For this reason, the inner parts of the detector,
 especially the tracking device, 
are in a strong magnetic field. 
The signs of the charged particles can easily be 
read from their paths, since 
positive and negative particles curve in opposite 
directions in the same magnetic field.
The momenta of particles can be calculated since the paths of particles with 
greater momentum bend less than those of lesser momentum. This is 
because a particle with greater momentum will spend less time in the 
magnetic field or have 
greater inertia than the particle 
with lesser momentum, and thus bends less in a magnetic field.