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Pair Production Cross-Sections
Name: Phil G.
Status: other
Age: old
Location: N/A
Country: N/A
Date: 2001-2002
Question:
Pair production cross-sections
If two particles, with kinetic energy (in the centre of mass frame)
exceeding 2mc^2, collide sufficient surplus mass-energy is available to
produce an electron-positron pair. If one or both of the particles is a
lepton is there any conservation law that forbids this process?
If so, references please. If not, has any theoretical pair production
cross-section ever been published for electron-electron collisions?
Replies:
Phil,
I am not aware of any such conservation laws. At the same time, I am not
aware of any such collisions. If none exist, it would not surprise me.
Getting a high energy electron to collide with an electron would be
difficult to make happen. If it did happen, it would be difficult to track.
Electrons are too small. Hitting a bowling ball with a bullet is hard
enough. Hitting a bullet with a bullet is often not worth trying. Mass of
an electron is also too small. To make a proton have enough extra energy to
produce an electron-positron pair is fairly easy. The proton mass is huge
compared to an electron. Not much speed is required (compared to the speed
of light). To give an electron that much extra energy would require
relativistic speeds (near the speed of light). This can cause the electron
to do things like emitting photons before the collision occurs.
Detection is difficult. Although detecting an electron is fairly easy, you
won't know which electron you are seeing: incoming, target, produced. You
would have to detect the positron and identify it as such, or else detect
all three electrons.
I am sorry I could not be more definite about things. If nothing is
available, now you understand why. Have a good day.
Dr. Ken Mellendorf
Physics Instructor
Illinois Central College
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