

Ralf Seidl 


Fragmentation functionsFragmentation functions describe the transition of high energetic, massless and asymptoticallyfree partons into confined, massive finalstate hadrons. It is therefore at the haert of the remaining open questions about confinement and the formation of mass via the strong interaction, QCD. As nonperturbative objects, fragmentation functions cannot be calculated from first principles and need to be measured in experiment. The most straightforward access to fragmentation functions comes from electronpositron annihilation, where the initial process is very well understood and hadrons only appear in the final state. I have been extracting fragmentation functions in particular at the Belle experiment with about 1fb1 of accumulated data and hope to continue working on the Belle II experiment. Apart from trying to understand QCD via fragmentation, fragmentation functions also a great tool to in accessing the nucleon structure. Unpolarized fragmentation functions allow to get information about the parton flavor of unpolarized or polarized distribution functions. Transverse spin depedendent fragmentation functions (Collins and interference FFs) are the nearly only tool to get the nucleon's transversity distribution. For transverse momentum dependent distribution functions, such as the Sivers function, the BoerMulders function and several others also require explicitly transverse momentum dependent fragmentation functions. 


Ongoing Fragmentation Research activities: 


Previous results:  
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