Search for Θ+ production in the γd → ΛK+n reaction

The study of the Θ+ production in photoreactions is one of the main topics of the experimental program of the CLAS Collaboration. Among the various possible reaction channels, one of the most interesting one is the reaction γd → ΛK+n, because, having only one kaon in the final state, there are no background contributions from mesonic resonances, and also the number of possible baryonic resonances are very limited. Here the preliminary results of the data collected in 2004 at CLAS will be shown. The final state is identified by detecting in CLAS the proton and pion coming from the Λ and the kaon, while the neutron is detected via missing mass

Studies of Transverse Momentum Dependent Parton Distributions and Bessel Weighting

In this paper we present a new technique for analysis of transverse momentum dependent parton distribution functions, based on the Bessel weighting formalism. The procedure is applied to studies of the double longitudinal spin asymmetry in semi-inclusive deep inelastic scattering using a new dedicated Monte Carlo generator which includes quark intrinsic transverse momentum within the generalized parton model. Using a fully differential cross section for the process, the effect of four momentum conservation is analyzed using various input models for transverse momentum distributions and fragmentation functions. We observe a few percent systematic offset of the Bessel-weighted asymmetry obtained from Monte Carlo extraction compared to input model calculations, which is due to the limitations imposed by the energy and momentum conservation at the given energy/Q2. We find that the Bessel weighting technique provides a powerful and reliable tool to study the Fourier transform of TMDs with controlled systematics due to experimental acceptances and resolutions with different TMD model inputs.Comment: 30 pages, 8 figures, enhanced discussion and interpretation of results, new section on errors with an appendix, added references. Accepted for publication in JHE

Complete angular distribution measurements of two-body deuteron photodisintegration between 0.5 GeV and 3 GeV

Nearly complete angular distributions of the two-body deuteron photodisintegration differential cross section have been measured using the CEBAF Large Acceptance Spectrometer detector and the tagged photon beam at the Thomas Jefferson National Accelerator Facility. The data cover photon energies between 0.5 and 3.0GeV and center-of-mass proton scattering angles 10°–160°. The data show a persistent forward-backward angle asymmetry over the explored energy range, and are well described by the nonperturbative quark gluon string model

Investigation of Hamamatsu H8500 phototubes as single photon detectors

We have investigated the response of a significant sample of Hamamatsu H8500 MultiAnode PhotoMultiplier Tubes (MAPMTs) as single photon detectors, in view of their use in a ring imaging Cherenkov counter for the CLAS12 spectrometer at the Thomas Jefferson National Accelerator Facility. For this, a laser working at 407.2nm wavelength was employed. The sample is divided equally into standard window type, with a spectral response in the visible light region, and UV-enhanced window type MAPMTs. The studies confirm the suitability of these MAPMTs for single photon detection in such a Cherenkov imaging application

Single and double spin asymmetries for deeply virtual Compton scattering measured with CLAS and a longitudinally polarized proton target

Single-beam, single-target, and double spin asymmetries for hard exclusive electroproduction of a photon on the proton (e) over right arrow(p) over right arrow. e\u27p\u27gamma are presented. The data were taken at Jefferson Lab using the CEBAF large acceptance spectrometer and a longitudinally polarized (NH3)-N-14 target. The three asymmetries were measured in 165 four-dimensional kinematic bins, covering the widest kinematic range ever explored simultaneously for beam and target-polarization observables in the valence quark region. The kinematic dependences of the obtained asymmetries are discussed and compared to the predictions of models of generalized parton distributions. The measurement of three DVCS spin observables at the same kinematic points allows a quasi-model-independent extraction of the imaginary parts of the H and (H) over tilde Compton form factors, which give insight into the electric and axial charge distributions of valence quarks in the proton

Polarization observables in high-energy deuteron photodisintegration within the Quark-Gluon Strings Model

Deuteron two-body photodisintegration is analysed within the framework of the Quark-Gluon Strings Model. The model describes fairly well the recent experimental data from TJNAF in the few GeV region. Angular distributions at different $\gamma$-energies are presented and the effect of a forward-backward asymmetry is discussed. New results from the QGSM for polarization observables from 1.5 -- 6 GeV are presented and compared with the available data.Comment: 3 pages, LaTeX, 4 postscript figures; contribution to QNP2002, Juelich, June 10-14, 200

A description of the ratio between electric and magnetic proton form factors by using space-like, time-like data and dispersion relations

We use the available information on the ratio between the electric and magnetic proton form factors coming from recently published space-like data and from the few available time-like data. We apply a dispersive procedure on these data to evaluate the behaviour of this ratio, as a complex function, for all values of q^2.Comment: 12 pages, 7 Encapsulated Postscript figures, uses epsfig, rotating, exscale, amsmath, cite, latexsym, graphics, color packages, added reference