A search for supersymmetric electron production via the reaction e+e−→e±γ̃ẽ∓ followed by the decay ẽ∓→e∓γ̃ has been performed with the MAC detector at the electron-positron storage ring PEP. No candidates were found in a sample corresponding to an integrated luminosity of 36.4 pb−1. For a massless γ̃ this corresponds to a lower limit on the ẽ mass of 22.4 GeV/c2 at the 95% confidence level.
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We have studied several features of the production of charged-hardon pairs by γγ collisions. We have measured the f0 partial width Γf0→γγ(Q2) for Q2 in the range 0<Q2<1.4 GeV2/c2, and obtained Γf0→γγ=2.52±0.13±0.38 keV at Q2≈0. The measured Q2 dependence is in agreement with the generalized vector-dominance model. The cross section for γγ→(π+π−+K+K−) in the mass region 1.6≤Mππ≤2.5 GeV/c2 has also been measured and the result compared with that expected from the QCD continuum.
Data read from graph.. Both statistical and systematic errors included.
We present data on the multiplicity structure of inclusive charged hadron production in charged current neutrino and antineutrino freon interactions in the energy range 3–30 GeV resulting from an experiment with the bubble chamber SKAT. Average multiplicities, dispersions and correlation coefficients are investigated. Furthermore, KNO-scaling is studied and average net charges are calculated in different kinematical regions. Our data are compared with results from\(\begin{array}{*{20}c}{( - )}\\v\\ \end{array} \)-interactions on an isoscalar target of “free” nucleons to study the influence of nuclear effects.
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THE DATA ARE SATISFACTORILY DESCRIBED BY A LINEAR FUNCTION IN LN(W**2): <N> = A + B * LN(W**2) A=0.15+-0.09, B=0.84+-0.05 FOR CHARGED+ AND A=-0.49+-0.06, B=0.63+-0.04 FOR CHARGED-.
We present inclusive spectra of charged hadrons produced in\(\begin{array}{*{20}c}{( - )}\\v\\ \end{array}\)-Freon interactions at average beam energies of about 6 GeV. The experiment was done using the bubble chamber SKAT at the 70 GeV Serpukhov accelerator. In the hadronic energy range,W<5 GeV, dominantly isotropic events are found. The transverse momentum of the produced particles shows no strongW2-dependence. Feynman-scaling may be reached forW2≳10 GeV2, where also theż-spectra are described by the predictions of the parton model. All experimental data are reproduced rather well also by a Monte Carlo model based on ordinary phase space.
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We present an analysis of electroweak leptonic couplings from high statistics experiments on Bhabha scattering and μ pair production at an energy of 34.5 GeV. The forward-backward charge asymmetry of the μ pairs was measured to be −0.098±0.023±0.005. The data were found to agree well with the standard theory of electroweak interaction giving sin2θW=0.27±0.07. The leptonic weak couplings were determined to begv=0.000±0.170 andgA=−0.481±0.055. The data were also used to investigate a class of composite models for leptons.
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A search for single electrons from the decay of singly produced scalar electrons has been made at the PEP storage ring at SLAC. No events of this type have been found in 123 pb−1 of data, resulting in a cross-section limit of less than 2.4×10−2 pb within the detector acceptance, and a 95%-confidence-level lower limit on the scalar-electron mass of 22.2 GeV/c2.
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We have determined the cross section for γγ→π+π+π−π− in a way free of assumptions about the relative contributions fromρ0ρ0,ρ02π and 4π (uncorrelated phase space). We find a sharp onset above threshold and a rather high cross section of about 200 nb aroundWγγ=1.5 GeV which consists to about 40% ofρ0ρ0 production with sizeable contributions fromρ02π and 4π (PS). The total cross section as well as theρ0ρ0 content fall rather fast at higher c.m. energies. Attempts to explain this behaviour in terms of production of known resonances are not successful so far. The angular distributions do not show any significant structure pointing to resonance formation in the 4π-system. Only theρ0-meson is observed in the moment analysis. The decay distributions of theρ0 for forward produced rhos are fairly consistent with helicity conservation of the produced rhos in accordance with the VDM picture.
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RESULTS OF DECOMPOSITION OF THE CROSS SECTION INTO RHO RHO, RHO 2PI, AND 4PI(PHASE SPACE) USING TWO WIDE W BINS. SEE TEXT OF PAPER FOR DISCUSSION OF FITS.
RESULTS OF DECOMPOSITION OF THE CROSS SECTION INTO THE RHO RHO, RHO PI, AND 4PI (PHASE SPACE) USING SMALL W BINS. SEE TEXT OF PAPER FOR DISCUSSION OF FITS.
Inclusive ϱ 0 meson production has been measured in 120 GeV and 280 GeV muon-proton interactions. Distributions of z and p T 2 are presented. Primary ϱ 0 production is found to be equal to that of π 0 production within errors.
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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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We present evidence for the production of Ξ· − , Ξ − in e + e − annihilation into hadrons. Our measurements yields: 0.026 ± 0.008 (stat.) ± 0.009 (syst.) Ξ − , Ξ − per hadronic event at W ∼ 34 GeV. Using our previous measurements of Λ, Λ and p, p production we obtain the relative yields (Ξ − , Ξ − /(Λ, Λ = 0.087 ± 0.03 ( stat. ) ± 0.03 ( syst. ) and (Ξ − , Ξ − /( p , p = 0.033 ± 0.011 ( stat. ) ± 0.011 ( syst. ) .
TOTAL YIELD PER HADRONIC EVENT AND COMPARISON WITH PREVIOUS TASSO MEASUREMENTS OF OTHER BARYONS PRODUCTION. EXTRAPOLATION HAS BEEN MADE TO MOMENTA LOWER THAN IN THE EXPERIMENTAL RANGE.
NUMERICAL VALUES SUPPLIED BY P. JOOS.
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