Data are presented on the reaction pp → pX in the range of four-momentum transfer squared 0.04< − t <0.80 GeV 2 and of c.m. energy squared 550 < s < 3880 GeV 2 . Invariant cross sections are given as a function of M 2 / s , where M is the mass of the missing system X, and of t . The cross sections are shown to scale in the variable M 2 / s , for M 2 / s > 0.01. The total diffractive cross section integrated over t and M 2 / s up to M 2 / s =0.05 rises by approximately 15% from σ dif =6.5±0.2 mb at 550 GeV 2 to σ dif =7.5±0.3 mb at 3880 GeV 2 .
The inclusive production of charged hadrons in the collisions of quasi-real photons e+e- -> e+e- +X has been measured using the OPAL detector at LEP. The data were taken at e+e- centre-of-mass energies from 183 to 209 GeV. The differential cross-sections as a function of the transverse momentum and the pseudorapidity of the hadrons are compared to theoretical calculations of up to next-to-leading order (NLO) in the strong coupling constant alpha{s}. The data are also compared to a measurement by the L3 Collaboration, in which a large deviation from the NLO predictions is observed.
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We present the first direct measurements of charged-particle multiplicity distributions for pp collisions at ISR energies. The measurements are performed by means of a streamer chamber detector with large solid-angle coverage and excellent multitrack efficiency. Particle densities are observed to rise in the central region as s increases. The multiplicity distributions in this region deviate from a Poisson Law, thus giving evidence for correlations. These correlations are of the same type as those obtained from clustering of the collision products. The mean charged multiplicity over the full rapidity range increases faster than log s . Our data do not support an early onset of KNO multiplicity scaling.
Charged- and neutral-particle production from 400-GeV/c pp collisions are measured simultaneously using the Fermilab 15-ft bubble chamber. The π0 and K0 cross sections are rising at Fermilab energies, while the Λ0 cross section remains fairly constant. Similarly, the average number of π0's and K0's increases as a function of the number of negative particles in an event, yet no such dependence is noted for the Λ0's. The ratio of average number of π0 to average number of π− per inelastic collisions is found to be constant at Serpukhov and Fermilab energies (40 to 400 GeV/c) and equal to 1.22±0.02. Cross sections for Σ0 and Σ¯0 production are measured and limits are found for η0 and ω0 production. Neutral- and charged-pion correlations are compared with five pion-production models.
The inclusive production of ϱ 0 mesons in pp collisions has been measured at five c.m. energies from √ s = 23.6 to 63.0 GeV. The cross sections and the production spectra as a function of transverse momentum and rapidity are discussed.
The NA50 Collaboration has measured heavy-quarkonium production in p-A collisions at 450 GeV incident energy (sqrt(s) = 29.1 GeV). We report here results on the production of the Upsilon states and of high-mass Drell-Yan muon pairs (m > 6 GeV). The cross-section at midrapidity and the A-dependence of the measured yields are determined and compared with the results of other fixed-target experiments and with the available theoretical estimates. Finally, we also address some issues concerning the transverse momentum distributions of the measured dimuons.
We report on χc1 and χc2 production in the Feynman-x range 0.1<xF<0.8 in 515GeV/c π−Be collisions. The χc states are observed via their radiative decays into J/ψ's. The resulting photons are detected either as showers in the electromagnetic calorimeter or after conversion in the target as e+e− pairs in the tracking system. The fraction of J/ψ production due to χc1 and χc2 decays is 0.443±0.041±0.035. The ratio of the χc1 to χc2 cross section is 0.57±0.18±0.06. Our results on J/ψ, ψ(2S), and χc production indicate that 0.454±0.044±0.042 of J/ψ's are produced directly.
Muon pair production in p-A, S-U and Pb-Pb collisions has been studied by the NA38 and NA50 collaborations at the CERN SPS. In this paper we present an analysis of the dimuon invariant mass region bet
Large transverse energy cross sections of 300 GeV/ c pions and protons on hydrogen have been measured with a segmented calorimeter covering the central rapidity region −0.88 < y < 0.67 and 2 π in azimuth. The selected events show large multiplicities and no jet-like event structure. Processes more complicated than the scattering of two constituents appear to dominate these inelastic collisions.
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