BESIII recently reported its first result of the inclusive production cross sections of the neutral hadrons, i.e., the π⁰ and K_S⁰ mesons, which has been published in Phys. Rev. Lett. 130, 231901 (2023) on 6 June 2023.

Due to the corresponding large strong-coupling constant α_s, the fragmentation functions (FFs) are used to describe the hadronization processes of the quarks and gluons at the small four-momentum transfer region. Consequently, calculations based on the FFs should describe the inclusive production cross section of the hadron under investigation. Therefore, the precise measurement of the inclusive production cross sections of typical hadrons, especially in the region not well covered by previous data, will provide unique constraint of the FFs thereby improve our interpretation of hadronization and hadron structure.

Based on the electron-positron collision data collected by BESIII at the center-of-mass energies from 2.2324 to 3.6710 GeV, the differential cross sections of inclusive π⁰ and K_S⁰ production as a function of hadron momentum and normalized by the total cross section of the inclusive hadronic process are measured. Our results significantly deviate from several theoretical calculations based on the existing FFs, as shown in following figure. These results provide new ingredients for the global data fits of the FFs, in which almost no single inclusive annihilation data measured in this special energy region has been included.

URL: https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.130.231901