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.
We have obtained the branching ratios for p p annihilation at rest into π + π − and K + K − in a pure p p initial angular momentum state L = 1. A gaseous hydrogen target at normal pressure and temperature was used and events associated with transitions of the antiprotonic atom to the 2p level were selected by detecting the Balmer X-ray series. The branching ratios for p p annihilation into π + π − and K + K − from the 2p state are (4.81 ± 0.49) × 10 −3 and (2.87 ± 0.51) × 10 −4 , respect The pion yield is slightly larger than in liquid hydrogen, where L = 0 annihilation dominates, while the kaon yield is suppressed by a factor of four. Using these and previous data, we derive the branching ratios for pp annihilation into all ππ and K K modes from S and P states. A measurement in gaseous hydrogen, without X-ray requirement, yields the branching ratios (4.30 ± 0.14) × 10 −3 and (6.92 ± 0.41) × 10 −4 . With the known branching ratios of (3.33 ± 0.17) × 10 −3 and (1.01 ± 0.05) × 10 −3 in liquid hydrogen, we find that (50.3 ± 6.4)% of all annihilations in gas at NTP occur in the initial angular momentum state L = 1.
Axis error includes +- 0.0/0.0 contribution (?////).
Axis error includes +- 0.0/0.0 contribution (?////).
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.
No description provided.
p̄p total cross sections have been measured from 220 to 413 MeV/ c in small (⩽ 10 MeV/ c ) steps of momentum with statistics of ± 0.5 %. There is no evidence for structure in the cross section, and a limit of 8 mb MeV/ c 2 is set with 90% confidence on the strength of any narrow resonance down to 250 MeV/ c .
Data taken with long target.
Data taken with short target.
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).
The interaction between antiprotons and protons has been studied in the range 1910 to 1990 MeV center-of-mass energy in a drift-chamber experiment at the Brookhaven Alternating Gradient Synchrotron. The total cross section has been determined at eleven different incident momenta, and the elastic cross section between 8 and 30 deg in the laboratory has been measured with an energy resolution of about 5 MeV. The cross section for annihilation into charged mesons has also been measured, with the same resolution. There is no evidence in any of these channels for the existence of a narrow resonance.
Data are for total sample with nuclear physics calculation as described in the paper.
Partial elastic cross sections.
Partial annihilation cross sections.
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.
Results are presented on the charge exchange reaction\(\bar pp \to \bar nn\) and\(\bar np\) annihilations from bubble chamber exposures to antiproton beam of momenta 700 and 760 MeV/c. The differential cross section of\(\bar pp \to \bar nn\) shows a forward spike followed by a clear dip bump structure. Total annihilation cross section of\(\bar np\) for average\(\bar n\) momentum of 700 MeV/c has been evaluated to be 55.4±2.2 mb. The multiplicity, Feynmanx andpT2 distributions for inclusive charged pions in\(\bar pp\) and\(\bar np\) annihilations are found to be similar. The emission of charged pions from\(\bar np\) annihilations are found to be consistent with thermodynamic models with temperature ∼110 MeV.
No description provided.
No description provided.
No description provided.
The p̄p annihilation cross section has been measured with good resolution (∼2 MeV rms) in the mass range 1900–1960 MeV. No narrow structures are seen, the 90% confidence level upper limit being 8–12 mb‐MeV for the integrated area of a resonance in this mass range. However, we do not rule out a very narrow bump‐dip structure seen in an earlier experiment in the 1935–1941 MeV mass interval. The data also do not support the existence of a broad structure previously reported at 1937 MeV.
Fit of form A + B/D gives A = 8.5 +- 2.5mb and B = 40.7 +- 1.3mb in the mass range 1900 to 1960 MeV.
The proton-antiproton total cross section was measured at the CM energy √s = 546 GeV . The result is σ tot = 61.9± 1.5 mb . The ratio of the elastic to the total cross section is σ e ℓ / σ tot = 0.215±0.005. A comparison to the lower energy data shows that the increase of the total cross section with energy is very close to a log 2 s behaviour.
CROSS SECTIONS ASSUMING RHO = 0.15.
RATIO OF ELASTIC TO TOTAL CROSS SECTION.
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