1. in AliMixedEvent, the method GetMagneticField() returns -999. Is it possible to have, instead, the magnetic field of the first
event used to build the mixed event?
2. in AliMixedEvent, there are 2 methods to get the primary vertex: one is GetPrimaryVertex and returns a null pointer, the second
is GetPrimaryVtx and returns the mean vertex. Would it be possible to remove the second one and let the first one return the mean
vertex?
Yes to 1 and 2