A positive tau is moving with 2200 MeV of kinetic energy in a circular path perpendicular to a uniform 1.2-T magnetic field. (a) We have to calculate the momentum of the tau in . (b) We have to find the radius of the circular path.

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(a)

The kinetic energy K of a relativistic particle of rest mass energy and momentum p is given by the equation

The kinetic energy of the , is 2200 MeV. We find the momentum of the particle from the relation

Therefore, the momentum of is

(b)

The particle is moving in a circular orbit of radius R in a uniform magnetic field , which is perpendicular to the plane of the orbit of the charged particle. For a relativistic particle of momentum p the equation of motion is

.

Therefore, the radius of the orbit of the particle will be equal to