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■ Reaction

作者：李中义; 代安鑫; 谢聚军^*

来源：Chinese Physics Letters, 2022, 39(01): 23-28.

The near-threshold e+e-→Λ■ reaction is studied with the assumption that the production mechanism is due to a near-Λ■-threshold bound state. The cross section of the e+e-→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■ reaction from a new narrow state with quantum numbersJPC= 1--is dominant for energies very close to threshold. The mass of this new state is around 2231 Me V,which is very close to the mass threshold of Λ■, while its width is just a few Me V. 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■ reaction. We also note that the near-threshold enhancement can also be reproduced by including these well established vector resonances ω(1420), ω(1650), Φ(1680), or Φ(2170) with a Flatté form for their total decay width, and a strong coupling to the Λ■ channel.

• 单位
  郑州大学; 中国科学院大学