H. Foeth

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.

Λ0 polarization in proton-proton interactions at √s = 53 and 62 GeV

Abstract Λ 0 s produced in the inclusive reaction pp → Λ° + X with √s = 53 and 62 GeV at the CERN Intersecting Storage Rings are observed to be polarized along the normal to the production plane. In the ranges of longitudinal and transverse momenta, 15–24 and 0.6-1.4 GeV/ c , respectively, the mean polarization is found to be −(0.357±0.055).

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.

Observation of diffraction excitation in pp → (pπ+π−)+X at the CERN-ISR and tests of limiting fragmentation

Abstract In a single-arm magnetic spectrometer experiment at the CERN Intersecting Storage Rings (ISR), a prominent diffractive enhancement is observed for inclusive production of (pπ+π−) systems near x ∼ 1 at √s = 53 and 35 GeV. In testing limiting fragmentation and scaling for this system, inclusive pπ+π− diffractive excitation into a fixed invariant mass range is found to possess a cross-section independent of s to within (3 ± 5)%. The main component in the (pπ+π−) system is Δ(1236)π, with a charge structure compatible with the break-up of an isotopic spin 1 2 system.

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.

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.

Evidence for double diffractive excitation in pp → (pπ+ π−) + X at the CERN ISR and test of factorization

Abstract In a magnetic spectrometer experiment at the CERN Intersecting Storage Rings (ISR), evidence is obtained for the existence of double diffractive excitation in the reaction pp → (pπ+π−) + X at 〈pt2〉 = 0.03 GeV2 and S = 53 GeV . X is observed to be a multi-body low-mass system 12% of the time, in agreement with the same rate observed in pp → p + X.

Improvement of the wire gain near the frame of a time projection chamber

Abstract We have quantitatively studied the behaviour of a time projection chamber (TPC for the DELPHI detector) at small distances from the frame (less than 1 cm). The severe drop in gain near the frame can be overcome by shaping the electric field with guard rings.

Event classification with the BEBC internal picket fence

Abstract The internal picket fence is a proportional tube detector close to the pressure vessel of the big european bubble chamber, BEBC, that can provide timing information which can be linked with the tracks observed in the chamber and recorded on film. We give a general account of the IPF detector, its efficiency and use in our data analysis to improve the classification of charged current and neutral current neutrino interactions.

Construction and beam test results for the DELPHI two metre straw detector

Abstract A straw tube detector has been built as part of the 1995 upgrade for the DELPHI experiment at LEP. The detector is cylindrical in design, with inner wall and outer wall radii of 25 cm and 30 cm respectively. It consists of 960 straws in 5 layers, with a length of 2.1 m, running at atmospheric pressure with a 50:50 argon-ethane gas mixture. The efficiency and spatial resolution arising from the measurement of the drift time have been measured in a test beam. Preliminary results with a full scale prototype and a 2:1 argon-isobutane gas mixture at a gain of 2 × 104 give a coordinate resolution of 99 μm per straw, a resolution for a track element in the detector of 49 μm and an efficiency per straw of more than 99%.