In a joint effort the CERES/NA45 and TAPS collaborations have measured low-mass electron pairs in p–Be and p–Au collisions at 450 GeV/c at the CERN SPS. In the range covered up to ≈ 1.5 GeV/c2 the mass spectra from p–Be and p–Au collisions are well explained by electron pairs from decays of neutral mesons. For p–Au our result is new. For p–Be, the simultaneously measured electron pair inclusive pair spectrum in which instrumental uncertainties are highly reduced. We confirm the earlier finding of HELIOS-1 with significantly reduced systematic uncertainties of 23% in the mass range below 450 MeV/c2, and of 28% in the mass range above 750 MeV/c2 at 90% confidence limit. Any unconventional source of electron pairs is limited by these error margins as the percentage fraction of the hadronic contribution.
Relative production cross sections.
This paper reports on the charged K / π production ratios and on the shape of the p T distributions of π fluxes measured by the SPY/NA56 experiment for 450 GeV/c proton interactions on beryllium targets. The present data cover a secondary momentum range from 7 GeV/c to 135 GeV/c in the forward direction and with p T values up to 600 MeV/c. An experimental accuracy of about 3% has been achieved. These results will reduce the uncertainty on the estimation of the ν e component of neutrino beams.
No description provided.
No description provided.
Additional systematic error of 1.3 PCT.
A study has been performed of the reaction pbar p -> 4K using in-flight antiprotons from 1.1 to 2.0 GeV/c incident momentum interacting with a hydrogen jet target. The reaction is dominated by the production of a pair of phi mesons. The pbar p -> phi phi cross section rises sharply above threshold and then falls continuously as a function of increasing antiproton momentum. The overall magnitude of the cross section exceeds expectations from a simple application of the OZI rule by two orders of magnitude. In a fine scan around the xi/f_J(2230) resonance, no structure is observed. A limit is set for the double branching ratio B(xi -> pbar p) * B(xi -> phi phi) < 6e-5 for a spin 2 resonance of M = 2.235 GeV and Width = 15 MeV.
No description provided.
No description provided.
Fine scan of the PHI PHI cross section.
Inclusive production of the f_0(980), f_2(1270) and \phi(1020) resonances has been studied in a sample of 4.3 million hadronic Z^0 decays from the OPAL experiment at LEP. A coupled channel analysis has been used for the f_0 in simultaneous fits to the resonances in inclusive \pi+\pi- and K+K- mass spectra. Fragmentation functions are reported for the three states. Total inclusive rates are measured to be 0.141 +/- 0.007 +/- 0.011 f_0, 0.155 +/- 0.011 +/- 0.018 f_2, and 0.091 +/- 0.002 +/- 0.003 \phi mesons per hadronic Z^0 decay. The production properties of the f_0, including those in three-jet events, are compared with those of the f_2 and \phi, and with the Lund string model of hadron production. All measurements are consistent with the hypothesis that the f_0 is a conventional qq(bar) scalar meson.
Total inclusive production rates.
Fragmentation functions. Additional systematic errors of 7.6 PCT for F0, 11.6 PCT for F2 and 3.5 PCT for PHI. The uncorrelated systematic errors for F0 and F2 are negligible in comparison to the other errors.
An analysis based on 124 000 selected $\tau$ pairs recorded by the ALEPH detector at LEP provides the vector $(V)$ and axial-v
Total vector spectral function. The error has been set to zero if it is smaller than the point size.
Invariant mass-squared distributions of the decay $\tau^- \to 2\pi^- \pi^+ \nu_\tau$. The error has been set to zero if it is smaller than the point size.
Invariant mass-squared distributions of the decay $\tau^- \to \pi^- 2\pi^0 \nu_\tau$. The error has been set to zero if it is smaller than the point size.
A measurement of the spin alignment of charged D^* mesons produced in continuum e^+ e^- \to c \bar{c} events at \sqrt{s}=10.5 GeV is presented. This study using 4.72 fb^{-1} of CLEO II data shows that there is little evidence of any D^* spin alignment.
Systematic errors are not given.
Systematic errors are not given.
Two decay modes of D0 --> K- PI+ and D0 --> K- PI+ PI0 are combined.
Inclusive jet differential cross sections for the reaction e+ p --> e+ + jet + X with quasi-real photons have been measured with the ZEUS detector at HERA. These cross sections are given for the photon-proton centre-of-mass energy interval 134 < W < 277 GeV and jet pseudorapidity in the range -1 < eta(jet) < 2 in the laboratory frame. The results are presented for three cone radii in the eta-phi plane, R=1.0, 0.7 and 0.5. Measurements of dsigma/deta(jet) above various jet-transverse-energy thresholds up to 25 GeV and in three ranges of W are presented and compared to next-to-leading order (NLO) QCD calculations. For jets defined with R=1.0 differences between data and NLO calculations are seen at high eta(jet) and low E_T(jet). The measured cross sections for jets defined with R=0.7 are well described by the calculations in the entire measured range of eta(jet) and E_T(jet). The inclusive jet cross section for E_T(jet) > 21 GeV is consistent with an approximately linear variation with the cone radius R in the range between 0.5 and 1.0, and with NLO calculations.
Jet defining cone radius R = 1.0.
Jet defining cone radius R = 1.0.
Jet defining cone radius R = 1.0.
Measurements are reported of the proton and deuteron spin structure functions g1 at beam energies of 29.1, 16.2, and 9.7 GeV and g2 at a beam energy of 29.1 GeV. The integrals of g1 over x have been evaluated at fixed Q**2 = 3 (GeV/c)**2 using the full data set. The Q**2 dependence of the ratio g1/F1 was studied and found to be small for Q**2 > 1 (GeV/c)**2. Within experimental precision the g2 data are well-described by the Wandzura-Wilczek twist-2 contribution. Twist-3 matrix elements were extracted and compared to theoretical predictions. The asymmetry A2 was measured and found to be significantly smaller than the positivity limit for both proton and deuteron targets. A2 for the proton is found to be positive and inconsistent with zero. Measurements of g1 in the resonance region show strong variations with x and Q**2, consistent with resonant amplitudes extracted from unpolarized data. These data allow us to study the Q**2 dependence of the first moments of g1 below the scaling region.
Averaged A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
Detailed A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
Detailed A1(P) for the DIS (W**2 > 4 GeV) region. Additional normalization uncertainty 3.7%.
A determination of the number of light neutrino families performed by measuring the cross section of single photon production in e + e − collision near the Z resonance is reported. From an integrated luminosity of 100 pb −1 , collected during the years 1991–94, we have observed 2091 single photon candidates with an energy above 1 GeV in the polar angular region 45°< θ γ <135°. From a maximum likelihood fit to the single photon cross section, the Z decay width into invisible particles is measured to be Γ inv =498±12 (stat) ±12 (sys) MeV . Using the Standard Model couplings of neutrinos to the Z, the number of light neutrino species is determined to be N ν =2.98±0.07(stat)±0.07(sys).
No description provided.
Using a sample of 10 8 triggered events, produced in π − −Cu interactions at 350 GeV/ c , we have identified 26 beauty events. The estimated background in this sample is 0.6 ± 0.6 events. From these data, assuming a linear A-dependence, we measure a beauty production cross section integrated over all χ F of 5.7 −1.1 +1.3 (stat.) −0.5 +0.6 (syst.) nb/N.
No description provided.
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