Invariant Mass Calculation for Pion Decay
Invariant mass calculation: Located in
Select events with two clusters
M^2 = 2 * p_1 * p_2 * (1 - cos(theta))
here p_1 = E_1 first cluster energy, p_2 = E_2 second cluster energy, and theta = angle between two photons
@whit For angle between two photons, need to know momentum vector of two photons? or know where decay position since we know two clusters' positions.