Gideon Alexander

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.

A Kπ resonant state at 726 MeV

Author(s): Miller, Donald H.; Alexander, Gideon; Dahl, Orin I.; Jacobs, Laurence; Kalbfleisch, Goerge R.; Smith, Gerald A.

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 .

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.

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.

Study of the I = 2 Σπ system in π + N interactions

A study of the effective-mass distributions for systems recoiling against mesons (k/sup +/) produced both in pi /sup -/ + p and pi /sup -/ + n interactions is reported. Although all the known energetically accessible resonances are produced the data show no systematic enhancement that can be identified as arising from an I = 2 Y pi resonant state. A more favorable situation exists for SIGMA /sup -/ pi /sup 0/ and SIGMA /sup 0/ pi /sup -/ systems recoi ling against mesons(k/sup +/). The effective-mass distributions for all two-body final states produced in association with mesons(k/sup +/) are plotted. (C.E.S.) perimentally observed nucleon-nucleon scattering. Requirements of unitarity were not imposed, and the dispersion relations depend only on causality and the empirical spectrum of masses, spins, parities, and coupling constants. (C.E.S.)

EVIDENCE FOR THE EXISTENCE OF A K

Author(s): Miller, Donald H.; Alexander, Gideon; Dahl, Orin I.; Jacobs, Laurence; Kalbfleisch, George R.; Smith, Gerald A.