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Beam-Remnant Kinematics

The longitudinal momenta of the initiator partons have been defined by the $x$ values picked. The remaining longitudinal momentum is shared between the remnants in accordance with their character. A valence quark receives an $x$ picked at random according to a small-$Q^2$ valence-like parton density, proportional to $(1-x)^a/\sqrt{x}$, where $a = 2$ for a $\u $ quark in a proton and $a = 3.5$ for a $\d $ quark. A sea quark must be the companion of one of the initiator quarks, and can have an $x$ picked according to the $q_{\c }(x_{\c }; x_{\mathrm{s}})$ distribution introduced above. A diquark would obtain an $x$ given by the sum of its constituent quarks. (But with the possibility to enhance this $x$, to reflect the extra gluon cloud that could go with such a bigger composite object.) If a baryon or meson is in the remnant, its $x$ is equated with the $z$ value obtainable from the Lund symmetric fragmentation function, again with the possibility of enhancing this $x$ as for a diquark. A gluon only appears in an otherwise empty remnant, and can thus be given $x = 1$. Once $x$ values have been picked for each of the remnants, an overall rescaling is performed such that the remnants together carry the desired longitudinal momentum.


next up previous contents
Next: Multiple Interactions (and Beam Up: Beam Remnants (and Multiple Previous: Primordial   Contents
Stephen_Mrenna 2012-10-24