Qausi-elastic ω production by ep scattering in the kinematic region 0.3. < Q 2 < 1.4 GeV 2 and 1.7 < W < 2.8 GeV was studied using a streamer chamber at DESY. The production angular distribution for γ V p → ω p has a strong non-peripheral component for W < 2 GeV. The ω production cross section falls by a factor of 4 as W changes from 1.7 to 2.8 GeV. In contrast the cross section for ω production with | t | < 0.5 GeV 2 is W independent between 1.7 and 2.8 GeV and for W > 2.0 GeV consistent in both W and Q 2 dependence with the predictions of a model based on one-pion exchange and diffraction.
FOR ALL T-VALUES. THE GAMMA* P TOTAL CROSS SECTION WAS TAKEN FROM A FIT TO THE DATA OF S. STEIN ET AL., PR D12, 1884 (1975). 'PPD'.
'PPD'. PERIPHERAL OMEGA PRODUCTION.
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As part of a program of measurements of the πp system we have measured the backward differential cross section for π+p elastic scattering at 16 momenta from 1.25 to 2.0 GeV/c inclusive. The angular region covered is -0.46 to -0.97 in cosθc.m.. The high resolution in u of 0.03 to 0.04 (GeV/c)2, together with good statistics, enables a detailed examination of the momentum and angular dependence of structure in this channel. The data are compared with distributions from other experiments and with the most recent phaseshift fit.
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New data on the K−p elastic and charge exchange reactions are presented in the K− momentum range between 1.934 GeV/c and 2.516 GeV/c. A conventional energy-dependent partial-wave analysis covering the widerPK- range from 1.6 GeV/c to 2.516 GeV/c is presented together with a p.w.a. in which the duality ands-helicity conservation ideas are explicitly imposed in the fits. Finally the new Y*’s observed in this experiment are classified inSU3 multiplets.
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We present the results of a bubble chamber study of the pure-isospinI = 0 reaction K−p → ωΛ at 7 incident momenta between 1.934 and 2.516 GeV/c. An energy-dependent partial-wave analysis in the c.m. energy range (2070 ÷ 2436) MeV including these new data confirms the coupling of theG7 Λ(2100) to this channel and yields evidence for the existence of a new resonant stateD3or P3 Λ(2325). A semi-energy-independent partial-wave analysis is also carried out, by means of all available data from the threshold of the K−p → ωΛ reaction up to 2436 MeV. This supplies clear and unambiguous evidence for the contribution of the knownP3 Λ(1860) and of the above-proposedD3 Λ(2325) to the ωΛ channel.
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The reaction γ V p → p π + π − was studied in the W , Q 2 region 1.3–2.8 GeV, 0.3–1.4 GeV 2 using the streamer chamber at DESY. A detailed analysis of rho production via γ V p→ ϱ 0 p is presented. Near threshold rho production has peripheral and non-peripheral contributions of comparable magnitude. At higher energies ( W > 2 GeV) the peripheral component is dominant. The Q 2 dependence of σ ( γ V p→ ϱ 0 p) follows that of the rho propagator as predicted by VDM. The slope of d σ /d t at 〈 Q 2 〉 = 0.4 and 0.8 GeV 2 is within errors equal to its value at Q 2 = 0. The overall shape of the ϱ 0 is t dependent as in photoproduction, but is independent of Q 2 . The decay angular distribution shows that longitudinal rhos dominate in the threshold region. At higher energies transverse rhos are dominant. Rho production by transverse photons proceeds almost exclusively by natural parity exchange, σ T N ⩾ (0.83 ± 0.06) σ T for 2.2 < W < 2.8 GeV. The s -channel helicity-flip amplitudes are small compared to non-flip amplitudes. The ratio R = σ L / σ T was determined assuming s -channel helicity conservation. We find R = ξ 2 Q 2 / M ϱ 2 with ξ 2 ≈ 0.4 for 〈 W 〉 = 2.45 GeV. Interference between rho production amplitudes from longitudinal and transverse photons is observed. With increasing energy the phase between the two amplitudes decreases. The observed features of rho electroproduction are consistent with a dominantly diffractive production mechanism for W > 2 GeV.
DIPION CHANNEL CROSS SECTION.
THE TOTAL CROSS SECTION WAS OBTAINED BY THE AUTHORS FROM A FIT TO THE SINGLE ARM DATA OF S. STEIN ET AL., PR D12, 1884 (1975).
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Elastic and inelastic scattering of 1.044 GeV protons have been studied on isotopically enriched even 40, 42, 44, 48 Ca isotopes and 48 Ti. A spin independent Glauber theory analysis of the elastic scattering allowed the extraction of neutron and nuclear matter densities for these targets.
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We present the results of a formation experiment for the reactions K±p→Σ±π± in the c.m.s. energy between 2200 and 2436 MeV with a total statistics of 10 ev/μb. A partial-wave analysis including these new data gives evidence for the existence of three resonances in theD15,G19 andH09 states and confirms the existence of anF05 state.
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Measurements of the differential cross sections for π−d elastic scattering in the backward angular region are presented. These measurements were made at thirteen incident-pion momenta ranging from 496 to 1050 MeV/c, over the center-of-mass angular range 148° to 177°. The experiment was performed at the LBL Bevatron. Experimental apparatus consisted of a liquid deuterium target and a double-arm spectrometer which included scintillation-counter hodoscopes. Center-of-mass differential cross sections were found to be generally smooth over the angular range covered and can be fitted with low-order polynomials. The extrapolated differential cross sections at 180° scattering angle were found to decrease rapidly with increasing momentum, with a prominent peak near 700 MeV/c and a shoulder near 900 MeV/c. These data are discussed in terms of existing models employing "d*" structures, and are compared with other similar measurements.
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The differential cross section for π ± p elastic scattering below 2 GeV/ c has been measured at small forward pion angles by an electronics experiment. The interference effects observed between the Coulomb and the nuclear interaction have been used to determine the magnitude and sign of the real parts of the π ± p forward scattering amplitude. The latter are compared to the values predicted by the dispersion relations.
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The K − p reactions with final states Λπ 0 , Σ 0 π 0 , Λπ 0 π 0 , Λη and Σ 0 η have been studied at 14 momenta between 685 and 934 MeV/ c using optical spark chambers. The charged decay products of the Λ are detected by low mass spark chambers while γ-rays from π 0 and Σ 0 decays are detected in high mass chambers. Approximately 250 000 photographs were analysed from which partial and differential cross sections were determined. These results are presented with an energy dependent, single channel partial-wave analysis.
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