Measurement of Inclusive Spin Structure Functions of the Deuteron

We report the results of a new measurement of spin structure functions of the deuteron in the region of moderate momentum transfer ($Q^2$ = 0.27 -- 1.3 (GeV/c)$^2$) and final hadronic state mass in the nucleon resonance region ($W$ = 1.08 -- 2.0 GeV). We scattered a 2.5 GeV polarized continuous electron beam at Jefferson Lab off a dynamically polarized cryogenic solid state target ($^{15}$ND$_3$) and detected the scattered electrons with the CEBAF Large Acceptance Spectrometer (CLAS). From our data, we extract the longitudinal double spin asymmetry $A_{||}$ and the spin structure function $g_1^d$. Our data are generally in reasonable agreement with existing data from SLAC where they overlap, and they represent a substantial improvement in statistical precision. We compare our results with expectations for resonance asymmetries and extrapolated deep inelastic scaling results. Finally, we evaluate the first moment of the structure function $g_1^d$ and study its approach to both the deep inelastic limit at large $Q^2$ and to the Gerasimov-Drell-Hearn sum rule at the real photon limit ($Q^2 \to 0$). We find that the first moment varies rapidly in the $Q^2$ range of our experiment and crosses zero at $Q^2$ between 0.5 and 0.8 (GeV/c)$^2$, indicating the importance of the $\Delta$ resonance at these momentum transfers.Comment: 13 pages, 8 figures, ReVTeX 4, final version as accepted by Phys. Rev.

Study of polarized-e polarized-p --> e-prime p pi0 in the Delta(1232) mass region using polarization asymmetries

Measurements of the angular distributions of target and double spin asymmetries for the Delta(1232) in the exclusive channel (polarized-p polarized-e,e-prime p)pi0 obtained at Jefferson Lab in the Q2 range from 0.5 to 1.5 gev2 are presented. Results of the asymmetries are compared with the unitary isobar model, dynamical models, and the effective Lagrangian theory. Sensitivity to the different models was observed, particularly in relation to the description of background terms on which the target asymmetry depends significantly.Comment: 14 pages, 13 figure

Exclusive electroproduction of \u3c6 mesons at 4.2 GeV

We studied the exclusive reaction ep\u20d7e\u2032p\u2032\u3c6 using the \u3c6\u20d7K+K- decay mode. The data were collected using a 4.2 GeV incident electron beam and the CEBAF Large Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator Facility. Our experiment covers the range in Q2 from 0.7 to 2.2 GeV2, and W from 2.0 to 2.6 GeV. Taken together with all previous data, we find a consistent picture of \u3c6 production on the proton. Our measurement shows the expected decrease of the t slope with the vector-meson formation time c\u394\u3c4 below 2 fm. At \u3008c\u394\u3c4\u3009=0.6 fm, we measure b\u3c6=2.27\ub10.42 GeV-2. The cross section dependence on W as W0.2\ub10.1 at Q2=1.3 GeV2 was determined by comparison with \u3c6 production at HERA after correcting for threshold effects. This is the same dependence as observed in photoproduction

Electroproduction of the \u39b(1520) hyperon

The reaction ep\u20d7e\u2032K+\u39b(1520) with \u39b(1520)\u2192p\u2032K- was studied at electron beam energies of 4.05, 4.25, and 4.46 GeV, using the CLAS detector at the Thomas Jefferson National Accelerator Facility. The cos\u3b8K+, \u3c6K+, Q2, and W dependencies of \u39b(1520) electroproduction are presented for the kinematic region 0.9<Q2<2.4\u2002GeV2 and 1.95<W<2.65\u2002GeV. Also, the Q2 dependence of the \u39b(1520) decay angular distribution is presented for the first time. The cos\u3b8K+ angular distributions suggest t-channel diagrams dominate the production process. Fits to the \u39b(1520) t-channel helicity frame decay angular distributions indicate the mz=\ub11/2 parentage accounts for about 60% of the total yield, which suggests this reaction has a significant contribution from t-channel processes with either K+ exchange or longitudinal coupling to an exchanged K*. The Q2 dependence of the \u39b(1520) production cross section is the same as that observed for \u39b(1116) photo- and electroproduction

&#951; Photoproduction on the proton for photon energies from 0.75 to 1.95 GeV

Differential cross sections for \u3b3p\u2192\u3b7p have been measured with tagged real photons for incident photon energies from 0.75 to 1.95 GeV. Mesons were identified by missing mass reconstruction using kinematical information for protons scattered in the production process. The data provide the first extensive angular distribution measurements for the process above W=1.75\u2009\u2009GeV. Comparison with preliminary results from a constituent quark model support the suggestion that a third S11 resonance with mass 3c1.8\u2009\u2009GeV couples to the \u3b7N channel