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arXiv · 2609.24674

Resolving the universality and polarization puzzles in $J/ψ$ hadroproduction

An-Ping Chen·Jun Guo·Yan-Qing Ma
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Abstract

Prompt $J/ψ$ hadroproduction poses two related puzzles: fixed-order hadronic and $e^+e^-$ analyses give incompatible constraints on the same color-octet (CO) long-distance matrix element (LDME) combination, and the weak observed polarization is difficult to reproduce together with the yield. We analyze high-$p_T$ production in the fragmentation-function formalism with leading-logarithmic threshold resummation in both nonrelativistic QCD (NRQCD) and soft-gluon factorization (SGF). Combining the resummed hadroproduction fit with bounds from resummed $e^+e^-$ production, we find in both frameworks a common LDME region satisfying the two constraints simultaneously: threshold resummation resolves the universality tension present at fixed order. There, the $^{1}S_{0}^{[8]}$ contribution is small and the yield is governed by the $^{3}S_{1}^{[8]}$ and $^{3}P_{J}^{[8]}$ channels, whose leading transverse contributions largely cancel. The cancellation amplifies spin-symmetry-breaking transitions in the $^{3}S_{1}^{[8]}$ channel, so that within a one-parameter spin-flip ansatz a contribution of natural order $v^4$ accommodates both the measured yields and the weak polarization. A similar sensitivity holds for $ψ(2S)$ production.

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An-Ping Chen, Jun Guo, Yan-Qing Ma. 2026-09-21. Resolving the universality and polarization puzzles in $J/ψ$ hadroproduction. https://arxiv.org/abs/2609.24674

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