Single-inclusive hadron production in electron-positron annihilation at next-to-next-to-next-to-leading order in QCD

Single-inclusive hadron production in electron-positron annihilation (SIA) represents the cleanest process for investigating the dynamics of parton hadronization, as encapsulated in parton fragmentation functions. In this letter, we present, for the first time, the analytical computation of Quantum Chromodynamics (QCD) corrections to the coefficient functions for SIA at next-to-next-to-next-to-leading order (N$^3$LO) accuracy, achieving the highest precision to date for hadron production processes. Utilizing the BaBar measurement as a benchmark, we assess the phenomenological implications of this high-precision calculation. Our findings demonstrate a substantial reduction in scale uncertainties at N$^3$LO and offer an improved description of the experimental data compared to lower-order calculations. This advancement underscores the importance of higher-order corrections in achieving a more accurate understanding of hadronization processes.