  We present improved predictions of a class of event-shape distributions
called angularity for a contribution from an effective operator $H\to gg$ in
Higgs hadronic decay that suffers from large perturbative uncertainties. In the
frame of Soft-Collinear Effective Theory, logarithmic terms of the distribution
are resummed at NNLL$^{'}$ accuracy, for which 2-loop constant of gluon-jet
function for angularity is independently determined by a fit to fixed-order
distribution at NLO corresponding to ${\mathcal{O}}(\alpha_s^2)$ relative to
the born rate. Our determination shows reasonable agreement with value in a
thesis recently released. In the fit, we use an asymptotic form with a
fractional power conjectured from recoil corrections at one-loop order and it
improves the accuracy of determination in positive values of angularity
parameter $a$. The resummed distribution is matched to the NLO fixed-order
results to make our predictions valid at all angularity values. We also discuss
the first moment and subtracted moment of angularity as a function of $a$ that
allow to extract information on leading and subleading nonperturbative
corrections associated with gluons.
