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Qi-Nan Wang

Publications and source records attributed to Qi-Nan Wang.

At least 19 recordsLinked to original sources

Subtraction of infrared divergences in light-quark QCD sum rules

In QCD sum rules for light-quark systems, infrared (IR) divergences can appear in the Wilson coefficients of certain condensates. These divergences manifest explicitly in the coordinate-space expressions of the light-quark propagators. We propose an improved method to eliminate these IR divergences at the propagator level and present a subtraction formula that implements this procedure. Compared to the existing methods that rely on the mixing between quark and gluon condensates of the same dimension to eliminate IR divergences, this method is more intuitive and easier to apply in practical QCD sum rule calculations.

hep-ph

Interpretation of $Ω(2012)$ as a $Ξ(1530)K$ molecular state

We investigate the mass and strong decay properties of the $Ω(2012)$ resonance using QCD sum rules, assuming it to be an S-wave $Ξ(1530)\bar{K}$ molecular pentaquark state with $I(J^{P})= 0(\frac{3}{2}^{-})$. A unified interpolating current is constructed, and the two-point correlation functions and three-point functions are calculated up to dimension-13 and 10 condensate terms in the OPE series, respectively. The negative-parity contribution is isolated by employing parity-projected sum rules. The two-body strong decays to $Ξ^0 K^-$ and $Ξ^- \bar{K}^0$ are studied via their three-point correlation functions. Our analysis yields a mass of $2.00 \pm 0.15~\mathrm{GeV}$ and a total two-body decay width of $Γ= 0.96^{+0.79}_{-0.41}~\mathrm{MeV}$ for the $Ξ(1530)\bar{K}$ molecular state. The ratio of the two-body decay branching fractions is obtained as $\mathcal{R}^{Ξ^- \bar{K}^0}_{Ξ^0 K^-} = 0.85$. These results are compatible with the experimental data for the $Ω(2012)$ within uncertainties and support its interpretation as a $Ξ(1530)\bar{K}$ molecular pentaquark state.

hep-ph

Investigations on heavy quarkonium hybrid mesons with exotic quantum numbers $J^{PC}=2^{+-}$

We investigate the heavy quarkonium hybrid mesons with exotic quantum numbers $J^{PC}=2^{+-}$ via QCD sum rule method. We construct the currents with three Lorentz indices and calculate the correlation functions up to dimension six at the leading order of $α_{s}$. The states with $J^{PC}=2^{+-}$ are extracted by constructing the corresponding projection operators. The obtained results indicate that the masses of $2^{+-}$ $\bar{c}Gc$ and $\bar{b}Gb$ hybrid states are about $4.49~\mathrm{GeV}$ and $10.48~\mathrm{GeV}$, respectively. We suggest to search for $\bar{c}Gc$ hybrid meson with $J^{PC}=2^{+-}$ in $J/ψf_{0,1,2}$ and $χ_{c0,1,2} ω$ final states.

hep-ph

Predictions of masses for light hybrid baryons

Within the method of parity-projected QCD sum rules, we study the mass spectra of light hybrid baryons with $I(J^{P})=1/2(1/2^{\pm}), 3/2(1/2^{\pm}), 1/2(3/2^{\pm}), 3/2(3/2^{\pm})$ by constructing the local $qqqg$ interpolating currents. We calculate the correlation functions up to dimension eight condensates at the leading order of $α_{s}$. The stable QCD Lapalce sum rules can be established for the positive-parity $N_{1/2^+}, Δ_{3/2^+}, Δ_{1/2^+}$ and negative-parity $N_{1/2^-}, N_{3/2^-}, Δ_{1/2^-}$ channels to extract their mass spectra. The lowest-lying hybrid baryons are predicted to be the positive-parity $N_{1/2^+}$ state around 2.01 GeV. These hybrid baryons mainly decay into conventional baryon plus meson final states. We propose to search for the light hybrid baryons through the $Υ/ψ(3686)$ decays via the three-gluon emission mechanism in BESIII and BelleII experiments. Hopefully our studies of the light hybrid baryons will be useful for understanding the excited baryon spectrum and the behavior of gluonic degrees of freedom in QCD.

hep-ph

Doubly charmed pentaquark states with strangeness $S=0, -1$

In this work, we have studied the mass spectra of doubly charmed pentaquark states with strangeness $S=0, -1$ by using the method of QCD sum rules. We use the parity projected sum rules to separate the contributions of negative and positive parities from the two-point correlation functions induced by the pentaquark interpolating currents. Our results predict the existence of some potential doubly charmed pentaquark bound states.

hep-ph

Light hybrid baryons in QCD sum rules

We have calculated the mass spectra of nucleon and delta hybrid baryons with both positive-parity and negative-parity by using the method of QCD sum rules. We predicte that the lowest-lying hybrid baryons are the negative-parity $N_{1/2^-}$ and $Δ_{1/2^-}$ states, while the positive-parity ones are much heavier. We suggest to search for these light hybrid baryons via the $χ_{cJ}/Υ$ decay processes in the future.

hep-ph

Interpreting the $X(2370)$ and $X(2600)$ as light tetraquark states

Inspired by the states $X(2370)$ and $X(2600)$ reported by the BESIII Collaboration, we systematically investigate the mass spectra of light compact tetraquark states with configurations $ud\bar{u}\bar{d}$, $us\bar{u}\bar{s}$, and $ss\bar{s}\bar{s}$ in the $J^{PC}=0^{-+}$ and $2^{-+}$ channels using the QCD sum rules approach. To effectively describe these tetraquark states, we construct appropriate interpolating tetraquark currents featuring three Lorentz indices while avoiding derivative operators. Through meticulous calculations of correlation functions up to dimension 10 condensates, we extract the mass spectra for both $0^{-+}$ and $2^{-+}$ states by employing the projection operator technique. Our results indicate that the masses of light tetraquarks span $1.5-2.5~\text{GeV}$ for $0^{-+}$ states and $2.4-2.7~\text{GeV}$ for $2^{-+}$ states. Notably, our analysis suggests that the $X(2370)$ state could be interpreted as a $0^{-+}$ $us\bar{u}\bar{s}$ or $ss\bar{s}\bar{s}$ tetraquark state, while the $X(2600)$ state is likely to be a $2^{-+}$ $us\bar{u}\bar{s}$ tetraquark. These intriguing findings warrant further detailed investigation in future studies to better understand the nature of these states.

hep-ph

Towards heavy double-gluon hybrid mesons with exotic quantum numbers in QCD sum rules

The double-gluon hybrid meson configuration was recently proposed and investigated within QCD sum rules. In this talk, we discuss the color structures of the double-gluon hybrid meson and construct current operators with exotic quantum numbers $J^{PC}=1^{-+}$ and $2^{+-}$ for two of the structures. In the framework of QCD sum rules, we consider the condensates up to dimension-8 at the leading order of $α_{s}$ for both charmonium and the bottomonium systems. The results indicate that the masses of the $1^{-+}$ and $2^{+-}$ charmonium double-gluon hybrid mesons are approximately $6.1-7.2$ GeV and $6.3-6.4$ GeV, respectively. As for the bottomonium systems, their masses fall within the range of $13.7-14.3$ GeV and $12.6-13.3$ GeV for the $1^{-+}$ and $2^{+-}$ channels, respectively. Additionally, the charmonium hybrids could be produced in the radiative decays of bottomonium mesons in BelleII experiment.

hep-ph

Light tetraquark states with exotic quantum numbers $J^{PC}=2^{+-}$

We study the masses of light tetraquark states $ud\bar{u}\bar{d}$ , $us\bar{u}\bar{s}$ and $ss\bar{s}\bar{s}$ with exotic quantum numbers $J^{PC}=2^{+-}$ using the method of QCD sum rules. It is found that there is no tetraquark operator with two Lorentz indices coupling to the $2^{+-}$ quantum numbers. To investigate such tetraquark states, we construct the interpolating tetraquark currents with three Lorentz indices and without derivative operator. We calculate the correlation functions up to dimension 10 condensates, and extract the $2^{+-}$ invariant functions via the projector operator. Our results show that the masses of the $ud\bar{u}\bar{d}$, $us\bar{u}\bar{s}$ and $ss\bar{s}\bar{s}$ tetraquark states with $J^{PC}=2^{+-}$ are about $3.3-3.5 ~\mathrm{GeV}$, $3.5-3.7 ~\mathrm{GeV}$ and $3.67 ~\mathrm{GeV}$, respectively. We further discuss the strong decays of these light tetraquarks into the two-meson and baryon-antibaryon final states, and suggest to search for them in the $ρπ, ωπ, ϕπ$, $b_{1}π$, $h_{1}π$, $K\bar K^\ast, K\bar{K}_{1}$, $Δ\barΔ$, $Σ^{\ast} \bar{Σ}^{\ast}$, $Ξ^{\ast} \bar{Ξ}^{\ast}$, $Ω\bar{Ω}$ channels in the future.

hep-ph

Revisit the heavy quarkonium double-gluon hybrid mesons with exotic quantum numbers

We revisit the masses of heavy quarkonium double-gluon hybrid mesons with exotic quantum numbers $J^{PC}=1^{-+}$ and $2^{+-}$ in the framework of the QCD sum rules. Considering the double-gluon hybrid meson operators in the octet-octet color structure, we have constructed two independent interpolating currents with $J^{PC}=1^{-+}$ and five independent currents with $J^{PC}=2^{+-}$. For the interpolating currents with antisymmetric glueball operator, there exist non-local divergences in one kind of additional Feynman diagrams of the tri-gluon condensate, which will give important contributions to the sum rule stabilities and mass predictions. We use the diagrammatic renormalization to cancel out such divergences. At the leading order of $α_s$, the two-point correlation functions and spectral densities can be expressed in the analytic form of the generalized hypergeometric functions and Meijer's G-functions. After performing the numerical analysis, we predict the masses of the $1^{-+}$ and $2^{+-}$ charmonium double-gluon hybrid mesons to be around $6.1-7.2$ GeV and $6.3-6.4$ GeV, respectively. For the bottomonium systems, their masses are predicted to be $13.7-14.3$ GeV and $12.6-13.3$ GeV for the $1^{-+}$ and $2^{+-}$ channels, respectively. Besides, it is possible to hunt for these charmonium hybrids in the radiative decays of bottomonium mesons in BelleII experiment. Further investigations on these hybrid states in various theoretical and phenomenological methods are also anticipated in the future.

hep-ph

Doubly charmed pentaquark states in QCD sum rules

We have studied the mass spectra of doubly charmed pentaquark states in the $Λ_{c}^{(*)}D^{(*)}$ and $Σ_{c}^{(*)}D^{(*)}$ channels with $J^P=1/2^\pm$, $3/2^\pm$ and $5/2^\pm$ within the framework of QCD sum rules. We use the parity projected sum rules to separate the contributions of negative and positive parities from the two-point correlations induced by the pentaquark interpolating currents. Our results show that the bound states of $P_{cc}$ pentaquarks may exist in the $Λ_cD\, (\frac{1}{2}^-)$, $Σ_cD\, (\frac{1}{2}^-)$, $Σ_cD^*\, (\frac{3}{2}^-)$, $Λ_c^*D\, (\frac{3}{2}^-)$, $Λ_c^*D^*\, (\frac{5}{2}^-)$ channels with negative-parity and $Σ_cD\, (\frac{1}{2}^+)$, $Σ_cD^\ast\, (\frac{3}{2}^+)$, $Σ_c^\ast D\, (\frac{3}{2}^+)$ channels with positive-parity, since their masses are predicted to be lower than the corresponding meson-baryon thresholds. However, they are still allowed to decay into the $Ξ_{cc}^{(\ast)}π$ final states via strong interaction. The triply charged $P_{cc}^{+++}(ccuu\bar d)$ and neutral $P_{cc}^{0}(ccdd\bar u)$ in the isospin quartet would definitely be pentaquark states due to their exotic charges. We suggest searching for these characteristic doubly charmed pentaquark signals in the $P_{cc}^{+++}\toΞ_{cc}^{(\ast) ++}π^+/ρ^+$, $Σ_c^{(\ast)++}D^{(\ast)+}$ and $P_{cc}^{0}\toΞ_{cc}^{(\ast) +}π^-/ρ^-$, $Σ_c^{(\ast)0}D^{(\ast)0}$ decays in the near future.

hep-ph

Predictions of the hybrid mesons with exotic quantum numbers $J^{PC}=2^{+-}$

We study the non-strange and strangeonium light hybrid mesons with $J^{PC}=2^{+-}$ by using the method of QCD sum rules. The local hybrid interpolating currents with three Lorentz indices are constructed to couple to such exotic quantum numbers. We calculate the correlation functions up to dimension eight condensates at the leading order of $α_{s}$. In our results, the masses of the non-strange $b_2$ and $h_2$ hybrids are about $2.65~\mathrm{GeV}$, while that of the strangeonium $h_2^\prime$ hybrid is about $2.72~\mathrm{GeV}$. Such exotic $2^{+-}$ hybrids can be generated through both the two-gluon and three-gluon emission processes in the radiative decays of $χ_{cJ}$. Moreover, these hybrid mesons may be detectable due to their peculiar decay behaviors and small decay widths. Using the high-statistics data samples of $ψ(3686)$ in BESIII and BelleII, it is possible to hunt for such hybrid states through the partial wave analyses in the $b_2\toω/a_1/h_1/a_2π\to4π$, $h_2\toρπ\to3π$ and $h_2\to b_1π\to5π$ processes.

hep-ph

Searching for fully-heavy tetraquark states in QCD moment sum rules

In this talk, we briefly report the investigations of the mass spectra for the $cc\bar c\bar c, bb\bar b\bar b$, $bc\bar b\bar c$ and $cc\bar b\bar b$ tetraquark states by using the QCD moment sum rule method. The calculations for the fully-charm $cc\bar c\bar c$ tetraquarks have been successfully predicted the existence of di-$J/ψ$ resonances including $X(6900)$ in LHCb's observation. The quantum numbers for these resonance structures are also suggested. More efforts are still needed in both theoretical and experimental aspects to study the properties of these fully-heavy tetraquark states. They may be observed at facilities such as LHCb, CMS and RHIC in the future.

hep-ph

Exotic fully-heavy $Q\bar QQ\bar Q$ tetraquark states in $\mathbf{8}_{[Q\bar{Q}]}\otimes \mathbf{8}_{[Q\bar{Q}]}$ color configuration

We have systematically calculated the mass spectra for S-wave and P-wave fully-charm $c\bar{c}c\bar{c}$ and fully-bottom $b\bar{b}b\bar{b}$ tetraquark states in the $\mathbf{8}_{[Q\bar{Q}]}\otimes \mathbf{8}_{[Q\bar{Q}]}$ color configuration, by using the moment QCD sum rule method. The masses for the fully-charm $c\bar cc\bar c$ tetraquark states are predicted about $6.3-6.5$ GeV for S-wave channels and $7.0-7.2$ GeV for P-wave channels. These results suggest the possibility that there are some $\mathbf{8}_{[c\bar{c}]}\otimes \mathbf{8}_{[c\bar{c}]}$ components in LHCb's di-$J/ψ$ structures. For the fully-bottom $b\bar{b}b\bar{b}$ system, their masses are calculated around 18.2 GeV for S-wave tetraquark states while 18.4-18.8 GeV for P-wave ones, which are below the $η_bη_b$ and $Υ(1S)Υ(1S)$ two-meson decay thresholds.

hep-ph

Investigation of the stability for fully-heavy $bc\bar{b}\bar{c}$ tetraquark states

We study the existence of fully-heavy hidden-flavor $bc\bar{b}\bar{c}$ tetraquark states with various $J^{PC}=0^{\pm+}, 0^{--},1^{\pm\pm}, 2^{++}$, by using the moment QCD sum rule method augmented by fundamental inequalities. Using the moment sum rule analyses, our calculation shows that the masses for the S-wave positive parity $bc\bar{b}\bar{c}$ tetraquark states are about $12.2-12.4$ GeV in both $[\mathbf{\bar{3}_c}]_{bc}\otimes[\mathbf{3_c}]_{\bar{b}\bar{c}}$ and $[\mathbf{6_c}]_{bc}\otimes[\mathbf{\bar{6}_c}]_{\bar{b}\bar{c}}$ color configuration channels. Except for two $0^{++}$ states, such results are below the thresholds $T_{η_cη_b}/T_{Υψ}$ and $T_{B_cB_c}$, implying that these S-wave positive parity $bc\bar{b}\bar{c}$ tetraquark states are probably stable against the strong interaction. For the P-wave negative parity $bc\bar{b}\bar{c}$ tetraquarks, their masses in the $[\mathbf{\bar{3}_c}]_{bc}\otimes[\mathbf{3_c}]_{\bar{b}\bar{c}}$ channel are around $12.9-13.2$ GeV, while a bit higher in the $[\mathbf{6_c}]_{bc}\otimes[\mathbf{\bar{6}_c}]_{\bar{b}\bar{c}}$ channel. They can decay into the $c\bar c+b\bar b$ and $c\bar b+b\bar c$ final states via the spontaneous dissociation mechanism, including the $J/ψΥ$, $η_cΥ$, $J/ψη_b$, $B_c^+B_c^-$ channels.

hep-ph

Exotic $\bar{D}_s^{(*)}D^{(*)}$ molecular states and $sc\bar q\bar c$ tetraquark states with $J^P=0^+, 1^+, 2^+$

We have calculated the mass spectra for the $\bar{D}_s^{(*)}D^{(*)}$ molecular states and $sc\bar q\bar c$ tetraquark states with $J^P=0^+, 1^+, 2^+$. The masses of the axial-vector $\bar{D}_sD^{*}$, $\bar{D}_s^{*}D$ molecular states and $\mathbf{1}_{[sc]} \oplus \mathbf{0}_{[\bar q \bar{c}]}$, $\mathbf{0}_{[sc]} \oplus \mathbf{1}_{[\bar q \bar{c}]}$ tetraquark states are predicted to be around 3.98 GeV, which are in good agreement with the mass of $Z_{cs}(3985)^-$ from BESIII \cite{besiii2020Zcs}. In both the molecular and diquark-antidiquark pictures, our results suggest that there may exist two almost degenerate states, as the strange partners of the $X(3872)$ and $Z_c(3900)$. We propose to carefully examine the $Z_{cs}(3985)$ in future experiments to verify this. One may also search for more hidden-charm four-quark states with strangeness not only in the open-charm $\bar{D}_s^{(*)}D^{(*)}$ channels, but also in the hidden-charm channels $η_c K/K^\ast$, $J/ψK/K^\ast$.

hep-ph

Mass spectra for the $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$ tetraquark states

We have studied the masse spectra for the $cc\bar{b}\bar{b}$/$bb\bar{c}\bar{c}$ tetraquark states with quantum numbers $J^{P}=0^{\pm},1^{\pm}$, and $2^{+}$. We systematically construct the interpolating currents with various spin-parity quantum numbers and calculate their two-point correlation functions in the framework of QCD moment sum rule method. Our calculations show that the masses are about $12.3-12.4$ GeV for the positive parity $cc\bar{b}\bar{b}$ tetraquark ground states with $J^{P}=0^+, 1^+, 2^+$, while $12.8-13.1$ GeV for the negative parity channels with $J^{P}=0^-, 1^-$. The mass predictions for the positive parity $cc\bar{b}\bar{b}$ ground states are lower than the $B_{c}B_{c}$ threshold, implying that these tetraquarks can only decay via weak interaction and thus are expected to be stable and narrow.

hep-ph

Mass spectra of $NΩ$ dibaryons in the $^{3}S_1$ and $^{5}S_2$ channels

We study the mass spectra of the $NΩ$ dibaryons in the $^{3}S_1$ and $^{5}S_2$ channels with $J^{P}=1^{+}$ and $2^{+}$ respectively, by using the method of QCD sum rules. We construct two dibaryon interpolating currents in the molecular picture and calculate their correlation functions and spectral densities up to dimension-16 condensates. Our results indicate that there may exist an $NΩ$ dibaryon bound state in the $^{5}S_2$ channel with a binding energy of about $21\ \mathrm{MeV}$. The masses of the $^{3}S_1$ $NΩ$ dibaryons with $J^{P}=1^{+}$ are predicted to be higher than the $NΩ$ and $ΛΞ$ thresholds, and thus can decay into these final states directly in S-wave. The $NΩ(^{5}S_2)$ dibaryon bound state can decay into the octet-octet final states $ΛΞ$ and $ΣΞ$ in D-wave via the quark rearrangement mechanism. The existence of these $NΩ$ dibaryons may be identified in the relativistic heavy-ion collision experiments in the future.

hep-ph