Search for pentaquarks at Belle

We search for the strange pentaquark $\Theta^+$ using kaon interactions in the material of the Belle detector. No signal is observed in the $p K_S$ final state, while in the $p K^-$ final state we observe $\sim 1.6 \cdot 10^4$ $\Lambda(1520) \to p K^-$ decays. We set an upper limit on the ratio of $\Theta^+$ to $\Lambda(1520)$ yields $\sigma(\Theta^+) / \sigma(\Lambda(1520)) < 2$ at 90% CL assuming that the $\Theta^+$ is narrow. We also report on searches for strange and charmed pentaquarks in B meson decays. These results are obtained from a 155$fb^{-1}$ data sample collected with the Belle detector near the $\Upsilon(4S)$ resonance, at the KEKB asymmetric energy $e^+ e^-$ collider.Comment: 10 pages, 6 figures. To appear in the Proceedings of the PENTA04 conference in Kobe, Japan. These results were also presented by Belle at the ICHEP04 conference in Beijing, China and at the FPCP04 conference in Daegu, Korea. Minor correctio

Small size pentaquark width: calculation in QCD sum rules

The pentaquark width is calculated in QCD sum rules. The higher dimension operators contribution is accounted. It is shown, that $\Gamma_{\Theta}$ should be very small, less than $1Mev$.Comment: 10 peges, 7 figure

Model-independent Study of Electric Dipole Transitions in Quarkonium

The paper contains a systematic, model-independent treatment of electric dipole (E1) transitions in heavy quarkonium. Within the effective field theory framework of potential non-relativistic QCD (pNRQCD), we derive the complete set of relativistic corrections of relative order v^2 both for weakly and strongly-coupled quarkonia. The result supports and complements former results from potential model calculations.Comment: 42 pages, 9 figure

A practical parametrization for line shapes of near-threshold states

Numerous quarkonium(like) states lying near $S$-wave thresholds are observed experimentally. We propose a self-consistent approach to these near-threshold states compatible with unitarity and analyticity. The underlying coupled-channel system includes a bare pole and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting analytical parametrization is ideally suited for a combined analysis of the data available in various channels that is exemplified by an excellent overall description of the data for the charged $Z_b(10610)$ and $Z_b(10650)$ states.Comment: LaTeX2e, 5 pages, 1 figure, typos corrected, version published in Phys. Rev. Let

Interplay of quark and meson degrees of freedom in near-threshold states: A practical parametrisation for line shapes

We propose a practical parametrisation for the line shapes of near-threshold states compatible with all requirements of unitarity and analyticity. The coupled-channel system underlying the proposed parametrisation includes bare poles and an arbitrary number of elastic and inelastic channels treated fully nonperturbatively. The resulting formulae are general enough to be used for a simultaneous analysis of the data in all available production and decay channels of the (system of) state(s) under consideration for a quite wide class of reactions. As an example, we fit the experimental data currently available for several decay channels for the charged $Z_b^{(\prime)}$ states in the spectrum of bottomonia and find a good overall description of the data. We find the present data to be consistent with the $Z_b(10610)$ as a virtual state and with the $Z_b(10650)$ as a resonance, both residing very close to the $B\bar{B}^*$ and $B^*\bar{B}^*$ threshold, respectively.Comment: LaTeX2e, 19 pages, 10 figures, version published in Phys.Rev.

Charged charmonium-like states as rescattering effects in B -> D_sJ D^(*) decays

Using purely phenomenological approach we show that the peaking structures observed in the psi(2S) pi+ and chi_c1 pi+ mass spectra in B -> psi(2S)(chi_c1) pi+ K decays can be result of (D \bar{D}^(*))+ -> (ccbar)_res pi+ rescattering in the decays B -> D_sJ (-> \bar{D}(*) K) D(*). In particular, the position of the peak in the chain B -> D_s(2S) D+ -> K- \bar{D}*0 D+ -> K- psi(2S) pi+ coincides well with the measured Z(4430) mass, assuming the mass of D_s(2S) (the first radial excitation of D_s) to be 2610 MeV/c2. The widths of the Z(4430) peak is also well reproduced in this approach independent on the width of D_s(2S). Although the decay B -> D_s(2S) D+ has not been observed so far and even D_s(2S)-meson is not discovered yet, this decay is expected to be large, and the mass of D_s(2S) is predicted in the range (2600-2650)MeV/c2. The broad bump in chi_c1 pi+ spectrum can be attributed to the B -> D_s*(2S) D+ -> K- \bar{D}0 D+ decay observed with a large branching fraction followed by rescattering \bar{D}0 D^+ -> chi_c1 pi+.Comment: 4 pages, 3 figure