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Differential cross sections for p p elastic scattering have been measured for very small momentum transfers at six different incident antiproton momenta in the range 3.7 to 6.2 GeV/c by the detection of recoil protons at scattering angles close to 90°. Forward scattering parameters σ T , b , and ϱ have been determined. For the ϱ-parameter, up to an order of magnitude higher level of precision has been achieved compared to that in earlier experiments. It is found that existing dispersion theory predictions are in disagreement with our results for the ϱ-parameter.
Results of the SIG(T)-free analysis. Errors include systematic uncertainties.
Results of the SIG(T)-fixed analysis. Errors include systematic uncertainties.
CT values of the total cross section from the SIG(T)-free analysis. Errors include systematic uncertainties.
We have measured ρ, the ratio of the real to the imaginary part of the p¯p forward elastic-scattering amplitude, at √s =1.8 TeV. Our result, ρ=0.140±0.069, is compared with extrapolations from lower-energy data based on dispersion relations, and with the UA4 value at √s =546 GeV.
Results of least square's fit to the distribution.
Total cross section from fit to data.
We report a measurement of the proton-antiproton total cross section σT at c.m.s. energies √s =546 and 1800 GeV. Using the luminosity-independent method, we find σT=61.26±0.93 mb at √s =546 GeV and 80.03±2.24 mb at √s =1800 GeV. In this energy range, the ratio σel/σT increases from 0.210±0.002 to 0.246±0.004.
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Assuming RHO = 0.15.
We report a measurement of the p p total cross section at √ s =1.8 TeV using a luminosity-independent method. Our result is σ T =72.1±3.3 mb ; we also derive the total elastic cross section σ el =16.6±1.6 mb. A value is obtained for the total single diffraction cross section of 11.7±2.3 mb.
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Assuming RHO = 0.145.
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We have measured the antiproton-proton total cross section at √s =1.8 TeV at the Fermilab Tevatron Collider; the value obtained is 78.3±5.9 mb. B, the nuclear slope parameter for elastic scattering, was measured to be 16.3±0.5 (GeV/c)−2. From these data, we derive a value for the total elastic cross section.
Nuclear Store Parameter.
Total cross section measurement. Errors contain systematic effects folded including a 15 PCT error in luminosity measurement which dominates the error.
Total cross section assuming RHO = 0.145 (low energy fit). If RHO is taken as 0.24 obtained by UA4 at sqrt(s) = 546 GeV, the value of SIG is reduced by 1.8 PCT.
This is the first full solid angle analysis of large transverse energy events in\(p\bar p\) collisions at the CERN collider. Events with transverse energies in excess of 200 GeV at\(\sqrt s= 630 GeV\) are studied for any non-standard physics and quantitatively compared with expectations from perturbative QCD Monte Carlo models. A corrected differential cross section is presented. A detailed examination is made of jet profiles, event jet multiplicities and the fraction of the transverse energy carried by the two jets with the highest transverse jet energies. There is good agreement with standard theory for events with transverse energies up to the largest observed values\(( \approx \sqrt {s/2} )\) and the analysis shows no evidence for any non-QCD mechanism to account for the event characteristics.
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Data on antiproton-proton cross sections at the c.m. energies 200 and 900 GeV are presented. The data were obtained at the CERN antiproton-proton Collider operated in a new pulsed mode in which the same beams were accelerated and decelerated between beam energies of 450 and 100 GeV. The properties of the machine determine the ratio of the luminosities at the two energies to about 1% and thus an accurate measurement of the ratioR of the inelastic cross sections could be made. We findR (=σ900/σ200)=1.20±0.01±0.02, where the first error is statistical and the second systematic. Interpolating existing data to estimateσine1(200 GeV) this measurement ofR leads toσine1(900 GeV)=50.3+0.4+1.0 mb. Using an extrapolated value ofσe1/σtot we estimate the total cross section at 900 GeV to be 65.3±0.7±1.5 mb. Both the inelastic and total cross sections are compatible with a ln2s dependence. Comparisons are made with different fits to the total cross section energy dependence.
Ratio of inelastic cross sections at 900 and 200 Gev.
Estimate of 900 Gev total cross section based on a) interpolation to obtain total cross section at sqrt(s)=200 Gev (51.6 +- 0.4mb.) b) interpolation and extrapolation to obtain the ratio of elastic to total cross sections at 200 & 900 Gev (0.19 +- 0.01 and 0.23 +- 0.01 respectively).
New data are presented on charged particle multiplicity distributions for non single-diffractive events produced at CM energies s = 200 and 900 GeV . The data were obtained at the CERN antiproton-proton collider operated in a new pulsed mode. The multiplicity distributions are very well described by a negative binomial distribution. The highest energy data show no sign of approaching scaling, confirming our earlier results on the breaking of KNO scaling. The energy variation of the average charged multiplicity can be fitted to a quadratic in ln s or a s 0.13 dependence.
Figure gives uncorrected multiplicity distributions. Here we give the corrected distributions. Data supplied by D. Ward.
Results for multiplicity moments based on negative binomial fit to corrected data. Errors reflect both statistical and systematic effects. Results from earlier data at 546 Gev cm energy are also given.
C moments for corrected data where CQ=<N**Q>/<N>**Q.
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