The infrared behaviour of vertex functions in an SU(N) Yang–Mills theory in Landau gauge is investigated employing a skeleton expansion of the Dyson–Schwinger equations. The three- and four-gluon ...vertices become singular if and only if all external momenta vanish while the dressing of the ghost-gluon vertex remains finite in this limit. The running coupling as extracted from either of these vertex functions possesses an infrared fixed point. In general, diagrams including ghost-loops dominate in the infrared over purely gluonic ones.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Hadron masses show a specific dependence on the quark masses. Therefore, the variation of these masses can cause a resonance in a hadronic scattering amplitude to become a bound state. Consequently, ...the amplitude exhibits a non-analytic behavior at this transition. Crossed amplitudes, where the resonance can be exchanged in the t-channel, can be shown to exhibit the same phenomenon by s→t analytic continuation. This entails possible kinks in lattice quark-mass extrapolations needed to compute hadronic observables.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Coulomb gauge approach to qq̄g hybrid mesons General, I.J.; Llanes-Estrada, F.J.; Cotanch, S.R.
The European physical journal. C, Particles and fields,
7/2007, Volume:
51, Issue:
2
Journal Article
Peer reviewed
Open access
An effective Coulomb gauge Hamiltonian, Heff, is used to calculate the light (uūg), strange (ss̄g) and charmed (cc̄g) hybrid meson spectra. For the same two parameter Heff providing glueball masses ...consistent with lattice results and a good description of the observed u,d,s and c quark mesons, a large-scale variational treatment predicts that the lightest hybrid has JPC=0++ and mass 2.1 GeV. The lightest exotic 1-+ state is just above 2.2 GeV, near the upper limit of lattice and flux tube predictions. These theoretical formulations all indicate that the observed 1-+ π1(1600) and, more clearly, π1(1400) are not hybrid states. The Coulomb gauge approach further predicts that in the strange and charmed sectors, respectively, the ground state hybrids have 1+- with masses 2.1 and 3.8 GeV, while the first exotic 1-+ states are at 2.4 and 4.0 GeV. Finally, using our hybrid wavefunctions and the Franck–Condon principle, a novel experimental signature is presented to assist heavy hybrid meson searches.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
We highlight the progress, current status, and open challenges of QCD-driven physics, in theory and in experiment. We discuss how the strong interaction is intimately connected to a broad sweep of ...physical problems, in settings ranging from astrophysics and cosmology to strongly coupled, complex systems in particle and condensed-matter physics, as well as to searches for physics beyond the Standard Model. We also discuss how success in describing the strong interaction impacts other fields, and, in turn, how such subjects can impact studies of the strong interaction. In the course of the work we offer a perspective on the many research streams which flow into and out of QCD, as well as a vision for future developments.
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A computation of the quotient of shear viscosity and entropy density, or the Kovtun, Son and Starinets (KSS) number η/s, is performed in the non-relativistic and classical regime, first in chiral ...perturbation theory, and then in the SO(g+1)/SO(g) non-linear sigma model in the large g limit. Both are field theories stemming from a renormalizable sigma model, but, in spite of that, we explicitly calculate how one avoids the KSS bound by increasing the number of degenerate pions sufficiently. However, we argue that particle production could still keep the validity of the KSS bound in the weak sense. We also show how a large number of molecular isomers (which we estimate in terms of simple molecular properties) could avoid the bound in the strong sense. This might be possible with carbon based molecules. We finally argue that a measurement of η/s in heavy-ion collisions might be turned into an upper bound on the number of hadron resonances.
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J-- glueballs and a low odderon intercept Llanes-Estrada, Felipe J; Bicudo, Pedro; Cotanch, Stephen R
Physical review letters,
03/2006, Volume:
96, Issue:
8
Journal Article
Peer reviewed
Open access
We report an odderon Regge trajectory emerging from a field theoretical Coulomb gauge QCD model for the odd signature J(PC) (P = C = -1) glueball states. The trajectory intercept is clearly smaller ...than the Pomeron and even the omega trajectory's intercept which provides an explanation for the nonobservation of the odderon in high energy scattering data. To further support this result we compare to glueball lattice data and also perform calculations with an alternative model based upon an exact Hamiltonian diagonalization for three constituent gluons.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The BES f0(1810): a new glueball candidate Bicudo, P.; Cotanch, S.R.; Llanes-Estrada, F.J. ...
The European physical journal. C, Particles and fields,
10/2007, Volume:
52, Issue:
2
Journal Article
Peer reviewed
Open access
We analyze the f0(1810) state recently observed by the BES collaboration via radiative J/ψ decay to a resonant φω spectrum and confront it with DM2 data and glueball theory. The DM2 group only ...measured ωω decays and reported a pseudoscalar but no scalar resonance in this mass region. A rescattering mechanism from the open flavored KK̄ decay channel is considered to explain why the resonance is only seen in the flavor asymmetric ωφ branch along with a discussion of positive C-parity charmonia decays to strengthen the case for preferred open flavor glueball decays. We also calculate the total decay width of a glueball with this mass to be roughly 100 MeV, in agreement with the narrow, newly found f0, and smaller than the expected estimate of 200–400 MeV. We conclude that this discovered scalar hadron deserves further experimental investigation, especially in the KK̄ channel, and if shown to be different from the f0(1710), will become a solid glueball candidate. Finally we comment on other, but less likely, possible assignments for this state.
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DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Shear viscosity in a CFL quark star Manuel, Cristina; Dobado, Antonio; Llanes-Estrada, Felipe J
The journal of high energy physics,
09/2005, Volume:
2005, Issue:
9
Journal Article
We show how to fix the renormalization scale for hard-scattering exclusive processes such as deeply virtual meson electroproduction by applying the BLM prescription to the imaginary part of the ...scattering amplitude and employing a fixed-t dispersion relation to obtain the scale-fixed real part. In this way, we resolve the ambiguity in BLM renormalization scale-setting for complex scattering amplitudes. We illustrate this by computing the H generalized parton distribution at leading twist in an analytic quark-diquark model for the parton-proton scattering amplitude that can incorporate Regge exchange contributions characteristic of the deep inelastic structure functions.
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DOBA, FZAB, GEOZS, IJS, IMTLJ, IZUM, KILJ, KISLJ, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
We evaluate the ratio of shear viscosity to entropy density in a pion gas employing the Uehling–Uehlenbeck equation and experimental phase-shifts parameterized by means of the SU(2) inverse amplitude ...method. We find that the ratio for this monocomponent gas stays well above the KSS 1/(4π) bound. We find similar results with other sets of phase-shifts and conclude that the bound is nowhere violated.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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