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The title is the question: Would the Standard Model allow two energetic photons to form a particle-like, zero-spin resonance?

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up vote 4 down vote accepted

Sure. Neutral pions do it all the time. Look for 2-gamma decay of the $\pi^0$. Here's a quick article to get you started: And if a neutral pion can decay into two photons, then the opposite reaction is also possible.

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Nice answer and reference, thanks! This is of the positives of Stack Exchange: It's unlikely I would ever have found or recognized the relevance of that particular paper to my question by using only keyword searches. Again, thanks. – Terry Bollinger Jul 5 '12 at 23:45
Try:… – Carl Brannen Jul 6 '12 at 1:50

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