K. Kramer, D. S. Armstrong, T. D. Averett, W. Bertozzi, S. Binet, C. Butuceanu, A. Camsonne, G. D. Cates, J.-P. Chen, Seonho Choi, E. Chudakov, F. Cusanno, A. Deur, P. Djawotho, D. Dutta, J. M. Finn, H. Gao, F. Garibaldi, O. Gayou, R. Gilman, A. Glamazdin, V. Gorbenko, K. A. Griffioen, J.-O. Hansen, D. W. Higinbotham, W. Hinton, T. Horn, C.W. de Jager, X. Jiang, W. Korsch, J. LeRose, D. Lhuillier, N. Liyanage, D. J. Margaziotis, K. McCormick, Z.-E. Meziani, R. Michaels, B. Milbrath, B. Moffit, S. Nanda, C. F. Perdrisat, R. Pomatsalyuk, V. Punjabi, B. Reitz, J. Roche, R. Roché, M. Roedelbronn, N. Savvinov,0 J. Secrest, J. Singh, S. Širca, K. Slifer, P. Solvignon, D. J. Steiner, R. Suleiman, V. Sulkosky, A. Tobias, A. Vacheret, Y. Xiao, X. Zheng, J. Zhou, L. Zhu, X. Zhu, P. A. Żo lnierczuk,

X. Zheng, K. Aniol, D. S. Armstrong, T. D. Averett, W. Bertozzi , S. Binet , E. Burtin, E. Busato, C. Butuceanu , J. Calarco, A. Camsonne , G. D. Cates , Z. Chai , J.-P. Chen , Seonho Choi , E. Chudakov, F. Cusanno , R. De Leo, A. Deur, S. Dieterich, D. Dutta, J. M. Finn, S. Frullani , H. Gao, J. Gao, F. Garibaldi , S. Gilad, R. Gilman, J. Gomez , J.-O. Hansen , D. W. Higinbotham, W. Hinton, T. Horn, C.W. de Jager , X. Jiang, L. Kaufman, J. Kelly, W. Korsch, K. Kramer, J. LeRose , D. Lhuillier, N. Liyanage, D.J. Margaziotis , F. Marie, P. Markowitz, K. McCormick, Z.-E. Meziani , R. Michaels, B. Moffit, S. Nanda, D. Neyret , S. K. Phillips, A. Powell, T. Pussieux , B. Reitz, J. Roche, R. Roche, M. Roedelbronn, G. Ron, M. Rvachev, A. Saha, N. Savvinov, J. Singh, S. Širca, K. Slifer, P. Solvignon, P. Souder , D.J. Steiner , S. Strauch, V. Sulkosky, A. Tobias, G. Urciuoli, A. Vacheret , B. Wojtsekhowski , H. Xiang, Y. Xiao, F. Xiong, B. Zhang, L. Zhu, X. Zhu, P.A.Żołnierczuk,

We describe the design and operation of a detector system for measuring all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5 x 10(7) tagged photons per second. Photons from meson decays were detected with a lead-glass calorimeter with an energy resolution of 11% at I GeV. Various veto and trigger components were also present. Final states with as many as six photons were successfully detected and reconstructed. (c) 2006 Elsevier B.V. All rights reserved.

We present the first measurement of the Q2 dependence of the neutron spin structure function g2(n) at five kinematic points covering 0.57 (GeV/c)2 < or = Q2 < or = 1.34 (GeV/c)2 at x approximately = 0.2. Though the naive quark-parton model predicts g2 = 0, nonzero values occur in more realistic models of the nucleon which include quark-gluon correlations, finite quark masses, or orbital angular momentum. When scattering from a noninteracting quark, g2(n) can be predicted using next-to-leading order fits to world data for g1(n). Deviations from this prediction provide an opportunity to examine QCD dynamics in nucleon structure. Our results show a positive deviation from this prediction at lower Q2, indicating that contributions such as quark-gluon interactions may be important. Precision data obtained for g1(n) are consistent with next-to-leading order fits to world data.

We have measured the neutron spin asymmetry A(n)(1) with high precision at three kinematics in the deep inelastic region at x=0.33, 0.47, and 0.60, and Q(2)=2.7, 3.5, and 4.8 (GeV/c)(2), respectively. Our results unambiguously show, for the first time, that A(n)(1) crosses zero around x=0.47 and becomes significantly positive at x=0.60. Combined with the world proton data, polarized quark distributions were extracted. Our results, in general, agree with relativistic constituent quark models and with perturbative quantum chromodynamics (PQCD) analyses based on the earlier data. However they deviate from PQCD predictions based on hadron helicity conservation.

We report on measurements of the neutron spin asymmetries A(1,2)(n) and polarized structure functions g(1,2)(n) at three kinematics in the deep inelastic region, with x=0.33, 0.47, and 0.60 and Q(2)=2.7, 3.5, and 4.8 (GeV/c)(2), respectively. These measurements were performed using a 5.7 GeV longitudinally polarized electron beam and a polarized He-3 target. The results for A(1)(n) and g(1)(n) at x=0.33 are consistent with previous world data and, at the two higher-x points, have improved the precision of the world data by about an order of magnitude. The new A(1)(n) data show a zero crossing around x=0.47 and the value at x=0.60 is significantly positive. These results agree with a next-to-leading-order QCD analysis of previous world data. The trend of data at high x agrees with constituent quark model predictions but disagrees with that from leading-order perturbative QCD (PQCD) assuming hadron helicity conservation. Results for A(2)(n) and g(2)(n) have a precision comparable to the best world data in this kinematic region. Combined with previous world data, the moment d(2)(n) was evaluated and the new result has improved the precision of this quantity by about a factor of 2. When combined with the world proton data, polarized quark distribution functions were extracted from the new g(1)(n)/F-1(n) values based on the quark-parton model. While results for Deltau/u agree well with predictions from various models, results for Deltad/d disagree with the leading-order PQCD prediction when hadron helicity conservation is imposed.

We describe the construction and performance of a detector system for measuring the all-photon decays of mesons photoproduced in a tagged photon beam with energies between 4.3 and 5.4 GeV and a flux of 5 · 10 tagged photons per second. The detector was optimized for the detection of the rare radiative decays of the φ(1020) meson. The primary detector element was a lead glass calorimeter. A single photon energy resolution of 11% at 1 GeV was achieved. Various veto and trigger components were also present. Final states with as many as seven photons were successfully detected and reconstructed.