There several ideas how to decrease the systematic uncertainties in absolute energy scale calibration of the CAL, noticed in data/MC comparison for 2006 beam test.
- We can use proton and GCR tracks crossing a crystal at small angles alpha to crystal axis (i.e. with big angles theta to vertical axis) to intercalibrate the peaks of energy depositions from nuclei with different charge:
- Using the energy deposition of vertical protons as a reference, calibrate the enrgy deposition of He
- if protons at alpha=0 have most probable energy deposition 10.6 MeV in a crystal
- protons at theta=0.25 rad (14 degrees) to crystal axis deposit ~40 MeV (very precisely measured because angle alpha is measured by tracker)
- by finding the alpha angle at which protons have the same most probable energy deposition as vertical He we'll get the and could be used to calibrate the energy depositions of He ions at theta=0, having also ~40 MeV most probable energy deposition
- He ions at
- Using the energy deposition of vertical protons as a reference, calibrate the enrgy deposition of He