This is the declaration of the CheckId class.
This is a pure static class which provides some useful methods for checking the PDG id of particles. Notice that the name "quark" in the methods below means any of the following: d , u , s , c , b anti-d , anti-u , anti-s , anti-c , anti-b that is we do not distinguish between particle or antiparticle ( because can be done directly by the user: id > 0 for particles ; id < 0 for anti-particles ) and we do not include t (and anti-t ) because we are interested in components of mesons and baryons. Similarly for the name "diquark" which include all diquarks (id > 0) and anti-diquarks (id < 0) not made with t ( anti-t ) component.
NB) Other useful methods (even some implemented in CheckId class!) are in ThePEG/PDT/StandardMatchers.h
CLASS
CheckId