...1,2,

Fellow of CONICET, Argentina.

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...1,2,

Member of CONICET, Argentina.

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... section

This approximation considers only the most energetic neutral pion that is produced in the pp reaction aside of a fireball composed by a certain number of less energetic $\pi$-mesons of each flavor. See a discussion in Pfrommer & En$\beta$lin (2004).

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