F.W. Büsser

Observation of πo mesons with large transverse momentum in high-energy proton-proton collisions

Abstract Invariant cross-sections are presented for the inclusive reaction p + p → π o + anything, Measurements of large transverse momentum π o s (2.5 GeV/ c p ⊥ c ) were made near 90° at the CERN ISR at five centre-of-mass energies (√ s = 23.5, 30.6, 44.8, 52.7 and 62.4 GeV. At large p ⊥ , the invariant cross-sections are seem to vary with s and p ⊥ , in good agreement with a fit of the form Ap ⊥ − n F ( p ⊥ /√ s ), with n ≈8 and F ( p ⊥ /√ s )≈ exp (−26 p ⊥ /√ s ).

A Study of Inclusive Spectra and Two Particle Correlations at Large Transverse Momentum

Abstract The inclusive production of π and η mesons at 90° from proton-proton collisions has been measured at the CERN ISR at centre-of-mass energies between 23.5 and 62.4 GeV. The momentum correlation of charged particles emitted together with a large transverse momentum pion has also been studied, using two magnetic spectrometers each centred at 90°.

Observation of high transverse momentum electrons at the CERN ISR

Abstract A search for high transverse momentum electrons directly produced in proton-proton collisions has been performed at the CERN ISR. The apparatus included a magnetic spectrometer with wire spark chambers, a lead-glass counter array, and a threshold gas Cerenkov counter. At a centre-of-mass energy √ s = 52.7 GeV, a signal has been observed in the range 1.6 T ∗ GeV /c . The signal occurs at a level of approximately 10 −4 of the inclusive pion cross-section.

A lead-glass cherenkov detector for electrons and photons

Abstract An apparatus for the detection of high-energy electrons and photons is described. Lead-glass Cherenkov counters measure the energies, and charged particle tracks are reconstructed using an array of wire spark chambers. The mode of operation, calibration, and stability of the system are described, and details are given of the ability to discriminate electrons from hadrons.

Observation of high mass electron-positron pairs produced in proton-proton collisions at the CERN ISR

Abstract In an experiment performed at the CERN Intersecting Storage Rings (ISR), 11 e+e− pairs of high invariant mass value (> 2.5 GeV/c2) have been observed. Of these events, 9 can be interpreted as arising from the reaction p + p → J (3.1) + anything. the cross-section for this reaction is estimated and compared with the result obtained at lower centre-of-mass energies.

A Measurement of Single Electrons, electron Pairs, and Associated Phenomena, in Proton Proton Collisions at the CERN ISR

Abstract Measurements of single-electron production in proton-proton collisions at the CERN ISR are presented for five centre-of-mass energies √s = 23.5, 30.6, 44.8, 52.7, and 62.4 GeV. The invariant cross sections for single electrons with transverse momenta of 0.60 to 4.7 GeV/c are given. Measurements of electron-positron pairs and measurements of charged hadrons produced in association with the single electrons, are also reported.

Ko and λ production at the CERN ISR

Transverse momentum distributions of λo, λo, and Ko, produced in pp collisions at x = 0, have obtained at the CERN ISR. The Ko yield is in agreement with published K+, K− results, obtained at this centre-of-mass energy (√s≈44 GeV). The results on λo and λo production obtained in this experiment are compared with results obtained at lower centre-of-mass energies.

A study of high transverse momentum η and π0 mesons at the CERN ISR

Abstract The production of high transverse momentum η mesons from proton-proton collisions has been studied at the CERN ISR. The decay η→γγ was identified in an array of lead-glass Cerenkov counters. The preliminary results, obtained at a total centre-of-mass energy √s=52.7 GeV, show an η signal, which amounts to approximately one half of the π0 cross-section for centre-of-mass transverse momenta between 3 and 5 GeV/c. The production of high transverse momentum π0s was also measured and compared with previous results.

Correlations between two large transverse momentum πO mesons at the CERN ISR

Abstract The correlations between two πOs of high transverse momentum were studied at the CERN ISR at a centre-of-mass energy s = 52.7 GeV . Results are presented for two πOs detected with an azimuthal separation near 180° and also near 0°. Angular and p⊥ correlations are discussed, as well as invariant mass plots. The observations are compared with some theoretical models of high p⊥ phenomena. The most striking feature of the data is a strong correlation in the transverse momentum of the two πOs.

Correlations between large transverse momentum π0 mesons and charged particles at the CERN ISR

Abstract A study of the charged particles emitted together with a large transverse momentum πO was made at the CERN ISR at a centre-of-mass energy s = 52.7 GeV . The πO mesons and the charged particles were observed in two detectors, each centred at θcm = 90° and each covering a laboratory solid angle of 0.59 sr for πos and 1.1 sr for charged particles. The multiplicity of charged particles, observed in the same and in the opposite hemisphere as the πO, was found to be larger than the average multiplicity for inelastic interactions. Some rapidity and azimuthal correlations were observed.