Moderate-to-Large-$x$ Gluon Helicity from $J/ψ$ Production at $\sqrt{s}=27~\mathrm{GeV}$
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arXiv
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| Auteurs principaux: | , , , , |
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| Format: | Preprint |
| Publié: |
2026
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| _version_ | 1866910271820267520 |
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| author | Sharma, Shubham Aparin, Alexey Puhan, Satyajit Kumar, Narinder Dahiya, Harleen |
| author_facet | Sharma, Shubham Aparin, Alexey Puhan, Satyajit Kumar, Narinder Dahiya, Harleen |
| contents | We present a feasibility study of the longitudinal double-spin asymmetry $A_{LL}$ in inclusive $J/ψ$ production in polarized proton-proton collisions at $\sqrt{s}\approx 27~\mathrm{GeV}$ at the Spin Physics Detector (SPD) of the Nuclotron-based Ion Collider fAcility (NICA). At these moderate energies, $J/ψ$ production is dominated by gluon-gluon fusion, probing gluon momentum fractions $x\approx 0.1$-$0.2$ at central rapidity and highly asymmetric configurations at forward rapidity, where one parton can reach $x\approx 0.5$-$0.9$. This provides direct sensitivity to the poorly constrained moderate- to large-$x$ region of the gluon helicity distribution $Δg(x)$. We estimate $A_{LL}$ as a function of transverse momentum and rapidity using polarized parton distribution functions, focusing on the underlying partonic spin asymmetry. Nonperturbative long-distance effects are treated in a simplified manner and largely cancel in the asymmetry, enabling a direct assessment of gluon polarization sensitivity. We find asymmetries reaching $|A_{LL}|\approx 0.09$ at $p_T=3~\mathrm{GeV}$, with enhanced sensitivity at forward rapidity. The dominant theoretical uncertainty arises from polarized parton distribution functions. These results demonstrate that inclusive $J/ψ$ measurements at SPD/NICA provide a sensitive and complementary probe of gluon polarization at moderate and large $x$, extending constraints from RHIC into a kinematic regime not directly accessible to the EIC. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2605_30945 |
| institution | arXiv |
| publishDate | 2026 |
| record_format | arxiv |
| spellingShingle | Moderate-to-Large-$x$ Gluon Helicity from $J/ψ$ Production at $\sqrt{s}=27~\mathrm{GeV}$ Sharma, Shubham Aparin, Alexey Puhan, Satyajit Kumar, Narinder Dahiya, Harleen High Energy Physics - Phenomenology We present a feasibility study of the longitudinal double-spin asymmetry $A_{LL}$ in inclusive $J/ψ$ production in polarized proton-proton collisions at $\sqrt{s}\approx 27~\mathrm{GeV}$ at the Spin Physics Detector (SPD) of the Nuclotron-based Ion Collider fAcility (NICA). At these moderate energies, $J/ψ$ production is dominated by gluon-gluon fusion, probing gluon momentum fractions $x\approx 0.1$-$0.2$ at central rapidity and highly asymmetric configurations at forward rapidity, where one parton can reach $x\approx 0.5$-$0.9$. This provides direct sensitivity to the poorly constrained moderate- to large-$x$ region of the gluon helicity distribution $Δg(x)$. We estimate $A_{LL}$ as a function of transverse momentum and rapidity using polarized parton distribution functions, focusing on the underlying partonic spin asymmetry. Nonperturbative long-distance effects are treated in a simplified manner and largely cancel in the asymmetry, enabling a direct assessment of gluon polarization sensitivity. We find asymmetries reaching $|A_{LL}|\approx 0.09$ at $p_T=3~\mathrm{GeV}$, with enhanced sensitivity at forward rapidity. The dominant theoretical uncertainty arises from polarized parton distribution functions. These results demonstrate that inclusive $J/ψ$ measurements at SPD/NICA provide a sensitive and complementary probe of gluon polarization at moderate and large $x$, extending constraints from RHIC into a kinematic regime not directly accessible to the EIC. |
| title | Moderate-to-Large-$x$ Gluon Helicity from $J/ψ$ Production at $\sqrt{s}=27~\mathrm{GeV}$ |
| topic | High Energy Physics - Phenomenology |
| url | https://arxiv.org/abs/2605.30945 |