We have performed a simultaneous measurement of the large transverse momentum (1.6 to 3.8 GeV/ c ) yields of single photons and of photon pairs at 90° production angle in pp collisions at ISR energies. Production cross sections for each of these two processes are compared.
Measurements of the double differential cross sections for ππ and pπ production in pp collisions at the CERN ISR are presented for 5 c.m. energies s = 22, 30, 44, 53, 62 GeV . Charge and transverse momentum correlations are also reported.
We report on measurements of inclusive π 0 production at c.m. energies of 53 and 63 GeV, θ ≅90°, from p-p collisions at the CERN ISR. In the range 0.2< x t <0.45 the data can be described by a form: Ed 3 σ d p 3 ∝p − (6.6±0.8) t (1−x t ) (9.6±1.0) .
Data on inclusive jet production in the transverse-momentum (p⊥) range 0-8 GeV/c for 200-GeV/c p, π−, π+, K−, K+, and p¯ incident on a hydrogen target are presented. The jet cross section is fully corrected for losses and biases, and compared with the predictions of a model based on quantum chromodynamics. Both the absolute cross section and the inclusive charged-particle distributions inside and outside the jet are in qualitative agreement with the model.
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.
Measurements are presented of the inclusive π 0 production cross section, in the transverse momentum range 2.3 ⪅ p T ⪅4.5 GeV/c, for dd and dp interactions at total c.m. energies of √ s = 52.7 GeV and √ s = 63.2 GeV and for pp interactions at √ s = 52.7 GeV. The produced π 0 's are detected by identifying both protons from the decay π 0 → γγ . As in pp interactions, the data can be adequately described by a p T −n ƒ(x T ) dependence with n ≌ 8 . The data are approximately consistent with the expectations of free nucleon scattering. No significant differenceare observed in either the charged or the neutral particle distributions associated with π 0 , for dd, dp and pp interactions.
We report the results of an experiment made at the CERN ISR to investigate the possible diret production of single photons in pp collisions at √ s = 53.2 GeV at 90° and in the p t interval 2.3 to 5.7 GeV/ c . The value of the ratio R = n γ / n π 0 is compatible with zero for low p t ⪅ 3 GeV/ c but, in spite of the large error, shows a trend to increase for larger p t .
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.
The inclusive cross section for larger p T π 0 production near 90° in p-p collisions at the CERN ISR is presented for centre-of-mass energies 30.7, 53.1 and 62.4 GeV. The data are inconsistent with scaling of the form p T − n F ( x T ), with constant n or with n allowed to depend on x T = 2p T / s . For s = 53.1 and 62.4 GeV , the value of n found for 3.5 < p T < 7.0 GeV/ c is n = 8.0 ± 0.5, in agreement with previous experiments. However, for 7.5 < p T < 14.0 GeV/ c the value becomes n = 5.1 ± 0.4.
As part of a study of large p T phenomena in photon-proton collisions at the CERN ISR, a search for direct single photon production has been performed. A statistical division of the data sample into the fraction consistent with single photon and the fraction due to multiphoton decays of neutral hadrons is accomplished by measuring the average conversion probability for the sample in a one radiation length thick converter. The fraction of the sample attributable to direct single photon production is 〈 γ /all〉 = 0.074 ± 0.012 for 6 GeV/ c < p T 10 GeV/ c , and 〈 γ /all〉 = 0.26 ± 0.04 for p T > 10 GeV/ c , with an additional systematic uncertainty of ±0.05 for both values.
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