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.
Hadronic event shapes have been measured in proton-proton collisions at sqrt(s)=7 TeV, with a data sample collected with the CMS detector at the LHC. The sample corresponds to an integrated luminosity of 3.2 inverse picobarns. Event-shape distributions, corrected for detector response, are compared with five models of QCD multijet production.
The relative yields of kaons and protons compared with the yield of pions at highpT and polar angles θ away from 90° (in the range from 10° to 45°) are presented forpp, dd, and αα interactions at a centre-of-mass energy\(\sqrt {s_{NN} }= 31\) GeV per nucleon-nucleon collision. The measured particle ratios depend on the atomic mass numberA of the beam particles and on θ. TheA dependence of the ratios becomes stronger for largerpT and is more pronounced at smaller polar angles.
Event-shape variables, which are sensitive to perturbative and nonperturbative aspects of quantum chromodynamic (QCD) interactions, are studied in multijet events recorded in proton-proton collisions at sqrt(s) = 7 TeV. Events are selected with at least one jet with transverse momentum pt > 110 GeV and pseudorapidity abs(eta) < 2.4, in a data sample corresponding to integrated luminosities of up to 5 inverse femtobarns. The distributions of five event-shape variables in various leading jet pt ranges are compared to predictions from different QCD Monte Carlo event generators.
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