We report a new measurement of the exclusive electroproduction reaction gamma(*)p-->pi(0)p to explore the evolution from soft nonperturbative physics to hard processes via the Q(2) dependence of the ...magnetic (M(1+)), electric (E(1+)), and scalar (S(1+)) multipoles in the N-->Delta transition. 9000 differential cross section data points cover W from threshold to 1.4 GeV/c(2), 4pi center-of-mass solid angle, and Q(2) from 3 to 6 GeV(2)/c(2), the highest yet achieved. It is found that the magnetic form factor G(M)(*) decreases with Q(2) more steeply than the proton magnetic form factor, the ratio E(1+)/M(1+) is small and negative, indicating strong helicity nonconservation, and the ratio S(1+)/M(1+) is negative, while its magnitude increases with Q(2).
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
A search for exotic mesons in the {pi}{sup +}{pi}{sup +}{pi}{sup -} system photoproduced by the charge exchange reaction {gamma}p{yields}{pi}{sup +}{pi}{sup +}{pi}{sup -}(n) was carried out by the ...CLAS Collaboration at Jefferson Lab. A tagged-photon beam with energies in the 4.8 to 5.4 GeV range, produced through bremsstrahlung from a 5.744 GeV electron beam, was incident on a liquid-hydrogen target. A partial wave analysis was performed on a sample of 83 000 events, the highest such statistics to date in this reaction at these energies. The main objective of this study was to look for the photoproduction of an exotic J{sup PC}=1{sup -+} resonant state in the 1 to 2 GeV mass range. Our partial wave analysis shows production of the a{sub 2}(1320) and the {pi}{sub 2}(1670) mesons, but no evidence for the a{sub 1}(1260), nor the {pi}{sub 1}(1600) exotic state at the expected levels. An upper limit of 13.5 nb is determined for the exotic {pi}{sub 1}(1600) cross section, less than 2% of the a{sub 2}(1320) production.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q{sup 2}=1.0-4.8 GeV{sup 2} with the CLAS detector at Jefferson Lab. High ...precision was achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The neutron elastic magnetic form factor was extracted from quasielastic electron scattering on deuterium over the range Q;{2}=1.0-4.8 GeV2 with the CLAS detector at Jefferson Lab. High precision was ...achieved with a ratio technique and a simultaneous in situ calibration of the neutron detection efficiency. Neutrons were detected with electromagnetic calorimeters and time-of-flight scintillators at two beam energies. The dipole parametrization gives a good description of the data.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The differential cross section, d sigma/dt, for rho(0) meson photoproduction on the proton above the resonance region was measured up to a momentum transfer -t = 5 GeV2 using the CLAS detector at the ...Thomas Jefferson National Accelerator Facility. The rho(0) channel was extracted from the measured two charged-pion cross sections by fitting the pi(+)pi(-) and p pi(+) invariant masses. The low momentum transfer region shows the typical diffractive pattern expected from Reggeon exchange. The flatter behavior at large -t cannot be explained solely in terms of QCD-inspired two-gluon exchange models. The data indicate that other processes, like quark interchange, are important to fully describe rho photoproduction.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The reaction {sup 2}H(e,e{sup '}p)n has been studied with full kinematic coverage for photon virtuality 1.75<Q{sup 2}<5.5 GeV{sup 2}. Comparisons of experimental data with theory indicate that for ...very low values of neutron recoil momentum (p{sub n}<100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100<p{sub n}<750 MeV/c, proton-neutron rescattering dominates the cross section, while {delta} production followed by the N{delta}{yields}NN transition is the primary contribution at higher momenta.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
The reaction 2H(e,e'p)n has been studied with full kinematic coverage for photon virtuality 1.75<Q2<5.5 GeV2. Comparisons of experimental data with theory indicate that for very low values of neutron ...recoil momentum (p(n)<100 MeV/c) the neutron is primarily a spectator and the reaction can be described by the plane-wave impulse approximation. For 100<p(n)<750 MeV/c, proton-neutron rescattering dominates the cross section, while Delta production followed by the NDelta-->NN transition is the primary contribution at higher momenta.
Full text
Available for:
CMK, CTK, FMFMET, IJS, NUK, PNG, UM
PDF
