| 1. |
- Chirapatpimol, K, et al.
(författare)
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Precision Measurement of the p(e,e′p)π0 Reaction at Threshold
- 2015
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Ingår i: Physical Review Letters. - 1079-7114. ; 114:19
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Tidskriftsartikel (refereegranskat)abstract
- New results are reported from a measurement of π^{0} electroproduction near threshold using the p(e,e^{'}p)π^{0} reaction. The experiment was designed to determine precisely the energy dependence of s- and p-wave electromagnetic multipoles as a stringent test of the predictions of chiral perturbation theory (ChPT). The data were taken with an electron beam energy of 1192 MeV using a two-spectrometer setup in Hall A at Jefferson Lab. For the first time, complete coverage of the ϕ_{π}^{*} and θ_{π}^{*} angles in the pπ^{0} center of mass was obtained for invariant energies above threshold from 0.5 up to 15 MeV. The 4-momentum transfer Q^{2} coverage ranges from 0.05 to 0.155 (GeV/c)^{2} in fine steps. A simple phenomenological analysis of our data shows strong disagreement with p-wave predictions from ChPT for Q^{2}>0.07 (GeV/c)^{2}, while the s-wave predictions are in reasonable agreement.
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| 2. |
- Dutta, D, et al.
(författare)
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Nuclear transparency with the gamma n ->pi(-)p process in He-4
- 2003
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 68:2: 021001
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 3. |
- Zhu, LY, et al.
(författare)
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Cross-section measurement of charged-pion photoproduction from hydrogen and deuterium
- 2003
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Ingår i: Physical Review Letters. - 1079-7114. ; 91:2: 022003
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Tidskriftsartikel (refereegranskat)abstract
- We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma)greater than or similar to3.3 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.
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| 4. |
- Zhu, L Y, et al.
(författare)
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Cross section measurements of charged pion photoproduction in hydrogen and deuterium from 1.1 to 5.5 GeV
- 2005
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Ingår i: Physical Review C (Nuclear Physics). - 0556-2813. ; 71:4
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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