The reaction e + e − → τ + τ − has been measured using the high resolution spectrometer at PEP. The angular distribution shows a forward-backward asymmetry of −(6.1±2.3±0.5)%, corresponding to an axial-vector coupling if g a τ g a e = 0.28 ±0.11± 0.03, in good agreement with the standard model of electroweak interactions. The measured cross section yields ifR ττ = 1.10± 0.03±0.04, consistent with QED and giving QED cutoff parameters of Λ + >92 GeV and Λ − >246 GeV at 95% C.L.
Comparison of total tau pair cross section with O(alpha**3) QED prediction.
Corrected for acceptance backgraound, and O(alpha**3) radiative effects.
Forward-backward asymmetry based on fit to angular distributions.
Interactions of 40 GeV/c πp-,K− and\(\bar p\) on Li, C, S, Cu, CsI and Pb were studied with the RISK-streamer chamber spectrometer. We present multiplicities of negatively charged particles, as well as of protons, and the correlations between them. The normalized mean multiplicity of negative particles,R−, depends on\(\bar v\), the average number of inelastic collisions as\(R^ -= (0.73 \pm 0.04) + (0.34 \pm 0.02)\bar v\). The dependence of the normalized dispersion of negative particles,D−/
AVERAGE MULTIPLICITIES OF ALL CHARGED PARTICLES.
AVERAGE MULTIPLICITIES OF ALL NEGATIVELY CHARGED PARTICLES.
We have measured the cross sections for e + e − → e + e − , e + e − → μ + μ − , e + e − → γγ and e + e − → hadrons in an energy scan at center of mass energies between 39.79 and 46.72 GeV in 30 MeV steps. New spinless bosons, whose existence has been postulated as a possible means to explain the anomalously large radiative width of the Z 0 found at the CERN SPS p p collider, are ruled out in the scan region. The data are used to set limits on the couplings to lepton, photon and quark pairs of bosons with masses above 46.72 GeV.
SIG(C=SM) is the Standard Model predicted cross section.
We present a measurement of the production of muon pairs in 194 GeV/c π−-tungsten interactions. A sample of 155,000 events with mass higher than 4.07 GeV/c2 has been used to determine the differential cross-section as a function of the scaling variables\(\sqrt \tau\) andxF.
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.21-0.24. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.24-0.27. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
The cross section ${\rm d}^2\sigma/{\rm d}\sqrt{\tau}{\rm d}x$ integrated over each $\sqrt{\tau}$-$x_F$ cell as a function of $x_F$ for $\sqrt{\tau}$ = 0.27-0.30. The $\Upsilon$ region has been excluded. The integrated luminosity is $L = (8.58 \pm 0.53)\times 10^{37}$ [cm$^2$/W nucleus]$^{-1}$. Note that these data have been re-analysed by the NA10 experimenters using a better estimate of Fermi motion effects (see Tables 11-19 of this record).
A high-statistics measurement is presented of the cross section for the process e+e−→τ+τ− at s=29 GeV from the MAC detector at PEP. A fit to the angular distribution of our sample of 10 153 events with |cosθ|<0.9 gives an asymmetry Aττ=−0.055±0.012±0.005 from which we find the product of electron and tau axial-vector weak neutral couplings gAegAτ=0.22±0.05.
Data fully corrected up to O(ALPHA**3) radiative effects. Data requested from authors.
Data extrapolated to full acceptance.
No description provided.
Using the ARGUS detector at DORIS, we have observed the production of F ± mesons in e + e − annihilation at a centre of mass energy of 10 GeV through their subsequent decays into φπ ± and φπ + π − π ± . The values obtained for [ R (e + e − →FX). Branching Ratio] are (1.47 ± 0.32 ± 0.20)% and (1.63 ± 0.42 ± 0.41)% respectively. The observed mass is (1973.6 ± 2.6 ± 3.0) MeV c 2 . The F momentum spectrum is as expected for the fragmentation of c quarks into charmed mesons, but is somewhat softer than for fragmentation into D ∗ mesons. The relevant angular distributions are consistent with a spin-zero assignment of the F meson.
RESULTS OF FITS FOR SPECIFIED DECAY CHANNELS.
ACCEPTANCE CORRECTED FRAGMENTATION FUNCTION FOR THE TWO DECAY CHANNELS COMBINED. X IS PF/PMAX. DATA HAVE BEEN READ FROM THE GRAPH.
The cross sections for J ψ production have been measured in interactions of 280 GeV μ + on hydrogen and deuterium (H, D) and also in interactions of 250 GeV μ + on iron. The single-nucleon cross sections in iron are found to be larger than those in H, D. The mean ratio of the iron to H, D photoproduction cross sections in the range 60 < v < 200 GeV is 1.45 ±0.12 (statistical) ±0.22 (systematic error). Within the framework of the photon-gluon fusion model, this indicates that the gluon density per nucleon is ∼45% larger in iron than in H, D in the range 0.026 < x < 0.085, on a mass scale Q 2 eff ∼M 2 J ψ .
First table is from combined H and DEUT data at 280 Gev. Second table is from FE data at 250 Gev.
First table is from combined H and DEUT data at 280 Gev. Second table is from FE data at 250 Gev.
THIS TABLE IS THE RATIO OF THE EFFECTIVE GLUON DISTRIBUTIONS IN IRON AND HYDROGEN(DEUTERIUM) ASSUMING THAT PHOTON-GLUON FUSION IS THE RELEVANT MECHANISM FOR J/PSI PRODUCTION.
Using the Mark-J detector at the high-energy e+e− collider PETRA, we compare the data from hadron production with the complete second-order QCD calculation over the energy region 22 to 46.78 GeV. We determine the QCD parameter Λ=100±30−45+60 MeV which yields the strong-coupling constant αs=0.12±0.02 for s=44 GeV.
No description provided.
Axis error includes +- 0.0/0.0 contribution (DUE TO FRAGMENTATION MODEL).
The differential cross section of the reactione+e−→e+e− at a c.m. energy of 34.7 GeV has been measured. The result, together with our previously measurede+e−→α+α− data, are compared with the standard model predictions. We obtain for the weak neutral current couplings the valuesgv2=0.09×0.06,ga2=0.38×0.08. A fit of the Weinberg mixing angle gives the valuegv2=0.09×0.06,ga2=0.038×0.08. The data are also used to set limits on possible deviations from the pointlike structure of leptons. An upper limit for thee+e− coupling to a heavy spin 0 boson is also given.
Fully corrected results for Bhabha scattering.
The differential cross section for Bhabha scattering.
??? CONSTANTS ???.
The inclusive process π++P→K¯ *0(890)+X is studied at 16 GeV/c using a 2-m streamer chamber containing a central liquid hydrogen target. From photographs triggered by detection of a forward K− meson, the signal K¯ K−*0π+ is extracted. The inclusive rate for K¯ * production into the forward hemisphere σ(xF>0.3) is 115±27 μb; the pT2 distribution is found to have a slope constant of 3.3±0.6 (GeV/c)2. The Feynman-x distribution for K¯ *0 is consistent with a Kuti-Weisskopf model in which the valence and sea quarks of the incident pion interact with only the sea quarks of the target proton.
No description provided.
No description provided.