QCD Laplace sum-rules are used to examine the constituent mass spectrum of
JPβ{0+,1+} heavy-light [Qq] diquarks with Qβ{c,b} and
qβ{u,d,s}. As in previous sum-rule studies, the negative parity
JPβ{0β,1β} [Qq] diquark mass predictions do not stabilize, so the
sum-rule analysis focuses on positive parity [Qq] diquarks. Doubly-strange
JP=1+ [ss] diquarks are also examined, but the resulting sum rules do not
stabilize. Hence there is no sum-rule evidence for JP=1+ [ss] diquark
states, aiding the interpretation of sum-rule analyses of fully-strange
tetraquark states. The SU(3) flavour splitting effects for [Qq] diquarks are
obtained by calculating QCD correlation functions of JPβ{0+,1+}
diquark composite operators up to next-to-leading order in perturbation theory,
leading-order in the strange quark mass, and in the chiral limit for
non-strange (u,d) quarks with an isospin-symmetric vacuum =<uΛu>=. Apart from the strange quark mass parameter msβ, the strange
quark condensate parameter ΞΊ=/ has an important impact
on SU(3) flavour splittings. A Laplace sum-rule analysis methodology is
developed for the mass difference M[Qs]ββM[Qn]β between the strange and
non-strange heavy-light diquarks to reduce the theoretical uncertainties from
all other QCD input parameters. The mass splitting is found to decrease with
increasing ΞΊ, providing an upper bound on ΞΊ where the
M[Qs]ββM[Qn]β mass hierarchy reverses. In the typical QCD sum-rule range
0.56<ΞΊ<0.74, 55Β MeV<M[cs]ββM[cn]β<100Β MeV and 75Β MeV<M[bs]ββM[bn]β<150Β MeV, with a slight tendency for larger splittings for
the JP=1+ channels. These constituent mass splitting results are discussed
in comparison with values used in constituent diquark models for tetraquark and
pentaquark hadronic states.Comment: 30 pages, 19 figures, 7 tables. v2 contains extended discussio