The Ξ0 asymmetry parameters are measured using entangled quantum Ξ0 − Ξ ̄ 0 pairs from a sample of (448.1 pm 2.9) × 10^6 ψ(3686) events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the Ξ0Ξ ̄ 0 helicity states is measured to be ΔΦ = −0.050 pm 0.150 pm 0.020 rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the Ξ0 hyperon (αΞ0 ; αΞ ̄ 0 ; φΞ0 ; φΞ ̄ 0 ) and the angular distribution parameter [αψ(3686)] and ΔΦ are measured simultaneously for the first time. In addition, the CP asymmetry observables are determined to be AΞ0 = −0.007 pm 0.082 pm 0.025 and ΔφΞ0^{CP} = −0.079 pm 0.082 pm 0.010 rad, which are consistent with CP conservation
First simultaneous measurement of Ξ0 and Ξ ̄0 asymmetry parameters in ψ(3686) decay
I. Garzia;S. Gramigna;M. Scodeggio;
2023
Abstract
The Ξ0 asymmetry parameters are measured using entangled quantum Ξ0 − Ξ ̄ 0 pairs from a sample of (448.1 pm 2.9) × 10^6 ψ(3686) events collected with the BESIII detector at BEPCII. The relative phase between the transition amplitudes of the Ξ0Ξ ̄ 0 helicity states is measured to be ΔΦ = −0.050 pm 0.150 pm 0.020 rad, which implies that there is no obvious polarization at the current level of statistics. The decay parameters of the Ξ0 hyperon (αΞ0 ; αΞ ̄ 0 ; φΞ0 ; φΞ ̄ 0 ) and the angular distribution parameter [αψ(3686)] and ΔΦ are measured simultaneously for the first time. In addition, the CP asymmetry observables are determined to be AΞ0 = −0.007 pm 0.082 pm 0.025 and ΔφΞ0^{CP} = −0.079 pm 0.082 pm 0.010 rad, which are consistent with CP conservationI documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
