This parameters have been obtained from 2005 data. 
The definitions of eta2, eta3 and eta4 have been modified according to the
discussion with Prof. Landi.
In particular:
- the baricenter with 2,3 or 4 strips is calculated even if not all the strip
are over threshold
- the correction function for eta4 is defined in the range -0.5:0.5 
and not -1:1 as it was before.

For the moment the multiplicity selection is kept.
The next improved parameters sets should have:
- no multiplicity cut (eventually replaced with a cut on the cluster charge)
- defined as a function of the effective angle (corrected for the magnetic
field)
- implemented the systematic shift due to charge distribution asimmetry
