First study of polarized proton-proton scattering with small-$x$ helicity evolution
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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866910895174582272 |
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| author | Adamiak, Daniel Baldonado, Nicholas Kovchegov, Yuri V. Li, Ming Melnitchouk, W. Pitonyak, Daniel Sato, Nobuo Sievert, Matthew D. Tarasov, Andrey Tawabutr, Yossathorn |
| author_facet | Adamiak, Daniel Baldonado, Nicholas Kovchegov, Yuri V. Li, Ming Melnitchouk, W. Pitonyak, Daniel Sato, Nobuo Sievert, Matthew D. Tarasov, Andrey Tawabutr, Yossathorn |
| contents | We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-$x$ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton ($pp$) scattering at parton momentum fractions $x < 0.1$. We also simultaneously include double-longitudinal spin asymmetries in inclusive and semi-inclusive deep-inelastic scattering probing $x < 0.1$. Employing the polarized small-$x$ pure-glue calculation of $pp\to gX$ for the jet production cross section, we modify the large-$N_c\&N_f$ KPS-CTT evolution equations by setting $N_f = 0$ to replicate the large-$N_c$ (pure-glue) limit, while retaining external quark flavors for the spinor field operators. We find that the $pp$ data have a considerable impact on the helicity PDFs at small $x$, reducing their uncertainties and leading to a total quark and gluon helicity in the proton for $x < 0.1$ of $-0.04 \pm 0.23$. Combining our analysis with the a recent JAM helicity PDF analysis of the world polarized data, which includes $x > 0.1$, we find a total quark and gluon helicity contribution for $x > 10^{-7}$ of between 0.02 and 0.51. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2503_21006 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | First study of polarized proton-proton scattering with small-$x$ helicity evolution Adamiak, Daniel Baldonado, Nicholas Kovchegov, Yuri V. Li, Ming Melnitchouk, W. Pitonyak, Daniel Sato, Nobuo Sievert, Matthew D. Tarasov, Andrey Tawabutr, Yossathorn High Energy Physics - Phenomenology High Energy Physics - Experiment Nuclear Experiment Nuclear Theory We perform a phenomenological study of helicity-dependent parton distribution functions (PDFs) using small-$x$ helicity evolution equations, incorporating for the first time single-inclusive jet production data in polarized proton-proton ($pp$) scattering at parton momentum fractions $x < 0.1$. We also simultaneously include double-longitudinal spin asymmetries in inclusive and semi-inclusive deep-inelastic scattering probing $x < 0.1$. Employing the polarized small-$x$ pure-glue calculation of $pp\to gX$ for the jet production cross section, we modify the large-$N_c\&N_f$ KPS-CTT evolution equations by setting $N_f = 0$ to replicate the large-$N_c$ (pure-glue) limit, while retaining external quark flavors for the spinor field operators. We find that the $pp$ data have a considerable impact on the helicity PDFs at small $x$, reducing their uncertainties and leading to a total quark and gluon helicity in the proton for $x < 0.1$ of $-0.04 \pm 0.23$. Combining our analysis with the a recent JAM helicity PDF analysis of the world polarized data, which includes $x > 0.1$, we find a total quark and gluon helicity contribution for $x > 10^{-7}$ of between 0.02 and 0.51. |
| title | First study of polarized proton-proton scattering with small-$x$ helicity evolution |
| topic | High Energy Physics - Phenomenology High Energy Physics - Experiment Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2503.21006 |