Octupole parton structure of spin-3/2 targets
Abstract
In spin-3/2 targets, octupole polarization can reveal quark and gluon correlations beyond those probed by vector polarization and quadrupole alignment. Here, we construct the complete leading-twist gluon transverse-momentum-dependent distribution basis, with 32 independent coefficients for each specified Wilson-line and color structure. Fourteen of these describe octupole dependence in gluon number, helicity, and linear polarization. In heavy-quark-pair leptoproduction at small, nonzero pair imbalance, comparing target states with opposite octupoles and identical lower moments isolates the octupole contribution. Beam-helicity reversal and joint angular projections in target orientation and pair-imbalance azimuth can then separate all fourteen gluon octupole responses at leading-power Born order. We also derive the incoming-target quark responses in semi-inclusive deep-inelastic scattering and Drell-Yan production. Time-reversal relations between distributions remain valid under symmetry-preserving renormalization and evolution, while predictions across processes require factorization formulas connecting those distributions to scattering observables. Finally, we connect this framework to polarized 7Li through its collinear limits and nuclear spin-orbital correlations.
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BibTeX
@misc{le2026octupole,
title = {{Octupole parton structure of spin-3/2 targets}},
author = {Brandon B. Le and Dustin Keller},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.17624},
eprint = {2610.17624},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.17624},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Octupole parton structure of spin-3/2 targets
AU - Brandon B. Le
AU - Dustin Keller
PY - 2026
DA - 2026/10/13
PB - arXiv
DO - 10.48550/arxiv.2610.17624
UR - https://arxiv.org/abs/2610.17624
AB - In spin-3/2 targets, octupole polarization can reveal quark and gluon correlations beyond those probed by vector polarization and quadrupole alignment. Here, we construct the complete leading-twist gluon transverse-momentum-dependent distribution basis, with 32 independent coefficients for each specified Wilson-line and color structure. Fourteen of these describe octupole dependence in gluon number, helicity, and linear polarization. In heavy-quark-pair leptoproduction at small, nonzero pair imbalance, comparing target states with opposite octupoles and identical lower moments isolates the octupole contribution. Beam-helicity reversal and joint angular projections in target orientation and pair-imbalance azimuth can then separate all fourteen gluon octupole responses at leading-power Born order. We also derive the incoming-target quark responses in semi-inclusive deep-inelastic scattering and Drell-Yan production. Time-reversal relations between distributions remain valid under symmetry-preserving renormalization and evolution, while predictions across processes require factorization formulas connecting those distributions to scattering observables. Finally, we connect this framework to polarized ^7Li through its collinear limits and nuclear spin-orbital correlations.
ER -