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arXiv 2401.06404hep-ph
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Zγ对产生过程不对称性探针的NNLO QCD预言

NNLO QCD predictions of the asymmetry probe of the $Zγ$ pair-production process

Kadir Saygin

备注：
25 pages, 10 figures
发表信息：
Phys. Scr. 99 025302 (2024)
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AI总结：

本文首次提出利用Zγ过程的轻子衰变与不可见衰变微分截面不对称性作为探针，并给出NNLO QCD预言，证明其在高不变质量和高横动量区域对超出标准模型的新物理（如高质量共振和暗物质）具有显著敏感性。

摘要：

本文首次提出一种新思路，利用质子-质子（pp）碰撞中Zγ对产生的微分截面之间的不对称性，其中末态分别为带电轻子对加一个光子pp→Zγ→l⁺l⁻γ（轻子衰变）和中微子对加一个光子pp→Zγ→νν̄γ（不可见衰变）。通过在量子色动力学（QCD）微扰理论中纳入次次领先阶（NNLO）辐射修正，利用固定阶预言研究了Zγ过程的轻子衰变与不可见衰变之间的不对称性。给出了在不同pp碰撞能量下、作为若干关键观测量（包括Zγ衰变产物的横动量和方位角间隔）的函数的NNLO QCD预言。基于与相关强子对撞机测量一致的实际基准相空间要求，提供了Zγ不对称性的预言分布。在不同pp碰撞能量和不同相空间区域（如更高的轻子对不变质量m^{l⁺l⁻}或更高的中微子对横动量p_T^{νν̄}要求）下评估了预言分布。结果表明，Zγ不对称性在不同相空间区域（包括高m^{l⁺l⁻}和高p_T^{νν̄}区域）具有显著敏感性。因此，Zγ不对称性可转化为探测偏离标准模型（SM）预言的重要物理量。就此而言，不对称性探针被提议作为间接搜寻超越标准模型物理（包括高质量共振和暗物质扇区）的灵敏指标。

英文摘要：

The paper presents for the first time a novel idea of exploiting asymmetry between differential cross sections of the $Zγ$ pair-production in proton-proton ($pp$) collisions for the final states of a charged-lepton pair plus a photon $pp \rightarrow Zγ\rightarrow l^{+}l^{-}γ$ (leptonic decay) and of a neutrino pair plus a photon $pp \rightarrow Z γ\rightarrow ν\barνγ$ (invisible decay). Asymmetry between the leptonic and invisible decays of the $Zγ$ process is investigated by using fixed-order predictions through inclusion of next-to-next-to-leading (NNLO) radiative corrections in quantum chromodynamics (QCD) perturbation theory. NNLO QCD predictions are presented at various $pp$-collision energies as functions of several key observables including transverse momenta and azimuthal-angle separation, regarding the $Zγ$ decay products. The predicted distributions for the $Zγ$ asymmetry are provided based on realistic fiducial phase-space requirements in line with the related hadron-collider measurements. The predicted distributions are assessed at various $pp$-collision energies and in different phase-space regions such as with higher lepton-pair invariant mass $m^{l^{+}l^{-}}$ or higher neutrino-pair transverse momentum $p_{\rm{T}}^{ν\barν}$ requirements. The $Zγ$ asymmetry is shown to be significantly sensitive in different regions of phase space including high-$m^{l^{+}l^{-}}$ and high-$p_{\rm{T}}^{ν\barν}$ regions. The $Zγ$ asymmetry can therefore be translated into an important quantity for probing deviation from the Standard Model (SM) predictions. In this regard, the asymmetry probe is proposed as a sensitive indicator for indirect searches for physics beyond the SM encompassing high-mass resonances and dark-matter sector.

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