In the context of the Big Bung model, when the Universe was about 4 seconds old
ID: 2076659 • Letter: I
Question
In the context of the Big Bung model, when the Universe was about 4 seconds old and the temperature had dropped to about 6 billion Kelvin, a massive annihilation e^+ + e^- rightarrow gamma gamma took place. All positrons disappeared in this process, but about 10^-9 of the electrons survived, just like 10^-9 of the protons had survived the pp annihilation that had taken place in an earlier stage. If this electron excess was entirely due to CP violation in K_L^0 decay (through the K_L^0 rightarrow pi e nu decay mode), estimate the fraction of the total number of electrons (before the annihilation took place) that originated from K_L^0 decay.Explanation / Answer
Solution:
Given
e+ + e- -->
All positrons disappeared in this process, but about 10^-9 of the electrons survived, just like 10^-9 of the photons had survived the pp aninhilation that had taken place in earlier stage
If this electron was entitrely due to CP violation in KLo delay --> pi()*e*v decay mode
So the fraction of the total number of electrons before the annhilation took place thT ORIGINATED from KLo decay
= 2/ 10^-9+10^-9
= 2 / 2*10^-9
= 1* 10^-9
= 10^9 :1 or 10^9/1