48 DVCS : remark on scales DVCS and VM universality of W dependence (a P (0)) and t dependence (b), for scale taken as   = Q 2 for GPD (LO ~60% of cross section, NLO 40%)   = (Q 2 + M 2 )/4 for dipole model (2 gluon exchange) LO = quark sea - scale = Q 2 NLO = gluons - scale = (Q 2 + M 2 )/4 NB separation between LO and NLO depends on factorisation scale -> indication from data that DVCS scale ~ Q 2 rather than (Q 2 + M 2 )/4 .
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