I型双希格斯二重态模型中CP-偶希格斯玻色子衰变到Vγ的双圈QCD修正
Two-loop QCD corrections to $CP$-even Higgs boson decays into $Vγ$ in the Type-I Two-Higgs-Doublet Model
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中文总结 AI 辅助
研究I型双希格斯二重态模型中重CP-偶希格斯玻色子H→Vγ衰变的双圈QCD修正，发现衰变宽度依赖m_H和tanβ，修正幅度约-20%至+20%，相关修正对HL-LHC数据解释有意义。
中文摘要 AI 辅助
我们在I型双希格斯二重态模型（THDM）框架下，研究重CP-偶希格斯玻色子的圈诱导衰变H→Vγ（V=Z,γ）的QCD修正。由于 underlying 圈拓扑的相似性，这两个衰变道表现出密切关联的行为。在施加相关的唯象约束后，我们在对齐极限下计算了5000个可行参数点在QCD次领头阶（NLO）的衰变宽度。H→γγ的宽度约为H→Zγ的4倍，两者均由顶夸克圈主导：W贡献在对齐极限下消失，而带电希格斯圈在大部分可行参数区域中被压低。修正表现出对重希格斯玻色子质量m_H的显著依赖，在t\bar{t}产生阈值附近达到最大值。为阐明各参数依赖关系，我们分析了专用基准情景，发现衰变宽度随tanβ增大而单调减小，随m_H增大而增大。两个衰变道的QCD修正通常在约-20%至+20%之间，非对齐情景下修正更大：在H→γγ道中，大tanβ时修正可达+38%，在H→Zγ道中修正会过零变为正值。CP选择规则迫使t\bar{t}对在阈值处处于P波组态，这强烈压低了库仑修正并确保了固定阶预测的微扰稳定性。与ATLAS限制的比较表明，当前数据尚未约束该参数空间，而O(15%)的NLO修正可能对解释高亮度大型强子对撞机（HL-LHC）的排除限具有重要意义。
英文摘要
We investigate the QCD corrections to the loop-induced decays of the heavy $CP$-even Higgs boson, $H \to Vγ$ ($V = Z, γ$), within the framework of the Type-I Two-Higgs-Doublet Model (THDM). Owing to the similarity of the underlying loop topologies, the two decay channels exhibit closely correlated behaviour. After imposing relevant phenomenological constraints, we evaluate the decay widths for 5000 viable parameter points at next-to-leading order (NLO) in QCD under the alignment limit. The $H\toγγ$ width exceeds that of $H\to Zγ$ by roughly a factor of four. Both are dominated by the top-quark loop: the $W$ contribution vanishes in the alignment limit, and the charged-Higgs loop is suppressed throughout most of the viable parameter region. The corrections exhibit a pronounced dependence on the heavy Higgs boson mass $m_H$, attaining a maximum in the vicinity of the $t\bar{t}$ production threshold. To elucidate the individual parameter dependences, dedicated benchmark scenarios are analysed, revealing that the decay widths diminish monotonically with increasing $\tanβ$ while growing with $m_H$. The QCD corrections for both decay modes typically span approximately $-20\%$ to $+20\%$, with larger corrections in the non-alignment scenario: in the $H\toγγ$ channel they reach up to $+38\%$ at large $\tanβ$, and in the $H\to Zγ$ channel they cross zero to become positive. The $CP$ selection rule forces the $t\bar{t}$ pair into a $P$-wave configuration at threshold, which strongly suppresses the Coulomb corrections and secures the perturbative stability of the fixed-order prediction. A comparison with ATLAS limits shows that current data do not yet constrain the parameter space, whereas the $\mathcal{O}(15\%)$ NLO corrections may become relevant for interpreting exclusion bounds at the HL-LHC.
发表机构
- Kunming University of Science and Technology（昆明理工大学）
- University of Science and Technology of China（中国科学技术大学）
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