The Fermilab hybrid 30-in. bubble-chamber spectrometer was exposed to a tagged 147-GeV/c positive beam containing π+, K+, and p. A sample of 3003 K+p, 19410 pp, and 20745 π+p interactions is used to derive σn, 〈n〉, f2cc, and 〈nc〉D for each beam particle. These values are compared to values obtained at other, mostly lower, beam momenta. The overall dependence of 〈n〉 on Ea, the available center-of-mass energy, for these three reactions as well as π−p and pp interactions has been determined.
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We measured the elastic scattering of αα at s = 126 GeV and of α p at s = 89 GeV . For αα , the differential cross section d σ /d t has a diffractive pattern minima at | t | = 0.10 and 0.38 GeV 2 . At small | t | = 0.05−0.07 GeV 2 , this cross section behaves like exp[(100 ± 10) t ]. Extrapolating a fit to the data to the optical point, we obtained for the total cross section α tot ( αα ) = 250 ± 50 mb and an integrated elastic cross section σ e1 ( αα ) = 45 ± mb. Another method of estimating σ tot ( αα ), based on measuring the interaction rate, yielded 295 ± 40 mb. For α p, d σ /d t has aminimum at | t | = 0.20 GeV 2 , and for 0.05 < | t | < 0.18 GeV 2 behaves like exp[(41 ± 2) t ]. Extrapolating this slope to | t | = 0, we found σ tot ( α p) = 130 ± 20 and σ e1 ( α p) = 20 ± 4mb. Results on pp elastic scattering at s = 63 GeV agree with previous ISR experiments.
Axis error includes +- 15/15 contribution.
Axis error includes +- 15/15 contribution.
METHOD 1 FOR SIG IS USING OPTICAL THEOREM. METHOD 2 FOR SIG IS BASED ON THE MEASURED LUMINOSITY-MONITOR CROSS SECTIONS.
We measured the total cross section for p p scattering at s = 52.8 GeV at the CERN ISR, using the direct, total-rate method. The result obtained, σ tot ( p p ) = 44.70 ± 0.53 mb , shows that, in common with σ tot (pp), this cross section also starts to rise in the ISR energy range. We remeasured the total cross section for pp scattering at the same energy, obtaining σ tot (pp) = 43.26 ± 0.33 mb, and found for the difference, Δσ tot = σ tot ( p p ) − σ tot ( pp ) , a value of 1.44±0.45 mb.
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An experiment using the Fermilab Single Arm Spectrometer (SAS) facility and an associated nonmagnetic vertex detector studied the reactions a+p→c+X, where a and c were π±, K±, p, or p¯. Extensive measurements were made at 100 and 175 GeV/c beam momenta with the outgoing hadrons detected in the SAS covering a kinematic range 0.12<x<1.0 and pT<1.25 GeV/c. Additional data covering a more restricted range in x were also gathered at 70 GeV/c incident momentum. In this high-statistics experiment, the identification of both the incoming and outgoing charged hadrons were made with a total of eight Čerenkov counters. New and extensive single-particle inclusive data for charged-particle production in low-pT hadronic fragmentation are presented. The average associated charged-particle multiplicity and pseudorapidity distributions are also given.
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We measured the total cross section for p p scattering at √ s = 53 GeV at the CERN ISR. The method was based on the measurement of the total interaction rate and of the ISR luminosity. The result obtained, σ tot = 44.1 ± 2.0 mb, suggests that σ tot ( p p) starts increasing at ISR energies. A measurement of the p p differential cross section was also performed: the results show a change in the slope at | t | ≈ 0.1 GeV 2 , similar to that observed in pp scattering.
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Neutral-pion production in pp interactions has been studied using 8000 photon conversions in the Fermilab 15-ft bubble chamber. Inclusive π0 multiplicity moments and ππ correlation integrals are presented; f200 is determined to be + 3.0±0.8. For the semi-inclusive π0 multiplicity distributions we find 〈n(π0)〉n− to increase with n−, while the dispersions are n− independent. Results on f2−0, f200, and f2,n−00 are compared to predictions of simple cluster models.
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The measurement of the proton-proton total cross section performed by the CERN-Pisa-Rome-Stony Brook Collaboration at the CERN ISR is discussed in detail. The total interaction rate, the elastic scattering rate in the forward direction, and the machine luminosity were measured simultaneously to obtain three different determinations of the total cross section. Consistent results were found, which made it possible to prove the reliability of the Van der Meer luminosity calibration within +-0.9% and to achieve a precision of +-0.6% in the measurement of the total cross section.
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Measurements of the proton-proton total cross section have been made with increased precision (±0.6%) over the ISR energy range s =23.5−62.7 GeV . Two different experimental methods gave consistent results, showing that the total cross section increases 10% over the ISR range and in addition that the absolute value of the ISR luminosity can be measured to ±0.9%.
CROSS SECTIONS ARE A WEIGHTED AVERAGE OF THOSE OBTAINED BY THE PISA-STONY BROOK METHOD AND BY THE CERN-ROME (OPTICAL THEOREM) METHOD.
We present a measurement of the total cross section σ t in proton-proton collisions at the CERN ISR. The method involves determination of the total interaction rate and machine luminosity. A two-arm scintillation hodoscope observes ∼ 90% of the total interaction rate, while a streamer chamber is employed for event topologies missed by the main trigger. An increase of about 10% in σ t is observed in the energy range √ s = 23.6 to √ s = 62.8 GeV/ c in agreement with previous experiments.
VAN DER MEER METHOD.
We have measured the total inelastic cross section (σinel) and charged-particle multiplicities obtained in pp collisions at 405 GeV/c. The data are from a preliminary 12 000-picture bubble-chamber exposure. We find σinel=32.8±1.0 mb; the low moments of the multiplicity distribution for negative particles are 〈n−〉=3.50±0.07, D−=2.37±0.05, f2−=2.1±0.2, and f3−=0.1±0.9. We also present updated results at 102 GeV/c.
SUPERCEDES PRELIMINARY RESULTS IN J. W. CHAPMAN ET AL., PRL 29, 1686 (1972).
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FIT TO ELASTIC DIFFERENTIAL CROSS SECTION FOR 0.05 < -T < 0.7 GEV**2.
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