Nucleon D-term in holographic QCD

TL;DR

This paper calculates the nucleon's D-term using holographic QCD, revealing a dominance of glueball exchanges and a slight negative value due to meson contributions, advancing understanding of hadron structure.

Contribution

It introduces a holographic QCD model calculation of the nucleon D-term, highlighting glueball dominance and meson contributions in a novel framework.

Findings

D-term is slightly negative due to meson contributions.

Form factor D(t) is saturated by infinite glueball exchanges.

At zero momentum transfer, D(0) is interpreted via meson exchanges.

Abstract

The D-term is one of the conserved charges of hadrons defined as the forward limit of the gravitational form factor $D(t)$. We calculate the nucleon's D-term in a holographic QCD model in which the nucleon is described as a soliton in five dimensions. We show that the form factor $D(t)$ is saturated by the exchanges of infinitely many $0^{++}$ and $2^{++}$ glueballs dual to transverse-traceless metric fluctuations on the Wick rotated AdS$_7$ black hole geometry. We refer to this phenomenon as `glueball dominance', in perfect analogy to the vector meson dominance of the electromagnetic form factors. However, the value at vanishing momentum transfer $D(t=0)$ can be interpreted as due to the exchange of pairs of pions and infinitely many vector and axial-vector mesons without any reference to glueballs. We find that the D-term is slightly negative as a result of a cancellation between the isovector and isoscalar meson contributions.