obtain informations about some electromagnetic features of the absorber. For instance the calorimeter critical energy and the radiation length $X_{o}$ can be obtained looking at the longitudinal profile of electron initiated showers. Such distribution can be parametrised by using the relation:

$$\frac{dE}{dt} = E_{o}b \frac{(bt)^{\alpha-1}e^{-bt}}{\Gamma(a)}$$ (1)

where t=x/$X_{o}$ [7]. Figure 11 shows the distribution of the longitudinal profile of a 2 GeV electron initiated shower and the fit obtained using equation(1.2), giving $E_{c}$=59.7 MeV and $X_{o}$=5.0 cm. Using 4 GeV electrons the fit results are $E_{c}$=56.8 MeV and $X_{o}$=5.0 cm.

The value of the critical energy obtained with this procedure is somewhat higher with respect to the value used in the Montecarlo simulation, previously computed by the stechiometry of the chemical composition of the absorber, neglecting the air between the iron ore grains.