We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-π₯ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton (πβ’π) scattering at parton momentum fractions π₯ <0.1. We also simultaneously include double-longitudinal spin asymmetries in inclusive and semi-inclusive deep-inelastic scattering probing π₯ <0.1. Employing the polarized small-π₯ pure-glue calculation of πβ’π β πβ‘π for the jet production cross section, we modify the large-ππ&ππ KPS-CTT evolution equations by setting ππ = 0 to replicate the large-ππ (pure-glue) limit, while retaining external quark flavors for the spinor field operators. We find that the πβ’π data have a considerable impact on the helicity PDFs at small π₯, reducing their uncertainties and leading to a total quark and gluon helicity in the proton for π₯ < 0.1 of β0.04 Β±0.23. Combining our analysis with a recent JAM helicity PDF analysis of the world polarized data, which includes π₯ > 0.1, we find a total quark and gluon helicity contribution for π₯ >10β7 of between 0.02 and 0.51.
Adamiak, Daniel, et al. "First study of polarized proton-proton scattering with small-π₯ helicity evolution." Physical Review. D., vol. 112, no. 9, Nov. 2025. https://doi.org/10.1103/9gnx-ycs4
Adamiak, Daniel, Baldonado, Nicholas, Kovchegov, Yuri V., Li, Ming, Melnitchouk, W., Pitonyak, Daniel, Sato, Nobuo, Sievert, Matthew D., Tarasov, Andrey, & Tawabutr, Yossathorn (2025). First study of polarized proton-proton scattering with small-π₯ helicity evolution. Physical Review. D., 112(9). https://doi.org/10.1103/9gnx-ycs4
@article{osti_3004721,
author = {Adamiak, Daniel and Baldonado, Nicholas and Kovchegov, Yuri V. and Li, Ming and Melnitchouk, W. and Pitonyak, Daniel and Sato, Nobuo and Sievert, Matthew D. and Tarasov, Andrey and Tawabutr, Yossathorn},
title = {First study of polarized proton-proton scattering with small-π₯ helicity evolution},
annote = {We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-π₯ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton (πβ’π) scattering at parton momentum fractions π₯ <0.1. We also simultaneously include double-longitudinal spin asymmetries in inclusive and semi-inclusive deep-inelastic scattering probing π₯ <0.1. Employing the polarized small-π₯ pure-glue calculation of πβ’π β πβ‘π for the jet production cross section, we modify the large-ππ&ππ KPS-CTT evolution equations by setting ππ = 0 to replicate the large-ππ (pure-glue) limit, while retaining external quark flavors for the spinor field operators. We find that the πβ’π data have a considerable impact on the helicity PDFs at small π₯, reducing their uncertainties and leading to a total quark and gluon helicity in the proton for π₯ < 0.1 of β0.04 Β±0.23. Combining our analysis with a recent JAM helicity PDF analysis of the world polarized data, which includes π₯ > 0.1, we find a total quark and gluon helicity contribution for π₯ >10β7 of between 0.02 and 0.51.},
doi = {10.1103/9gnx-ycs4},
url = {https://www.osti.gov/biblio/3004721},
journal = {Physical Review. D.},
issn = {ISSN 2470-0010},
number = {9},
volume = {112},
place = {United States},
publisher = {American Physical Society (APS)},
year = {2025},
month = {11}}
Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States)
Sponsoring Organization:
European Research Council (ERC); National Science Foundation (NSF); Research Council of Finland (RCF); USDOE Office of Science (SC), Nuclear Physics (NP)
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Vol. 1056https://doi.org/10.1016/j.nima.2023.168563