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No description provided.
THE RESONANCE PARAMETERS: MASS=1437 +-3 MEV, WIDTH=169 +-2 MEV.
THE RESONANCE PARAMETERS: MASS=1418 +-3 MEV, WIDTH=60 +-5 MEV.
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No description provided.
Results of systematic measurements of the asymmetry parameter in the elastic scattering of pions on polarized protons at 1.4–2.1 GeV/ c in the backward hemisphere are presented together with a test of the isospin invariance of the data set available on pion-proton scattering in the investigated momentum range. The transversity isodoublet amplitudes at 1.98 and 2.07 GeV/ c are reconstructed. The obtained data, the isospin analysis and amplitude reconstruction results are compared with the current phase-shift analysis predictions.
No description provided.
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NAME=THEORY DENOTES THE MONTE-CARLO GENERATED CROSS SECTIONS.
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Axis error includes +- 0.0/0.0 contribution (DUE TO QUAZIELASTIC BACKGROUND AND ERRORS IN POLARIZATION OF BEAM AND TARGET).
Axis error includes +- 0.0/0.0 contribution (DUE TO QUAZIELASTIC BACKGROUND AND ERRORS IN POLARIZATION OF BEAM AND TARGET).
Axis error includes +- 0.0/0.0 contribution (DUE TO QUAZIELASTIC BACKGROUND AND ERRORS IN POLARIZATION OF BEAM AND TARGET).
We have measured absolute differential cross sections and analyzing powers for neutron-proton elastic scattering for momentum transfer 0.01 < | t |< 0.08 (GeV/ c ) 2 at several energies between 378 and 1135 MeV. The ionization chamber IKAR filled with methane was used as both a gas target and recoil detector. For the analyzing-power measurements the scattered neutron was detected in scintillation counters in coincidence with the recoil proton detected in IKAR. Special care was taken to ensure a precise absolute normalization of the cross sections, with overall systematic uncertainties of 4–7%.
TOTAL SYSTEMATIC UNCERTAINTIES IN D(SIG)/D(T)=6.4 PCT.
TOTAL SYSTEMATIC UNCERTAINTIES IN D(SIG)/D(T)=5.4 PCT.
TOTAL SYSTEMATIC UNCERTAINTIES IN D(SIG)/D(T)=6.5 PCT.
Results are presented on the exclusive production of four-prong final states in photon-photon collisions from the TPC/Two-Gamma detector at the SLAC e+e− storage ring PEP. Measurement of dE/dx and momentum in the time-projection chamber (TPC) provides identification of the final states 2π+2π−, K+K−π+π−, and 2K+2K−. For two quasireal incident photons, both the 2π+2π− and K+K−π+π− cross sections show a steep rise from threshold to a peak value, followed by a decrease at higher mass. Cross sections for the production of the final states ρ0ρ0, ρ0π+π−, and φπ+π− are presented, together with upper limits for φρ0, φφ, and K*0K¯ *0. The ρ0ρ0 contribution dominates the four-pion cross section at low masses, but falls to nearly zero above 2 GeV. Such behavior is inconsistent with expectations from vector dominance but can be accommodated by four-quark resonance models or by t-channel factorization. Angular distributions for the part of the data dominated by ρ0ρ0 final states are consistent with the production of JP=2+ or 0+ resonances but also with isotropic (nonresonant) production. When one of the virtual photons has mass (mγ2=-Q2≠0), the four-pion cross section is still dominated by ρ0ρ0 at low final-state masses Wγγ and by 2π+2π− at higher mass. Further, the dependence of the cross section on Q2 becomes increasingly flat as Wγγ increases.
UNTAGGED DATA.
TAGGED DATA, RESULTS OBTAINED USING TRANSVERSE-TRANSVERSE LUMINOSITY ONLY. DATA FOR Q2=0 ARE FROM UNTAGGED SAMPLE, ERRORS DUE TO RELATIVE NORMALISATION OF THESE SAMPLES IS INCLUDED INTO ERRORS QUOTED.
UNTAGGED DATA.
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No description provided.
We report cross sections for the process γγ→pp¯ at center-of-mass energies W from 2.0 to 2.8 GeV. These results have been extracted from measurements of e+e−→e+e−pp¯ at an overall center-of-mass energy of 29 GeV, using the TPC/Two-Gamma facility at the SLAC storage ring PEP. Cross sections for the untagged mode [both photons nearly real] are shown to lie well above QCD predictions. Results are also presented for the single-tagged mode [one photon in the range 0.16<Q2<1.6 (GeV/c)2].
Data read from graph in preprint. Statistical errors only.
Data read from graph. Statistical errors only.
Data read from graph. Statistical errors only.
The differential cross section in free n-p forward elastic scattering has been measured for incident neutron energies of 378, 481, 582, 683, 784, 884, and 1085 MeV and for momentum transfer 0.01<‖t‖<0.08 (GeV/c)2. The experiment used a recoil-detector ionization chamber which served at the same time as a gas target. Special care has been taken to obtain a precise absolute normalization.
No description provided.
No description provided.
No description provided.