On the hadron mass decomposition

Abstract

We argue that the standard decompositions of the hadron mass overlook pressure effects, and hence should be interpreted with great care. Based on the semiclassical picture, we propose a new decomposition that properly accounts for these pressure effects. Because of Lorentz covariance, we stress that the hadron mass decomposition automatically comes along with a stability constraint, which we discuss for the first time. We show also that if a hadron is seen as made of quarks and gluons, one cannot decompose its mass into more than two contributions without running into trouble with the consistency of the physical interpretation. In particular, the so-called quark mass and trace anomaly contributions appear to be purely conventional. Based on the current phenomenological values, we find that in average quarks exert a repulsive force inside nucleons, balanced exactly by the gluon attractive force.

The gauge-invariant canonical energy-momentum tensor

“…Generalized Parton Distributions (GPDs) accessed in exclusive scatterings [43] and Transverse-Momentum dependent Distributions (TMDs) accessed in semi-inclusive scatterings [20]. The detailed relations between the EMT scalar functions and two-parton GPDs and TMDs of any twist can be found in [34]. Among the interesting results, let us just mention that we derived the following sum rules…”

“…is the adjoint covariant derivative, can be used to relate the various EMTs [14,34]. Because of the first identity in Eq.…”

“…We present here the first complete parametrization of the EMT obtained in [34] which can be applied to virtually any form of the EMT discussed in the literature, provided that the non-locality appears only along the light-front (LF) direction n.…”

Heavy Quarkonium Production at Threshold from JLab to EIC

“…This difference might find its origin in the fact that, while the proton spin lend itself to a frame independent decomposition [4], this is is not the case for its mass decomposition. Nevertheless, it is natural to discuss the mass of the nucleon in its rest frame as originally noted by Ji [5] in its mass decomposition and more recently by Lorcé [6].…”

“…Two examples of mass decomposition in the rest frame of the nucleon are given by Ji [5] and more recently by Lorcé [6]. These decompositions, while not unique, are very useful to speak about the nucleon mass in terms of its constituents, similar to other fields of Physics.…”