The kaon electroproduction reaction 1H(e,e'K+)Lambda was studied as a function of the virtual-photon four-momentum, Q2, total energy, W, and momentum transfer, t, for different values of the virtual- photon polarization parameter. Data were taken at electron beam energies ranging from 3.40 to 5.75 GeV. The center of mass cross section was determined for 21 kinematics corresponding to Q2 of 1.90 and 2.35 GeV2 and the longitudinal, sigmaL, and transverse, sigmaT, cross sections were separated using the Rosenbluth technique at fixed W and t. The separated cross sections reveal a flat energy dependence at forward kaon angles not satisfactorily described by existing electroproduction models. Influence of the kaon pole on the cross sections was investigated by adopting an off-shell form factor in the Regge model which better describes the observed energy dependence of sigmaT and sigmaL.

We report on the design and commissioning of two silica aerogel Cherenkov detectors with different refractive indices. In particular, extraordinary performance in terms of the number of detected photoelectrons was achieved through an appropriate choice of PMT type and reflector, along with some design considerations. After four years of operation, the number of detected photoelectrons was found to be noticeably reduced in both detectors as a result of contamination, yellowing, of the aerogel material. Along with the details of the set-up, we illustrate the characteristics of the detectors during different time periods and the probable causes of the contamination. In particular we show that the replacement of the contaminated aerogel and parts of the reflecting material has almost restored the initial performance of the detectors.

We have measured the parity-violating electroweak asymmetry in the elastic scattering of polarized electrons from protons. Significant contributions to this asymmetry could arise from the contributions of strange form factors in the nucleon. The measured asymmetry is A = −15.05 ± 0.98(stat) ± 0.56(syst) ppm at the kinematic point 〈θlab〉 = 12.3 and 〈Q2〉 = 0.477 (GeV/c)2. Based on these data as well as data on electromagnetic form factors, we extract the linear combination of strange form factors GE + 0.392G s M = 0.014 ± 0.020 ± 0.010 where the first error arises from this experiment and the second arises from the electromagnetic form factor data. This paper provides a full description of the special experimental techniques employed for precisely measuring the small asymmetry, including the first use of a strained GaAs crystal and a laser-Compton polarimeter in a fixed target parity-violation experiment. PACS numbers: 13.60.Fz; 11.30.Er; 13.40.Gp; 14.20.Dh Electronic address: finn@physics.wm.edu Now at: Duke University, Durham, North Carolina 27708 USA Now at: University of Chicago, IL, 60637, USA Electronic address: souder@phy.syr.edu

INTRODUCTION:Occupational infectious respiratory diseases are underestimate pathology because of an asymptomatic infection or the general, unspecific symptoms. STATE OF THE ART:The most part of patients are among health care and agriculture or forestry workers (15% employee exposure of infectious risks in according with SUMMER study 2003). Biological risks interest two-third of health care workers, one-third of agriculture and food industry employees and one-forth of house-workers. Occupational diseases occur as flu-like illness, pneumonia, lung abscess or pleurisy. A possible classification for this pathology is by clinical manifestations: with respiratory predominance like tuberculosis, pasteurelosis, psittacosis or diseases like anthrax, brucellosis or tularemia with non respiratory predominance. PERSPECTIVES AND CONCLUSION:The authors remind the data of occupational respiratory infectious diseases, microbiological data and links between clinical symptoms and patients professions leading to diagnosis.

We measured angular distributions of differential cross section, beam analyzing power, and recoil polarization for neutral pion electroproduction at Q^2 = 1.0 (GeV/c)^2 in 10 bins of W across the Delta resonance. A total of 16 independent response functions were extracted, of which 12 were observed for the first time. Comparisons with recent model calculations show that response functions governed by real parts of interference products are determined relatively well near 1.232 GeV, but variations among models is large for response functions governed by imaginary parts and for both increases rapidly with W. We performed a nearly model-independent multipole analysis that adjusts complex multipoles with high partial waves constrained by baseline models. Parabolic fits to the W dependence of the multipole analysis around the Delta mass gives values for SMR = (-6.61 +/- 0.18)% and EMR = (-2.87 +/- 0.19)% that are distinctly larger than those from Legendre analysis of the same data. Similarly, the multipole analysis gives Re(S0+/M1+) = (+7.1 +/- 0.8)% at W=1.232 GeV, consistent with recent models, while the traditional Legendre analysis gives the opposite sign because its truncation errors are quite severe. Finally, using a unitary isobar model (UIM), we find that excitation of the Roper resonance is dominantly longitudinal with S1/2 = (0.05 +/- 0.01) GeV^(-1/2) at Q^2=1. The ReS0+ and ReE0+ multipoles favor pseudovector coupling over pseudoscalar coupling or a recently proposed mixed-coupling scheme, but the UIM does not reproduce the imaginary parts of 0+ multipoles well.

The differential cross sections for the gamma n ->pi(-)p and the gamma p ->pi(+)n processes were measured at Jefferson Lab. The photon energies ranged from 1.1 to 5.5 GeV, corresponding to center-of-mass energies from 1.7 to 3.4 GeV. The pion center-of-mass angles varied from 50(degrees) to 110(degrees). The pi(-) and pi(+) photoproduction data both exhibit a global scaling behavior at high energies and high transverse momenta, consistent with the constituent counting rule prediction and the existing pi(+) data. The data suggest possible substructure of the scaling behavior, which might be oscillations around the scaling value. The data show an enhancement in the scaled cross section at center-of-mass energy near 2.2 GeV. The differential cross section ratios [d sigma/dt(gamma n ->pi(-)p)/d sigma/dt(gamma p ->pi(+)n)] at high energies and high transverse momenta can be described by calculations based on one-hard-gluon-exchange diagrams.

L. Y. Zhu, J. Arrington, T. Averett, 4 E. Beise, J. Calarco, T. Chang, J. P. Chen, E. Chudakov, M. Coman, B. Clasie, C. Crawford, S. Dieterich, F. Dohrmann, D. Dutta, K. Fissum, S. Frullani, H. Gao, 12 R. Gilman, 9 C. Glashausser, J. Gomez, K. Hafidi, O. Hansen, D. W. Higinbotham, R. J. Holt, C. W. de Jager, X. Jiang, E. Kinney, K. Kramer, G. Kumbartzki, J. LeRose, N. Liyanage, D. Mack, P. Markowitz, K. McCormick, D. Meekins, Z.-E. Meziani, R. Michaels, J. Mitchell, S. Nanda, D. Potterveld, R. Ransome, P. E. Reimer, B. Reitz, A. Saha, E. C. Schulte, 7 J. Seely, S. Širca, S. Strauch, V. Sulkosky, B. Vlahovic, L. B. Weinstein, K. Wijesooriya, C. Williamson, B. Wojtsekhowski, H. Xiang, F. Xiong, W. Xu, J. Zeng, and X. Zheng

We measured angular distributions of recoil-polarization response functions for neutral pion electroproduction for W = 1.23 GeV at Q(2) = 1.0 (GeV/c)(2), obtaining 14 separated response functions plus 2 Rosenbluth combinations; of these, 12 have been observed for the first time. Dynamical models do not describe quantities governed by imaginary parts of interference products well, indicating the need for adjusting magnitudes and phases for nonresonant amplitudes. We performed a nearly model-independent multipole analysis and obtained values for Re (S(1+)/M(1+)) = -(6.84 +/- 0.15)% and Re (E(1+)/M(1+)) = -(2.91 +/- 0.19)% that are distinctly different from those from the traditional Legendre analysis based upon M1+ dominance and ll(pi) < or = 1 truncation.

The electric form factor of the neutron was determined from measurements of the d-->(e-->,e'n)p reaction for quasielastic kinematics. Polarized electrons were scattered off a polarized deuterated ammonia (15ND3) target in which the deuteron polarization was perpendicular to the momentum transfer. The scattered electrons were detected in a magnetic spectrometer in coincidence with neutrons in a large solid angle detector. We find G(n)(E)=0.0526+/-0.0033(stat)+/-0.0026(sys) and 0.0454+/-0.0054+/-0.0037 at Q(2)=0.5 and 1.0 (GeV/c)(2), respectively.

The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electro- and photo-induced reactions at very high luminosity and good momentum and angular resolution for at least one of the reaction products. The central components of Hall A are two identical high resolution spectrometers, which allow the vertical drift chambers in the focal plane to provide a momentum resolution of better than 2×10−4. A variety of Cherenkov counters, scintillators and lead-glass calorimeters provide excellent particle identification. The facility has been operated successfully at a luminosity well in excess of 1038cm−2s−1. The research program is aimed at a variety of subjects, including nucleon structure functions, nucleon form factors and properties of the nuclear medium.

We have measured the nuclear transparency of the fundamental process γ→nπ−p in 4He. These measurements were performed at Jefferson Lab in the photon energy range of 1.6–4.5 GeV and at θπcm=70° and 90°. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations that include the quantum chromodynamics phenomenon of color transparency.Received 9 May 2003DOI:https://doi.org/10.1103/PhysRevC.68.021001©2003 American Physical Society

K. Wijesooriya, 3 C. F. Williamson, 2 B. Wojtsekhowski, 5 H. Xiang, W. Xu, J. Zeng, 17 and X. Zheng ~Jefferson Lab E94104 Collaboration ! Duke University, Durham, North Carolina 27708, USA Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA Argonne National Laboratory, Argonne, Illinois 60439, USA College of William and Mary, Williamsburg, Virginia 23185, USA Thomas Jefferson National Accelerator Facility, Newport News, Virginia 23606, USA University of Maryland, College Park, Maryland 20742, USA University of New Hampshire, Durham, New Hampshire 03824, USA University of Illinois, Urbana, Illinois 61801, USA Florida International University, Miami, Florida 33199, USA Rutgers University, New Brunswick, New Jersey 08903, USA Lund University, S-221 00 Lund, Sweden INFN/Sezione Sanita, 00161 Roma, Italy University of Colorado, Boulder, Colorado 80302, USA Temple University, Philadelphia, Pennsylvania 19122, USA North Carolina Central University, Durham, North Carolina 27707, USA Old Dominion University, Norfolk, Virginia 23529, USA University of Georgia, Athens, Georgia 30601, USA ~Received 9 May 2003; published 15 August 2003 !

We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90 degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma) greater, similar 3.3 GeV exhibit a global scaling behavior for both pi(-) and pi(+) photoproduction, consistent with the constituent counting rule and the existing pi(+) photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi(-) to pi(+) photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams.

We have measured the nuclear transparency of the fundamental process gamman-->pi(-)p in He-4. These measurements were performed at Jefferson Lab in the photon energy range of 1.6-4.5 GeV and at theta(cm)(pi)=70degrees and 90degrees. These measurements are the first of their kind in the study of nuclear transparency in photoreactions. They also provide a benchmark test of Glauber calculations based on traditional models of nuclear physics. The transparency results suggest deviations from the traditional nuclear physics picture. The momentum transfer dependence of the measured nuclear transparency is consistent with Glauber calculations that include the quantum chromodynamics phenomenon of color transparency.