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Xiao-Fu Lü

Publications and source records attributed to Xiao-Fu Lü.

6 recordsLinked to original sources
arXiv2009

Reply to the Comment of X. Ji on "Do gluons carry half of the nucleon momentum?" [PRL 103:062001 (2009)]

We affirm that the proper momentum defined in [PRL 103:062001 (2009)] does respect exact gauge symmetry and is as measurable as the kinetic momentum. The physical part of the gauge field is also as measurable as the electromagnetic field. The Comment of Ji [arXiv:0910.5022] is due to a misunderstanding of our work, and a typical confusion of our gauge-invariant formalism with the specific Coulomb-gauge calculation.

hep-ph↗
arXiv2009

Do gluons carry half of the nucleon momentum?

We examine the conventional picture that gluons carry about half of the nucleon momentum in the asymptotic limit. We reveal that this large fraction is due to an unsuitable definition of the gluon momentum in an interacting theory. If defined in a gauge-invariant and consistent way, the asymptotic gluon momentum fraction is computed to be only about one fifth. This result suggests that the asymptotic limit of the nucleon spin structure should also be reexamined. Possible experimental test of our finding is discussed in terms of novel parton distribution functions.

hep-ph↗
arXiv2007

Spin and orbital angular momentum in gauge theories (II): QCD and nucleon spin structure

Parallel to the construction of gauge invariant spin and orbital angular momentum for QED in paper (I) of this series, we present here an analogous but non-trivial solution for QCD. Explicitly gauge invariant spin and orbital angular momentum operators of quarks and gluons are obtained. This was previously thought to be an impossible task, and opens a more promising avenue towards the understanding of the nucleon spin structure.

hep-ph↗
arXiv2005

Quantum Version of Gauge Invariance and Nucleon Internal Structure

The conflict between cononical commutation relation and gauge invariance, which both the momentum and angular momentum of quark and gluon should satisfy, is clarified. The quantum version of gauge invariance is studied. The gauge independence of the matrix elements of quark momentum and angular momentum operators between physical states are proved. We suggest to use the canonical quark momentum and angular momentum distributions to describe the nucleon internal structure in order to establish an internal consistent description of hadron spectroscopy and hadron structure. The same problem for the atomic spectroscopy and structure is discussed.

hep-ph↗