The production of $K^*+(892)$, $K^{*0}+(892)$, $\rho^{0}(770)$ and $\omega(783)$ vector mesons in $q\bar{q}$ events as well as in the gluonic $\Upsilon(1S)$ decays and $\Upsilon(4S) \to B\bar{B}$ decays has been studied using the ARGUS detector. Combining these results with data on pseudoscalar meson, $\phi$ meson and baryon production collected with the same detector allow comprehensive studies of quark and gluon fragmentation. Model independent information on $s$ quark and vector meson suppression $(s/u = 0.37 \pm 0.04, V/(V+P)_{\pi} = 0.21 \pm 0.04$ and $V/( V+ P)_K = 0.34 \pm 0.03))$ are derived. The data are compared with predictions from the models Jetset 7.3 and UCLA 7.31.
Vector meson multiplicities in the continuum region (sqrt(s) = 10.45 GeV). Data is also given for production of the pseudoscalar phi meson.
Vector meson multiplicities from Direct UPSI(1S) decays. Data is also givenfor production of the pseudoscalar phi meson.
Vector meson multiplicities from Direct UPSI(4S) decays. Data is also givenfor production of the pseudoscalar phi meson.
The cross section for exclusive π+ electroproduction on the proton has been measured near threshold for the first time at two different values of the virtual photon polarization (ɛ∼0.2 and ɛ∼0.7). Using the low energy theorem for this reaction we deduce the axial and pseudoscalar weak form factors GA and GP at ‖t‖=0.073, 0.139, and 0.179 (GeV/c)2. The slope of GA agrees with the value obtained in neutrino experiments. GP satisfies the pion pole dominance hypothesis, which is thus verified for the first time in this range of transfer.
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Final results of the measurement of the analysing power A On of the p p → n n reaction are presented. Eight measurements in the range 546–1287 MeV/ c incoming p momentum have been performed over the full angular range using a solid polarized proton target and the Low Energy Antiproton Ring (LEAR) at CERN antiproton extracted beams.
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Total cross-section measurements of the π+p→π+π+n reaction at pion kinetic energies of 180, 184, 190, and 200 MeV are reported. The threshold value for the amplitude a(π+π+) as well as the s-wave, isospin 2, ππ scattering length a20 were determined. The results were found to be in agreement with chiral perturbation theory and inconsistent with the calculations of Jacob and Scadron and the model of dominance by quark loop anomalies.
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The yields and average transverse momenta of pions, kaons, and antiprotons produced at the Fermilab p¯p collider at s=300, 540, 1000, and 1800 GeV are presented and compared with data from the energies reached at the CERN collider. We also present data on the dependence of average transverse momentum 〈pt〉 and particle ratios as a function of charged particle density dNcdη; data for particle densities as high as six times the average value, corresponding to a Bjorken energy density 6 GeV/fm3, are reported. These data are relevant to the search for quark-gluon phase of QCD.
PT RANGE FROM 0 TO INFINITY.
PT RANGE FROM 0 TO INFINITY.
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Quasielastic e-d cross sections have been measured at forward and backward angles. Rosenbluth separations were done to obtain RL and RT at Q2=1.75, 2.50, 3.25, and 4.00 (GeV/c)2. The neutron form factors GEn and GMn have been extracted using a nonrelativistic model. The sensitivity to deuteron wave function, relativistic corrections, and models of the inelastic background are reported. The results for GMn are consistent with the dipole form, while GEn is consistent with zero. Comparisons are made to theoretical models based on vector meson dominance, perturbative QCD, and QCD sum rules, as well as constituent quarks.
Magnetic form factors.
Electric form factors.
Measurements of the forward-angle differential cross section for elastic electron-proton scattering were made in the range of momentum transfer from Q2=2.9 to 31.3 (GeV/c)2 using an electron beam at the Stanford Linear Accelerator Center. The data span six orders of magnitude in cross section. Combinded statistical and systematic uncertainties in the cross section measurements ranged from 3.6% at low Q2 to 19% at high Q2. These data have been used to extract the proton magnetic form factor GMp(Q2) and Dirac form factor F1p(Q2) by using form factor scaling. The logarithmic falloff of Q4F1p expected from leading twist predictions of perturbative quantum chromodynamics is consistent with the new data at high Q2. Some nonperturbative and hybrid calculations also agree with our results.
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Formfactor scaling assumes (Ge=Gm/mu).
We present a measurement of the cross section for production of isolated prompt photons in p¯p collisions at √s =1.8 TeV. The cross section, measured as a function of transverse momentum (PT), agrees qualitatively with QCD calculations but has a steeper slope at low PT.
Additional normalization systematic uncertainty of 27 pct for first eleven entries, and +32 pct(-46 pct) for last four entries.
We have measured the slope parameter of the π 0 electromagnetic form factor by measuring the partial branching ratio of the Dalitz decay π 0 → γe + e − into high-invariant-mass electron-positron pairs. We obtain a value a =0.026 with a total (statistical and systematic) error of ±0.054, in agreement with vector dominance and quark loop calculations.
The PI0 form factor is parameterized as F(M(ee)**2) = 1 + SLOPE*(M(ee)/M(pi))**2. Two metod are used (see text for detail).
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