G. H. Trilling

Λp interactions in momentum range 300 to 1500 MeV/c☆

A sample of approximately 250 Λp interactions has been obtained in the Λ-hyperon momentum range of about 300 to 500 MeV/c. An enhanced Λ-hyperon production rate was obtained by exposing an internally-mounted platinum target to the incident 1.5 GeV/c meson beam. Cross sections and angular distributions are obtained for the reactions: Λp → Λp, Λp → Σop and Λp → Λpπo. In the elastic channel, no strong evidence is seen near the Σop threshold for the presence of a 3S1 resonance, which has been reported, although there is some evidence for a small enhancement in this mass region. There is evidence for the presence of P-waves and probably also D-waves above about 800 MeV/c, but not below this momentum.

The Properties of Charmed Particles

Abstract The present experimental information on the spectroscopy and decay properties of particles with non-zero values of the charm quantum number (charmed particles) is reviewed. The discussion is introduced by a historical account of the discovery of charm. An extensive description of the properties of D mesons, principally based on e + e − annihilation experiments, is given. This is followed by a summary of the considerably less complete information on F meson properties, based on e + e − annihilation, photoproduction and neutrino production. The relation between the experimental results on charmed mesons and theoretical models based on spectator-quark and non-spectator-quark decay mechanisms is discussed. Experimental information on Λ c and Σ c charmed baryons based on hadroproduction, phtoproduction neutrio production and e + e − annihilation is summarized. The existing information on the lowest-excited D states, the D ∗ , is discussed. Finally brief comments on future propespects for further advances in this area are given

Experimental study of Λp and Ξ0p interactions in the range 1 – 10 GeV/c

Abstract The reactions Λ p → Λ p, → Σ ± p π ∓ , → Λ p π + π − and → Σ 0 p have been studied in the SLAC 82 inch bubble chamber for incident Λ particles in the momentum range 1–10 GeV/ c . The incident Λ flux was produced by the exposure of a platinum target mounted inside the chamber to a 12 GeV K − beam. A total of 992 events have been analyzed. The reactions are found to be qualitatively similar to corresponding nucleon-nucleon reactions. In particular, the slope parameter B in the elastic cross section d σ /d t = A e Bt has been determined as a function of incident momentum and found to be consistent with that for proton-proton elastic scattering. Angular distributions for the inelastic channels are compared with those of similar nucleon-nucleon reactions, and predictions of relevant exchange models.

Pion pair production in photon-photon collisions at spear

Abstract We report a measurement of the cross section for the process γγ → π + π − at invariant masses 500 MeV/ c 2 m ππ c 2 . A value for the radiative width of the f(1270) tensor meson Γ f→ γγ = 3.6 ± 0.3 ± 0.5 KeV (helicity λ = 2) has been obtained from a fit to the observed ππ mass spectrum.

Inclusive ϱ° production in π−p interactions at 205 GeV/c

Abstract The inclusive ϱ ° production cross section has been measured in the reaction π − p → π + π − X at 205 GeV/ c . We find σ ( ϱ ° ) = 13.5 ± 3.4 mb, with most of the production occuring in the central region. Assuming σ ( ϱ + ) ≈ σ ( ϱ − ) ≈ σ ( ϱ ° ), it is concluded that approximately one-third of the pions at this energy come from ϱ -decay.

Evidence for structure in the Kπ mass system near 1.85 GeV

Abstract We present evidence for structure in the Kπ system at a mass near 1.85 GeV in the reaction K+n→K+π−p at 12 GeV/c. One interpretation of the observations is the production by pion exchange of a J P = 3 − K ∗ resonance at about this mass, which interferes strongly with other processes.

Observation of correlations between vector-meson and baryon-resonance decays☆

Author(s): Goldhaber, Gerson; Brown, John L.; Butterworth, Ian; Goldhaber, Sulamith; Hirata, Allan A.; Kadyk, John A.; Shen, Benjamin C.; Trilling, George H.

The K+p interaction from 864 to 1585 MeV/c; Cross sections and mass distributions☆

Abstract In this paper we present, for five momenta from 864 to 1585 MeV/c, cross sections for stable final states and for resonance production, and an analysis of the KNπ Dalitz plots including the effects of K ∗ (891) − Δ(1236) interference. We see strong interference at all momenta where the K∗ is present, with the relative phase of the K∗N and KΔ amplitudes remaining constant as a function of momentum. We combine our cross-section results with those from other experiments to study the momentum dependence of the partial cross sections in the region of the 1250 MeV/c peak in the total cross section; we find that the total cross-section curve can be represented as the sum of partial cross-section curves, each one smooth and without a peak corresponding to that in the total cross section. Thus this structure is not due to structure in any single partial cross section, but rather to the sharp rises of the single- and double-pion-production channels at widely separated thresholds. This interpretation is at variance with a conventional resonance interpretation of the observed structure in the total cross section.

Observation of the Decay 00

The prompt photon decay psi(3095)..--> gamma pi../sup +/..pi../sup -/..pi../sup +/..pi../sup -/ has been studied with the Mark II detector at SPEAR. This channel is found to contain a ..gamma..rho/sup 0/rho/sup 0/ component with rho/sup 0/rho/sup 0/ masses concentrated between 1.4 and 2.0 GeV/c/sup 2/. The branching fraction for the psi..--> gamma..rho/sup 0/rho/sup 0/ decay with masses less than 2.0 GeV/c/sup 2/ is measured to be (1.25 +- 0.35 +- 0.40) x 10/sup -3/.The prompt photon decay (3095)+-+- has been studied with the Mark II detector at SPEAR. This channel is found to contain a 00 component with 00 masses concentrated between 1.4 and 2.0 GeV/c2. The branching fraction for the 00 decay with masses less than 2.0 GeV/c2 is measured to be (1.25±0.35±0.40)×10-3.

Single-pion production in K+p interactions at 4.6 GeV/c

Abstract A study of K + p interactions at 4.6 GeV/ c leading to single-pion production is presented. Cross sections for the final states KΔ, K ∗ (891)p, K ∗ (1420)p are given. Comparison of the results of this study with published K − p and K − n data at the same momentum indicates that corresponding K − cross sections are significantly smaller, but other features such as momentum transfer distributions and density matrix elements are very similar.