The existence of a shallow or virtual tetraquark state, c c ū d̄, is discussed. Using the putative masses for the doubly charmed baryons (c c u/c c d) from SELEX, the mass of the c c ū d̄ state is estimated to be about 3.9GeV , only slightly above the DD threshold. The experimental signatures for various c c ū d̄ masses are also discussed. Typeset using REVTEX 1

The study of two-pseudoscalar and two-photon decays for the scalar meson nonet below 1 GeV is performed within an effective approach in which the scalar resonances are described as (Jaffe’s) tetraquark states. The dominant (fall apart decay) and the subdominant (one transverse gluon as intermediate state) decay amplitudes are systematically taken into account. The latter improves the agreement ...

The quantum chromo-dynamics (QCD) may not preclude the presence of the multi-quark hadrons such as tetraquark (qqq̄q̄), pentaquark (qqqqq̄), dibaryon (qqqqqq) and so on, because of the color confinement. Especially, we are let to be interested in exotic multi-quark hadrons, which should have exotic quantum numbers. Now, let us address ourself to the pentaquark state. Consider the SU(3) flavor case...

Abstract Inspired by the recent observation of a very narrow state, called , LHCb collaboration, possible bound states and low-lying resonance doubly-heavy tetraquark cc\bar{u}\bar{d} ( T_{cc} ) bb\bar{u}\bar{d} T_{bb} are searched in framework chiral quark model with an accurate few-body method, Gaussian expansion method. The real scaling method is also applied to identi...

We calculate the masses of $qq\overline{q}\overline{q}$ tetraquark ground state and first radial excited in a constituent quark model where Cornell-like potential one-gluon exchange spin-spin coupling are employed. The three parameters for proposed mass-dependent accordance with lattice QCD data, all predetermined by studying light, charmed, bottom mesons. theoretical predictions light tetraqua...

The four–quark system cc̄nn̄ is studied in the framework of the constituent quark model. Using different types of quark-quark potentials, we solve the four–body Schrödinger equation by means of the hyperspherical harmonic formalism. Exploring the low laying JPC states for different isospin configurations no four-quark bound states have been found. Of particular interest is the possible four-quark...

We perform a QCD sum rule analysis for the light scalar meson σ (f0(600)) with a tetraquark current related to the instanton picture for QCD vacuum. We demonstrate that instanton current, including equal weights of scalar and pseudoscalar diquarkantidiquarks, leads to a strong cancelation between the contributions of high dimension operators in the operator product expansion (OPE). Furthermore,...