Abstract
I discuss the scope and naturalness of the proton mass decomposition (or sum rule) published in Phys. Rev. Lett. 74, 1071 (1995) and answer a few criticisms that appeared recently in the literature, focusing particularly on its interpretation and the quantum anomalous energy contribution. I comment on the so-called frame-independent or invariant-mass decomposition from the trace of the energy-momentum tensor. I stress the importance of measuring the quantum anomalous energy through experiments. Finally, I point out a large discrepancy in the scalar radius of the nucleon extracted from vector-meson productions and lattice QCD calculations.
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Acknowledgements
We thank K. F. Liu, Y. Z. Liu, D. Kharzeev, A. Metz, Z.-E. Meziani, B. Pasquini, S. Rodini, A. Schaefer, F. Yuan, and I. Zahed for discussions and comments on the manuscript, and Y. Guo and Y. Su for help. I particularly thank Y. Z. Liu for hel** with the gravitational form factors. This material was supported by the U.S. Department of Energy, Office of Science, Office of Nuclear Physics, under contract number DE-SC0020682, and Southeastern Universities Research Association.
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ar**v: 2102.07830. This article can also be found at http://journal.hep.com.cn/fop/EN/10.1007/s11467-021-1065-x.
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Ji, X. Proton mass decomposition: Naturalness and interpretations. Front. Phys. 16, 64601 (2021). https://doi.org/10.1007/s11467-021-1065-x
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DOI: https://doi.org/10.1007/s11467-021-1065-x