Related papers: Narrow Tetraquarks at Large N
We show that one can re-arrange the Heavy Quark Expansion for inclusive weak decays of charmed hadrons in such a way that the resulting expansion is an expansion in $\Lambda_{\rm QCD} / m_c$ and $\alpha_s (m_c)$ with order-one coefficients.…
Common lore suggests that $N$-color QCD with massive quarks has no useful order parameters which can be non-trivial at zero baryon density. However, such order parameters do exist when there are $n_f$ quark flavors with a common mass and…
The masses of heavy quark baryons are studied in an expansion in 1/N_c, SU(3) flavor symmetry breaking, and heavy-quark symmetry breaking. Very accurate model-independent mass relations are obtained for charm and bottom baryons.
It is suggested that the narrow meson state seen in the the SELEX experiment is a $(c\bar{s} s\bar{s})$ tetraquark state. Characteristics of other possible tetraquarks formed out of $c$ and $s$ quarks and antiquarks are considered.
We use the twist dimensions of the operators underlying the dynamical behavior of exclusive production processes as a tool for determining the structure of exotic heavy-quark states such as the $Z_c^+(4430)$ tetraquark. The resulting…
The 1/N expansion for exotic baryons is developed, and applied to the masses, meson couplings and decay widths. Masses and widths of the 27 and 35 pentaquark states in the same tower as the Theta+ are related by spin-flavor symmetry. The 27…
There are experimental evidences for the existence of narrow states $\Theta^+$ and $\Theta_c$ with the same quantum numbers of $uudd\bar s$ and $uudd\bar c$ pentaquarks and also $NK^{(*)}$ and $ND^{(*)}$ molecular states. Their masses…
Recent discoveries of manifestly exotic, narrow baryon resonances present a fundamental challenge for our theoretical understanding of low-energy QCD. This is a brief survey of their interpretation, emphasizing the possibility that diquark…
The fully heavy scalar tetraquarks $T_{\mathrm{4Q}}=QQ\overline{Q}\overline{Q }$, ($Q=c, b$) are explored in the context of QCD sum rule method. We model $ T_{\mathrm{4Q}}$ as diquark-antidiquark systems composed of pseudoscalar…
I review new results on particles containing a charm or bottom quark, focusing on measurements that give insight into the dynamics of the decay process. Leptonic and semileptonic decays are the simplest modes, and they provide detailed…
Multiquark correlations inside hadrons can have a significant and in some cases even striking impact on the hadron spectrum. We show how such correlations in general, and mesons with a dominant tetraquark content in particular, emerge…
Scalar mesons are a key expression of the strong coupling regime of QCD. How those with $I_3=0$ couple to two photons supplies important information about which is transiently ${\bar q}q$ or ${\bar {qq}} qq$ or multi-meson molecule or…
We calculate the widths of the various pentaquarks in a relativistic model in which the pentaquark is considered to be composed of a scalar diquark and a spin 1/2 triquark. We consider both positive and negative parity for the pentaquark.…
A generalized linear sigma model for low energy QCD is employed to study the quark structure of eight low lying scalar isomultiplets as well as eight low lying pseudoscalar isomultiplets. The model, building on earlier work, assumes the…
Motivated by recent developments in tetraquark studies, we investigate the mass spectra and decay properties of light-strange tetraquarks ($sq\bar{s}\bar{q},ss\bar{q}\bar{q}$) in diquark-antidiquark formalism. By considering different…
If connecting properties of a multiquark hadron with those exhibited by its constituents, QCD sum rules inferred along the routes of traditional wisdom necessarily involve contributions not related at all to and thus not presenting…
We have recently studied hidden-charm pentaquarks, $c\bar c qqq$, using dynamical correlations between the heavy quarks arising from the Coulomb-like nature of the short-range interaction. A pattern was obtained that compares well with the…
We study excited baryon decay widths in large N_c QCD. It was suggested previously that some spin-flavor mixed-symmetric baryon states have strong couplings of O(N_c^{-1/2}) to nucleons [implying narrow widths of O(1/N_c)], as opposed to…
It has become clearer recently that the regular pattern of three flavor nonets describing the low spin meson multiplets seems to require some modification for the case of the spin 0 scalar mesons. One picture which has had some success,…
We explore the anomaly induced effective QCD meson potential in the framework of the effective Lagrangian approach. We suggest a decoupling procedure, when a flavored quark becomes massive, which mimics the one employed by Seiberg for…