Heavy baryon decay widths in the large N_{c} limit in chiral theory

Abstract We propose large $$N_c$$ Nc generalizations for the “diquark” representations of $$\hbox {SU}(3)_\mathrm{flav}$$ SU(3)flav relevant for positive parity heavy baryons, including putative exotic states. Next, within the framework of the Chiral Quark Soliton Model, we calculate heavy baryon masses and decay widths. We show that in the limit of $$N_c \rightarrow \infty$$ Nc→∞ all decay widths vanish, including the widths of exotica. This result is in fact more general than the model itself, as it relies only on the underlying symmetries: i.e. $$\hbox {SU}(3)_\mathrm{flav}$$ SU(3)flav and hedgehog symmetry. Furthermore, using explicit model formulae for the decay constants in the non-realtivistic limit, we show that there is a hierarchy of the decay couplings, which may explain observed pattern of experimental widths

The width of Θ+\Theta^{+} for large NcN_{c} in chiral quark soliton model

In the chiral quark soliton model the smallness of $\Theta^+$ width is due to the cancellation of the coupling constants which are of different order in $N_c$. We show that taking properly into account the flavor structure of relevant SU(3) representations for arbitrary number of colors enahnces the nonleading term by an additional factor of $N_c$, making the cancellation consistent with the $N_c$ counting. Moreover, we show that, for the same reason, $\Theta^+$ width is suppressed by a group-theoretical factor ${\cal O}(1/N_c)$ with respect to $\Delta$ and discuss the $N_c$ dependence of the phase space factors for these two decays.Comment: 9 pages, 3 eps figures, in v2 reference added, minor typos correcte

Regge limit in QCD

It is shown that the perturbative calculations in Regge limit in nonabelian gauge theories are in agreement with the hypothesis of the reggeization of vector meson (gluon). The infrared properties of the integral equations for various quantum numbers exchange in the t-channel are studied in the spontaneously broken theory; the role of the Higgs particles is investigated. Some connections with deep inelastic scattering are also discussed. The integral equation describing the three gluon exchange in a colour singlet state is formulated and its infrared properties are studied. It is argued that it generates a fixed branch point in j-plane

Exotic and nonexotic magnetic transitions in the context of the SELEX and GRAAL experiments

We calculate magnetic transition moments in the chiral quark-soliton model, with explicit SU(3)-symmetry breaking taken into account. The dynamical model parameters are fixed by experimental data for the magnetic moments of the baryon octet and from the recent measurements of $\Theta^{+}$ mass. Known magnetic transition moments $\mu_{\Lambda\Sigma}$, $\mu_{N\Delta}$ are reproduced and predictions for other octet-decuplet and octet-antidecuplet transitions are given. In particular $\mu_{\Sigma\Sigma^{\ast}}$ recently constrained by SELEX is shown to be below $0.82 \mu_N$. The recent GRAAL data on $\eta$ photoproduction off the nucleon are explained in terms of a new narrow antidecuplet neutron-like resonance.Comment: 14 pages, 9 figures. Final version accepted for publication in Phys.Rev.

Doubly heavy tetraquarks in the chiral quark soliton model

The chiral quark soliton model has been successfully applied to describe the heavy baryon spectrum, both for charm and bottom, leading to the conclusion that the heavy quark has no effect on the soliton. This suggests that replacing a heavy quark by a heavy antidiquark $\bar{Q}\bar{Q}$ in color triplet should give a viable description of heavy tetraquarks. We follow this strategy to compute tetraquark masses. To estimate heavy diquark masses, we use the Cornell potential with appropriately rescaled parameters. The lightest charm tetraquark is 70 MeV above the $DD^{*}$ threshold. On the contrary, both nonstrange and strange bottom tetraquarks are bound by approximately 140 and 60 MeV, respectively

Saturation and geometrical scaling : from small x deep inelastic ep scattering to high energy proton-proton and heavy ion collisions

Gluon distributions of colliding hadrons saturate as a result of the non-linear evolution equations of QCD. As a consequence there exists the so called saturation momentum, which is related to the gluon density per unit rapidity per transverse area. When saturation momentum is the only scale for physical processes, different observables exhibit geometrical scaling (GS). We show a number of examples of GS and its violation in different reactions

Nonleptonic Ω−\Omega^{-} decays and the Skyrme model

Nonleptonic $\Omega^{-}$ decay branching ratios are estimated by means of the QCD enhanced effective weak Hamiltonian supplemented by the SU(3) Skyrme model used to estimate the nonperturbative matrix elements. The model has only one free parameter, namely the Skyrme charge $e$, which is fixed through the experimental values of the octet-decuplet mass splitting $\Delta$ and the axial coupling constant $g_{A}$. The whole scheme is equivalent to that which works well for the nonleptonic hyperon decays. The ratios of calculated amplitudes are in agreement with experiment. However, the absolute values are about twice too large if short-distance corrections and only ground intermediate states are included.Comment: 4 pages, 1 figure, 1 table, version to appear in Phys.Rev.

Chiral models : pions and baryons

Various aspects of chiral models are discussed with special emphasis on the chiral quark model and the Skyrme model. Firstly, the ability of the chiral quark model to reproduce pion scattering data is reviewed. Secondly the soliton sector of the model is studied. The soliton solution is interpreted as a baryon — nucleon or dilambda. Next, on the example of the Skyrme, model we study inclusion of strangeness, large limit and quantization. It is argued that effective chiral models qualitatively reproduce the low energy limit of QCD