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### Photon Beams

A resolved photon is similar in spirit to a meson. A VMD photon is associated with either , , or , and so corresponds to a well-defined valence flavour content. Since the and are supposed to add coherently, the mixing is in the ratio . Similarly a GVMD state is characterized by its classification, in rates according to times a mass suppression for heavier quarks.

In the older photon physics options, where a quark content inside an electron is obtained by a numerical convolution, one does not have to make the distinction between valence and sea flavour. Thus any quark (antiquark) initiator leaves behind the matching antiquark (quark), and a gluon leaves behind a quark + antiquark pair. The relative quark flavour composition in the latter case is assumed proportional to among light flavours, i.e. into , into , and into . If one wanted to, one could also have chosen to represent the remnant by a single gluon.

Stephen_Mrenna 2012-10-24