Measurement of thep¯p→Λ¯Λ andp¯p→Σ¯0Λ+c.c. reactions at 1.726 and 1.771 GeV/c

Abstract

Interest in the production of hyperon-antihyperon pairs following antiproton-proton annihilation stems largely from attempts to understand the nature of flavor production. To date the major focus of both the experimental and the theoretical effort has been on the pp→⌳⌳ reaction. In this paper, we present data on the complementary channels pp→⌺ 0 ⌳ and pp→⌳⌺ 0. Events from the kinematically similar pp→⌳⌳ reaction were obtained in parallel. The procedure to distinguish these three separate reactions is described and results for all channels are presented. These include the total and differential cross sections, hyperon polarizations, and spin correlation coefficients. Data were obtained at incident antiproton lab momenta of 1.726 and 1.771 GeV/c which correspond to excess kinetic energies in the pp→⌳⌺ 0 ϩc.c. reaction of 26 and 40 MeV, respectively, above threshold. Comparisons are made to earlier work at similar excess energies in the pp→⌳⌳ channel. The low-energy regime has been highlighted in this experiment to reduce the complexity in the theoretical analysis. ͓S0556-2813͑96͒01612-3͔

Measurement of Spin-Transfer Observables inp¯p→Λ¯Λat1.637 GBassalleck1, Berdoz2, Bradtke3 et al. 2002Phys. Rev. Lett.Self Cite15060View full textAdd to dashboardCite

“…Details of the extraction of scattering matrix parameters and the uncertainty analysis, along with results for a larger set of observables, will be presented in a future publication. For those observables which could also be extracted from previous measurements performed without target polarization, good agreement is found between the published results [2] and the corresponding observables found from this fit of the complete set of parameters of the spin scattering matrix. Figure 1 shows results for the depolarization D nn and polarization transfer K nn , along with predictions from full QG [9] and MEX [6] calculations which include ISI and FSI effects.…”

“…MEX calculations lead to a dominant tensor force resulting from a constructive interference of the K and K * in the tensor channel. This tensor interaction couples only to triplet (S = 1) final states, and serves to explain the near absence of singlet-state production seen in earlier measurements [1,2]. The QG approach, which includes only couplings to triplet-state quantum numbers, incorporates complete triplet dominance by construction while finding only a relatively small tensor interaction, even when fully accounting for the ISI and FSI.…”

“…These reactions have been extensively studied by the PS185 collaboration at the Low Energy Antiproton Ring (LEAR) facility at CERN, which has produced the overwhelming majority of the existing data on exclusivepp →Ȳ Y near-threshold, including cross-sections and final-state polarization and spin-correlations [1,2]. In particular, high precision measurements have made ofΛΛ production over a kinematic range from very-near threshold to about 200 MeV of excess energy in the center-of-mass system.…”

Energy dependence of the Λ/Σproduction cross-section ratio in p-p interactions

“…It is interesting to note that a comparable cross section ratio was determined in antiprotona e-mail: p.kowina@fz-juelich.de proton annihilation experiments leading toΛ-Λ,Σ 0 -Λ + c.c. andΣ ± -Σ ∓ as performed by the PS185 collaboration at LEAR [13,14].…”

Experimental determination of the complete spin structure forp¯p→Λ¯ΛatFields1, Paschke2, Quinn3 et al. 2006Phys. Rev. CSelf Cite230100View full textAdd to dashboardCite

“…This experiment, carried out by the PS185 collaboration, expands upon a series ofȲ Y production and related experiments [1,2,3,4] which have previously been performed by this collaboration using the same detector system. These covered wide-ranging kinematics from very near threshold to higher energies at which the larger cross section allowed high-statistics studies to be made.…”