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arXiv 2108.13089hep-phhep-exhep-lat
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双胶球求和规则、I=0标量介子与共形反常

Di-Gluonium Sum Rules, I = 0 Scalar Mesons and Conformal Anomaly

Stephan Narison, LUPM, iHEPMAD

AI总结:

本文利用N2LO阶SVZ展开的标量双胶球求和规则,提取了I=0标量介子中最低胶球及其径向激发态的质量和耦合,并结合低能顶点求和规则预言了强子衰变宽度,将胶球候选者分为σ型和G型两类。

摘要:

我们重新审视、仔细检查、改进、确认并完善了先前在标量双胶球求和规则中得到的结论[1-3]。该工作基于标准SVZ展开的N2LO阶、不含瞬子,并超越了最小对偶假设,即谱函数的“单共振态+QCD连续谱”参数化方式,这对于更好地理解I=0标量介子的复杂谱结构是必要的。我们选取阶数≤4的不同(未)减除求和规则(USR)矩来提取两个最低胶球的质量和耦合。得到:[M_{σ_B},f_{σ_B}]=[1.07(13),0.46(16)],[M_{G_1},f_{G_1}]=[1.55(12),0.37(11)] GeV,以及相应的径向激发态质量:M_{σ'_B}=1.11(12) GeV和M_{G'_1}=1.56(14) GeV,它们(出人意料地)与基态几乎简并。发现第二径向激发态的质量要重得多:M_{G_2}≈2.99(22) GeV。将这些结果与一些低能顶点求和规则(LEV-SR)相结合,我们预言了若干强子宽度并将其分为两类:σ型(σ_B,σ'_B)通过OZI破坏过程大量衰变到ππ,而σ'_B通过σσ衰变到2(ππ)S;G型(G_1, G'_1以及可能的G_2)通过U(1)_A胶子顶点衰变到η'η和ηη。除了一些可能与夸克偶素态的混合外,我们可以预期观测到的σ/f_0(500)和f_0(137)是σ型,而f_0(1.5)和f_0(1.7)是G型胶球。高质量态G_2(2.99)也可以与G_1、G'_1混合,从而将胶球候选者的胶子成分提升到2 GeV以上。我们还估计了共形荷ψ_G(0)=2.09(29) GeV^4及其斜率10^2ψ'_G(0)=-22(29) GeV^2。我们的结果总结在表1中。

英文摘要:

We revisit, scrutinize, improve, confirm and complete our previous results [1-3] from the scalar di-gluonium sum rules within the standard SVZ-expansion at N2LO without instantons and beyond the minimal duality ansatz : "one resonance + QCD continuum" parametrization of the spectral function which is necessary for a better understanding of the complex spectra of the $I=0$ scalar mesons. We select different (un)subtracted sum rules (USR) moments of degree $\leq$ 4 for extracting the two lowest gluonia masses and couplings. We obtain: $[M_{σ_B},f_{σ_B}]=[1.07(13),0.46(16)],~[M_{G_1},f_{G_1}][1.55(12),0.37(11)]$ GeV and the corresponding masses of the radial excitations : $M_{σ'_B}$= 1.11(12) and $M_{G'_1}=1.56(14)$ GeV which are (unexpectedly) almost degenerated with the ground states. The 2nd radial excitation is found to have a much heavier mass: $M_{G_2}\simeq$ 2.99(22) GeV. Combining these results with some Low-Energy Vertex Sum Rules (LEV-SR), we predict some hadronic widths and classify them into two groups : -- The $σ$-like ($σ_B,σ'_B$) which decay copiously to $ππ$ from OZI-violating process and the $σ'_B$ to $2(ππ)S$ through $σσ$. -- The $G$-like $(G_1,~G'_1$ and eventually $G_2$) which decay into $η'η, ~ηη$ through the $U(1)_A$ gluonic vertex. Besides some eventual mixings with quarkonia states, we may expect that the observed $σ/f_0(500)$ and $f_0(137)$ are $σ$-like while the $f_0(1.5)$ and $f_0(1.7)$ are $G$-like gluonia. The high mass $G_2(2.99)$ can also mix with the $G_1,~G'_1$ to bring the gluon component of the gluonia candidates above 2 GeV. We also estimate the conformal charge $ψ_G(0)=2.09(29)$ GeV$^4$ and its slope $10^2ψ'_G(0)=-22(29)$ GeV$^2$. Our results are summarized in Table 1.

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