The ρ0-meson spin alignment is studied in p¯p interactions at 22.4 and 12 GeV/c and in the reaction p¯p→2π++2π−+neutrals at 5.7 GeV/c. An essential ρ0-meson spin alignment is observed. The values of the ρ00T element of the ρ0-meson spin-density matrix in the transversity frame are 0.56 ± 0.07, 0.53 ± 0.05, and 0.54 ± 0.04 for the above-mentioned interactions, respectively. An increase of ρ00T with ρ0 transverse momentum is obtained.
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Hydrogen and deuterium gases have been bombarded in a gas target at a temperature of 77°K and at a pressure of about 140 atmospheres by the 318±10 Mev "spread-out" bremsstrahlung photon beam of the Berkeley electron synchrotron. The charged π-mesons which were produced were collimated at angles of 45°, 90°, and 135° to the beam direction. The π+ mesons were detected with trans-stilbene scintillation crystals using πμ, πβ, and πμβ delayed coincidences and π+ and π− mesons were detected with Ilford C-2 200-micron nuclear emulsions. The ratios of the numbers of π− to π+ mesons produced in deuterium were 0.96±0.10, 1.09±0.12, and 1.21±0.17 for the angles of 45°, 90°, and 135°, respectively. No variation of the ratio with meson energy, outside statistics, was observed. Absolute values for the π+ meson energy distribution functions from hydrogen and deuterium per "equivalent quantum" have been measured at each of the above production angles. The differential and total cross sections have been obtained by integrating over energy and angle, respectively. The experimental ratios of the deuterium to hydrogen cross sections are in good agreement with the phenomenological theory of Chew and Lewis when the Hulthén deuteron function with β=6α is used in the initial state, plane waves are used for the nucleons in the final state, and the bremsstrahlung cutoff is taken into account. The statistics of the data are, however, not sufficient to determine the amount of spin interaction. The excitation functions for hydrogen and deuterium and points on the angular distribution curves in the center-of-mass system have been obtained. An upper limit of 0.08 of the charged π-meson cross section was obtained for μ-meson production from deuterium.
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The production of very large transverse momentum hadron jets has been measured in the UA2 experiment at the CERN p p Collider for s = 540 GeV using a highly segmented calorimeter. The range of previously available cross sections for inclusive jet production is extended to p T = 150 GeV and the two-jet invariant mass distribution to m jj = 280 GeV with the largely increased data sample collected during the 1983 running period. The results are compared with the predictions of QCD models.
LISTED ERRORS INCLUDE STATISTICAL AND THE PT-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
LISTED ERRORS INCLUDE STATISTICAL AND THE M-DEPENDENT UNCERTAINTIES. THE ADDITIONAL OVERALL SYSTEMATIC UNCERTAINTY IS 45PCT.
Jet production properties at s = 540 GeV have been measured in the UA2 detector at the CERN p p Collider. Results on the total transverse momentum of the jet system, on the parton density in the nucleon (structure function) and on the two-jet angular distributions are reported. The data are compared with QCD predictions and extrapolations from lower energy experiments.
DISTRIBUTION OF THE SCATTERING ANGLE OF THE 2-JET AXIS IN THE 2-JET COM FRAME WITH A NORMALISATION FIXED AT 1 FOR COS(THETA*) = 0.
STRUCTURE FUNCTION IS DEFINED AS F(X) WHERE D3(SIG)/DX1/DX2/DCOS(THETA) = (F(X1)/X1)*(F(X2)/X2)*D(SIG)/DCOS(THETA).
Data from an exposure of the BEBC bubble chamber filled with deuterium to neutrino and antineutrino wide band beams have been used to extract the x dependence of the structure functions for scattering on protons and neutrons and the fractional momentum distributions of the valence quarks and the antiquarks of different flavours. The difference F n 2 − F p 2 is compared with recent data from high energy μD scattering. A result is also obtained on the sum rule giving the difference between the number of up and down quarks in the nucleon.
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The production of electron-positron pairs of masses below 1200 MeV/ c 2 and of transverse momentum above 1.8 GeV/ c has been studied in pp collisions at √ s = 53 and 63 GeV. The cross section for ϱ, ω, and φ production are presented. The continuum below 600 MeV/ c 2 is consistent with origination from Dalitz decays of η and ω mesons and from semileptonic decay of D and D mesons.
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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.
GLOBAL NORMALIZATION UNCERTAINTY = 12 PCT. RELATIVE NORMALIZATION UNCERTAINTY = 5 PCT.
GLOBAL NORMALIZATION UNCERTAINTY = 10 PCT. RELATIVE NORMALIZATION UNCERTAINTY = 6 PCT.
GLOBAL NORMALIZATION UNCERTAINTY = 15 PCT. RELATIVE NORMALIZATION UNCERTAINTY = 7 PCT.
The inclusive spectra for p p collisions at 22.4 GeV/ c are investigated. We show that the transverse momentum distributions resemble those in high-energy pp interactions and discuss the influence of annihilation processes on the p T 2 distributions. The invariant inclusive cross section for pions in the central region is found to be 28 ± 1 mb. A charge asymmetry is indicated by the y ∗ spectrum in the central region, the asymmetry parameter having the value 0.15 ± 0.01. Finally, we estimate the upper limit of the diffraction dissociation of the beam particle to be 3.68 −0.15 +0.45 mb.
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The inclusive reaction pp → Λ + X ++ at 19 GeV/ c beam momentum has been analyzed in terms of the triple-Regge formalism. A good description of the structure function is achieved for events with | t | < 4 (GeV/ c ) 2 . The effective trajectory obtained from fits to the M 2 / s distribution in different t bins is α R ( t ) = −(0.38 ± 0.11) + (1.15 ± 0.07) t , which holds up to a | t | value of 4 (GeV/ c ) 2 . This is consistent with the K trajectory rather than the K ∗ trajectory which has been reported from other experiments.
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