Decay Process

Aim: To identify the parent particle, which decays into the positive and negative tracks that have been measured. One can use a trail and error method based on assigning  and proton  p masses to both of the two particles and comparing with the  and  masses.

    Fig.1 Bubble chamber picture. The dark lines are trails of tiny bubbles created as charged particles force their way through a tank of transparent liquid enclosed in a powerful magnet. The tracks which curl to the left are electrons-The magnetic field direction is out of the screen. By measuring the curvature of the tracks in the event, one can determine  their  momenta. Here they are highly relativistic.

Step 1: Looking at the bubble chamber picture, one can see that the positive and negative tracks correspond to highly relativistic particles, for which , or . The bubble chamber therefore cannot distinguish between particles of different masses!

Step 2:  Each final particle momentum was measured in terms of three variables ( ) , from the track curvature.

Step3: A computer program calculate from them, the momentum components:

 Step4:  Table 1 contains the momentum components for each positive and negative particle. Assuming that they are  and  with known masses

( ), one can calculate their final energy, by using the relativistic formula

Table 1

Step5: There are possible three decay processes:

or                                                                          

Energy conservation gives the initial particle energy:

Momentum conservation gives: 

Its magnitude can be calculated using momentum components of each particle:

Knowing the energy and momentum of the initial particle, one can get its rest mass:

            or    in GeV units

The experimental data gives:  very close to the  mass ( )

If one replace  by a proton p , the initial particle mass will be  which is very much larger than the , ( ), which is not consistent with these processes.

K0 decay process