Minimum Bias production cross sections of $\eta$ mesons have been measured in 200AGeV S+Au and S+S collisions at the CERN SPS by reconstructing the $\eta\rightarrow\gamma\gamma$ decay. The measurements have been made over the rapidity range $2.1 \leq y \leq 2.9$ using the leadglass spectrometer of WA80. Within the statistical and systematical uncertainties the spectral shapes of $\pi~0$ and $\eta$ mesons yields are identical when their invariant differential cross section is plotted as a function of the transverse mass. The relative normalization of the $\eta$ to $\pi~0$ transverse mass spectra is found to be $0.53 \pm 0.07$ for S+Au and $0.43 \pm 0.15$ for S+S reactions. Extrapolation to full phase space leads to an integrated cross section ratio of $\eta$ to $\pi~0$ mesons of $0.15 \pm 0.02 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$, and $0.12 \pm 0.03 {\rm (stat.)} \pm 0.02 {\rm (syst.)}$ for S+Au and S+S collisions, respectively.
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Deep inelastic $e~-p$ scattering has been studied in both the charged-current (CC) and neutral-current (NC) reactions at momentum transfers squared, $Q~2$, between 400 GeV$~2$ and the kinematic limit of 87500 GeV$~2$ using the ZEUS detector at the HERA $ep$ collider. The CC and NC total cross sections, the NC to CC cross section ratio, and the differential cross sections, $ d\sigma/dQ~2 $, are presented. For $Q~2 \simeq M_W~2$, where $M_W$ is the mass of the $W$ boson, the CC and NC cross sections have comparable magnitudes, demonstrating the equal strengths of the weak and electromagnetic interactions at high $Q~2$. The $Q~2$ dependence of the CC cross section determines the mass term in the CC propagator to be $M_{W} = 76 \pm 16 \pm 13$GeV.
Data requested from authors.
Neutral current cross sections.
Charged current cross sections.
A search for excited states of the standard model fermions was performed using the ZEUS detector at the HERA electron-proton collider, operating at a centre of mass energy of 296 GeV. In a sample corresponding to an integrated luminosity of 0.55 pb−1, no evidence was found for any resonant state decaying into final states composed of a fermion and a gauge boson. Limits on the coupling strength times branching ratio of excited fermions are presented for masses between 50 GeV and 250 GeV, extending previous search regions significantly.
The cross sections times branching ratio.
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Light ion collisions with carbon target at 4.2 GeV/c/N are studied. Pion multiplicity distributions, momentum and angular spectra are analysed. These data are described in terms of models assuming independent interactions of nucleons from the projectile nucleus with the target.
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We have examined the inclusive production of nonstrange particle resonances in νp interactions using the Fermilab 15-ft bubble chamber. A sample of 2437 charged-current events with visible longitudinal momentum greater than 10 GeV/c was obtained. The ρ0 and Δ++(1232) are seen. An overall rate of 0.21±0.04 ρ0 per event is found. For five-prong events, the rate is 0.44±0.08 ρ0 per event. The ρ0Z distribution falls rapidly for Z greater than 0.4. The production of Δ++ is seen clearly in events with an identified proton. No evidence is seen for Δ0 production. An upper limit of 0.34 is placed on the ratio of ηπ0 (90% confidence level).
NO CLEAR DEL0 SIGNAL.
We present results for the reactions νp→μ−π+p and νp→μ−K+p at energies above 5 GeV. The average cross section for the first reaction between 15 and 40 GeV is (0.80±0.12) × 10−38 cm2 and for events with Mπ+p<1.4 GeV is (0.55±0.08) × 10−38 cm2. The ratio of the cross section for the second reaction to that for the first is 0.017±0.010.
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RAPIDITY IS MEASURED IN 'QUARK' REST FRAME DEFINED AS Y(Q)=Y(LAB)-LOG(W**2/M**2) WHERE Y(LAB)=0.5*LOG((E+PL)/(E-PL)).
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