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 horizontal (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, we measure the nonlinearity for energies 10-40 MeV and get the quenching factor for He
- protons at alpha=90 degrees (theta=0) have most probable energy deposition 10.6 MeV in a crystal
- protons at alpha=0.25 rad (14 degrees) to horizontal deposit ~40 MeV (very precisely measured because angle alpha is measured by tracker)
- by looking at the evolution of pathlength-corrected energy deposition versus full (uncorrected) energy deposition we'll get the measurement of CAL nonlinearity in the energy range 10-40 MeV, completely independent from charge injection calibration
- by finding the alpha angle at which protons have the same most probable energy deposition as vertical He we'll measure the quenching factor of He independently of 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, we measure the nonlinearity for energies 10-40 MeV and get the quenching factor for He