Deeply pseudoscalar meson electroproduction with CLAS and Generalized Parton Distributions

We discuss the recent data of exclusive $\pi^0$ (and $\pi^+$) electroproduction on the proton obtained by the CLAS collaboration at Jefferson Lab. It is observed that the cross sections, which have been decomposed in $\sigma_T +\epsilon\sigma_L$, $\sigma_{TT}$ and $\sigma_{LT}$ structure functions, are dominated by transverse amplitude contributions. The data can be interpreted in the Generalized Parton Distribution formalism provided that one includes helicity-flip transversity GPDs.Comment: 4 pages, 2 figures PANIC14 conference proceedin

Study of narrow baryon resonance decaying into Ks0pK^0_s p in pApA-interactions at 70GeV/c70 GeV/c with SVD-2

The inclusive reaction $p A \to pK^0_s + X$ was studied at IHEP accelerator with $70 GeV$ proton beam using SVD-2 detector. Two different samples of $K^0_s$, statistically independent and belonging to different phase space regions were used in the analyses and a narrow baryon resonance with the mass $M=1523\pm 2(stat.)\pm 3(syst.) MeV/c^2$ was observed in both samples of the dataComment: 3 pages, 6 figures, to be published in the Proceedings of the XXXIII International Conference of High Energy Physics (ICHEP'06), Moscow, 200

Deeply Virtual Pseudoscalar Meson Production with CLAS

Deeply virtual meson scattering cross sections and asymmetries for the pi^0 and eta exclusive electroproduction in a very wide kinematic range of Q^2, t and x_B have been measured with CLAS (JLab). Initial analysis is already showing remarkable results. These data will help us to better understand the transition from soft to hard mechanisms.Comment: Prepared for XII Workshop on High Energy Spin Physics DSPIN-07, Dubna, September 3-7, 200

Status of Pentaquark Search at Jlab

We review the current experimental situation of pentaquark searches, and second generation experiments, with emphasis on the Jefferson Lab program.Comment: Invited talk at the 6th International Conference on Hyperons, Charm and Beauty Hadrons (BEACH2004), Chicago, USA, June 28 - July 3, 2004. 10 pages, 14 figures. One reference adde

Observation of an exotic baryon with S = +1 in photoproduction from the proton

The reaction γp→π+K−K+n was studied at Jefferson Laboratory using a tagged photon beam with an energy range of 3–5.47 GeV. A narrow baryon state with strangeness S=+1 and mass M=1555±10  MeV/c2 was observed in the nK+ invariant mass spectrum. The peak’s width is consistent with the CLAS resolution (FWHM=26  MeV/c2), and its statistical significance is (7.8±1.0)σ. A baryon with positive strangeness has exotic structure and cannot be described in the framework of the naive constituent quark model. The mass of the observed state is consistent with the mass predicted by the chiral soliton model for the Θ+ baryon. In addition, the pK+ invariant mass distribution was analyzed in the reaction γp→K−K+p with high statistics in search of doubly charged exotic baryon states. No resonance structures were found in this spectrum

Search for Θ^{++} Pentaquarks in the Exclusive Reaction γp→ K^{+} K^{-} p.

The reaction γp→pK+K− was studied at Jefferson Lab with photon energies from 1.8 to 3.8 GeV using a tagged photon beam. The goal was to search for a Θ++ pentaquark, a narrow, doubly charged baryon state having strangeness S=+1 and isospin I=1, in the pK+ invariant mass spectrum. No statistically significant evidence of a Θ++ was found. Upper limits on the total and differential cross section for the reaction γp→K−Θ++ were obtained in the mass range from 1.5 to 2.0  GeV/c2, with an upper limit for a narrow resonance with a mass MΘ++=1.54  GeV/c2 of about 0.15 nb, 95% C.L.. This result places a stringent upper limit on the Θ++ width ΓΘ++\u3c0.1  MeV/c2