A. Böhm

OBSERVATION OF A DIFFRACTION MINIMUM IN THE PROTON-PROTON ELASTIC SCATTERING AT THE ISR

Abstract We have investigated the pp elastic scattering at the CERN Intersecting Storage Rings (ISR). We report results for centre-of-mass scattering angles between 30 and 100 mrad and for centre-of-mass energies of 23.5,30.7, 44.9 and 53 GeV. The elastic differential cross-section shows a diffraction-like shape with a sharp minimum at about t = −1.4 GeV 2 .

Measurements of the proton-proton total cross section and small angle elastic scattering at ISR energies

Measurements of the total cross section have been performed at the ISR with c.m. energies between 23.5 GeV and 62.5 GeV. Two independent experimental methods have been applied, a measurement of total interaction rate and of small angle elastic scattering. Both experiments give consistent results showing that the total cross section increases by (11.8±1.5) % over the ISR energy range. n nThis experiment has also measured the slope of the forward diffraction peak in elastic scattering at small momentum transfer. The elastic cross section shows the same relative rise as the total cross section, and the ratio λ of elastic to total cross section approaches a constant value of λ=0.178±0.003.

Production of nucleon resonances by single diffraction dissociation at the CERN ISR

The single diffraction dissociation process pp → (pπ+π−)p has been studied at the CERN ISR at √s = 45 GeV and 0.1 < −t < 0.6 GeV2. The reaction is dominated by nucleon resonance production: pp → pN (1520) and pp → pN(1688) with cross-sections (0.25 ± 0.08) mb and (0.56 ± 0.19) mb respectively.

On KL - KS regeneration in copper

Abstract The transmission regeneration amplitude after a thick copper block has been measured. The quantity ∣ƒ(0)− ƒ (0)∣ k varies from 20.0 ± 1.4 mb at 2.75 GeV/ c to 13.6 ± 1.2 mb at 7.25 GeV/ c . Results are in agreement with optical model calculations in which real and imaginary parts of the amplitudes for single nucleon scattering are determined from forward dispersion relations and total cross-sections.

Evidence for double Pomeron exchange at the CERN ISR

Abstract We have observed events at the CERN Intersecting Storage Rings (ISR) which are consistent with the double Pomeron exchange process p + p → p + X + p, where X represents a system of particles in the central region of the rapidity distribution separated by at least two units from the outgoing protons in the forward directions. The observed low charge multiplicity of the central cluster X indicates that this process is dominated by the formation of a low-mass system in the central region. In particular, we find that the differential cross-section for the process p + p → p + h + + h - + p, where h represents a charged particle, shows no correlation between t A and t B and has an exponential slope of 9.9 ± 1.8 GeV −2 independent of energy. The cross-section for this process is found to be approximately 20 μb over the ISR energy range.

Diffraction dissociation in the reaction p+p→Λ°+K++p at the CERN ISR

The exclusive reaction pp→Λ°K+p has been studied at 0.1<−tpp<0.6 GeV2 and energies √s=45 GeV and 53 GeV at the CERN ISR. Diffractive excitation p→Λ°K+ occurs predominantly in the mass range M(Λ°K+)≈2.1 GeV and peaks at 1.7 GeV. The cross section for pp→Λ°K+p is 10±3μb for M(Λ°K+)<2.5 GeV, and the tpp dependence is exp (bt) with b=7.0±0.5 GeV−2.

Multiwire proportional chamber spectrometer for the CERN intersecting storage rings

Abstract The design, construction, and performance of a multiware proportional chamber (MWPC) system (∼10 k wires) constructed for use at the CERN Intersecting Storage Rings (ISR) is described. This system employs hybrid integrated circuity for pulse detection and storage, and is read out via a CAMAC compatible system. The chambers plus two large-aperture magnets with accompanying scintillation and Cherenkov counters form a versatile multiparticle spectrometer system which has been used to investigate particle systems produced near 0° at the CERN ISR.

Observation of time-dependent KS and KL interference in the π+π− decay channel from an initial K0 state

Abstract The phase ϕ +− between the amplitudes K L → π + π − and K S → π + π − has been measured. The result is 46 0 ± ± 15 0 for a K L - K S mass difference Δm/ h = (0.526±0.20) × 10 10 s −1 , in good agreement with the “superweak model” of Wolfenstein which predicts ϕ +− SW = 42.6 0 ± 1.0 0 .

Double diffraction dissociation and test of pomeron factorization at the CERN ISR

Abstract We report the observation of double diffraction dissociation in the process p + p → (p π + π − ) + X at √ s of 45 GeV and momentum transfer in the − t range 0.15−0.53 GeV 2 at the CERN ISR. The relative rates for elastic, single and double dissociation reactions measured here are found to agree with the prediction of Pomeron factorization.

The phase difference between KL → π+π− and KS → π+π− decay amplitudes

The phase difference between the KL → π+π− and KS → π+π− decay amplitudes has been measured by observing the time dependence of the π+π− decay intensity from an initial K° (strangeness = +1) state. n nThe phase difference φ/+− is found to be 41° ± 12° for a KL − KS mass difference Δm/h = 0.526 × 1010sec−. The error includes statistical and systematic uncertainties. The phase φ+− is strongly correlated to the value adopted for Δm/h. The present uncertainty on Δm/h increases our error on φ+− from 12° to 15°. n nThe result is in agreement with the prediction of the ‘superweak model’ of CP violation.