A possible explanation of the threshold enhancement in the process *

Abstract

Inspired by the recent measurement of the process , we calculate the mass spectrum of the meson with the GI model. For the excited vector strangeonium states and , we investigate the electronic decay width with the Van Royen-Weisskopf formula, and the partial widths of the , , and decay modes with the extended quark-pair creation model. We find that the electronic decay width of the -wave vector strangeonium is about times larger than of the -wave vector strangeonium. Around 2232 MeV, the partial decay width of the mode can be up to several MeV for , while the partial decay width of is keV. If the threshold enhancement reported by the BESIII collaboration arises from the strangeonium meson, this state is very likely the state. We also note that the and partial decay widths of the states and are several MeV, which is sufficient to be observed in future experiments.

Experimental Review of ΛΛ¯ Production

“…This narrow state could be the φ excitation as predicted in Ref. [32], or a Λ Λ quasi-bound state with quantum numbers J PC = 1 − . It has also been pointed out that the Coulomb correction factor C in Equation (1), which takes the pointlike fermion pair production account, need to be further corrected since the baryons are non-pointlike particles in the energy scale near threshold [34,35].…”

“…The unexpected features of Λ Λ production cross section from e + e − annihilation near threshold have driven a wide theoretical studies, including the final-states interactions (FSI) [30] and scenarios that invoke bound states or unobserved meson resonances [31][32][33], and interpretations that an attractive Coulomb interaction happens at the constituent quark level [34,35].…”

“…In Ref. [32], the mass spectrum of the strangeonium system is investigated with the double baryon decay widths from the excited vector strangeonium state φ * . It is found that the partial decay width of the Λ Λ mode can reach up to 5.84 MeV for φ(3S), while the partial Λ Λ decay width of the states φ(2D) is about O(10 −3 ) keV.…”

“…It is concluded from Ref. [32] that, if the threshold enhancement reported by the BESIII experiment in the process e + e − → Λ Λ does arise from an unobserved strangeonium meson, the resonance is most likely to be the strangeonium state φ(3S). In Ref.…”

Probing the internal structure of baryons

“…Therefore the observed threshold enhancement implies the existence of a complicated underlying physics scenario. The unexpected features of baryon pair production near threshold have driven a lot of theoretical studies, including scenarios that invoke bound states or unobserved meson resonances [42,52,53]. It was also interpreted as an attractive Coulomb interaction on the constituent quark level [54,55].…”