Abstract
Exclusive hyperon-antihyperon production provides a unique insight for understanding of the intrinsic dynamics when strangeness is involved. In this paper, we review the results of ΛΛ¯ production via different reactions from various experiments, e.g., via p¯p annihilation from the LEAR experiment PS185, via electron-positron annihilation using the energy scan method at the CLEO-c and BESIII experiments and the initial-state-radiation approach utilized at the BaBar experiment. The production cross section of ΛΛ¯ near the threshold is sensitive to QCD based prediction. Experimental high precision data for p¯p→Λ¯Λ close to the threshold region is obtained. The cross section of e+e−→ΛΛ¯ is measured from its production threshold to high energy. A non-zero cross section for e+e−→ΛΛ¯ near threshold is observed at BaBar and BESIII, which is in disagreement with the pQCD prediction. However, more precise data is needed to confirm this observation. Future experiments, utilizing p¯p reaction such as PANDA experiment or electron-positron annihilation such as the BESIII and BelleII experiments, are needed to extend the experimental data and to understand the ΛΛ¯ production.
Highlights
The Λ hyperon, as the first baryon discovered containing the strange quark [1,2], is of great importance in the elaboration of the Standard Model (SM)
Exclusive ΛΛproduction, whose four-momenta transfer is of the same magnitude as the asymptotic scale parameter ΛQCD, allows us to study the internal dynamics with strangeness and can be used to probe various QCD-motivated models
The aim of the PS185 experiment operating at Low Energy Antiproton Ring (LEAR) is to study how the strange quarks are produced, where one of the most precise results at PS185 is the study of pp → Λ Λ [8,9,10]
Summary
The Λ hyperon, as the first baryon discovered containing the strange quark [1,2], is of great importance in the elaboration of the Standard Model (SM). The ΛΛproduction can be studied in reactions with strangeness exchange like the process pp → Λ Λ with an intermediate strange meson, e.g., K or K∗. The OGE model relies on the perturbative gluon exchange in the lowest order, is typically S-wave It predicts the cross section of pp → Λ Λ near threshold follows a (s − s0)1/2 energy dependence, where s is the center-of-mass (c.m.) energy square and s0 = 4m2Λ with mΛ the mass of Λ from PDG [4]. Two kinds of experimental approaches are available, the energy scan method, where measurements of the cross sections are performed by taking data at fixed c.m. energies, taking advantage of the finite beam energy resolution of e+e− colliders; and the initial-state-radiative (ISR) approach, where the higher order of the examined process is used for the measurement.
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