The ep -> e(')pi(+)n reaction was studied in the first and second nucleon resonance regions in the 0.25 GeV2< Q(2)< 0.65 GeV2 range by use of the CLAS detector at Thomas Jefferson National Accelerator Facility. For the first time, to our knowledge, the absolute cross sections were measured, covering nearly the full angular range in the hadronic center-of-mass frame. We extracted the structure functions sigma(TL),sigma(TT), and the linear combination sigma(T)+epsilon sigma(L) by fitting the phi dependence of the measured cross sections and compared them with the MAID and Sato-Lee models.

We report on the first measurement of exclusive Xi-(1321) hyperon photoproduction in gamma p --> K+ K+ Xi- for 3.2 < E(gamma) < 3.9 GeV. The final state is identified by the missing mass in p(gamma,K+ K+)X measured with the CLAS detector at Jefferson Laboratory. We have detected a significant number of the ground-state Xi-(1321)1/2+, and have estimated the total cross section for its production. We have also observed the first excited state Xi-(1530)3/2+. Photoproduction provides a copious source of Xi's. We discuss the possibilities of a search for the recently proposed Xi5-- and Xi5+ pentaquarks.

As part of a measurement [E. Anciant , Phys. Rev. Lett. 85, 4682 (2000)] of the cross section of phi meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing K+ in the channel phi-->K+K- in the phi center-of-mass frame (the helicity frame). We find that s-channel helicity conservation (SCHC) holds in the kinematical range where t-channel exchange dominates (up to -tsimilar to2.5 GeV2 for E-gamma=3.6 GeV). Above this momentum, u-channel production of a phi meson dominates and induces a violation of SCHC. The deduced value of the phiNN coupling constant lies in the upper range of previously reported values.

We describe the design, construction, readout, tests, and performance of planar drift chambers, based on 5-mm-diameter copperized Mylar and Kapton straws, used in an experimental search for rare kaon decays. The experiment took place in the high-intensity neutral beam at the Alternating Gradient Synchrotron of Brookhaven National Laboratory, using a neutral beam stop, two analyzing dipoles, and redundant particle identification to remove backgrounds.

High-statistics cross sections and recoil polarizations for the reactions gamma+p-->K++Lambda and gamma+p-->K++Sigma(0) have been measured at CLAS for center-of-mass energies between 1.6 and 2.3 GeV. In the K(+)Lambda channel we confirm a resonance-like structure near W=1.9 GeV at backward kaon angles. Our data show more complex s- and u- channel behavior than previously seen, since structure is also present at forward angles, but not at central angles. The position and width change with angle, indicating that more than one resonance is playing a role. Large positive Lambda polarization at backward angles, which is also energy dependent, is consistent with sizable s- or u-channel contributions. Presently available model calculations cannot explain these aspects of the data.

We have measured the 3He(e,e'pp)n reaction at 2.2 GeV over a wide kinematic range. The kinetic energy distribution for "fast" nucleons (p>250 MeV/c) peaks where two nucleons each have 20% or less, and the third nucleon has most of the transferred energy. These fast pp and pn pairs are back to back with little momentum along the three-momentum transfer, indicating that they are spectators. Calculations by Sargsian and by Laget also indicate that we have measured distorted two-nucleon momentum distributions by striking one nucleon and detecting the spectator correlated pair.

We report the first evidence for a nonzero beam-spin azimuthal asymmetry in the electroproduction of positive pions in the deep-inelastic kinematic region. Data for the reaction ep-->e'pi(+)X have been obtained using a polarized electron beam of 4.3 GeV with the CEBAF Large Acceptance Spectrometer at the Thomas Jefferson National Accelerator Facility. The amplitude of the sin phi modulation increases with the momentum of the pion relative to the virtual photon, z. In the range z=0.5-0.8 the average amplitude is 0.038+/-0.005+/-0.003 for a missing mass M-X>1.1 GeV and 0.037+/-0.007+/-0.004 for M-X>1.4 GeV.

M. Ripani, V. D. Burkert, V. Mokeev, M. Battaglieri, R. DeVita, E. Golovach, M. Taiuti, G. Adams, E. Anciant, M. Anghinolfi, B. Asavapibhop, G. Audit, T. Auger, H. Avakian, H. Bagdasaryan, J. P. Ball, S. Barrow, K. Beard, M. Bektasoglu, M. Bellis, B. L. Berman, N. Bianchi, A. S. Biselli, S. Boiarinov, B. E. Bonner, S. Bouchigny, R. Bradford, D. Branford, W. J. Briscoe, W. K. Brooks, J. R. Calarco, D. S. Carman, B. Carnahan, A. Cazes, C. Cetina, L. Ciciani, P. L. Cole, A. Coleman, D. Cords,* P. Corvisiero, D. Crabb, H. Crannell, J. P. Cummings, E. De Sanctis, P.V. Degtyarenko, H. Denizli, L. Dennis, K.V. Dharmawardane, C. Djalali, G. E. Dodge, D. Doughty, P. Dragovitsch, M. Dugger, S. Dytman, M. Eckhause, H. Egiyan, K. S. Egiyan, L. Elouadrhiri, A. Empl, R. Fatemi, G. Fedotov, G. Feldman, R. J. Feuerbach, J. Ficenec, T. A. Forest, H. Funsten, S. J. Gaff, M. Gai, M. Garçon, G. Gavalian, S. Gilad, G. P. Gilfoyle, K. L. Giovanetti, P. Girard, K. Griffioen, M. Guidal, M. Guillo, L. Guo, V. Gyurjyan, C. Hadjidakis, J. Hardie, D. Heddle, P. Heimberg, F.W. Hersman, K. Hicks, R. S. Hicks, M. Holtrop, J. Hu, C. E. Hyde-Wright, B. Ishkhanov, M. M. Ito, D. Jenkins, K. Joo, J. H. Kelley, J. D. Kellie, M. Khandaker, K.Y. Kim, K. Kim, W. Kim, A. Klein, F. J. Klein, A.V. Klimenko, M. Klusman, M. Kossov, L. H. Kramer, Y. Kuang, S. E. Kuhn, J. Kuhn, J. Lachniet, J. M. Laget, D. Lawrence, Ji Li, K. Livingston, A. Longhi, K. Lukashin, J. J. Manak, C. Marchand, S. McAleer, J. McCarthy, J.W. C. McNabb, B. A. Mecking, M. D. Mestayer, C. A. Meyer, K. Mikhailov, R. Minehart, M. Mirazita, R. Miskimen, L. Morand, S. A. Morrow, M. U. Mozer, V. Muccifora, J. Mueller, L.Y. Murphy, G. S. Mutchler, J. Napolitano, R. Nasseripour, S. O. Nelson, S. Niccolai, G. Niculescu, I. Niculescu, B. B. Niczyporuk, R. A. Niyazov, M. Nozar, G.V. O’Rielly, A. K. Opper, M. Osipenko, K. Park, E. Pasyuk, G. Peterson, S. A. Philips, N. Pivnyuk, D. Pocanic, O. Pogorelko, E. Polli, S. Pozdniakov, B. M. Preedom, J.W. Price, Y. Prok, D. Protopopescu, L. M. Qin, B. Quinn, B. A. Raue, G. Riccardi, G. Ricco, B. G. Ritchie, F. Ronchetti, P. Rossi, D. Rowntree, P. D. Rubin, F. Sabatié, K. Sabourov, C. Salgado, J. P. Santoro, V. Sapunenko, R. A. Schumacher, V. S. Serov, A. Shafi, Y. G. Sharabian, J. Shaw, S. Simionatto, A.V. Skabelin, E. S. Smith, L. C. Smith, D. I. Sober, M. Spraker, A. Stavinsky, S. Stepanyan, P. Stoler, I. I. Strakovsky, S. Taylor, D. J. Tedeschi, U. Thoma, R. Thompson, L. Todor, M. Ungaro, M. F. Vineyard, A.V. Vlassov, K. Wang, L. B. Weinstein, H. Weller, D. P. Weygand, C. S. Whisnant, E. Wolin, M. H. Wood, A. Yegneswaran, J. Yun, B. Zhang, J. Zhao, and Z. Zhou

The ratios of inclusive electron scattering cross sections of He-4, C-12, and Fe-56 to He-3 have been measured for the first time. It is shown that these ratios are independent of x(B) at Q(2)>1.4 GeV2 for x(B)>1.5, where the inclusive cross section depends primarily on the high momentum components of the nuclear wave function. The observed scaling shows that the momentum distributions at high-momenta have the same shape for all nuclei and differ only by a scale factor. The observed onset of the scaling at Q(2)>1.4 GeV2 and x(B)>1.5 is consistent with the kinematical expectation that two-nucleon short range correlations (SRC) dominate the nuclear wave function at p(m)greater than or similar to300 MeV/c. The values of these ratios in the scaling region can be related to the relative probabilities of SRC in nuclei with Agreater than or equal to3. Our data, combined with calculations and other measurements of the He-3/deuterium ratio, demonstrate that for nuclei with Agreater than or equal to12 these probabilities are 4.9-5.9 times larger than in deuterium, while for He-4 it is larger by a factor of about 3.8.

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 ((ND3)-N-15) and detected the scattered electrons with the CEBAF large acceptance spectrometer. From our data, we extract the longitudinal double spin asymmetry A(parallel toparallel to) 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)-->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.

Double-polarization asymmetries for inclusive ep scattering were measured at Jefferson Lab using 2.6 and 4.3 GeV longitudinally polarized electrons incident on a longitudinally polarized NH3 target in the CLAS detector. The polarized structure function g(1)(x,Q(2)) was extracted throughout the nucleon resonance region and into the deep inelastic regime, for Q(2)=0.15-1.64 GeV2. The contributions to the first moment Gamma(1)(Q(2))=integralg(1)(x,Q(2)) dx were determined up to Q(2)=1.2 GeV2. Using a parametrization for g(1) in the unmeasured low x regions, the complete first moment was estimated over this Q(2) region. A rapid change in Gamma(1) is observed for Q(2)<1 GeV2, with a sign change near Q(2)=0.3 GeV2, indicating dominant contributions from the resonance region. At Q(2)=1.2 GeV2 our data are below the perturbative QCD evolved scaling value.

The polarized longitudinal-transverse structure function sigma(LT') has been measured in the Delta(1232) resonance region at Q(2)=0.40 and 0.65 GeV2. Data for the p((e) over right arrow ,e'p)pi(0) reaction were taken at Jefferson Lab with the CEBAF large acceptance spectrometer (CLAS) using longitudinally polarized electrons at an energy of 1.515 GeV. For the first time a complete angular distribution was measured, permitting the separation of different nonresonant amplitudes using a partial wave analysis. Comparison with previous beam asymmetry measurements at MAMI indicate a deviation from the predicted Q(2) dependence of sigma(LT ') using recent phenomenological models.

The first measurements of the transferred polarization for the exclusive (e) over right arrow p --> e'K+(U) over right arrow reaction have been performed at Jefferson Laboratory using the CLAS spectrometer. A 2.567 GeV beam was used to measure the hyperon polarization over Q(2) from 0.3 to 1.5 (GeV/c)(2), W from 1.6 to 2.15 GeV, and over the full K+ center-of-mass angular range. Comparison with predictions of hadrodynamic models indicates strong sensitivity to the underlying resonance contributions. A nonrelativistic quark-model interpretation of our data suggests that the s (s) over bar quark pair is produced with spins predominantly antialigned. Implications for the validity of the most widely used quark-pair creation operator are discussed.

L. Zana, 27 and The CLAS Collaboration University of Connecticut, Storrs, Connecticut 06269, USA University of Virginia, Charlottesville, Virginia 22901, USA Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA Arizona State University, Tempe, Arizona 85287-1504, USA CEA-Saclay, Service de Physique Nucléaire, F91191 Gif-sur-Yvette, Cedex, France University of California at Los Angeles, Los Angeles, California 90095-1547, USA Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA Catholic University of America, Washington, D.C. 20064, USA Christopher Newport University, Newport News, Virginia 23606, USA Duke University, Durham, North Carolina 27708-0305, USA Edinburgh University, Edinburgh EH9 3JZ, United Kingdom Florida International University, Miami, Florida 33199, USA Florida State University, Tallahassee, Florida 32306, USA Physikalisches Institut der Universitaet Giessen, 35392 Giessen, Germany The George Washington University, Washington, D.C. 20052, USA University of Glasgow, Glasgow G12 8QQ, United Kingdom INFN, Laboratori Nazionali di Frascati, Frascati, Italy INFN, Sezione di Genova, 16146 Genova, Italy Idaho State University, Pocatello, Idaho 83209, USA Institut de Physique Nucleaire ORSAY, Orsay, France Institute of Theoretical and Experimental Physics, Moscow, 117259, Russia James Madison University, Harrisonburg, Virginia 22807, USA Kungpook National University, Taegu 702-701, South Korea Massachusetts Institute of Technology, Cambridge, Massachusetts 02139-4307, USA University of Massachusetts, Amherst, Massachusetts 01003, USA Moscow State University, General Nuclear Physics Institute, 119899 Moscow, Russia University of New Hampshire, Durham, New Hampshire 03824-3568, USA Norfolk State University, Norfolk, Virginia 23504, USA PHYSICAL REVIEW C 70, 042201(R) (2004) RAPID COMMUNICATIONS

The cross section for the reaction ep-->e'ppi(+)pi(-) was measured in the resonance region for 1.4<W<2.1 GeV and 0.5<Q(2)<1.5 GeV2/c(2) using the CLAS detector at Jefferson Laboratory. The data show resonant structures not visible in previous experiments. The comparison of our data to a phenomenological prediction using available information on N* and Delta states shows an evident discrepancy. A better description of the data is obtained either by a sizable change of the properties of the P-13(1720) resonance or by introducing a new baryon state, not reported in published analyses.