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Kui-Yong Liu

Publications and source records attributed to Kui-Yong Liu.

25 records · Page 2Linked to original sources

$J / ψ$ electromagnetic production associated with light hadrons at $B$ factories

The electromagnetic productions of $J ψ$ associated with light hadrons(LH) and leptonic pairs($μ^+μ^-$, $τ^+τ^-$) at $B$ factories are studied. We find that the direct electromagnetic production cross sections of $J / ψ$($ψ(2S)$) associated with light hadrons is about $0.10(0.04)$ pb. The direct production cross sections of $J / ψ$($ψ(2S)$) associated with $μ^+μ^-$ is about $0.056(0.020)$ pb. If we include the contributions from $ψ(2S)$ decay, we can get the prompt cross section $σ[e^+e^- \to J/ψ+μ^+μ^-]=(0.068 \pm 0.002)$ pb, about $(16 \pm 5) %$ of the Belle data $σ[e^+e^- \to J/ψ+X_{non-c\bar c}]=(0.43\pm 0.09\pm 0.09)$ pb, meanwhile the $e^+e^- \to J/ψ+τ^+τ^-$ process only contributes $2 %$. The prompt cross section $σ[e^+e^- \to J/ψ+Light Hadrons]=(0.121 \pm 0.005)$ pb is about $(28 \pm 8) %$ of the Belle data.

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Search for excited charmonium states in $e^+e^-$ Annihilation at $\sqrt{s}=10.6$ GeV

We suggest searching for excited charmonium states in $e^+e^-$ annihilation via double charmonium production at $\sqrt{s}=10.6$ GeV with $B$ factories, based on a more complete leading order calculation including both QCD and QED contributions for various processes. In particular, for the C=+ states, the $χ_{c0}(nP)$ (n=2,3) and $η_c(mS)$ (m=3,4) may have appreciable potentials to be observed; while for the C=- states, the $η_ch_c$ production and especially the $χ_{c1}h_c$ production might provide opportunities for observing the $h_c$ with higher statistics in the future. A brief discussion for the X(3940) observed in the double charmonium production is included.

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S-D mixing and $ψ(3770)$ production in $e^+e^-$ annihilation and B decay and its radiative transitions

The large decay rate observed by Belle for $B^+\toψ(3770)K^+$, which is comparable to $B^+\toψ(3686)K^+$, might indicate either an unexpectedly large S-D mixing angle $|θ|\approx 40^o$ or the leading role of the color-octet mechanism in D-wave charmonium production in B decay. By calculating the production rate of $ψ(3770)$ in the continuum $e^+e^-$ annihilation at $\sqrt{s}=10.6$ GeV with these two possible approaches (i.e. the large S-D mixing and the color-octet mechanism), we show that the measurement for this process at Belle and BaBar may provide a clear cut clarification for the two approaches. In addition, the radiative E1 transition ratio $Γ(ψ(3770)\to γχ_{c2})/Γ(ψ(3770)\to γχ_{c1})$ may dramatically change from $\sim$ 0.04 (for $θ\approx 0^o$) to $\sim$ 200 (for $θ\approx -40^o$) due to the large S-D interference effect, thus the E1 transition measurement of $ψ(3770)$ at BES and CLEO-c will also be very useful in clarifying this issue.

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Inclusive Charmonium Production via Double $c \bar c$ in $e^+e^-$ Annihilation

Motivated by the recent observation of double charm quark pair production by the Belle Collaboration, we calculate the complete ${\cal O}(α_{s}^{2})$ inclusive production cross sections for $η_{c}$, $J/ψ$, and $χ_{cJ}$(J=0, 1, 2) plus $c\bar{c}$ in $e^+ e^-$ annihilation through a virtual photon. We consider both color-singlet and color-octet contributions, and give the analytical expressions for these cross sections. The complete color-singlet calculations are compared with the approximate fragmentation calculations as functions of the center-of-mass energy $\sqrt{s}$. We find that most of the fragmentation results substantially overestimate the cross sections (e.g. by a factor of $\sim$4 for $χ_{c1}$ and $χ_{c2}$) at the Belle and BaBar energy $\sqrt{s}=10.6$GeV. The fragmentation results become a good approximation only when $\sqrt{s}$ is higher than about 100GeV. We further calculate the color-octet contributions to these cross sections with analytical expressions. We find that while the color-octet contribution to $J/ψ$ inclusive production via double charm is negligible (only about 3%), the color-octet contributions to $χ_{c1}$ and $χ_{c2}$ can be significant.

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Production of $J/ψ+c\bar{c}$ through two photons in $e^+e^-$ annihilation

We study the production of $J/ψ+c\bar{c}$ in $e^+e^-$ annihilation through two virtual photons. The cross section is estimated to be 23 fb at $\sqrt{s}=10.6$ GeV, which is smaller by a factor of six than the calculated cross section for the same process but through one virtual photon. As a result, while the annihilation into two photons may be important for certain exclusive production processes, the big gap between the inclusive production cross section $σ(e^+e^- \to J/ψ+ c\bar{c})\simeq$ 0.9pb observed by Belle and the current nonrelativistic QCD prediction of $\simeq$0.15pb still remains very puzzling. We find, however, as the center-of-mass energy increases ($\sqrt{s}>20$ GeV) the production through two virtual photons $e^+e^- \to 2γ^* \to J/ψ+ c\bar{c}$ will prevail over that through one virtual photon, because in the former process the photon fragmentation into $J/ψ$ and into the charmed quark pair becomes more important at higher energies.

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Problems of Double Charm Production in $e^+e^-$ Annihilation at $\sqrt{s}=10.6$ GeV

Using the nonrelativistic QCD(NRQCD) factorization formalism, we calculate the color-singlet cross sections for exclusive production processes ${e^++e^-\to J/ψ+η_c}$~ and ~$e^++e^-\to J/ψ+ χ_{cJ}$~$(J=0,1,2)$ at the center-of-mass energy $\sqrt{s}$=10.6 GeV. The cross sections are estimated to be 5.5fb, 6.7fb, 1.1fb, and 1.6fb for $η_c, χ_{c0}, χ_{c1}$ and $χ_{c2}$, respectively. The calculated $J/ψ+η_c$ production rate is smaller than the recent Belle data by about an order of magnitude, which might indicate the failure of perturbative QCD calculation to explain the double-charmonium production data. The complete $\cal{O}$$(α^2_{s})$ color-singlet cross section for ${e^++e^-\to χ_{c0}+ c\bar {c}}$ is calculated. In addition, we also evaluate the ratio of exclusive to inclusive production cross sections. The ratio of $J/ψη_c$ production to $J/ψc\bar{c}$ production could be consistent with the experimental data.

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D-wave Charmonium Production in $e^+e^-$ Annihilation at $\sqrt{s}=10.6$ GeV

We calculate the D-wave charmonium production in $e^+e^-$ annihilation at BELLE and BABAR at $\sqrt{s}=10.6$ GeV using the nonrelativistic QCD factorization formalism, including color singlet and color octet contributions. We analyze the contributions of various processes for $δ_J(J=1,2)$ production. We find that both the color singlet and color octet channels may give substantial contributions, and the production rates are estimated to be $σ(δ_1)\simeq 0.043-0.16pb$ and $σ(δ_2)\simeq 0.094-0.29pb$, which, however, are very sensitive to the choice of the color octet matrix elements of the D-wave charmonium states. The measurement of D-wave charmonium production at BABAR and BELLE in the future will be very helpful to test the color octet mechanism and to determine the color octet matrix elements.

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