First Simultaneous Measurement of $Ξ^0$ and $\barΞ^0$ Asymmetry Parameters in $ψ(3686)$ Decay

With data samples collected with the BESIII detector at seven energy points at $$ \sqrt{s} $$ s = 3.68 − 3.71 GeV, corresponding to an integrated luminosity of 333 pb−1, we present a study of the Λ transverse polarization in the e+e−→$$ \Lambda \overline{\Lambda} $$ Λ Λ ¯ reaction. The significance of polarization by combining the seven energy points is found to be 2.6σ including the systematic uncertainty, which implies a non-zero phase between the transition amplitudes of the $$ \Lambda \overline{\Lambda} $$ Λ Λ ¯ helicity states. The modulus ratio and the relative phase of EM-psionic form factors combined with all energy points are measured to be RΨ = $$ {0.71}_{-0.10}^{+0.10} $$ 0.71 − 0.10 + 0.10 ± 0.03 and ∆ΦΨ = $$ {23}_{-8.0}^{+8.8} $$ 23 − 8.0 + 8.8 ± 1.6°, where the first uncertainties are statistical and the second systematic.

Section: Introductionmentioning

confidence: 99%

Measurement of Λ transverse polarization in e+e− collisions at $$ \sqrt{s} $$ = 3.68 − 3.71 GeV

Ablikim,

Achasov,

Adlarson

et al. 2023

“…The systematic uncertainty due to the Σ + ( Σ− ) reconstruction efficiency incorporating the tracking efficiencies, π 0 reconstruction, and Σ + ( Σ− ) mass windows, is estimated by the control sample of ψ(3686) → Σ + Σ− with the same method as described in refs. [63][64][65][66][67][68][69][70][71][72]. The efficiency difference correlated with the angular distribution (cos θ) between data and MC is taken as the systematic uncertainty.…”

Section: σ + ( σ− ) Reconstructionmentioning

confidence: 99%

Measurement of Born cross section of $$ {e}^{+}{e}^{-}\to {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ at center-of-mass energies between 3.510 and 4.951 GeV

Ablikim,

Achasov,

Adlarson

et al. 2024

Using 24.1 fb−1 of e+e− collision data collected with the BESIII detector at the BEPCII collider, the Born cross sections and effective form factors of the $$ {e}^{+}{e}^{-}\to {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ e + e − → Σ + Σ ¯ − reaction are measured. The measurements are performed at center-of-mass energies ranging from 3.510 to 4.951 GeV. No significant evidence for the decay of the charmonium(-like) states, ψ(3770), ψ(4040), ψ(4160), Y(4230), Y(4360), ψ(4415), and Y(4660), into a $$ {\Sigma}^{+}{\overline{\Sigma}}^{-} $$ Σ + Σ ¯ − final state is observed. Consequently, upper limits for the products of the branching fractions and the electronic partial widths at the 90% confidence level are reported for these decays.

“…The systematic uncertainty due to the Ξ − reconstruction efficiency incorporating the tracking and PID efficiencies, the Λ reconstruction efficiency, the selection on Λ and Ξ − decay lengths, and the Λ and Ξ − mass windows, is estimated from a control sample of ψ(3686) → Ξ − Ξ+ decays with the same method as described in refs. [64][65][66][67][68][69][70][71][72]. The Ξ − reconstruction efficiency is defined as the ratio of the number of events from the double baryon-tag Ξ − Ξ+ to that from the single baryon-tag.…”

Section: ξ − Reconstructionmentioning

confidence: 99%

Measurement of the cross section of $$ {e}^{+}{e}^{-}\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ at center-of-mass energies between 3.510 and 4.843 GeV

Ablikim,

Achasov,

Adlarson

et al. 2023

Using e+e− collision data corresponding to a total integrated luminosity of 12.9 fb−1 collected with the BESIII detector at the BEPCII collider, the exclusive Born cross sections and the effective form factors of the reaction $$ {e}^{+}{e}^{-}\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ e + e − → Ξ − Ξ ¯ + are measured via the single baryon-tag method at 23 center-of-mass energies between 3.510 and 4.843 GeV. Evidence for the decay $$ \psi (3770)\to {\Xi}^{-}{\overline{\Xi}}^{+} $$ ψ 3770 → Ξ − Ξ ¯ + is observed with a significance of 4.5σ by analyzing the measured cross sections together with earlier BESIII results. For the other charmonium(-like) states ψ(4040), ψ(4160), Y(4230), Y(4360), ψ(4415), and Y(4660), no significant signal of their decay to $$ {\Xi}^{-}{\overline{\Xi}}^{+} $$ Ξ − Ξ ¯ + is found. For these states, upper limits of the products of the branching fraction and the electronic partial width at the 90% confidence level are provided.