C. Fabjan

Double parton scattering inpp collisions at\(\sqrt s = 63\) GeV

AbstractIn a study ofpp collisions at

Properties of a Fine Sampling Uranium - Copper Scintillator Hadron Calorimeter

\sqrt s = 63

The axial field spectrometer at the CERN ISR

GeV with more than 29 GeV total transverse energy emitted into 1.8 units of rapidity in the central region, we have extracted a sample of 4-jet events and compared it with models of the two sources of 4-jet production: double bremsstrahlung and double parton scattering. The data cannot be described by bremsstrahlung alone, and we extract the fraction of 4-jet events attributed to double parton scattering for various definitions of the 4-jet sample. We determine the double parton scattering/2-jet yield ratio, and this leads to a determination of the proton radius. We discuss the implications of our observations for the general understanding of high-ΣET events.

Coherent emission of transition radiation in periodic radiators

We present results from a study of centrally produced mesons in 3 × 106 events with two small-angle protons at the CERN Intersecting Storage Rings. A high-statistics sample of exclusive pp → ppπ+π− events at √s = 63 GeV has been obtained, where the reaction mechanism is dominated by double pomeron exchange. Scalar or tensor glueballs may be produced by this process. The π+π− mass spectrum has a distinctive structure, and analysis shows that the data are dominantly S-wave up to 1600 MeV. The behaviour of the D-wave provides evidence for a 2++ resonance (M = 1480 ± 50 MeV, Γ = 150 ± 50 MeV) in addition to the f(1270). We also show data on exclusive K+K−, pp, and π+π−π+π− production, and on the analogous reaction αα → ααπ+π− at √s = 126 GeV. Flavour independence is suggested by the observation of approximately equal numbers of K+K− and π+π− pairs for mass above 1 GeV. The mass spectra are also apparently independent of √s (45, 63, 126 GeV) and incident particle type (p, α).

Direct evidence for the emergence of jets in events triggered on large transverse energy in pp collisions at s = 63 GeV

Abstract We present results obtained with a uranium/copper scintillator fine-sampling calorimeter with wavelength shifter readout. Test beam measurements made with e±, π± and protons in the momentum range 0.3–40 GeV/c are presented. The calorimeter achieves energy resolutions of σ(E) E = 0.36 √E and 0.16 √E for hadrons and electrons, respectively. The measured ratio of response for electrons to that for hadrons is 1.11, for energies of 2 GeV or more. The spatial resolution achieved for single particles at normal incidence is ∼1 cm for electromagnetic showers and ∼3 cm for hadronic showers. Operational experience over three years of running at the CERN ISR, including operation at very high luminosities (∼1.4×1032 cm−2 s−1) is described.

Characteristics of J/ψ and ϒ production at the CERN intersecting storage rings

Abstract We describe the calorimeter system serving the HELIOS experiment at CERN, its calibration, and its performances measured in test experiments. The calorimeter signal for hadrons was found to be proportional to the energy to within 2% over the energy range 8–200 GeV. Over the same energy range the energy resolution σ E scales as 1 E for both electromagnetic and hadronic showers. The values found were (0.215 ± 0.007) E and (0.337 ± 0.012) E , respectively, for the detection of single particles. The signal ratios e/mip and e π are 0.70 ± 0.05 and 0.984 ± 0.006, where the latter ratio was found to be dependent on the signal integration time the quoted number being obtained for a 130 ns gate. The energy resolution for multiparticle detection was found to be about twice as large as for the detection of single particles in the actual calorimeter configuration. The energy flow logic, designed to provide trigger information on physics quantities such as transverse energy and missing energy, was shown to be very accurate and reliable.

Inclusive η production at high pT at the ISR

Abstract The axial field spectrometer is being exploited in a wide-ranging programme to study pp and p p -collisions which are characterized by a large transverse momentum. A specially shaped magnet together with an “imaging” drift chamber is used for efficient detection and momentum analysis of high multiplicity events at interaction rates of up to 5 × 106 s. Particle identification is accomplished over 1 sr; an uranium/scintillator hadron calorimeter will cover more than 8 sr in 1982 to provide an unbiased energy measurement.

Bose-Einstein correlations in αα, pp and pp interactions

Abstract Measurements have been made of X-ray transition radiation spectra, which were produced by relativistic electrons traversing periodic stacks of mylar and lithium foils. The dependence of the spectral yield on the stack parameters and on the momentum of the electrons establishes the influence of long-range coherence in the emission of transition radiation.