The dissociation of virtual photons, $\gamma^{\star} p \to X p$, in events with a large rapidity gap between $X$ and the outgoing proton, as well as in events in which the leading proton was directly measured, has been studied with the ZEUS detector at HERA. The data cover photon virtualities $Q^2>2$ GeV$^2$ and $\gamma^{\star} p$ centre-of-mass energies $40<W<240$ GeV, with $M_X>2$ GeV, where $M_X$ is the mass of the hadronic final state, $X$. Leading protons were detected in the ZEUS leading proton spectrometer. The cross section is presented as a function of $t$, the squared four-momentum transfer at the proton vertex and $\Phi$, the azimuthal angle between the positron scattering plane and the proton scattering plane. It is also shown as a function of $Q^2$ and $\xpom$, the fraction of the proton's momentum carried by the diffractive exchange, as well as $\beta$, the Bjorken variable defined with respect to the diffractive exchange.
The differential cross section DSIG/DT for the LRG and the LPS data samples.
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
The fitted exponential slope of the T distribution as a function of X(NAME=POMERON).
The reaction pp→p f ( π + π − π + π − )p s , where the π + π − π + π − system is centrally produced, has been studied at 300 GeV/ c in an experiment designed to search for gluonic states. The π + π − π + π − mass spectrum shows evidence for the f 1 (1285) with a mass of 1281±1 MeV and a width of 31±5 MeV. In addition there is evidence for two new enhancements at masses of 1449±4 and 1901±13 MeV with widths of 78±18 and 312±61 MeV respectively. An analysis of the state at 1.45 GeV indicates that it is not a π + π − π + π − decay mode of the f 1 (1420) or ι η(1440) .
No description provided.
No description provided.
No description provided.
The reaction pp→p f (K + K − K + K − )p s in which the K + K − K + K − system is centrally produced has been studied at 300 GeV/ c . φφ production has been observed and the ratio σ (φK + K − )/ σ ( φφ ) is 1.0±0.3. The cross section for central production of φφ is found to be the same at 300 GeV/ c and 85 GeV/ c . An angular analysis of the φφ system favours J P =2 + over 0 − .
No description provided.
Results are presented of an analysis of the reaction pp→p f (K S 0 K ± π ∓ )p s at 300 GeV/ c . Clear f 1 (1285) and f 1 (1420) signals are seen. A spin-parity analysis shows that both are consistent with being 1 ++ states. The f 1 (1420) is found to decay only to K ∗ K and no 0 −+ or 1 +− waves are required to describe the data. The production of the f 1 (1285) as a function of energy is not the same as that for the f 1 (1420) whose cross section is found to be constant with energy.
No description provided.
The reactionpp→pf(K+K-π+π-)ps, where theK+K− π+π- system is centrally produced, has been studied at 300 GeV/c. TheK*0\(K^{*0} \bar K^{*0} \) final state has been observed and the cross sections for its central production are found to be the same at 300 and 85 GeV/c. TheK*0\(K^{*0} \bar K^{*0} \) final state appears to be produced as a non-resonant threshold enhancement.
No description provided.
Cross sections for centrally produced vector-vector final states with mass greater than the phi-phi production threshold.
The reactione+e−→µ+µ− has been studied at centre of mass energies between 35.0 and 46.8 GeV using the TASSO detector at PETRA. We present measurements of the forward-backward charge asymmetry (Aμμ) and cross section σμμ for this reaction at three energies. At 35.0 GeV we obtain a cross section relative to the QED prediction ofRμμ=σμμ/σo=0.932±0.018±0.044 andAμμ=(−10.6−2.3+2.2±0.5)%. At 38.3 GeV we findRμμ=0.951±0.072−0.057+0.063 andAμμ=(+1.7−8.6+8.5±0.5)%. At 43.6 GeV we measureRμμ=0.921±0.037±0.055 andAμμ=(−17.6−4.3+4.4±0.5)%. Our results are in good agreement with the predictions of the standard model. Including previous TASSO data we present improved determinations of muonic electroweak parameters. We also report on lower limits of possible contributions from contact interactions.
If only one error is given, this is the sum of the statistical and systematic errors in quadrature.
The data are corrected for 'reduced QED' radiative corrections. Statistical errors only.
The data are corrected for 'reduced QED' radiative corrections. Statistical errors only.
We report on an analysis of the multiplicity distributions of charged particles produced ine+e− annihilation into hadrons at c.m. energies between 14 and 46.8 GeV. The charged multiplicity distributions of the whole event and single hemisphere deviate significantly from the Poisson distribution but follow approximate KNO scaling. We have also studied the multiplicity distributions in various rapidity intervals and found that they can be well described by the negative binomial distribution only for small central intervals. We have also analysed forward-backward multiplicity correlations for different energies and selections of particle charge and shown that they can be understood in terms of the fragmentation properties of the different quark flavours and by the production and decay of resonances. These correlations are well reproduced by the Lund string model.
RATIO of MULT/DISPERSION for the whole event to that for the single hemisphere data.
Complete event multiplicities.
Single hemisphere multiplicities.
A high statistics experiment was performed on Bhabha scattering at energies between 14 and 34 GeV. Good agreement with QED was observed. The combined data on Bhabha scattering and μ pair production were found to agree with the standard theory of electroweak interaction giving sin 2 θ = 0.27 −0.07 +0.06 . Assuming for the Z 0 mass a value of 90 GeV the leptonic weak coupling constants were determined to g V 2 = −0.04 ± 0.06 and g A 2 = 0.35 ± 0.09. A search for scalar leptons sets lower limits on the mass of scalar electrons of M s e > 16.6 GeV and of scalar muons of M s μ > 16.4 GeV.
No description provided.
No description provided.
We have observed ϱ 0 production in e + e − annihilation to hadrons at high energies. The differential cross section at a centre of mass energy W , of 34 GeV, is presented. In the range 0.2< x < 0.7, we measure 0.33 ± 0.06 (stat.) ± 0.07 (syst.), 0.22 ± 0.06 ± 0.05 and 0.22 ± 0.02 ± 0.05 ϱ 0 /event at W = 14, 22 and 34 GeV respectively.
No description provided.
No description provided.
INTEGRATION OVER RESTRICTED X RANGE.
The ration R = σ (e + e − → hadrons) σ μμ was measured between 12.0 and 36.7 GeV c.m. energy W with a precision of typically ± 5.2%. R is found to be constant with an average R = 4.01 ± 0.03 (stat) ± (syst.) for W ⩾ 14 GeV. Quarks are found to be point-like, the mass parameter describing a possible quark form-factor being larger than 186 GeV. Fits including QCD corrections and a weak neutral-current contribution are presented.
DATA OF RUNPERIOD 1.
DATA OF RUNPERIOD 2.
R MEASURED IN SCANNING MODE.
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