M. Edwards

Evidence for a narrow width boson of mass 2.95 GeV

Abstract In a search for resonances coupled to the p pπ − system, we have studied π − p interactions at 16 GeV/ c giving a forward antiproton, using the Omega spectrometer at CERN. In the final states involving a p , p and π − we observe a 5.6 (6.3) standard deviation enhancement in the p pπ − mass spectrum at (2.95 ± 0.01) GeV with a width consistent with the resolution ( σ = 15 MeV). The production cross section × branching ratio is estimated to be of the order 1 μb. The data are consistent with a resonance decaying partly via intermediate p p final states.

Evidence for a new pseudoscalar meson

Abstract Performing a PWA of the π − π − π + system over the −t p/p range 0.2 to 0.4 GeV 2 we find evidence for a J P = 0 − , J G =1 − meson of mass 1342 ± 20 MeV and width 220 ±70 MeV decaying into ϵπ. This state is produced by natural parity exchange with a slope similar to that of elastic scattering. It can be interpreted as a radial excitation of the π meson (π′).

Inclusive φ production in π− p interactions at 16 GeV/c

Abstract Inclusive φ production is studied in π − p collisions at 16 GeV/ c . The φ cross section for Feynman variable x φ > 0.2 is found to be (15.5 ± 3.6) μb. This leads to an extrapolated cross section of (29.9 ± 7.0) μb for x φ > 0.0. Fitting the momentum transfer squared distribution of the φ to the form e −bp 2 T gives an average slope of b = (2.4 ± 0.3) (GeV/ c −2 for x φ > 0.5.

Observation in the K+K− system of a new structure at 2.20 GeV

Abstract A sample of 56 909 events of the reaction π − p→K + K − n at 10 GeV/ c has been measured in the Omega Spectrometer at CERN. In the K + K − system, besides production of mesons in the S ∗ /φ, f 0 / A 2 , g /ω ∗ and h regions we observe a new structure at 2.20 GeV with a width of the order of 200 MeV.

Analysis of the reaction π−p→ppn at 10 and 16 GeV/c

Abstract Antiproton-proton pairs and antiproton-neutron pairs produced in the reaction π − p → p pn , were studied in the mass range from threshold to 2.6 GeV on the basis of 4 · 104 events at 10 GeV/c and 2 · 104 events at 16 GeV/c incident momentum. The cross section for peripheral production of p n pairs is significantly larger than for p p pairs. The p p production mechanism is consistent with the predictions of the one-pion exchange model, whereas the p n production cannot be sufficiently described by that model. A partial-wave analysis of the p p system, assuming pure one-pion exchange, shows that we need for a reasonable description of our data in addition to the JP = 3− resonance at 2.11 GeV and the 4+ resonance at 2.26 GeV found in an analysis of a formation experiment ( p p → π + π − ), two further resonances: a 1− state at 1.92 GeV and a 2+ state at 2.02 GeV.

K∗0(890) polarization measurements in the hypercharge exchange reaction π−p→K∗0(890) Λ0Σ0 at 10 GeV/c

K∗0(890) production in the hyperchange exchange reaction π−p→K∗0(890) Λ0Σ0 at 10 GeV/c (28 448 events) is discussed. An amplitude analysis in the t′ range up to 1 GeV2 shows that the production mechanism is dominated by natural parity exchange (∼84%). Comparisons are made with predictions from a Regge model and a quark model.

Inclusive production in π−p interactions at 16 GeV/c

Abstract Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.

Inclusive K∗0(890) production in π−p interactions at 16 GeV/c

Abstract Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.

Analysis of the inclusive reaction π−p→K∗0 (890) X0 at 10 GeV/c

Experimental results on the reaction π−p→K∗0 (890) X0 at 10 GeV/c are presented. By using the K∗0 polarization measurements, a detailed study of the production has been carried out as a function of the missing mass squared and of the four-momentum trasnfer squared to the K∗0. We found that: (a) K∗0 production is dominated by natural parity exchange; (b) K∗0 helicity-zero production dominates the unnatural parity exchange contribution and (c) the main features of the reaction are in agreement with the predictions of the finite mass sum rules.

Inclusive K

Abstract Inclusive K ∗0 production is studied in π − p interactions at 16 GeV/ c with x ϝ > 0.2. The K ∗0 is found to be pre-dominantly centrally produced with cross section σ( K ∗0 ) = (72 ± 12) μb for x ϝ > 0.2 and compares closely to data on K ∗0 production in π + p interactions at the same energy.