arXiv subjects

Gui-Yuan Zhang

Publications and source records attributed to Gui-Yuan Zhang.

3 recordsLinked to original sources

arXiv2023

Analysis of double-$J/ψ$ production in $Z$ decay at next-to-leading-order QCD accuracy

In this article, we study in detail the double-$J/ψ$ yield through $Z$ decay at the next-to-leading-order (NLO) QCD accuracy within the nonrelativistic QCD factorization. At the tree level, the pure QCD diagrams predict a branching ratio of $\mathcal{B}_{Z \to J/ψ+J/ψ} \sim 10^{-12}$; however, the inclusion of the QED diagrams would augment this prediction by approximately 2-3 orders of magnitude. After incorporating the QCD corrections, the QCD results exhibit a considerable increase, whereas the QED results undergo a substantial reduction. Combining the QCD and QED contributions at NLO in $α_s$, it is observed that the prediction of $\mathcal{B}_{Z \to J/ψ+J/ψ}=(1.110^{+0.334+0.054}_{-0.241-0.001})\times 10^{-10}$, which displays a fairly steady dependence on the renormalization scale, is significantly lower than the upper limits released by CMS.

hep-ph↗

arXiv2022

$X(3860)$ production in association with $J/ψ$ via $e^{+}e^{-}$ annihilation at Belle

In this paper, we study the $X(3860)$ production associated with $J/ψ$ via $e^{+}e^{-}$ annihilation at the next-to-leading-order (NLO) QCD accuracy, within the nonrelativistic QCD (NRQCD) framework. Under the hypothesis of $J^{PC}_{X(3860)}=0^{++}$, the predicted total cross sections agree well with the Belle's measurements at $\sqrt{s}=Υ(4S,5S)$, while the theoretical results given by the $2^{++}$ hypothesis significantly undershoot the data. This is consistent with the Belle's conclusion that the $0^{++}$ hypothesis is favored over the $2^{++}$ hypothesis for $X(3860)$. Despite the agreement of the total cross sections, the NRQCD predictions seem to be incompatible with the Belle-measured $J/ψ$ angular distributions. We also perform the NLO calculations of $σ_{e^{+}e^{-} \to J/ψ+X(3940)}$ on the assumption of $J^{PC}_{X(3940)}=0^{-+}$, discovering that the NRQCD predictions that coincide with the light-cone results are in good agreement with the experiment.

hep-ph↗

arXiv2022

Doubly-charmed baryon production in $Z$ boson decay

In this paper, we carry out a detailed study of doubly-charmed baryon production in $Z$ boson decay, on the basis of the nonrelativistic QCD factorization. With the inclusion of the di-quark states $(cc)[^3S_1]_{\bar{\textbf{3}}}$ and $(cc)[^1S_0]_{\textbf{6}}$, the branching ratio of $\mathcal{B}_{Z \to Ξ_{cc}+X}$ is predicted to be of the $10^{-5}$ order, indicating its experimental measurability. By comparing to the $Λ^{+}_{c}$ yield in $Z$ decay, we predict $\mathcal{R}_{Ξ_{cc}^{+}}(=\frac{Γ(Z \to Ξ^{+}_{cc}) \times \mathcal{B}(Ξ^{+}_{cc} \to Λ_c^{+}K^{-}π^{+})}{Γ(Z \to Λ_c^{+})})=(0.85^{+0.10}_{-0.07}) \times 10^{-4}$ and $\mathcal{R}_{Ξ_{cc}^{++}}(=\frac{Γ(Z \to Ξ^{++}_{cc}) \times \mathcal{B}(Ξ^{++}_{cc} \to Λ_c^{+}K^{-}π^{+}π^{+})}{Γ(Z \to Λ_c^{+})})=(1.70^{+0.20}_{-0.14}) \times 10^{-4}$, which are at clear variance with the SELEX measurements but comparable with the values given by the LHCb and Belle collaborations.

hep-ph↗