Results on photoproduction of π + π − π 0 in the photon energy range 20–70 GeV are presented. For the ω meson, the production cross-section is found to be 1010±15 (statistical)±290 (systematic) nb and is constant over the incident photon energy range. Spin-density matrix elements are evaluated for ω meson production. The φ meson is observed with a total photoproduction cross section (corrected for branching ratio to π + π − π 0 ) of 610±35±170 nb. A third resonance, at 1.67 GeV, is seen in the mass spectrum and its interpretation is discussed. The production of a broad π + π − π 0 continuum, mainly via ϱπ, and peaking at 1.2 GeV, contributes with a cross section of about 2.5 ωb. The spin-parity content is analysed by the moments of the π + π − π 0 decay angular distribution in the helicity frame and by maximum likelihood fits to the π + π − π 0 Dalitz plot. It is found that production of J P = 1 − states accounts for less than half of the total mass spectrum above 900 MeV. There is a broad enhancement in the 1 + wave around 1.15 GeV indicating photoproduction of the H(1190) meson.
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EXPONENTIAL FITS TO D(SIG)/DT IN OMEGA MASS REGION.
EXPONENTIAL FITS TO D(SIG)/DT OVER FULL ENERGY FOR THREE MASS REGIONS CORRESPONDING TO OMEGA, PHI AND OMEGA*.
Antiproton-proton and proton-proton small-angle elastic scattering have been measured for centre-of-mass energies √ s = 30.7 and 62.5 GeV at the CERN Intersecting Storage Rings (ISR). Antiproton-proton and proton-proton total cross sections are obtained using the optical theorem. The measurement of the Coulomb scattering and its interference with the nuclear scattering allows a determination of the ratio of the real-to-imaginary part of the forward nuclear scattering amplitude. Also presented are measurements for the nuclear slope parameter at √ s = 62.5 GeV. Our new results reinforce the conclusions drawn recently from our measurements at √ s = 52.8 GeV. In particular, the pp̄ total cross section is rising at ISR energies and should continue to rise well beyond these energies.
DATA REQUESTED FROM AUTHORS.
RESULTS OF FITS.
RESULTS OF FITS.
Proton-antiproton elastic scattering at CM energy 540 GeV has been studied in the t -range 0.04 < − t < 0.45 GeV 2 . The data are well fitted by the form exp ( bt ) with b = 17.1 ± 1.0 GeV −2 for | t | = 0.04 − 0.18 GeV su 2 and b = 13.7 ± 0.2 ± 0.2 GeV −2 for | t | = 0.21−0.45 GeV 2 . A luminosity measurement combined with the optical theorem gives σ tot = 67.6 ± 5.9 ± 2.7 mb and σ e1 / σ tot = 0.209 ± 0.018 ± 0.008.
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ELASTIC RATIO ASSUMES RHO=0.
Proton-antiproton elastic scattering was measured at a centre of mass energy s = 540 GeV . In the four-momentum transfer range 0.21 < − t < 0.50 GeV 2 the t -distribution of about 7000 events is well represented by the exponential shape exp ( bt ) with slope parameter b = 13.7 ± 0.3 GeV −2 . A new measurement of the slope for − t < 0.19 GeV 2 confirms our earlier result, giving evidence for a change of slope of about 4 GeV −2 around − l ̷ ≈ 0.15 GeV 2 .
NUMERICAL VALUES OF LOW T DATA GIVEN IN BOZZO 84. STATISTICAL ERRORS ONLY.
NUMERICAL VALUES OF MEDIUM T DATA TAKEN FROM BOZZO 84. THESE ARE THE EARLIER (BATTISTON 83) VALUES RENORMALISED TO THE NEW LOW T DATA IN THE OVERLAP REGION. ERRORS ARE STATISTICAL ONLY.
SLOPE VALUES FROM BATTISTON 83.
The np elastic differential cross section has been measured for incident neutron momenta 100–400 GeV/ c in the | t | range 6 · 10 −6 − 5 · 10 −1 (GeV/ c ) 2 . The np data of this experiment provide a first direct measurement of the hadronic amplitude for | t | < 10 −2 (GeV/ c ) 2 , which is consistent with the extrapolations from higher | t | values. Our data for | t | < 10 −4 (GeV/ c ) 2 are consistent with a rise which can be attributed to Schwinger scattering, caused by the interaction of the neutron magnetic moment with the proton.
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TheΞ-p differential elastic cross section has been measured in the SPS hyperon beam at 102 and 135 GeV/c. In the range 0.01<−<0.42(GeV/c)2, thet distributions are found to be compatible with the formA exp(Bt) whereB is 7.7±0.4(GeV/c)−2 at 102 GeV/c and 8.2 ±0.5(GeV/c)−2 at 135 GeV/c. The corresponding total elastic cross sections areσel=4.9±0.7 mb andσel=5.6±0.9 mb, respectively. These results are compared with the predictions of phenomenological models.
NUMERICAL VALUES OF DATA SUPPLIED BY P.ROSSELET.
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We have studied the reactionspp→ppπ+π-,K+p→K+pπ+π−π, π+p→ π+,pπ+π− and π−p →π+π− at 147 GeV/c using the 30-inch Fermilab hybrid system. All four reactions were detected with the same apparatus and analyzed in the same way. The energy dependence of the channel cross section was found to beAp−0.6+B for thepp reaction andAp−1+B for the other three. About 90% of the cross section at 147 GeV/c can be accounted for by either beam or target diffraction. Some of the remaining cross section may come from double Pomeron exchange reactions which we tried to isolate. We have tested the hypothesis of a factorizable Pomeron and our data indicates a violation of this hypothesis. We show that the 3π mass enhancement in the mass region 1.2–1.4 GeV is diffractively produced in the π± beam reactions. Fourprong, four-constraint and six-prong, four-constraint cross sections are reported.
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CROSS SECTIONS FOR DIFFRACTION DISSOCIATION OF BEAM. FEYNMAN X OF OUTGOING PROTON <-0.96.
We present results of a hybrid-bubble-chamber experiment examining the reaction π+p→π+pK+K− at an incident momentum of 11.46 GeV/c. The total cross section for this channel is determined to be 87.2±6.4 μb. A partial-wave analysis of the K+π+K− system reveals no unambiguous evidence of resonant activity, although mass enhancements are noted in the JP=0− κ¯K+ (S wave), JP=2− fπ (S wave), and JP=2−, K¯*0(892)K+ (P wave). This is the first published report of the relative phases of the waves seen in this reaction. We comment on the influence this channel may have on A1 and A3 production.
NOTE ERROR IN ABSTRACT IS +- 6.4 BUT TEXT QUOTES +- 9.3. FIGURE LOOKS CLOSER TO +- 6.4.
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Differential cross sections for π − p and pp elastic scattering have been measured at incident momenta ranging from 30 to 345 GeV and in the t range 0.002 (GeV/ c ) 2 ⩽ | t | ⩽ 0.04 (GeV/ c ) 2 . From the analysis of the data, the ratio ϱ ( t = 0) of the real to the imaginary parts of the forward scattering amplitude was determined together with the logarithmic slope b of the diffraction cone.
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Proton-antiproton and proton-proton elastic scattering have been measured in the four-momentum transfer range 0.001⩽| t |⩽0.06 GeV 2 for center-of-mass energy 52.8 GeV at the CERN Intersecting Storage Rings (ISR). Using the known pp total cross section, a simultaneous fit to the pp̄ and pp differential cross sections yields the pp̄ total cross section; in addition, we obtain the ratio of the real-to-imaginary part of the forward nuclear-scattering amplitude and the nuclear-slope parameter for both pp̄ and pp. Our results show conclusively that the pp̄ total cross section is rising at ISR energies and lend support to conventional theories in which the difference between the pp̄ and pp total cross section vanishes at very high energy.
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RESULTS OF FIT.
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