Yin-Zhen Xu, Khépani Raya, Zhu-Fang Cui, Craig D. Roberts, J. Rodríguez-Quintero

Empirical Determination of the Pion Mass Distribution

This publication describes research conducted in the context of high-energy nuclear and particle physics, which are together operating, building, and planning high-luminosity, high-energy facilities with the goal of explaining the emergence of the vast bulk (99%) of visible mass in the Universe.  Unveiling pion structure and exposing the impact thereupon of its Nambu-Goldstone boson character are key parts of this multi-billion-dollar international program. 
    Using only existing pion+nucleus Drell-Yan and electron+pion scattering data, we deliver the *first* extraction of the pion mass distribution form factor and associated radius.  Our model-independent analysis reveals that mass in the pion is concentrated in roughly 40% of the spacetime volume occupied by the pion's charge. 
    This work is of broad interest because Nambu Goldstone bosons feature in many fields of physics, and pions are the most fundamental Nambu-Goldstone bosons in Nature. 

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