R. Castaldi

Measurement of the total proton-proton cross-section at the ISR

Abstract We present the first results of a measurement of the total cross-section σ T in proton-proton collisions at equivalent laboratory momenta between 291 and 1480 GeV/ c at the CERN Intersecting Storage Rings (ISR). The method is based on the measurement of the ratio of the total interaction rate and the machine luminosity. The data show an increase of about 10% in σ T in this energy interval.

Measurement of inclusive two-particle rapidity correlations at the ISR

Abstract We present data on two-particle distributions in the approximate rapidity variable η = −1n tan θ /2 for secondaries produced in proton-proton collisions at the CERN Intersecting Storage Rings (ISR). The data at centre-of-mass energies of 23 and 62 GeV show the existence of energy-independent positive, short-range correlations between secondaries within the central region. Deviations from short-range correlation exist when one (or both) of the particles is near the boundary of the available phase space. In part, such deviations are interpreted as the effect of a diffractive-like component in multiparticle production.

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.

New measurements of proton-proton total cross section at the CERN intersecting storage rings

Abstract 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%.

Measurement of charged particle multiplicities associated with large transverse momentum photons in proton-proton collisions

Abstract We have measured the behaviour or charged-particle multiplicities as a function of the transverse momentum of photons produced at 90° in proton-proton collisions. The data were obtained at the CERN Intersecting Storage Rings (ISR) at a centre-of-mass energy of 53 GeV and cover the transverse momentum range 0

Experimental tests of limiting fragmentation at the ISR

Abstract We present direct tests of the hypothesis of limiting fragmentation from an experiment at the CERN Intersecting Storage Rings at centre-of-mass energies between 31 and 53 GeV. Single-particle inclusive distributions and partial multiplicity distributions are observed for the case in which the energy of one beam is fixed while varying the energy of the other beam. Within cones around the beam, limiting fragmentation is shown to be valid.

Associated hadronic production in μ-pair events at the CERN Intersecting Storage Rings

Abstract We have measured at √s=62GeV, at the CERN Intersecting Storage Rings, the associated charged hadrons with massive μ pairs, employing a vertex detector of ∼ 4π coverage. The experiment has provided the first data on hadron multiplicity, angular distributions, and correlations in lepton pair events at ISR energies. The average associated charged multiplicity 〈nch〉 is found to increase as the invariant mass of the hadronic system Mh increases, similarly to the observed √s dependence in e+e− annihilation into hadrons at high energies. The multiplicity also increases with pT in the hemisphere opposite to the transverse momentum pT of the dimuon. Small clusters appear to be produced, whose correlation with the μ-pair can be explained in a simple Monte Carlo model incorporating the production of a weakly collimated jet of low multiplicity, recoiling against the dimuon.

Photoproduction of ω-mesons from nuclei

Abstract We report on an experiment of ω-photoproduction from nuclei (C, Al, Zn, Ag, Ta, Pb; 5.7 GeV mean photon energy) performed at DESY. The experimental apparatus detects the πoγ decay of the produced ω-mesons. Results about the ω-photon coupling γω2/4π and about the ω-nucleon total cross section σω are derived. The dependence of these results on the different possible models of analysis is discussed.

Correlations of secondaries in events with a forward neutron at the ISR

Abstract Data, obtained from p-p collisions at centre-of-mass energies between 31 and 63 GeV, are presented on inclusive and semi-inclusive correlations between forward emitted neutrons and charged particles observed in an omnidirectional hodoscope. A total absorption spectrometer was used to detect the neutrons and to measure their energy. Significant correlations are observed over the whole rapidity range. The data suggest that neutrons result from the decay of clusters emitted in the fragmentation region.

An upper limit for the branching ratio Γ(φ → πo + γ)Γ(φ → all)

We report on an experimental performed at DESY to search for the πo + γ decay of the φ mesons, photoproduced at 5.5 GeV on a Zn target. From the known production cross-section and the calculated detection efficiency, an upper limit for the branching ratio B = Γ(φ → πo + γ)Γ(φ → all) of 0.35% was obtained.