The inclusive production cross sections of pions, kaons, protons, and antiprotons in p p and pp interactions at √ s =53 GeV are compared in the kinematic range | y | < 0.8 and p T < 1.5 GeV/ c . We observe differences in the K + /K − and p /p ratios for the two data samples. Although the bulk of the particles are produced with the same momentum and rapidity distributions in p p and pp collisions, we observe difference in these distributions for produced protons and antiprotons.
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We have studied the inclusive production of the hadrons π ± , K ± , p, p , Λ, Λ , ρ and ⋉ in the central region at the ISR s = 53 GeV , in both pp and p p collisions. Differences are observed only for K ± , p, and p production. We then study also correlations between low- p T pp and p p pairs in the two types of collisions, separating the contribution from baryon pair production and from the incident particles (stopping protons). We observe a positive correlation between two stopping protons; between the production of two pairs, and between a stopping proton and a pair production, there are negative correlations.
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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 studied the processpp→γγ+X at\(\sqrt s= 63 GeV\) GeV in the central rapidity region. We report a positive signal at 96% C.L., a ratio γγ/e+e−=4.0±3.0 when the transverse momentum of each photon is above 2 GeV/c, and a cross-sectiondσ/dydMγγ=(5.5±2.7)×10−34 cm2/GeV when |y|<0.5,4<Mγγ<6 GeV.
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Using annihilation in a calorimeter as a trigger on antiprotons, we have measured the relative production cross sections of p , Λ and Ξ at y∼0 in the transverse momentum range 1 to 2 GeV/ c in pp collisions at √ s =63 GeV. We investigate correlations between the antibaryons and associated produced particles, and find evidence for local baryon number conservation.
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Bose-Einstein correlations between pions produced in the central region of rapidity in αα, pp and p p interactions have been studied at the ISR. The parameters r and τ c -often interpreted as the radius and depth of the π-emitting region - are found to be independent of incident particle type but to depend on the mean charged multiplicity. In high multiplicity events, the pions appear to originate from a larger space-time region.
FOR DEFINITION OF R++ SEE PAPER.
FOR DEFINITION OF R++ SEE PAPER.
FOR DEFINITIONS OF R++ AND TAU*C SEE PAPER.
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 the production of one and two large transverse momentum hadrons in p p and pp interactions in the range 2 < p T < 6 GeV/ c for the central rapidity region |y| < 0.9 at s = 63 and 31 GeV . No statistically significant difference between p p and pp collisions is observed. The results are in accordance with lowest order QCS perturbative calculations and rule out a large contribution of Constituent Interchange Model (CIM), di-quark of quark-fusion subprocesses in this kinematic range.
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The production of direct photons has been measured relative to π 0 's in the rapidity range 2.00 < y < 2.75 in pp collisions at s = 63 GeV at the CERN Intersecting Storage Rings. The γ/π 0 ratio increases from ⪅2% at p T = 1.5 GeV/ c to ∼8% at p T = 4.25 GeV/ c , similar to the value observed near 90°. The results indicate no strong enhancement of single-photon production due to quark bremsstrahlung in this kinematic region.
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The inclusive production of η-mesons in pp collisions at √ s =63GeV and ϑ CM =90° has been measured for p T <1.5GeV/c. The η/π ratio decreases from its previously measured asymptotic value of η/π ∼ 0.5 at high transverse momentum, to η/π ≈0.3 at P T = 750MeV/c and η/π ≈ 0.01 at P T =300MeV/c, in a way that consistent with phase-space considerations, e.g. m T scaling. The η/π ratio, integrated from 0.2–1.5 GeV/ c , is found to be η/π=0.07±0.055.
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