https://doi.org/10.1140/epjc/s10052-025-14924-1
Regular Article - Theoretical Physics
Kaon and pion fragmentation functions
1
School of Physics, Nanjing University, 210093, Nanjing, Jiangsu, China
2
Institute for Nonperturbative Physics, Nanjing University, 210093, Nanjing, Jiangsu, China
a
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Received:
24
April
2025
Accepted:
11
October
2025
Published online:
15
November
2025
Abstract
The Drell–Levy–Yan relation is employed to obtain pion and kaon elementary fragmentation functions (EFFs) from the hadron-scale parton distribution functions (DFs) of these mesons. Two different DF sets are used: that calculated using a symmetry-preserving treatment of a vector 
vector contact interaction (SCI) and the other expressing results obtained using continuum Schwinger function methods (CSMs). Thus determined, the EFFs serve as driving terms in a coupled set of hadron cascade equations, whose solution yields the complete array of hadron-scale fragmentation functions (FFs) for pion and kaon production in high energy reactions. After evolution to scales typical of experiments, the SCI and CSM FF predictions are seen to be in semiquantitative agreement. Importantly, they conform with a range of physical expectations for FF behaviour on the endpoint domains 
, e.g., nonsinglet FFs vanish at 
and singlet FFs diverge faster than 1/z. Predictions for hadron multiplicities in jets are also delivered. They reveal SU(3) symmetry breaking in the charged-kaon/neutral-kaon multiplicity ratio, whose size diminishes with increasing reaction energy, and show that, with increasing energy, the pion/kaon ratio in 
diminishes to a value that is independent of hadron masses.
© The Author(s) 2025
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