  Witten's twistor string theory has led to new representations of S-matrix in
massless QFT as a single object, including Cachazo-He-Yuan formulas in general
and connected formulas in four dimensions. As a first step towards more
realistic processes of the standard model, we extend the construction to QCD
tree amplitudes with massless quarks and those with a Higgs boson. For both
cases, we find connected formulas in four dimensions for all multiplicities
which are very similar to the one for Yang-Mills amplitudes. The formula for
quark-gluon color-ordered amplitudes differs from the pure-gluon case only by a
Jacobian factor that depends on flavors and orderings of the quarks. In the
formula for Higgs plus multi-parton amplitudes, the massive Higgs boson is
effectively described by two additional massless legs which do not appear in
the Parke-Taylor factor. The latter also represents the first
twistor-string/connected formula for form factors.
