Photon energy threshold for γ+p→p+π, question *interpretation*

1. Oct 25, 2009

magiix

1. The problem statement, all variables and given/known data
Calculate the photon energy threshold for the reaction γ + p → p + π. Assume that the initial state proton is stationary.
<thats really it>

2. Relevant equations
< unknown, but suspects include: standard special relativity equations >
-- other useful relations:
proton rest mass, mp≈938MeV/c2
neutral pion rest mass, mπ0≈135MeV/c2

3. The attempt at a solution
< havent yet, see below >

Alright so I don't need help solving the problem yet, rather I need help understanding the problem. I admit, I may have missed class the day this was introduced, but I may not have... I'm still learning how to follow this professor. (wonderful person, bit of an accent, clears overheads before I can finish writing down notes, also often uses less-oftenly-used, granted commonly accepted, language ex: center of mass frame vs center of momentum frame. ).

I am not clear on what is meant by the "photon energy threshold". Is this the minimum energy of the photon needed to produce the reaction? or might it have something to do with the reaction carrier photon (think Feynman diagrams). Instead, is it somehow related to QM scattering... I really don't think this is so, I certainly can't see how, but that about covers what we have started so far this quarter.

I realize not many, if any, of you are in my class-- and therefore probably have minimal ideas of what my instructor my want from us. I might ask a fellow student but there are few I really know, and none whom I know how to contact. The index of my textbook makes no reference to "photon energy threshold" or variations there-of. Any, and all, suggestions you have on how to interpret this question will be full-heartedly appreciated and explored. Thank you.

Last edited: Oct 25, 2009
2. Oct 26, 2009

fantispug

Almost certainly. Ignore the word photon and just look up "threshold energy". From the information you're given it also seems like the most likely thing to calculate.

I can't really make much sense of the other ways you try to interpret the question.

3. Oct 26, 2009

overcyn

hey im in your class. but im in the same spot as you on this problem. which is why i found your post.

Last edited: Oct 26, 2009
4. Oct 26, 2009

magiix

hahaha~!! I haven't seen you in class for a few days! I thought you might have dropped out, but when I saw your screen name I knew who you were! I'll send you an email next time !