I review the lattice simulations of light scalar mesons with q̄q and tetraquark interpolating fields. Several difficulties which complicate the extraction of scalar meson masses from the scalar correlators are pointed out. One of the major difficulties is the presence of the twopseudoscalar scattering states, which often dominate the correlator at light quark masses. In the simulations with unph...

In the LHC collider a significant rate of events with double parton scattering is expected. This will be the leading mechanism for production of two bb̄ pairs. We estimate the probability of binding two b quarks into a diquark and the probability of dressing this diquark into a bbūd̄ (IS = 01) tetraquark. Calculations shows that that this bound state of two B mesons is stable against the strong i...

We study the light scalar mesons a0(980) and κ using N f = 2+ 1+ 1 flavor lattice QCD. In order to probe the internal structure of these scalar mesons, and in particular to identify, whether a sizeable tetraquark component is present, we use a large set of operators, including diquarkantidiquark, mesonic molecule and two-meson operators. The inclusion of disconnected diagrams, which are technic...

AdS/QCD correspondence allows to compute the quark-antiquark potential in the static limit. We use this piece of information together with the Salpeter equation (Schroedinger equation with relativistic kinematics) and a short range hyperfine splitting potential to describe the bound states of quark-antiquark. Comparison with experiment permits to fit the parameters of the model, namely the quar...

Based on the color-spin interaction in diquarks, we argue why some multiquark configurations could be stable against strong decay when heavy quarks are included. After showing the stability of previously discussed states we identify new possible stable states. These are the T 0 cb(udc̄b̄) tetraquark, the Θbs(udusb̄) pentaquark and the Hc(udusuc) dibaryon, and so forth. PACS. 25.75.Nq Quark deconfi...

The observed mass pattern of scalar resonances below 1 GeV gives preference to the tetraquark assignment over the conventional q̄q assignment for these states. We present a search for tetraquarks with isospins 0,1/2,1 in lattice QCD, where isospin channels 1/2 and 1 have not been studied before. Our simulation uses Chirally Improved fermions on quenched gauge configurations. We determine three e...

Abstract We study the mass spectra of D -wave excited tetraquark states with J^{PC}=1^{++} and 1^{+-} in both symmetric \mathbf{6}_{cs}\otimes\bar{\mathbf{6}}_{\bar{c}\bar{s}} antisymmetric \bar{\mathbf{3}}_{cs}\otimes\mathbf{3}_{\bar{c}\bar{s}} color configurations using QCD sum rule method. construct diquark-antidiquark type interpolating currents various excita...

Using the QCD sum rule approach we investigate the vertex associated with the decay D0(0+) → D+π−, where the scalar meson D0(0+) is considered as a four-quark state (cd)(ūd̄). Although our results for the mass and partial decay width are smaller than the mass and the total decay width of the broad scalar meson D∗0 0 (2308) reported by BELLE Collaboration, we can not discard the possibility that ...