A. Minten

Observation of jet structure in high pT events at the ISR and the importance of parton transverse momentum

Abstract Events with a charged particle of high transverse momentum were studied in pp collisions at √s = 52.5 GeV with the Split Field magnet (SFM) at the CERN-ISR, triggering on a charged particle of pT > 2 GeV/c, in the c.m. angular region θ ≅ 20° and θ ≅ 45°. The results provide further evidence for jet-like structure in high pT reactions. One of two produced jets is associated with the triggering hadron whereas the other is produced at an azimuthal angle that differs from that of the trigger by roughly 180°. The main features of the data are found to agree with the predictions of a simple parton-parton hard scattering model with vector gluon exchange, provided that one allows for partons in the proton to have transverse momentum. The ingredients of the model are all derived from data on deep inelastic lepton-proton scattering and from hadron production in e+e− annihilation. The model retains a simple pT−4 dependence for the parton-parton scattering. However, for pT ≲ 4GeV/c, the transverse movement of partons yields an approximate pT−8 scaling for the inclusive hadron distribution in agreement with observations. For the understanding of our data, it is found to be essential to take into account the soft component arising from the fragmentation of the spectator partons into hadrons.

Performance of the ALEPH Time Projection Chamber

Abstract The performance of the ALEPH Time Projection Chamber (TPC) has been studied using data taken during the LEP running periods in 1989 and 1990. After correction of residual distortions and optimisation of coordinate reconstruction algorithms, single coordinate resolutions of 173 μm in the azimuthal and 740 μm in the longitudinal direction are achieved. This results in a momentum resolution for the TPC of Δp / p 2 = 1.2 × 10 −3 (GeV/ c ) −1 . In combination with the ALEPH Inner Tracking Chamber (ITC), a total momentum resolution of Δp / p 2 = 0.8 × 10 −3 (GeV/ c ) −1 is obtained. With respect to particle identification, the detector achieves a resolution of 4.4% for the measurement of the ionisation energy loss.

The KN interaction from 800 to 1200 MeV/c (I). K−p cross sections

K−p reactions have been studied at 23 different momenta between 777 and 1226 MeV/c. This interval corresponds to a mass range of the KN system from 1688 to 1897 MeV. About 350 000 photographs were taken in the 81 cm Saclay hydrogen bubble chamber, exposed to a separated K− beam at the CERN proton synchrotron. A total of about 100 000 events were analysed and partial and differential cross sections were determined; polarisations were also obtained for those reactions where the decay of the Λ or Σ+ hyperon allowed their measurement. The data for all the channels are presented here except those corresponding to two-prong configurations, which make the subject of a separate investigation.

Charmed baryon production at the CERN Intersecting Storage Rings

Abstract The production of a Λ+c charmed baryon has been observed in pp collisions at the CERN ISR. A sharp peak at 2.26 GeV/c2 was found in the decay mode Λ+c → K ∗0 p in events triggered with a forward K− meson. Also the decay mode Λ+c → K− Δ++ seems to be present. The estimation of the total cross section for Λ+c production is given. However, the resulting value depends on the assumed form of the differential cross section. In addition, Λ+c production in events triggered by the presence of a direct electron is discussed.

Observation of charmed D meson production in pp collisions

Abstract Evidence for the forward production of D + mesons has been found in pp collisions at a c.m. energy of 52.5 GeV. A signal of 92 ± 18 events above background has been observed in the decay channel D + → K ∗ o π + → K − π + π + . The cross section in the phase space region of our experiment is given and implications for the total cross section for charmed D meson production are discussed.

Density, charge and transverse momentum correlations of particles in non-diffractive proton-proton collissions at √s = 52.5 GeV

Abstract Inelastic events with an observed charged multiplicity n obs ⩾ 7 have been studied at the CERN ISR using the split field magnet detector. Correlations of particle densities, charges and transverse momenta have been determined and a phenomenological analysis in the framework of cluster models has been performed. A good description of all results is obtained if one allows for charged clusters, produced in a mechanism with limited charge exchange. The mean transverse momentum of clusters is 0.65 ± 0.10 GeV/ c . Short-range correlations of particles of like charge due to the Bose-Einstein effect can be described as a second-order interferrence phenomenon with a radius R = 1.34 ± 0.31 fm and a lifetime of cτ = 1.38 ± 0.60 fm for the pion source.

Production of vector and tensor mesons in proton-proton collisions at\(\sqrt s = 52.5\) GeV

AbstractInclusive production of ϱ0,f, andg0 mesons and ofKs0,K*0 (892), ϕ andK*0(1430)mesons has been measured at ∼2.6 and ∼1.1 GeV/c in proton-proton interactions at

Study of double pomeron exchange in pp collisions at √s=31GeV☆

\sqrt s = 52.5