The cross section for the production of π+π− or K+K− pairs in γγ interactions is measured for mππ between 1.7 and 3.5 GeV/c2 and for two intervals of γγ center-of-mass scattering angle. Results are compared with predictions of a QCD model.
Data read off graph.
Data read off graph.
Antiproton-proton and proton-proton small-angle elastic scattering was measured for centre-of-mass energies s =30.6, 52.8 and 62.3 GeV at the CERN Intersectung Storage Rings. In addition, proton-proton elastic scattering was measured at s =23.5 GeV . Using the optical theorem, total cross sections are obtained with an accuracy of about 0.5% for proton-proton scattering and about 1% for antiproton-proton scattering. The measurement of the interference of the Coulomb scattering and the hadronic scattering permits a determination of the ratio of the real-to-imaginary part of the forward hadronic scattering amplitude. Also presented are measurements of the hadronic slope parameter.
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Proton-antiproton elastic scattering was measured at the center-of-mass energy s =546 GeV in the four-momentum transfer range 0.45⩽−⩽1.55GeV 2 . The shape of the t -distribution is quite different from that observed in proton-proton scattering at the ISR. Rather than a dip-bump structure, a kink is present at − ≈0.9GeV 2 followed by a shoulder. The cross section at the second maximum is more than one order of magnitude higher than at the ISR.
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Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
We have measured the coherent nuclear production of π+ω systems at 202.5 GeV. This final state is dominated by the B+(1235) meson with a measured mass and full width of 1.271 ± 0.011 GeV and 0.232 ± 0.029 GeV, respectively. A radiative width of 230 ± 60 keV was extracted for the process B+(1235)→π+γ.
DATA REQUESTED FROM THE AUTHORS.
We present measurements of the αα elastic scattering differential cross section at √ s = 126 GeV in the range 0.05 ⩽ ‖ t ‖
ERRORS ARE STATISTICAL ONLY.
EXPONENTIAL FIT TO CROSS SECTION BELOW T = 0.075 GEV**2.
OPTICAL THEOREM CALCULATION OF THE TOTAL CROSS SECTION ASSUMING RHO IS ZERO.
We have measured the coherent nuclear production of low-mass K+ω systems in K+A collisions at 202.5 GeV. Results for carbon, copper, and lead targets are similar to those found for π+π+π− production in π+A reactions at the same energy.
M(K+ OMEGA) < 1.5 GEV.
Results are presented from experiment WA7 at the CERN SPS, which has measured the elastic differential cross sections of π ± p, K ± p, p p and pp at incident momen ta of 20, 30 and 50 GeV/ c . The measurements cover the momentum transfer range 0.5 < | t | < 8 (GeV/ c ) 2 , corresponding to c.m. scattering angles between 10° and 50°. The experimental set-up, trigger logic and data analysis are described. The experimental results are compared with existing meson-proton and nucleon-proton data at lower and higher energies covering the medium- and large-| t | region. Some prominent models and their predictions for elastic scattering at WA7 energies and beyond are reviewed, with emphasis on geometrical scaling, factorizing eikonal models, lowest-order QCD and other dynamical exchange-type models. Results for p p two-body annihilation into π − π + and K − K + at 30 and 50 GeV/ c , obtained in parallel with the elastic p p data, are also presented.
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A study of ϕ-meson photoproduction by partially polarized photons of energy 20–40 GeV is reported. The production mechanism is found to conserves-channel helicity and to proceed via natural-parity exchange in thet channel. In the photoproduction of high-massK+K− states with photons of energy 20–70 GeV, there is evidence for an enhancement at a mass of 1.76 GeV with width 0.08 GeV.
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The reactionγp→π+π−π0π0p (excludingωπ0 production) has been studied for photon energies in the range 20–70 GeV. A peak is seen in the 4π mass spectrum at ∼1.66 GeV with a width of ∼0.3 GeV which is identified with theρ′(1600). Maximum likelihood fits show that the peak is dominantly inρ±π∓π0 withB(ρ′→ρ0π0π0)/B(ρ′→ρ±π∓π0)<0.1. This indicates anI=1ρπ final-state interaction. However, no evidence is found for any resonant ρπ state such as anA1 orπ′.
AFTER OMEGA EXCLUSION.
ERROR IS DOMINANTLY SYSTEMATIC.