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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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We report evidence for the production of the charged D ∗ mesons in pp̄ collisions at s = 540 GeV . The search was confined to the charged particle fragments of hadronic jets, which are expected to be predominantly gluon jets in this experiment. The fragmentation function and production rate for D ∗ in jets of average transverse momentum of 28 GeV/ c are given.
THE D*'S ARE CONSIDERED AS ARISING ONLY FROM FRAGMENTATION OF HADRONIC JETS ('GLUON' JETS). HERE THE <PT> OF THE JET IS AROUND 28 GEV THE DEFINITION OF Z IS P(D*).P(JET)/(P(JET))**2.
The two-jet cross section measured in the UA1 apparatus at the CERN p p Collider has been analysed in terms of the centre-of-mass scattering angle θ and the scaled longitudinal parton momenta x 1 and x 2 . The angular distribution d σ /d cos σ rises rapidly as cos → 1, independent of x 2 and x 2 , as expected in vector gluon theories (QCD). The differential cross section in x 1 and x 2 is consistent with factorization and provides a measurement of the proton structure function F(x) = G(x) + 4 9 [Q(x) + Q (x)] at values of the four-momentum transfer squared, -t̂ ≈ 2000 GeV 2 . Over the range x = 0.10−0.80 the structure function shows an exponential x dependence and may be parametrized by the form F ( x ) = 6.2 exp (−9.5 x ).
S(X1,X2) IS DEFINED BY X1*X2*D2(SIG)/DX1/DX2 NORMAISED APPROPRIATELY.
F(X) DEFINED AS G(X)+(4/9)*(Q(X)+QBAR(X)).
Muons of high transverse momentum p μ T have been observed in the large drift chambers surrounding the UA1 detector at the CERN 540 GeV pp̄ collider. For an integrated luminosity of 108 nb −1 , 14 isolated muons have been found with p T > 15 GeV/ c . They are correlated with a large imbalance in total transverse energy, and show a kinematic behaviour consistent with the muonic decay of the Intermediate Vector Boson W ± of weak interactions. The partial cross section is in agreement with previous measurements for electronic decays and with muon-electron universality. The W mass is determined to be m W = 81 +6 −7 GeV/ c 2 .
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We present results for the differential cross sections of neutrinos and antineutrinos on nucleons in the energy range E = 2−200 GeV, from the BEBC and Gargamelle experiments. The structure functions F 2 , 2 χF 1 and χF 3 have been evaluated as a function of χ and q 2 . Deviations are observed from Bjorken scaling, which are very similar to those found in electron and muon inelastic scattering. For the Callan-Gross ratio, we find 2χF 1 F 2 = 0.80 ± 0.12 and the corresponding value for 〈R〉 = 〈 σ S σ T 〉 = 0.15 ± 0.10 . Our results are consistent with the Gross-Llewellyn-Smith sum rule; we measure ⩾2.5 ± 0.5 valence quarks per nucleon. Quark and antiquark distributions are given. The Nachtmann moments of F 2 and χF 3 are quantitatively consistent with the predictions from QCD. The value of the strong interaction parameter is λ = 0.74 ± 0.05 GeV without corrections, and 0.66 ± 0.05 GeV including α S 2 corrections. The moments of the gluon distribution are found to be positive and indicate an χ distribution of gluons which is comparable with that of the valence quarks.
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Inclusive ϱ 0 production has been investigated in p p reactions at 22.4 GeV/ c . The total cross section for ϱ 0 production is 8.1 ± 2.0 mb. The average ϱ 0 's per event is 0.17 ± 0.03. The average transverse momentum, as obtained by extrapolation of a fitted simple exponential to the p T 2 distribution, is 0.52 ± 0.12 GeV/ c . The Feynman x and c.m. rapidity distributions show ϱ 0 to be “centrally” produced.
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New results on inclusive lambda polarization in K − p interactions at 14.3 GeV/ c are presented. At the kaon fragmentation vertex, the polarization is compared to that from inclusive experiments at lower momenta and to that from two-body reactions with a Λ. As predicted by the triple-Regge model with N α (or N γ ) exchange, the polarization is found to be independent of s and M X 2 / s . In particular it has the same value as that found in the two-body reactions.
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Using 20.5 GeV electrons on protons, we measured inclusive π 0 's (of transverse momentum, p T , from 0 to 1.4 GeV/ c ) produced by virtual photons of energy, ν, from 4 to 16.5 GeV and four-momentum squared, q 2 , from −1.8 to −8.5 (GeV/ c ) 2 . Comparing with charged pion data, we find σ π 0 = 1 2 (σ π + + σ π − ) , supporting the quark model. Photon knockout of a quark is favored as the interpretation of these data because of scaling in z = E π / ν and similarity in z -dependence of other pion production data. Consistent with this interpretation are the dependence of 〈 p T 〉 on q 2 , the azimuthal dependence, and fits to the constituent interchange model. We also observe a possible p T −4 dependence at large | q 2 | over a limited p T range.
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π±p elastic differential cross sections in the momentum range 1.72-2.80 GeV/c have been measured at the proton synchrotron "NIMROD" of the Rutherford High Energy Laboratory. The results are tabulated, and analyses of the differential cross sections employing optical models and Legendre polynomial expansions are advanced. A critical discussion of a recent interpretation of differential-cross-section structure in terms of interference between resonant and background amplitudes is presented.
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