8,742 research outputs found
Helicity Asymmetry in gamma p -> pi+ n with FROST
The main objective of the FROST experiment at Jefferson Lab is the study of
baryon resonances. The polarization observable E for the reaction gamma p to
pi+n has been measured as part of this program. A circularly polarized tagged
photon beam with energies from 0.35 to 2.35 GeV was incident on a
longitudinally polarized frozen-spin butanol target. The final-state pions were
detected with the CEBAF Large Acceptance Spectrometer. Preliminary polarization
data agree fairly well with present SAID and MAID partial-wave analyses at low
photon energies. In most of the covered energy range, however, significant
deviations are observed. These discrepancies underline the crucial importance
of polarization observables to further constrain these analyses.Comment: Contribution to the Proceedings of NSTAR 2011 - The 8th International
Workshop on the Physics of Excited Nucleons, May 17-20, 2011, Thomas
Jefferson National Accelerator Facility, Newport News, Virginia US
CLAS: Double-Pion Beam Asymmetry
Beam-helicity asymmetries for the gamma+p -> pi+ + pi- + p reaction have been
measured for center-of-mass energies between 1.35 GeV and 2.30 GeV at Jefferson
Lab with the CEBAF Large Acceptance Spectrometer using circularly polarized
tagged photons. The beam-helicity asymmetries vary with kinematics and exhibit
strong sensitivity to the dynamics of the reaction, as demonstrated in the
comparison of the data with results of various phenomenological model
calculations. These models currently do not provide an adequate description of
the data over the entire kinematic range covered in this experiment. Additional
polarization observables are accessible in an upcoming experiment at Jefferson
Lab with polarized beam and target.Comment: 10 pages, 8 Figures, Proc. Int. Workshop NSTAR 2005 at Tallahassee,
FL, October 200
Helicity-Dependent Angular Distributions in Double-Charged-Pion Photoproduction
Two-pion photoproduction in the reaction gamma + p -> p + pi^+ + pi^- has
been studied at Jefferson Lab Hall B using a circularly-polarized tagged photon
beam in the energy range between 0.6 GeV and 2.3 GeV. Owing to the large
angular acceptance of the CLAS detector, complete beam-helicity-dependent
angular distributions of the final-state particles were measured. The large
cross-section asymmetries exhibit strong sensitivity to the kinematics of the
reaction and provide valuable information on the reaction dynamics. Preliminary
results are presented.Comment: 7 pages, 4 figures. Proceedings of 2nd Int. Conf. on Nuclear and
Particle Physics with CEBAF at Jefferson Lab, Dubrovnik, 26-31 May 2003, to
be published in Fyzika
Methods for verifying the accuracy of wind profiles
Comparisons of radar-measured winds have been made with several types of measurements not only to verify radar data but also to seek a satisfactory comparison method. Three of the comparisons that have been made with Colorado Profiler radars are summarized. Radar measurements were compared with radiosonde measurements. Infrared lidar and 915 MHz radar were compared with radiosondes. A brief radar/radar comparison was made using the 50-MHz radar and a 3-cm wavelength meteorological Doppler radar during precipitation
Data analysis techniques: Spectral processing
The individual steps in the data processing scheme applied to most radars used for wind sounding are analyzed. This processing method uses spectral analysis and assumes a pulse Doppler radar. Improvement in the signal to noise ratio of some radars is discussed
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