G. Cocconi

The energy dependence of the proton-proton total cross-section for centre-of-mass energies between 23 and 53 GeV

Abstract Measurements of proton-proton elastic scattering at angles around 6 mrad have been made at centre-of-mass energies of 23, 31, 45 and 53 GeV using the CERN Intersecting Storage Rings. The absolute scale of the cross-section was established by determination of the effective density of the colliding beans in their overlap region. Proton-proton total cross sections were deduced by extrapolation of the elastic differential cross-section to the forward direction and by application of the optical theorem. The results indicate that over the energy range studied the proton-proton total cross-section increases from about 39 to about 43 mb.

PROTON-NUCLEI CROSS SECTIONS AT 20 Gev

Abstract Measurements of the differential cross section of 20 GeV protons scattered elastically and quasi-elastically by a series of nuclei, ranging from Li to U, are presented. The total and the elastic cross sections are also given. The light nuclei show, at the smallest angles, the characteristic center diffraction peak produced by an absorbing disc; at larger angles the quasi-elastic scattering produced by single nucleons predominates. The heavy nuclei exhibit diffraction rings up to the largest angles explored (≈ 20 mrad). The diffraction patterns are interpreted with an optical model that takes into account the contribution of both the nuclear and the Coulomb interactions. The radii of the heaviest nuclei turn out to be consistently larger than those deduced from electron scattering experiments. The opacity is found to be nearly complete only in the heaviest nuclei. Results at the largest angles measured show that only a small fraction of the nucleons in the nuclei can act as effectively independent scattering centres.

The Real Part of the Forward Proton Proton Scattering Amplitude Measured at the CERN Intersecting Storage Rings

The real part of the proton proton elastic scattering amplitude has been determined from its interference with the Coulomb amplitude at total centre-of-mass energies up to 62 GeV. The observed steady increase of ϱ with energy indicates that the total proton proton cross section continues to increase well beyond this energy.

Second Order Interference as a Tool for the Determination of Hadron Fireball Dimensions

Abstract Correlations between identical particles emitted simultaneously in hadron collisions can be used to determine the dimensions of the region where the secondaries are produced. The method is similar to that used by radio-astronomers to measure the angular dimensions of sources.

Measurements of the proton--proton total cross section by means of Coulomb scattering at the CERN Intersecting Storage Rings.

Abstract 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.

A detector for neutral-current interactions of high-energy neutrinod

Abstract The construction and performance of a large detector, designed principally to investigate neutral-current interactions of high-energy neutrinos, are described. The detector consists of an ionization calorimeter as a target to determine the energy and the direction of the shower produced by the neutrino scattering, and of a magnetic muon spectrometer. The calorimeter has also been used as a muon polarimeter.

Measurements of small angle proton-proton elastic scattering at the CERN intersecting storage rings

Abstract Proton-proton elastic scattering has been measured over the angular range 7 to 16 mrad at centre-of-mass energies of 31, 45 and 53 GeV using the CERN Intersecting Storage Rings. The results indicate that the diffraction peak has continued to shrink with increasing energy, but not as fast as suggested by the results at lower energies.

Experimental study of neutral-current and charged-current neutrino cross sections

Abstract Samples of 9200 muon-neutrino and 3800 muon-antineutrino interactions on nuclei were obtained with the fine-grain calorimeter of the CHARM Collaboration at the CERN 200 GeV narrow-band neutrino beam. The interactions were classified as either neutral-current or charged-current processes on an event-by-event basis. Neutral-current and charged-current cross sections in neutrino and antineutrino interactions are presented. From these results we deduce a statistically significant contribution of right-handed coupling to the neutral hadronic current, and a value of the electroweak mixing angle corresponding to sin 2 θ = 0.220 ± 0.014.

DISCONTINUOUS BEHAVIOUR IN LARGE ANGLE PROTON--PROTON ELASTIC SCATTERING AT HIGH ENERGIES.

Abstract Measurements of elastic proton-proton differential cross sections for angles between 65° and 90° c.m.s. have been made at 8, 9, 10, 11, 14, 15 and 21 GeV/c. The shape of the angular distribution is found to change suddenly between 8 and 11 GeV/c. An interpretation of this discontinuous behaviour in terms of the reactive effects of baryon-antibaryon pair production is proposed.

Precision measurement of proton-proton total cross section at the CERN intersecting storage rings

Abstract 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.