33 research outputs found
Mass Predictions for Pseudoscalar Charmonium and Bottomonium Hybrids in QCD Sum-Rules
Masses of the pseudoscalar charmonium and bottomonium
hybrids are determined using QCD Laplace sum-rules. The effects of the
dimension-six gluon condensate are included in our analysis and result in a
stable sum-rule analysis, whereas previous studies of these states were unable
to optimize mass predictions. The pseudoscalar charmonium hybrid is predicted
to have a mass of approximately 3.8 GeV and the corresponding bottomonium
prediction is 10.6 GeV. Calculating the full correlation function, rather than
only the imaginary part, is shown to be necessary for accurate formulation of
the sum-rules. The charmonium hybrid mass prediction is discussed within the
context of the X Y Z resonances.Comment: 10 pages, 7 embedded figures. Analysis extended and refined in v
Exploring the Spectrum of Heavy Quarkonium Hybrids with QCD Sum Rules
QCD Laplace sum rules are used to calculate heavy quarkonium (charmonium and
bottomonium) hybrid masses in several distinct channels. Previous
studies of heavy quarkonium hybrids did not include the effects of
dimension-six condensates, leading to unstable sum rules and unreliable mass
predictions in some channels. We have updated these sum rules to include
dimension-six condensates, providing new mass predictions for the spectra of
heavy quarkonium hybrids. We confirm the finding of other approaches that the
negative-parity states form the lightest hybrid
supermultiplet and the positive-parity
states are members of a heavier supermultiplet. Our results disfavor a pure
charmonium hybrid interpretation of the , in agreement with previous
work.Comment: Presented by RTK at the Theory Canada 9 Conference, held at Wilfrid
Laurier University in June 2014. Submitted for the conference proceedings to
be published in the Canadian Journal of Physics. 5 pages, 1 figure. Version
2: reference added, typo correcte
QCD Sum Rule Analysis of Heavy Quarkonium Hybrids
We have studied the charmonium and bottomonium hybrid states with various
quantum numbers in QCD sum rules. At leading order in , the
two-point correlation functions have been calculated up to dimension six
including the tri-gluon condensate and four-quark condensate. After performing
the QCD sum rule analysis, we have confirmed that the dimension six condensates
can stabilize the hybrid sum rules and allow the reliable mass predictions. We
have updated the mass spectra of the charmonium and bottomonium hybrid states
and identified that the negative-parity states with form the lightest hybrid supermultiplet while the positive-parity
states with belong to a heavier hybrid
supermultiplet.Comment: 7 pages, 1 figures. Some minor edits have been made. Presentation at
the DPF 2013 Meeting of the American Physical Society Division of Particles
and Fields, Santa Cruz, California, August 13-17, 201
Light-Quark Flavour Splitting of Heavy-Light Constituent Diquark Masses and Doubly-Strange Diquarks from QCD Sum-Rules
QCD Laplace sum-rules are used to examine the constituent mass spectrum of
heavy-light [Qq] diquarks with and
. As in previous sum-rule studies, the negative parity
[Qq] diquark mass predictions do not stabilize, so the
sum-rule analysis focuses on positive parity [Qq] diquarks. Doubly-strange
[ss] diquarks are also examined, but the resulting sum rules do not
stabilize. Hence there is no sum-rule evidence for [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
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 . Apart from the strange quark mass parameter , the strange
quark condensate parameter has an important impact
on SU(3) flavour splittings. A Laplace sum-rule analysis methodology is
developed for the mass difference 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 , providing an upper bound on where the
mass hierarchy reverses. In the typical QCD sum-rule range
, and , with a slight tendency for larger splittings for
the 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