Electromagnetic Form Factors of Λ Hyperon in the Vector Meson Dominance Model and a Possible Explanation of the Near-Threshold Enhancement of the e+e-→ Λ(Λ) Reaction

• 作者: Zhong-Yi Li An-Xin Dai Ju-Jun Xie
• 来源期刊: 中国物理快报（英文版）
• 年，卷（期）: 2022,（1）
• 所属期刊栏目: THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
• 页码范围: 19-24
• 页数: 6页
• 语种: 英文
• DOI: 10.1088/0256-307X/39/1/011201

摘要

The near-threshold e+e-→ Λ(Λ) reaction is studied with the assumption that the production mechanism is due to a near-Λ(Λ)-threshold bound state.The cross section of the e+e → Λ(Λ) reaction is parameterized in terms of the electromagnetic form factors of Λ hyperon,which are obtained with the vector meson dominance model.It is shown that the contribution to the e+e-→ Λ(Λ) reaction from a new narrow state with quantum numbers JPC =1-is dominant for energies very close to threshold.The mass of this new state is around 2231 MeV,which is very close to the mass threshold of Λ(Λ),while its width is just a few MeV.This gives a possible solution to the problem that all previous calculations seriously underestimated the near-threshold total cross section of the e+e-→ Λ(Λ) reaction.We also note that the near-threshold enhancement can also be reproduced by including these well established vector resonances w(1420),w(1650),φ(1680),or φ(2170) with a Flatté form for their total decay width,and a strong coupling to the Λ(Λ) channel.