T. Åkesson

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

AbstractIn a study ofpp collisions atn

Bose-Einstein correlations in αα, pp and pp interactions

sqrt s = 63

A study of exclusive central hadron production at the ISR as a search for gluonium states

n 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.

Pion interferometry in jet events at the CERN Intersecting Storage Rings

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).

Antibaryon production in the central region at the ISR

Abstract Bose-Einstein correlations between pions produced in the central region of rapidity in αα, pp and p p interactions have been studied at the ISR. The parameters r and τ c -often interpreted as the radius and depth of the π-emitting region - are found to be independent of incident particle type but to depend on the mean charged multiplicity. In high multiplicity events, the pions appear to originate from a larger space-time region.

A comparison of direct photon, π0 in pp and pp interactions at the CERN ISR

Abstract Events with a large transverse energy in a calorimeter with full azimuthal coverage and |y|

Evidence for a directional dependence of Bose-Einstein correlations at the CERN intersecting storage rings

Abstract We present first results from a study of the exclusive reaction pp→pπ + π − p at √s=63 GeV with π + and π − produced in the central region. This reaction has been suggested as a method of searching for gluonium states. The π + π − mass distribution shows rapid order of magnitude decreases in cross section at both 1000 MeV/ c 2 and 1500 MeV/ c 2 . Further structure is observed above 2000 MeV/ c 2 .

The transverse energy distribution in hadron-lead collisions

We have observed an enhanced production of pairs and triplets of identical charged particles at small momentum differences in events with two central jets produced inpp collisions at the CERN Intersecting Storage Rings. The size and structure of this ‘Bose-Einstein’ enhancement, shown by the particles within a jet, resembles that observed in minimum-bias events. The correlation function can be well parametrized by the single variableQ — the absolute value of the four-momentum transfer — and is more peaked than a single Gaussian.