I want to thank you for your response. It will help a great deal in my understanding of particle momenta in emulsions.
But, my problem is with definition of track, not particle momenta.
Here is a excerpt from the text I was reading through:
Each found track is fitted taking into account...
In experiments with nuclear emulsion (like CHORUS,OPERA...), the emulsion is scanned for tracks left by passing particles. In track analysis, there is a quantity called track momentum.
I don't know what the track momentum is, so if anyone could help me, i would be grateful.