212 interactions of 2.75-Bev protons have been observed in a hydrogen-filled diffusion cloud chamber. The data indicate an elastic cross section of 15 millibarns, with about 9 millibarns cross section for single pion production, 13 millibarns for double, and 4 for triple. There is one example of quadruple pion production. One definite example of the production of heavy unstable particles was observed, and two doubtful cases. The median elastic scattering angle was 19° in the c.m. system. Angle and momentum distributions for inelastic events are consistent with those observed at lower energies.
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Differential cross sections for the photoproduction of single charged pions from deuterium and hydrogen have been measured at pion center-of-mass angles between 30° and 90° and at photon energies between 3.0 and 3.7 GeV. The ratio of π− to π+ cross sections from deuterium is found to be appreciably smaller than 1.
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Proton-proton elastic scattering has been measured at the CERN Intersecting Storage Rings in the four-momentum transfer range 0.001 ⩽… t …⩽ 0.015 GeV 2 at centre-of-mass energies of 23 and 31 GeV. The detection of Coulomb scattering and of its interference with nuclear scattering leads to the determination of the real part of the nuclear amplitude and of the total proton-proton cross section by the optical theorem.
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Measurements are presented of the recoil-proton polarization for π0 photoproduction angles near 64° in the c.m. system. The steep angular dependence observed by others at lower energies persists to at least 1500 MeV, and the polarization crosses through zero near 63° over the entire 900-1600-MeV energy interval. Summary fits are made to available recoil-proton polarization data, 950-1250 MeV, and are found to require terms of order cos3θ, but no higher.
Axis error includes +- 0.0/0.0 contribution (?////).
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X ERROR D(EKIN) = 0.0600 MEV.
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.
A partial-wave analysis of the low-mass ( π + π − p) system produced in the reaction K − p → K − ( π + π − p) at 4.2 GeV/ c incident momentum is performed in order to study the two ( π + π − p) enhancements around 1500 and 1700 MeV. It is found that the low-mass ( π + π − p) system can be described using the spin-parity states J P = 1 2 + , 3 2 − and 5 2 + only. In the 1500 MeV region contributions are observed from the 1 2 + wave decaying into pϵ and the 3 2 − wave decaying into Δ ++ π − ; in the 1700 MeV region contributions are found from the 1 2 + wave decaying into Δ ++ π − , the 3 2 − wave decaying into pϵ, and the 5 2 + wave decaying into pϵ.
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The photoproduction of ρ0 and ρ− mesons has been studied at 3 GeV in the reactions γd→dπ±π−, γd→psnπ+π−, and γd→pspπ−π0. For ρ0 and ρ− production in these reactions we present the total and differential cross sections, the decay angular distributions, and the spin density matrix elements. The photoproduction of the ρ0 is found to be consistent with s-channel helicity conservation and is dominated by natural-parity exchange. The ρ− meson production has approximately equal natural- and unnatural-parity-exchange contributions. The unnatural-parity-exchange contribution is consistent with one-pion exchange and is used to estimate the value of Γρπγ.
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Charged current data of a spark chamber neutrino experiment at the 70 GeV Serpukhov accelerator (10 200 events in the v beam and 3600 events in the v beam with energies up to 30 GeV) have been analyzed. Total neutrino and antineutrino cross sections and v -distributions are obtained.
Measured charged current total cross section.
Measured charged current total cross section.
We present results on charged multiplicity nch=2 and nch>2 muon events produced in e+e− collisions with 〈s12〉=7.3 GeV at 90° to the beams. The background-subtracted inclusive cross section for the nch=2 events is 10.2±5.4 pb/sr, in agreement with the expected contribution from the heavy lepton τ. The cross section for the nch>2 events is 19.0±6.5 pb/sr whereas we expect only 2.9 pb/sr from the τ, indicating that we may be seeing the weak decays of charmed mesons.
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We present data on inclusive negative-hadron production from charged-current antineutrino interactions in a 21% Ne-H mixture. Inclusive single-particle distributions are presented and are shown to be insensitive to the momentum transferred to the hadron vertex. Comparisons made to inclusive data from π−p and π−n interactions indicate a close similarity between the hadrons resulting from π-nucleon and ν¯-nucleus interactions. The general features of the ν¯-nucleus data are found to be similar to those seen in ν¯p interactions. This last observation implies that ν¯p and ν¯n interactions are similar and that nuclear effects are small.
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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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On 8 K events of the reaction p p π + π − at 7.23 GeV/ c simple selection on angular parameters is performed yielding a sample of events with the typical features of diffraction dissociation. A cross section of 1.22 ± 0.08 mb (in two vertices) and a slope of the t distribution of 12.6 ± 1.0 GeV −2 for − t < 0.1 GeV 2 are obtained for the diffraction fraction dissociation p → p π + π − + c.c. Using an analogous selection procedure, another sample of events is isolated that is characterized by double resonance production. Cross sections for Δ Δ and Δ Δ ′ + c.c. production amount to 1.27 ± 0.09 mb and 0.23 ± 0.07 mb respectively. Diffraction dissociation and double resonance production together make up for 87% of the total cross section for the reaction p p → p p π + π − , which is 3.11 ± 0.13 mb.
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EXPONENTIAL FIT TO D(SIG)/DT IN THREE REGIONS OF T. FOR EVENTS WITH M(P PI+) AND M(AP PI-) < 1.4 GEV.
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The differential cross sections for γp→γp and γp→π0p have been measured for incident photon energies in the range of 2 to 6 GeV and for |t| ranging from 0.7 to 4.3 GeV2. This corresponds to a center-of-mass angle range of 45° to 128°. The energy dependence of the data is compared to that predicted by several parton models.
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We report experimental results on the cross section for the reaction e + e − → hadrons as a function of the total c.m. energy in the range W = 1.42–3.09 GeV. The results, combined with those already existing below the charm threshold, clearly indicate a structure for R ( W ) = α ( e + e − → hadrons)/ α ( e + e − → μ + μ − ) in that energy region.
THE ENERGY RANGES OF THE NEW DATA AND THE PREVIOUS (REVISED) DATA OVERLAP BETWEEN 1.9 AND 2.0 GEV. RADIATIVE CORRECTIONS HAVE BEEN APPLIED TO ALL DATA. THIS CROSS SECTION EXCLUDES TWO-BODY FINAL STATES.
AVERAGE CHARGED AND NEUTRAL MULTIPLICITY. QUOTED ERRORS ARE STATISTICAL ONLY.
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PRELIMINARY DATA.
PRELIMINARY DATA.
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FROM LEGENDRE POLYNOMIAL FIT TO D(SIG)/DOMEGA, USING VALUE AT THETA = 0 DEG OBTAINED BY ADDITION OF THE PI+ P AND PI- P FORWARD SCATTERING AMPLITUDES GIVEN BY DISPERSION RELATIONS.