How can we measure the mass of positron the electrons antipa

How can we measure the mass of positron, the electron\'s anti-particle, in a bubble chamber

Solution

The (initial) momentum can be detemined by measuring the initial curvature in a magnetic field: The Lorentz force on a charge in a B field is given by: F = qv X B .

And the direction (of curvature) is given by the type of charge. That force (classically) must equal the cetripetal force on the particle: F = mv^2/ R

Setting the two forces equal gives : qv X B = mv^2/ R so: mv = qBr = p..... (assuming perpendicular field)

You know the charge, radius and magnetic field so you can detemine momentum, p.