Measurement of Azimuthal Asymmetries in Inclusive Charged Dipion Production in e⁺e⁻ Annihilations at √s̅ = 3.65 GeV

We present a measurement of the azimuthal asymmetries of two charged pions in the inclusive process e⁺e⁻ → ππΧ based on a data set of 62 pb⁻¹ at the center-of-mass energy of 3.65 GeV collected with the SESIII detector. These asymmetries can be attributed to the Collins fragmentation function. We observe a nonzero asymmetry, which increases with increasing pion momentum. As our energy scale is close to that of the existing semi-inclusive deep inelastic scattering experimental data, the measured asymmetries are important inputs for the global analysis of extracting the quark transversity distribution inside the nucleon and are valuable to explore the energy evolution of the spin-dependent fragmentation function.