Paper

{
  "raw_xml": "<entry>\n    <id>http://arxiv.org/abs/2603.18874v1</id>\n    <title>Probing the Color-Octet Mechanism via Dihadron Fragmentation in $χ_b$ Decays</title>\n    <updated>2026-03-19T13:18:12Z</updated>\n    <link href='https://arxiv.org/abs/2603.18874v1' rel='alternate' type='text/html'/>\n    <link href='https://arxiv.org/pdf/2603.18874v1' rel='related' title='pdf' type='application/pdf'/>\n    <summary>The color-octet (CO) mechanism is a cornerstone of non-relativistic QCD, yet its long-distance matrix elements remain limited, preventing stringent tests of the theory. We demonstrate that the Artru-Collins asymmetry in hadronic decays of the $P$-wave bottomonium state $χ_{b2}$ provides a direct probe of CO dynamics. The asymmetry arises exclusively from the CO decay channel, whereas the color-singlet (CS) contribution affects only the unpolarized rate, so that a nonzero signal constitutes unambiguous evidence of the CO mechanism. This observable provides a novel way to extract the ratio $ρ_8$ between CO and CS matrix elements. Focusing on $e^+e^-\\toΥ(2S)\\toγ\\,χ_{b2}$ at Belle, we show that the asymmetric beam configuration preserves the asymmetry in the laboratory frame and avoids the strong suppression present in the center-of-mass frame. With the Belle II dataset, $ρ_8$ could be determined with sufficient precision to address the long-standing discrepancy between the lattice calculations and phenomenological determinations.</summary>\n    <category scheme='http://arxiv.org/schemas/atom' term='hep-ph'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='hep-ex'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='nucl-ex'/>\n    <category scheme='http://arxiv.org/schemas/atom' term='nucl-th'/>\n    <published>2026-03-19T13:18:12Z</published>\n    <arxiv:comment>5 pages, 3 figures</arxiv:comment>\n    <arxiv:primary_category term='hep-ph'/>\n    <author>\n      <name>Zhi-Guo He</name>\n    </author>\n    <author>\n      <name>Guanghui Li</name>\n    </author>\n    <author>\n      <name>Yu-Jie Tian</name>\n    </author>\n    <author>\n      <name>Xin-Kai Wen</name>\n    </author>\n    <author>\n      <name>Bin Yan</name>\n    </author>\n  </entry>"
}