Abstract
Using 5.9 pb−1 of e+e− annihilation data collected at center-of-mass energies from 3.640 to 3.701 GeV with the BESIII detector at the BEPCII Collider, we measure the observed cross sections of e+e−→KS0X (where X=anything). From a fit to these observed cross sections with the sum of continuum and ψ(3686) and J/ψ Breit-Wigner functions and considering initial state radiation and the BEPCII beam energy spread, we obtain for the first time the product of ψ(3686) leptonic width and inclusive decay branching fraction Γψ(3686)eeB(ψ(3686)→KS0X)=(373.8±6.7±20.0) eV, and assuming Γψ(3686)ee is (2.33±0.04) keV from PDG value, we measure B(ψ(3686)→KS0X)=(16.04±0.29±0.90)%, where the first uncertainty is statistical and the second is systematic.
Highlights
In the past few decades, many experiments have observed surprising behavior in the near-threshold region in the production cross section of nucleon pairs in e+e− collisions
In this Letter, we report a measurement of the Born cross section and the effective form factor for the process e+e− → 0 ̄ 0 using a single-baryon-tag method at center-of-mass (CM) energies between 2.644 and 3.080 GeV
The cylindrical core of the BESIII detector covers 93% of the full solid angle and consists of a helium-based multilayer drift chamber (MDC), a plastic scintillator time-of-flight system (TOF), and a CsI(Tl) electromagnetic calorimeter (EMC), which are all enclosed in a superconducting solenoidal magnet providing a 1.0 T magnetic field
Summary
In the past few decades, many experiments have observed surprising behavior in the near-threshold region in the production cross section of nucleon pairs in e+e− collisions. The BESIII collaboration performed high precision studies of possible threshold enhancement in the processes e+e− → ± ̄ ∓ [22] and − ̄ + [23] with an energy scan method, and reported a non-vanishing cross section near threshold. In this Letter, we report a measurement of the Born cross section and the effective form factor for the process e+e− → 0 ̄ 0 using a single-baryon-tag method at center-of-mass (CM) energies between 2.644 and 3.080 GeV. The data set used in this analysis corresponds to a total of about 500 pb−1 e+e− collision data [25,26] collected with the BESIII detector [27] at the BEPCII storage rings [28]
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