Production of Strange Particles inp−pCollisions at 2.85 Bev

Abstract

From a sample of 98 hyperon production events observed in a liquid hydrogen bubble chamber the partial cross sections for various final states are found to be: 2 + iT%-0.047,i:^7r 0 -0.011, (A°2°)i^7r + -0.014, (AW)K + mr + -0.002, all in millibarns. For the first four processes the values are in general agreement with those calculated by Ferrari using a one-pion-exchange model. Only one example of impair production was observed, indicating a cross section less than 0.01 mb.

The pK0Σ+ final state in proton-proton collisions

“…In 1962 Tsu Yao [32] calculated the total cross section for the present reaction at ǫ = 353 MeV considering solely single pion exchange. The resulting value of σ = 36 µb is in good agreement with the only experimental value [22] available at that time. The calculation by Ferrari and Serio in 1968 [33] (based on the pioneering work of Ferrari [31]) was aimed at the simultaneous description of various pp → N KY channels within a boson exchange model (explicitly excluding nucleon resonances).…”

“…Another early calculation of the cross sections simultaneously for all pp → N KY channels was performed by Tsu Yao [32] for a beam energy of T p = 2.85 GeV. This model is based solely on single pion exchange and the calculated total cross section for pp → pK 0 Σ + (ǫ = 353 MeV) is in rather good agreement with the prediction of Ferrari [31] and the only experimental value [22] known at that time. Later on, theoretical analyses and interpretations appeared mainly in experimental papers [23,24,26,27].…”

“…5 which show the world data for the reaction pp → pK 0 Σ + . All data above ǫ = 300 MeV stem from bubble chamber experiments [22,23,24,25,26,27,28,29,30]. The data show a relatively large scatter, however indicate a rather constant total cross section over a wide energy range.…”

“…In fact, the only exper-0 Σ + final state in proton-proton collisions imental data for this reaction stem from the search for the supposed pentaquark state Θ + (pp → Σ + Θ + , Θ + → pK 0 ) carried out by the COSY-TOF collaboration [21]. At higher excess energies measurements of total cross sections were published originating from the bubble chamber experiments in the 1960s [22,23,24,25,26,27,28,29] (compiled in [30]). These data show, although with a large scatter, the total cross section to be rather constant (≈ 20 µb) over a wide energy range (350 MeV < ǫ < 2000 MeV).…”

Strangeness production on the neutron

“…Although the ratio seems to depend only weakly upon the beam energy, it should be noted that many different hyperons (and even K + K − pairs) can be produced at 2.65 GeV and this can change the physics significantly. At low energies, where only Λ production is possible, the 0.5 ± 0.2 is comfortably above the isospin lower bound of R > 0.25 [7]. The result translates to It should, of course, be noted that, for a neutron target, half of the signal would be associated with K 0 production.…”