D. Linglin

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.

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.

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

Spin, branching ratios and production characteristics of the K∗(1420)

\sqrt s = 52.5

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

GeV. The negative particle from the two-body decays of these resonances were identified by a threshold Cerenkov counter and used for triggering. Starting from the measured differential cross section, total inclusive cross sections for the vector and tensor mesons were determined using various parametrizations for they andpT dependence of the differential cross section. The experimental results are discussed in the framework of production models based on the parton picture. The strangeness suppresion factor λ=(0.30±0.10) due toSU(3) symmetry breaking of the quark sea is derived.

Study of multi-body final states in K+p reactions at an incident momentum of 5 GeV/c

Abstract A recent publication by Basile et al. claims evidence for a hadronic state with beauty flavour, Λ b → D 0 p π − , produced in pp collisions at √ s =63 GeV. We report a negative result from an experiment which has used the same detector and has a significantly higher sensitivity. In addition we show that neither experiment can observe such a signal, the data available being about two orders of magnitude below the minimum required.

Quantum Number Effects in Events With a Charged Particle of Large Transverse Momentum. Part 2. Charge Correlations in Jets

Abstract The reactions (1) K + p → K ∗ (1420) p and (2) K + p → K ∗ (1420) N ∗ (1236) are studied at 5 GeV/c incident K+ momentum. The simultaneous fitting of the K π and K ∗ (892)π decayy modes of the K∗ (1420) in the same production reaction makes it possible to eliminate 1− as the spin of the K∗(1420). The most likely K∗(1420) spin-parity assignment is 2+ although 3− cannot be excluded. The various decay branching ratios of the K∗(1420) are determined. The ratio of the K ∗ (892)π to the Kπ decay modes is found to be 0.9 ± 0.2. The peripheral production of the K∗(1420) seems to be due predominantly to vector-meson exchange in reaction (1) and to pion exchange in reaction (2).

Observation of leading particles in pp interactions with large transverse momentum secondaries at the CERN-ISR

Abstract The study of K+p reactions at an incident momentum of 4.97 GeV/c suggests that the wide enhancement in the (Kππ)+ mass spectrum may be split into several resonant states. In particular, examination of the K ∗ (892)π decay mode indicates the existence of the states K∗(1230), K∗(1280) and K∗(1320), in addition to the well known K∗(1420). The K∗(1230) and K∗(1320) have the properties expected from 1+ states produced by 0+ exchange.