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C. A. Dominguez

Publications and source records attributed to C. A. Dominguez.

104 records · Page 6Linked to original sources
arXiv1996

Pions at Finite Temperature from QCD Sum Rules

The temperature corrections to the current algebra Gell-Mann, Oakes, and Renner (GMOR) relation in $SU(2)\otimes SU(2)$ are investigated in the framework of QCD sum rules. There are no corrections at leading order in the quark masses. At the next to leading order we find corrections of the form $m_{q}^2\; T^{2}$, which are small except near the critical temperature. As a by-product we obtain the temperature behaviour of the pion mass, which is essentially constant, except near the critical temperature where it increases with $T$.

hep-ph↗
arXiv1996

On the $b-$ Quark Kinetic Energy in the $Λ_b$

We consider the problem of determining the matrix element of the heavy quark kinetic energy operator between $Λ_b$ baryonic states by three point function QCD sum rules in the Heavy Quark Effective Theory. We discuss the main features and the uncertainties associated to such an approach. Numerically, we find the result: ${\langle{\cal K}\rangle}_{Λ_b} = - (0.6 \pm 0.1) \; GeV^2$. Within the uncertainty of the method, such result indicates a value of the heavy quark kinetic energy in the baryon similar in size to that in the meson.

hep-ph↗
arXiv1994

Phenomenological Analysis of a Dimension-Two Operator in QCD and its Impact on $α_{s}(M_τ)$

Fits to the ARGUS data on hadronic decays of the tau-lepton, which determine the vector and axial-vector spectral functions, are used in order to determine the size of a dimension $d=2$ term in the Operator Product Expansion. Constraints from the first Weinberg sum rule (in the chiral limit) are enforced in order to reduce the uncertainty of this determination. Results for the $d=2$ operator are consistent with a quadratic dependence on $Λ_{QCD}$. The impact of this term on the extraction of $α_{s}(M_τ)$ is assessed.

hep-ph↗
arXiv1994

Heavy Quark Masses from QCD Sum Rules

I review recent determinations of the (on-shell) charm- and beauty-quark masses in the framework of relativistic and non-relativistic ratios of Laplace transform QCD moment sum rules. The validity of the non-relativistic version of QCD sum rules in this particular application is discussed.

hep-ph↗
arXiv1994

Deconfinement and Chiral-Symmetry Restoration in Finite Temperature QCD

QCD sum rules are based on the Operator Product Expansion of current correlators, and on QCD-hadron duality. An extension of this program to finite temperature is discussed. This allows for a study of deconfinement and chiral-symmetry restoration. In addition, it is possible to relate certain hadronic matrix elements to expectation values of quark and gluon field operators by using thermal Finite Energy Sum Rules. In this way one can determine the temperature behaviour of hadron masses and couplings, as well as form factors. An attempt is made to clarify some misconceptions in the existing literature on QCD sum rules at finite temperature.

hep-ph↗
arXiv1994

Mass singularities in light quark correlators: the strange quark case

The correlators of light-quark currents contain mass-singularities of the form log(m^2/Q^2). It has been known for quite some time that these mass- logarithms can be absorbed into the vacuum expectation values of other operators of appropriate dimension, provided that schemes without normal- ordering are used. We discuss in detail this procedure for the case of the mass logarithms m^4 log(m^2/Q^2), including also the mixing with the other dimension-4 operators to two-loop order. As an application we present an improved QCD sum rule determination of the strange-quark mass. We obtain m_s(1 GeV)=171 \pm 15 MeV.

hep-ph↗
arXiv1994

Operator product expansion and duality at finite temperature

The operator product expansion of current correlators at short distances, and the notion of QCD-hadron duality are the cornerstone of QCD sum rules. The extension of this programme to $T \neq 0$ is discussed, together with applications to hot hadronic propagators. Indications are that the hadronic spectrum suffers a substantial rearrangement with increasing temperature, and hint on the existence of a quark deconfining phase transition. Phenomenological order parameters to characterize this phase transition are discussed.

hep-ph↗
arXiv1994

Electromagnetic pion form factor at finite temperature

The electromagnetic form factor of the pion in the space-like region, and at finite temperature, $F_π(Q^{2},T)$, is obtained from a QCD Finite Energy Sum Rule. The form factor decreases with increasing T, and vanishes at some critical temperature, where the pion radius diverges. This divergence may be interpreted as a signal for quark deconfinement.

hep-ph↗
arXiv1994

Mass of the charm-quark from QCD sum rules

Relativistic and non-relativistic ratios of Laplace transform QCD moment sum rules for charmonium are used in order to determine the value of the on-shell charm-quark mass. The validity of the non-relativistic version of QCD sum rules in this particular application is discussed. After using current values of the perturbative and non-perturbative QCD parameters, as well as experimental data on the $J/ψ$ system, we obtain $m_{c}(Q^{2}=m_{c}^{2}) = 1.46 \pm 0.07 \;\mbox{GeV}$.

hep-ph↗
arXiv1994

Comment on current correlators in QCD at finite temperature

We address some criticisms by Eletsky and Ioffe on the extension of QCD sum rules to finite temperature. We argue that this extension is possible, provided the Operator Product Expansion and QCD-hadron duality remain valid at non-zero temperature. We discuss evidence in support of this from QCD, and from the exactly solvable two- dimensional sigma model O(N) in the large N limit, and the Schwinger model.

hep-ph↗
arXiv1993

Radiative $B \to K^* γ$ transition in QCD

We evaluate the branching ratios of the radiative decays $B \to K^* γ$, and $B \to K_1 γ$ in the framework of three-point function QCD sum rules. We find: $ Γ(B \to K^* γ) / Γ(b \to s γ) = 0.17 \pm 0.05$ and $ Γ(B \to K_1 γ) / Γ(b \to s γ) = 0.30 \pm 0.15$. We also study, in the infinite quark mass limit, the connection between the form factor of the radiative $B \to K^* γ$ transition and the weak hadronic form factors entering the semileptonic B-meson decays.

hep-ph↗
arXiv1992

Spectral Functions for Heavy-Light Currents and Form Factor Relations in Hqet

We derive relations among form factors describing the current-induced transitions: (vacuum) $\rightarrow B,B^{*}, B π, B^{*} π, B ρ$ and $B^{*} ρ$ using heavy quark symmetry. The results are compared to corresponding form factor relations following from identities between scalar and axial vector, and pseudoscalar and vector spectral functions in the heavy quark limit.

hep-ph↗