Browsing by Author "Dominguez, Cesareo A"
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- ItemOpen AccessDetermination of the charm- and beauty-quark masses from QCD sum rules(1994) Gluckman, Gary Richard; Dominguez, Cesareo ARatios of Laplace QCD sum rules are used in order to determine the on-shell charm- and beauty-quark masses. After confronting the experimental data in the charmonium and bottonium systems with theory, we obtain mc = 1.46 ± 0.07 GeV and mb = 4.70 ± 0.07 GeV. The error is due to the uncertainties in the values of Λ and the gluon condensate.
- ItemOpen AccessElectromagnetic nucleon form factors from QCD sum rules(2005) Castillo, Hernan; Dominguez, Cesareo A; Loewe, MarceloThe electromagnetic form factors of the nucleon, in the space-like region, are determined from three-point function Finite Energy QCD Sum Rules. The QCD calculation is performed to leading order in perturbation theory in the chiral limit, and to leading order in the non-perturbative power corrections. The results for the Dirac form factor, F1(q2), are in very good agreement with data for both the proton and the neutron, in the currently accessible experimental region of momentum transfers. This is not the case, though, for the Pauli form factor F2(q2), which has a soft q2-dependence proportional to the quark condensate h0|q¯q|0i.
- ItemOpen AccessElectromagnetic pion form factor at finite temperature(1994) Rozowsky, Joel Solomon; Dominguez, Cesareo AThe electromagnetic form factor of the pion in the space-like region, and at finite temperature, Fπ(Q²,T), is obtained from a Finite Energy QCD Sum Rule. The form factor decreases with increasing T, and vanishes at some critical temperature, where the pion radius diverges, thus signalling quark deconfinement.
- ItemOpen AccessElectromagnetic proton form factors in large Nc QCD(2004) Dominguez, Cesareo A; Thapedi, TebohoThe electromagnetic form factors of the proton are obtained using a particular realization of QCD in the large Nc limit (QCD∞), which sums up the infinite number of zero-width resonances to yield an Euler's Beta function (Dual-QCD∞). The form factors F1(q2) and F2(q2), as well as GM(q2) agree very well with reanalyzed space-like data in the whole range of momentum transfer. In addition, the predicted ratio μpGE/GM is in good agreement with recent polarization transfer measurements at Jefferson Lab.
- ItemOpen AccessFlavour SU(3) symmetry breaking in quantum chromodynamics(2000) Ramlakan, Alastair; Dominguez, Cesareo AThe subject of this thesis is the determination of the size of SU(3) flavour symmetry breaking in the QeD vacuum, as measured by the ratio of the strange to non-strange quark vacuum condensates / (with <ūu>
- ItemOpen AccessHadronic matter: from vacuum to extreme temperature in the presence of magnetic fields(2016) Hernandez, Luis Alberto; Dominguez, Cesareo A; Weigert, Heribert; Schilcher, KarlThis work consists of two themes. First, we work with Finite Energy QCD Sum Rules (FESR) approach in the vacuum. We tackle the problem of quark-hadron duality violation (DV), using the vector and axial-vector hadronic spectral function from tau-decay. A pinched integration kernel is introduce in the FESR in order to quench potential duality violations on the real axis in the complex squared energy plane and effectively extend the analysis well beyond the kinematical Ƭ-decay end-point. As the sum rules are well satisfied, we conclude that possible DV must be buried under the experimental uncertainties. Also, using the latest updated ALEPH data on hadron decays, we use FESR to determine the vacuum condensates of dimension d = 2 and d = 4, to check the validity of the Weinberg sum rules, and to determine the chiral condensates of dimension d = 6 and d = 8, and values of the chiral perturbation theory L10 and C87.
- ItemOpen AccessThe mass of the strange quark(1991) Van Gend, Carel; Dominguez, Cesareo ASum rules in QCD are discussed and finite energy and Laplace transform sum rules are used to determine the strange-quark mass. We use improved QCD input and experimental data to obtain for the invariant mass: mₛ= 266 ± 29 MeV, or for the running mass at 1 GeV: mₛ(1 GeV) = 194 ± 4 MeV.
- ItemOpen AccessOctet and decuplet baryon masses at finite temperature(1995) Jonker, Jano; Dominguez, Cesareo AOctet and decuplet baryon masses are studied at finite temperature in the framework of finite energy QCD sum rules. In all cases it is found that the mass stays fairly constant over a range of temperatures, increasing sharply near the critical temperature for deconfinement Tc.
- ItemOpen AccessPion electromagnetic form factor in the Kroll-Lee-Zumino model at zero and finite temperature(2008) Willers, Bernard; Dominguez, Cesareo A; Viollier, Raoul DThe renormalizable Abelian quantum field theory model of Kroll, Lee and Zumino is used to calculate next-to-leading order corrections to the pion electromagnetic form factor in vector meson dominance. At zero temperature the predictions for both the form factor and electromagnetic radius are found to improve greatly over the tree level result, and are in good agreement with the experimental data. A calculation of the vertex and self energy functions in the Matsubara formalism at finite temperature do not agree with the results of the Gale & Kapusta calculations. The resulting prediction for the radius is found to increase with temperature, consistent vith ideas about haclronic deconfinernent.
- ItemOpen AccessPions and vector mesons at finite temperature from QCD sum rules(1998) Fetea, Mirela Simona; Dominguez, Cesareo AThe temperature corrections to the current algebra Gell-Mann, Oakes and Renner(GMOR) relation in SU(2) X SU(2), the temperature behaviour of the pion mass and the q2 and T dependence of the ρππ vertex function in the space-like region are investigated.
- ItemOpen AccessA quantum field theory for the interaction of pions and rhos(2017) Moodley, Preshin; Dominguez, Cesareo A; Schilcher, Karl; Tupper, Gary; Spiesberger, HubertWe extend the Kroll-Lee-Zumino model in its particle content to include the charged rho vector mesons and the neutral pion meson. This entailed using the larger SU(2) gauge group. The masses for the vector mesons were generated via spontaneous symmetry breaking using the Higgs mechanism. The Lagrangian was then quantized and gauge fixed using the generalized class of Rɛ gauges. Tree scattering lengths were calculated for pion-pion scattering and the values for the a₀⁰ and a₀² scattering lengths are found to be comparable with experiment. The one particle irreducible diagrams that contribute to the one loop corrections to the tree scattering lengths are renormalized.
- ItemOpen AccessRho-Meson propagator at two-loop order in the Kroll-Lee-Zumino quantum field theory(2017) Lushozi, Mawande; Dominguez, Cesareo A; Schilcher, KarlThe Kroll-Lee-Zumino theory, an Abelian renormalizable quantum field theory of charged pions and a neutral ρ meson, provides a framework to compute corrections to the tree-level Vector-Meson-Dominance model. Despite a large ρππ coupling (gρππ ≈ 5), the loop suppresion factor of 1=(4π)² helps give reasonably small NLO (one-loop) corrections. When it comes to describing hadronic physics, one might say, these one-loop results achieve moderate to excellent success. Where the one-loop results show less than impressive agreement with experiment, it seems plausible that the NNLO (two-loop) corrections would remedy the situation. In this thesis the two-loop contribution to the ρ⁰ meson is calculated. It turns out to be larger than the one-loop result and so one must conclude that perturbation theory breaks down at this level.
- ItemOpen AccessTwo-loop corrections to the rho-propagator in the Kroll-Lee-Zumino theory(2014) Lushozi, Mawande; Dominguez, Cesareo AThe Abelian Kroll-Lee-Zumino theory is a renormalizable quantum field theory of charged pions and neutral rho-mesons. It provides the quantum field theory platform for the vector meson dominance model, allowing for a systematic computation of quantum corrections in perturbation theory (the ρ-π-π coupling is small enough for perturbation theory to make sense). At one-loop level, the theory makes a prediction for the electromagnetic form factor of the pion in good agreement with experiment, but there is room for improvement. This makes the theory an attractive prospect for filling the gap between chiral perturbation theory (which is valid for low-energy interactions) and perturbative QCD (which is valid at high energies). In this thesis we perform a two-loop calculation of the rho-propagator. This quantity is closely related to the pion’s electromagnetic form factor, and will allow its calculation at this order.