Related papers: Lambda(1405) as a multiquark state
The radiative decay of $\Lambda (1405)$ is investigated from the viewpoint of compositeness, which corresponds to the amount of two-body states composing resonances as well as bound states. For a $\bar{K}N (I=0)$ bound state without…
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…
In the QCD Sum Rule determination of $m_s$ using the two-point correlator of divergences of $\Delta S=1$ vector currents, the final uncertainty on $m_s$ is mainly due to the hadronic spectral function. Using a specific parameterization…
QCD Laplace sum-rules for light-quark I=0,1 scalar currents are used to investigate candidates for the lightest $q\bar q$ scalar mesons. The theoretical predictions for the sum-rules include instanton contributions which split the…
We study the P-wave bottom baryons using the method of QCD sum rule and heavy quark effective theory. Our results suggest that Lambda_b(5912) and Lambda_b(5920) can be well described by the baryon doublet [3F_bar, 1, 1, rho], and they…
Building on our successful technique to isolate the otherwise-elusive $\Lambda$(1405) using correlation matrix techniques and multiple source and sink smearings, we present calculations of the quark sector contributions to the electric form…
QCD sum rules involving mixed inverse moment integration kernels are used in order to determine the running charm-quark mass in the $\bar{MS}$ scheme. Both the high and the low energy expansion of the vector current correlator are involved…
The light scalar meson sigma(600) is known to appear at low excitation energy with very large width on top of continuum states. We investigate it in the QCD sum rule as an example of resonance structures appearing above the corresponding…
The Coulomb gauge model, involving an effective QCD Hamiltonian in the Coulomb gauge, is applied to scalar hadrons. Mass predictions are presented for both conventional q-qbar meson and q-qbar-q-qbar tetra-quark states. Mixing matrix…
We calculate the "pi Sigma Lambda" and "pi Sigma Sigma" coupling constants in light cone QCD sum rules for the structure "sigma_{alpha beta} gamma_5 p^alpha q^beta". A comparison of our results on these coupling constants with prediction of…
Within the framework of the heavy quark effective theory, QCD sum rules are used to calculate the masses of p-wave (c-bar s) states. The results for 0^+ and 1^+ states with the angular momentum of the light component j_l=1/2 are consistent…
In the present work, we construct the diquark-antidiquark type four-quark currents to investigate the mass spectrum of the ground state hidden-charm-hidden-strange tetraquark states with the quantum numbers $J^{PC}=0^{++}$, $1^{+-}$,…
The scalar tetraquarks $T_{b}$ and $T_{c}$ with asymmetric contents $bb \overline{b}\overline{c}$ and $cc \overline{c}\overline{b}$ are explored using the QCD sum rule method. These states are modeled as the diquark-antidiquarks composed of…
We investigate light hybrid mesons composed of a light quark-antiquark pair and two gluons within the framework of QCD sum rules. We focus on states with quantum numbers $J^{\mathrm{PC}} = 0^{++}, 0^{+-}, 0^{-+}, 0^{--}$ and…
A lattice QCD computation of the coupled channel $\pi\Sigma-\bar{K}N$ scattering amplitudes in the $\Lambda(1405)$ region is detailed. Results are obtained using a single ensemble of gauge field configurations with $N_{\rm f} = 2+1$…
A recent extension of a variationally optimized perturbation, combined with renormalization group properties in a straightforward way, can provide approximations to nonperturbative quantities such as the chiral symmetry breaking order…
We perform a QCD sum rule study of the open-charmed $D_s (2317)$ as a four-quark state. Using the diquark-antidiquark picture for the four-quark state, we consider four possible interpolating fields for $D_s (2317)$, namely, scalar-scalar,…
We apply the method of QCD sum rules to study the $s s \bar s \bar s$ tetraquark states of $J^{PC} = 0^{-+}$. We construct all the relevant $s s \bar s \bar s$ tetraquark currents, and find that there are only two independent ones. We use…
We study a pentaquark model of the negative parity hyperon Lambda(1405). We choose a specific quark configuration for trial, and use the perturbative chiral quark model extended to four quarks and one anti-quark system. We calculate a…
In the framework of the Schwinger-Dyson equation and the Bethe-Salpeter equation in the improved ladder approximation, we calculate the pi^+ - pi^0 mass difference on the same footing as the pion decay constant and the QCD S parameter (or…