A. Firestone

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.

ρ0production inπ−pinteractions at 100, 200, and 360 GeV/c

Inclusive and semi-inclusive cross sections for rho/sup 0/ production in 100, 200, and 360 GeV/c ..pi../sup -/p interactions are presented. Differential cross sections for rho/sup 0/ production as functions of c.m. rapidity and transverse momentum are compared with the corresponding differential cross sections for pion production. Effects of various methods of estimating background on the values obtained for rho/sup 0/ production cross sections are discussed. About 10% of the final-state charged pions appear to come from rho/sup 0/ decay. Thus, while rho/sup 0/ production and decay is a significant source of final-state pions, other sources must contribute the majority of the produced pions.

Study of the reaction K+p → KOπ+p at 9 GeV/c

Abstract We present results on the study of the reaction K + p → K O π at GeV/ c . The reaction proceeds almost entirely through the production of K 890 ∗ , K 1420 ∗ and Δ 1236 ++ . The spin parity of the K 1420 ∗ is shown to be J P = 2 + , with 18% pseudoscalar and 72% vector exchange in its production, the same proportion as for K 890 ∗ production. The dependence of the cross sections on incident momentum for the reactions K + p → K 890 ∗ p , K 1420 ∗ p , and K O Δ 1236 ++ appear to fall somewhat more rapidly than the predictions of a simple Regge-pole-exchange model.

Antihyperon and antiproton production in K+p interactions at 9 GeV/c

Abstract We have analyzed the reactions of the type K + p → Y NN (π) in K + p interactions at 9 GeV/ c , where Ȳ refers to a ∧ or Σ antihyperon. We have also studied the production of ue5fc − in the reaction K + p → ue5fc − YN (π) and of antiprotons in the reaction K + p → K + p p p . With twice data previously reported we observe again a low-mass enhancement in the ∧ N final state and also observe some indications of a similar enhancement in the non-exotic Σ ± N final states. This enhancement has the quantum numbers of an I = 1 2 K ∗ resonance with mass M = 2240 +- 20 MeV and width Л = 80 ± 20 MeV .

Observation of the Ω

We have observed an Ω¯ event. The Ω¯ is produced in the reaction K+d→Ω¯ΛΛpπ+π− at 12xa0GeVc, and decays via the mode Ω¯→Λ¯K+. The fitted mass for this particle is MΩ¯=1673.1±1.0 MeV. The Ω¯-production cross section is of the order of 0.1 μb.

Decay analysis of the low-mass Kππ enhancement into K890∗ and π−π systems

Abstract The low-mass K ππ enhancement is studied in K + p→K + π + π − p and K + p→ →K 0 π + π 0 p interactions at 9 GeV/ c . This enhancement consists of two peaks of mass and width M =1260±10 MeV, Γ =40±10 MeV and M =1380±20 MeV, Γ = 120±20 MeV. The main decay modes are K 890 ∗ π and ϱK, which interfere strongly. A consistent description of the data requires either an additional decay mode into K + plus an I =0 s-wave π − π system 〈 ϵ 720 0 〉 or a large interference effect between two components of the Q , or both.

The Kπ system in the channel K+π−Δ++ at 9 GeV/c

Abstract The study of the Kπ system in the channel K+π−Δ++ is complicated by the presence of the broad low-mass Δ++π− enhancement centered near 1580 MeV. A cut which removes this effect reveals a break in the t′ distribution at |t′| ≈ 0.05 (GeV/c)2, with a very steep forward peak of slope a = 23.6±5.2 (GeV/c)−2 for 2. |t′| ;.sfnc;t′| ⩾ 0.05 (GeV/c) We associate this forward peak with a single-pion-exchange mechanism. A small enhancement at M(K+π−) ≈ 1100 MeV is observed in a t′ region dominated by non-pion-exchange mechanisms.

Antixi production in K+p interactions3at 9 GeV/c☆

Abstract We have observed charged antixi production in K + p interactions at 9 GeV/ c with σ ≈ 5.3 > b. Nothing observed indicates that these antixi hyperons are decay products of an intermediate resonance. We have found no event consistent with antiomega production.

OBSERVATION OF THE anti .

We have observed an Ω¯ event. The Ω¯ is produced in the reaction K+d→Ω¯ΛΛpπ+π− at 12xa0GeVc, and decays via the mode Ω¯→Λ¯K+. The fitted mass for this particle is MΩ¯=1673.1±1.0 MeV. The Ω¯-production cross section is of the order of 0.1 μb.

Search for S = 2 boson resonances in the mass region of 1.0 to 3.1 GeV

Abstract We present results on a search for S = 2 bosons in the final states K + K + ( I = 1), K 0 K + ( I = 1, I = 0) and KKnπ( π ⩾ 1) in a 9 GeV c K + p experiment. No statistically significant evidence for such resonances is observed in the mass region 1.0 to 3.1 GeV. The upper limit for the production cross section of the previously reported S = 2 enhancements at 1050 and 1280 MeV is estimated to be 1.5 and 2.0 μ, respectively.