A search has been made for direct photon production in pBe interactions at 200 and 300 GeV/ c over the kinematic region 1.5 < P ⊥ < 4.0 GeV/ c and −0.7 < X F < 0 (90° < θ cms < 160°). An excess of single photons above that which is predicted from the measured π 0 and η 0 production is observed. Theratio of γ / π 0 production is calculated assuming that the excess arises from direct photon production. We find that this ratio averages 0.070 ± 0.025 (including systematic errors) in this region of X F and P ⊥ for our 200 and 300 GeV/ c data. We have used our measured value of the η / π 0 ratio of 0.47 ± 0.10 in the determination of the γ / π 0 ratio. The variation of γ / π 0 with X F , P ⊥ , X R and θ cms presented.
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Using 20.5 GeV electrons on protons, we measured inclusive π 0 's (of transverse momentum, p T , from 0 to 1.4 GeV/ c ) produced by virtual photons of energy, ν, from 4 to 16.5 GeV and four-momentum squared, q 2 , from −1.8 to −8.5 (GeV/ c ) 2 . Comparing with charged pion data, we find σ π 0 = 1 2 (σ π + + σ π − ) , supporting the quark model. Photon knockout of a quark is favored as the interpretation of these data because of scaling in z = E π / ν and similarity in z -dependence of other pion production data. Consistent with this interpretation are the dependence of 〈 p T 〉 on q 2 , the azimuthal dependence, and fits to the constituent interchange model. We also observe a possible p T −4 dependence at large | q 2 | over a limited p T range.
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Measurements of recognized π0 production in p-Be collisions for 0.1<X⊥<0.5 and −0.8<XF<0.0 at 200, 300, and 400 GeV/c are presented. These invariant cross sections are fitted by Edσdp3=A(1−XR)MP⊥−N over this range of X⊥ and XF with M=4.88±0.14 and N=8.90±0.10 independent of energy. No significant evidence for breaking of this scaling is observed over this large kinematic region at these energies.
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Charged-particle multiplicity distributions in 400-GeV/c pd interactions have been studied in an experiment in the Fermilab 30-inch bubble chamber. From the fractions of odd-prong and backward-proton events, a rescatter fraction of 0.22±0.01 is found (for N≥3). The pn multiplicity distribution is obtained from the odd-prong distribution plus a no-cascade assumption. After making one-prong and two-prong estimates, mean charged-particle multiplicities of 9.49±0.12 for pd (including slow particles) and 8.57±0.12 for pn are obtained. In the incident momentum range 100 to 400 GeV/c, pd and pp distributions are very similar to each other and are different from pn distributions.
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
Axis error includes +- 0.0/0.0 contribution (?////SHORT PROTON VISIBILITY, UNOBSERVED DALITZ PAIRS, UNOBSERVED VEES, UNOBSERVED CLOSE SECONDARIES, UNCOUNTABLE EVENTSTHE ONE- AND TWO-PRONG EVENTS WERE NOT MEASURED AND WERE ESTIMATED USING ADDITIONAL ASSUMPTIONS AND DATA OF OTHER EXPERIMENTS//TO OBTAIN THE FREE-NEUTRON DISTRIBUTIONS THE ASSUMPTION THAT RESCATTERING IS MULTIPLICITY INDEPENDENT HAS BEEN MADE, AND CORRECTION FOR DEUTERON-FINAL-STATE EVENTS AND FOR WAVE-FUNCTION SYMMETRY REQUIREMENTS HAS BEEN MADE).
We have measured total hadronic photoproduction cross sections on carbon, copper, and lead. Tagged-photon energies ranged from 20 to 185 GeV for copper and from 45 to 82 GeV for carbon and lead. The energy and A dependence of shadowing were computed by comparing these results to the hydrogen cross section as measured nearly simultaneously with the same apparatus. We observed somewhat more shadowing than did most experiments at lower photon energies.
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Inclusive cross sections for the production of π ± and K ± mesons in proton-proton collisions have been measured at a c.m. energy √ s = 45 GeV, in the range 0.41 < x < 0.95 and 0.35 < p T < 1.45 GeV, where x = 2 p L/√ s and p L , p T are the longitudinal and transverse components of the momentum of the meson. Within the measured range the p T dependence of the invariant cross section is essentially independent of x and weakly dependent on the type of particle. For all particles the invariant cross sections at fixed p T fall by three orders of magnitude between x = 0.4 and 0.95. Except at the highest values of x and p T , the statistical accuracy is better than 10%. The data are compared with a triple-Regge model and with a simple quark-parton model.
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The photon total cross section on protons has been measured with high precision in the Fermilab tagged-photon beam for photon energies from 18 to 185 GeV. The cross section decreases to a broad minimum near 40 GeV, and then rises by about 4 μb over the remainder of the range. A ρ+ω+ϕ vector-dominance model (normalized to low-energy data) falls below the high-energy results by 2 to 6 μb, suggesting a contribution from charm-anticharm states.
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We present results on inclusive Δ ++ (1236) production in 100 GeV/ c p p interactions. In the region | t | < 1 GeV 2 we find a cross section of 1.29 ± 0.15 mb. Comparisons with pp interactions at high energies show Δ ++ production in pp and p p interactions to be very similar. The decay angular distributions of the Δ ++ are consistent with production predominantly through pion-exchange and the properties of the system recoiling from the Δ ++ are similar to those of real π + p interactions. However, the p π + background is found to show qualitatively similar behaviour. In contrast to the indications of Δ ++ production through pion exchange we also find evidence that events proceeding through diffraction dissociation are more likely to contain Δ ++ than other events. We present results on the forward production of Δ ++ in association with Δ ++ and protons.
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Data on coherent elastic and inelastic deuteron-proton scattering are presented. The measurements were made at the CERN ISR with a single arm spectrometer, at s = 2800 GeV 2 and momentum transfer squared (− t ) in the range 0.15 to 0.42 GeV 2 . The data are compared with elastic and inelastic diffractive proton-proton scattering data taken with the same apparatus at the same s and t values. The t dependence of the elastic dp → dp differential cross section is compared to simple predictions based on Glauber theory. The differential cross sections for pp → pX and dp → dX are also compared for M X 2 → 280 GeV 2 , where M X denotes the mass of system X recoiling against the measured proton and deuteron.
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INVARIANT AND SINGLE DIFFRACTIVE INCLUSIVE DIFFERENTIAL CROSS SECTIONS.
Inclusive and semi-inclusive $ρ^0$ production in 100-GeV/c $\bar{p}p$ interactions has been studied as a function of c.m. rapidity and transverse momentum. Cross sections are compared with those for $\bar{p}p$ interactions at other energies, as well as pp and π±p interactions, over the range ∼2 < $p_{lab} < 200$ GeV/c. A measurement of the $f^0$ production cross section has been made. Calculations of the contribution from $\rho^0$ decay to prompt lepton production are presented.
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