相关论文: Delta-Isobar Magnetic Form Factor in QCD
The Drell-Hearn-Gerasimov sum rule for the nucleon is investigated within a relativistic constituent quark model formulated on the light-front. The contribution of the N - Delta(1232) transition is explicitly evaluated using different forms…
We extend a covariant model, tested before in the spacelike region for the physical and lattice QCD regimes, to a calculation of the gamma* N -> Delta reaction in the timelike region, where the square of the transfered momentum, q^2, is…
We use QCD sum rules, in the framework of the Heavy Quark Effective Theory, to calculate the universal form factor $\tau_{1/2}(y)$ parameterizing the semileptonic transitions $B \to D_0 \ell \bar \nu$, $B \to D_1^* \ell \bar \nu$, where…
We calculate the electromagnetic pion form factor at intermediate space-like momentum transfer from the QCD sum rule for the correlation function of two {\it pseudoscalar } interpolating fields and the electromagnetic current. This…
In this paper we present the result of a direct QCD sum rule calculation of the transition form factor \gamma\gamma* -> pi^o in the region of moderately large invariant momentum Q^2 > 1GeV^2 of the virtual photon. In contrast to pQCD, we…
Hadron electromagnetic form factor in the time-like region at the boundary of the physical region is considered. The energy behavior of the form factor is shown to be determined by the strong hadron-antihadron interaction. Imaginary parts…
In-medium nucleon electromagnetic form factors are calculated in the quark meson coupling model. The form factors are typically found to be suppressed as the density increases. For example, at normal nuclear density and $Q^2 \sim 0.3 {…
The gauge invariant two-point correlator for the gluon field strength tensor in analysed by means of the QCD sum rule method. To this end, we make use of a relation of this correlator to a two-point function for a quark-gluon hybrid in the…
We present comprehensive calculations of the electromagnetic form factors, including the charge, magnetic-dipole, electric-quadrupole and magnetic-octupole form factors, of the $\Omega^-$ in the spacelike region using the quark-diquark…
The electromagnetic form factors of vector mesons are calculated in an explicitly Poincar\'e covariant formulation, based on the Dyson--Schwinger equations of QCD, that respects electromagnetic current conservation, and unambiguously…
Sum rules -- relating the static quark potential V(R) to the spatial distribution of the action and energy in the colour fields of flux-tubes -- are applied in three ways: 1) To extract generalised beta-functions: 2) As a consistency check…
Vector mesons show up in the electromagnetic current-current correlator. QCD sum rules provide a constraint on hadronic models for this correlator. This constraint is discussed for the case of finite nuclear density concerning the…
The concept of QCD sum rules is extended to bound states composed of particles with finite mass such as scalar quarks or strange quarks. It turns out that mass corrections become important in this context. The number of relevant corrections…
It is argued that it is valid to use QCD sum rules to determine the scalar and pseudoscalar two-point functions at zero momentum, which in turn determine the ratio of the strange to non-strange quark condensates $R_{su} = \frac{<\bar{s}…
We study the photon-quark-quark and Higgs-gluon-gluon form factors for on-shell massless quarks and gluons in perturbative QCD. Previous third-order results for the quark case are extended by calculating the fermion-loop contributions up to…
QCD sum rules for chiral partners in the open-charm meson sector are presented at nonzero baryon net density or temperature. We focus on the differences between pseudo-scalar and scalar as well as vector and axial-vector D mesons and derive…
Electromagnetic form factors of the transition $\pi+\gamma_{virt.}\ra A_1$ are calculated by QCD sum rules technique with the description of the pion in terms of the set of wave functions of increasing twist. Obtained results are compared…
We calculate gravitational form factors of vector mesons using a holographic model of QCD. These provide restrictions on the generalized parton distributions of vector mesons, via the sum rules connecting stress tensor form factors to GPDs.…
In this article, we assign the $Z_c^\pm(3900)$ to be the diquark-antidiquark type axialvector tetraquark state, study its magnetic moment with the QCD sum rules in the external weak electromagnetic field by carrying out the operator product…
Using the light-cone sum rules at leading order, we present an approach to perform the preliminary upper estimation for the nucleon gravitational form factor $D(t)$ ($D$-term contribution). Comparison with the experimental data and with the…