The inclusive π0 production cross-section and the η/π0 ratio have been measured inpp collisions at\(\sqrt s= 63 GeV\) at the CERN Intersecting Storage Rings in the rapidity range 2.00<y<2.75. The π0 cross-section exhibits a strongy-dependence and falls more steeply as a function ofpT, compared with the cross-section measured aty∼0. We find a value of 0.46±0.07 for the η/π0 ratio with no significantpT dependence over the range 2.0<pT<4.0 GeV/c.
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We present data obtained from a 1.7 sr hadron calorimeter, triggered on transverse energy, in pp collisions at s =63 GeV at the CERN-ISR. From the change in the distribution of energy in the calorimeter, we extract the cross section for two-constituent hard scattering for p T between 6 and 14 GeV at y = 0. The decrease of this jet cross section over this p T range is consistent with exp (− bp T ), with b = (1.02 ± 0.09) GeV −1 . The slope and normalization of the cross section agree well with a QCD motivated Monte Carlo model. The ratio between jet and single particle cross sections [ dσ JET / dp T )/( dσ π 0 / dp T )]| y = 0 changes from about 200 at 6 GeV to about 1500 at 14 GeV.
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We have measured transverse momentum spectra up to 10 GeV/ c for charged particles produced centrally in proton-antiproton collisions at 540 GeV in the centre of mass at the CERN collider. Our results are compared with data at ISR energies and with the predictions of a QCD model. The charged particle spectrum shows a clear dependence on charged track multiplicity.
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The production of charged hadrons with high p T in αα collisions at √ s =126 GeV and pp collisions at √ s =31 and 63 GeV is compared, and the structure of the events associated with the high- p T particles is studied. The probability of finding associated particles close to the trigger particle increases strongly between √ s =31 and 63 GeV for pp collisions. For p T >2.5GeV/ c the αα/pp cross section ratio at the same energy per nucleon is measured to be 18.7 ± 2.0, to be compared with A 2 = 16, and a higher associated multiplicity is observed for αα.
FIRST PP DATA IS AT SQRT(S)=31 AND THE SECOND PP DATA IS AT 63 GEV.
Production of ϱ 0 , K ∗0 , K ∗0 , and φ have been measured in proton-proton collisions at the CERN Intersecting Storage Rings (ISR) at low p T in the central region. The transverse mass spectra are well described by exp (− aμ T ), with a = −6.4±0.2 GeV −1 . The cross sections for d σ/ d y| y=0 are 6.5±0.8±1.2 mb for ϱ 0 , 1.9±0.3±0.3 mb for K ∗) , 1.9±03±03 mb for K ∗0 , and 60.±0.12±0.13 mb for φ , where the first error is statistical and the second is sytematic.
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Inclusive π 0 production has been measured at the CERN Intersecting Storage Rings in αα and α p collisions near 90°, for p T between 2 and 5 GeV/c. The differential cross sections show a slower exponential fall-off with p T than has been observed in pp collisions at the corresponding nucleon-nucleon centre-of-mass energies at large p T . The ratio of the π 0 production cross sections for αα collisions to those for pp collisions is observed to be larger than 16.
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The inclusive production of neutral kaons in 70 GeV/ c K + p interactions is studied with the CERN BEBC bubble chamber. The (semi-)inclusive cross sections are interpreted in terms of the various strangeness channels leading to neutral kaon production. The invariant inclusive cross section for kaon production is studied as a function of p t 2 and the Feynman variable x . The latter distributions are considered both “raw” and corrected for the presence of K 0 's resulting from K ∗ decay. They are compared with the predictions expected from the Regge-Mueller formalism, the recombination model and fragmentation models.
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The inclusive cross-section for π0 production near 90° inpp collisions at the CERN Intersecting Storage Rings has been studied for thepT range 3<pT<16GeV/c at four different centre-of-mass energies (\(\sqrt s = 30.6\), 44.8, 52.7, and 62.8 GeV). In this experiment the two photons from the π0→yy decay were resolved and measured separately forpT values up to 10 GeV/c. Results indicate an agreement with thepT−8 behaviour for the lower values ofpT and a slower decrease of the cross-section for the higher values ofpT. The high-pT data deviate from the scaling expressionpT−nF(xT), which holds for the lowerpT values (pT<8GeV/c).
USING RETRACTED GEOMETRY.
USING SUPER-RETRACTED GEOMETRY.
USING SUPER-RETRACTED GEOMETRY.
Inclusive π 0 production at 90° has been studied at the ISR at s 1 2 = 52.7 and 62.4 GeV over the p T range from 7 to 15 GeV/ c . The two photons from π 0 decay yielded overlapping electromagnetic showers in the liquid-argon-Pb plate calorimeter detector system. Any direct photon production is included in these measurements. For large values of p T , the cross section is observed to decrease with p T more slowly than the p T −8 behaviour which has been observed at lower values of p T .
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The inclusive η production cross section at the CERN ISR has been measured for p T values of up to 11 GeV/ c . We find that the η π 0 cross-section ratio has an average value of 0.55 ± 0.07 and varies little with p T .
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