I have a proton and an antiproton scattering, via a pion exchange.(adsbygoogle = window.adsbygoogle || []).push({});

The matrix element has the form:

[tex]M=g*(\bar{u}_{1}\gamma ^{5}u_{2})\frac {1} {q^2-m^2}( \bar{v}_{1}\gamma ^{5}v_2) [/tex]

Wher g is my coupling constant, and q the 4-momentum of the pion.

The problem is that when I compute the currents [tex](\bar{u}_{1}\gamma ^{5}u_2)[/tex] and [tex](\bar{v}_{1}\gamma ^{5}v_2)[/tex] in the helicity basis this terms are non zero only for a change of the helicity( my righthanded proton should change into a lefthanded proton and the same for my antiproton).

This would imply that the matrix element for a helicity 1 state going to a helicity -1 state is not zero, which implies helicity is not conserved.

Where am I getting it wrong?

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# Helicity violation in strong interaction?

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