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Hua-Xing Chen

Publications and source records attributed to Hua-Xing Chen.

At least 109 records · Page 6Linked to original sources
arXiv2018

A possible partner state of the $Y(2175)$

We study the $Y(2175)$ using the method of QCD sum rules. There are two independent $ss\bar s\bar s$ interpolating currents with $J^{PC} = 1^{--}$, and we calculate both their diagonal and off-diagonal correlation functions. We obtain two new currents which do not strongly correlate to each other, so they may couple to two different physical states: one of them couples to the $Y(2175)$, while the other may couple to another state whose mass is about $71 ^{+172}_{-~48}$ MeV larger. Evidences of the latter state can be found in the BaBar, BESII, Belle, and BESIII experiments.

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arXiv2018

Doubly hidden-charm/bottom $QQ\bar Q\bar Q$ tetraquark states

We study the mass spectra for the $cc\bar c\bar c$ and $bb\bar b\bar b$ tetraquark states by developing a moment sum rule method. Our results show that the $bb\bar b\bar b$ tetraquarks lie below the threshold of $η_b(1S)η_b(1S)$. They are probably stable and very narrow. The masses for the doubly hidden-charm states $cc\bar c\bar c$ are higher than the spontaneous dissociation thresholds of two charmonium mesons. We suggest to search for such states in the $J/ψJ/ψ$ and $η_c(1S)η_c(1S)$ channels.

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arXiv2017

Establishing low-lying doubly charmed baryons

We systematically study the $S$-wave doubly charmed baryons using the method of QCD sum rules. Our results suggest that the $Ξ_{cc}^{++}$ recently observed by LHCb can be well identified as the $S$-wave $Ξ_{cc}$ state of $J^P = 1/2^+$. We study its relevant $Ω_{cc}$ state, whose mass is predicted to be around 3.7 GeV. We also systematically study the $P$-wave doubly charmed baryons, whose masses are predicted to be around 4.1 GeV. Especially, there can be several excited doubly charmed baryons in this energy region, and we suggest to search for them in order to study the fine structure of the strong interaction.

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arXiv2017

$D$-wave heavy baryons of the $SU(3)$ flavor $\mathbf{6}_F$

We use the method of QCD sum rules to study the $D$-wave charmed and bottom baryons of the $SU(3)$ flavor $\mathbf{6}_F$, and calculate their masses up to the order $\mathcal{O}(1/m_Q)$ with $m_Q$ the heavy quark mass. Our results suggest that the $Ξ_c(3123)$ can be well interpreted as a $D$-wave $Ξ_c^\prime(\mathbf{6}_F)$ state, and it probably has a partner state close to it. Our results also suggest that there may exist as many as four $D$-wave $Ω_c$ states in the energy region $3.3\sim3.5$ GeV, and we propose to search for them in the further LHCb and BelleII experiments.

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arXiv2017

Hunting for exotic doubly hidden-charm/bottom tetraquark states

We develop a moment QCD sum rule method augmented by fundamental inequalities to study the existence of exotic doubly hidden-charm/bottom tetraquark states made of four heavy quarks. Using the compact diquark-antidiquark configuration, we calculate the mass spectra of these tetraquark states. There are 18 hidden-charm $cc\bar c\bar c$ tetraquark currents with $J^{PC} = 0^{++}$, $0^{-+}$, $0^{--}$, $1^{++}$, $1^{+-}$, $1^{-+}$, $1^{--}$, and $2^{++}$. We use them to perform QCD sum rule analyses, and the obtained masses are all higher than the spontaneous dissociation thresholds of two charmonium mesons, which are thus their dominant decay modes. The masses of the corresponding hidden-bottom $bb\bar b\bar b$ tetraquarks are all below or very close to the thresholds of the $Υ(1S)Υ(1S)$ and $η_b(1S)η_b(1S)$, except one current of $J^{PC}=0^{++}$. Hence, we suggest to search for the doubly hidden-charm states in the $J/ψJ/ψ$ and $η_c(1S)η_c(1S)$ channels.

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arXiv2017

Mass spectra for $qc\bar q\bar c$, $sc\bar s\bar c$, $qb\bar q\bar b$, $sb\bar s\bar b$ tetraquark states with $J^{PC}=0^{++}$ and $2^{++}$

We have studied the mass spectra of the hidden-charm/bottom $qc\bar q\bar c$, $sc\bar s\bar c$ and $qb\bar q\bar b$, $sb\bar s\bar b$ tetraquark states with $J^{PC}=0^{++}$ and $2^{++}$ in the framework of QCD sum rules. We construct ten scalar and four tensor interpolating currents in a systematic way and calculate the mass spectra for these tetraquark states. The $X^\ast(3860)$ may be either an isoscalar tetraquark state or $χ_{c0}(2P)$. If the $X^\ast(3860)$ is a tetraquark candidate, our results prefer the $0^{++}$ option over the $2^{++}$ one. The $X(4160)$ may be classified as either the scalar or tensor $qc\bar q\bar c$ tetraquark state while the $X(3915)$ favors a $0^{++}$ $qc\bar q\bar c$ or $sc\bar s\bar c$ tetraquark assignment over the tensor one. The $X(4350)$ can not be interpreted as a $sc\bar s\bar c$ tetraquark with either $J^{PC}=0^{++}$ or $2^{++}$.

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arXiv2017

Open-flavor charmed/bottom $sq\bar q\bar Q$ and $qq\bar q\bar Q$ tetraquark states

We provide comprehensive investigations for the mass spectrum of exotic open-flavor charmed/bottom $sq\bar q\bar c$, $qq\bar q\bar c$, $sq\bar q\bar b$, $qq\bar q\bar b$ tetraquark states with various spin-parity assignments $J^P=0^+, 1^+, 2^+$ and $0^-, 1^-$ in the framework of QCD sum rules. In the diquark configuration, we construct the diquark-antidiquark interpolating tetraquark currents using the color-antisymmetric scalar and axial-vector diquark fields. The stable mass sum rules are established in reasonable parameter working ranges, which are used to give reliable mass predictions for these tetraquark states. We obtain the mass spectra for the open-flavor charmed/bottom $sq\bar q\bar c$, $qq\bar q\bar c$, $sq\bar q\bar b$, $qq\bar q\bar b$ tetraquark states with various spin-parity quantum numbers. In addition, we suggest searching for exotic doubly-charged tetraquarks, such as $[sd][\bar u\bar c]\to D_s^{(\ast)-}π^-$ in future experiments at facilities such as BESIII, BelleII, PANDA, LHCb and CMS, etc.

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arXiv2017

Decay properties of $P$-wave charmed baryons from light-cone QCD sum rules

We study decay properties of the $P$-wave charmed baryons using the method of light-cone QCD sum rules, including the $S$-wave decays of the flavor $\mathbf{\bar 3}_F$ $P$-wave charmed baryons into ground-state charmed baryons accompanied by a pseudoscalar meson ($π$ or $K$) or a vector meson ($ρ$ or $K^*$), and the $S$-wave decays of the flavor $\mathbf{6}_F$ $P$-wave charmed baryons into ground-state charmed baryons accompanied by a pseudoscalar meson ($π$ or $K$). We study both two-body and three-body decays which are kinematically allowed. We find two mixing solutions from internal $ρ$- and $λ$-mode excitations, which can well describe both masses and decay properties of the $Λ_c(2595)$, $Λ_c(2625)$, $Ξ_c(2790)$ and $Ξ_c(2815)$. We also discuss the possible interpretations of $P$-wave charmed baryons for the $Σ_c(2800)$, $Ξ_c(2930)$, $Ξ_c(2980)$, and the recently observed $Ω_c(3000)$, $Ω_c(3050)$, $Ω_c(3066)$, $Ω_c(3090)$, and $Ω_c(3119)$.

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arXiv2017

Understanding the internal structures of the $X(4140)$, $X(4274)$, $X(4500)$ and $X(4700)$

We investigate the newly observed $X(4500)$ and $X(4700)$ based on the diquark-antidiquark configuration within the framework of QCD sum rules. Both of them may be interpreted as the $D$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P = 0^+$, but with opposite color structures, which is remarkably similar to the result obtained in Ref.~\cite{Chen:2010ze} that the $X(4140)$ and $X(4274)$ can be both interpreted as the $S$-wave $cs\bar{c}\bar{s}$ tetraquark states of $J^P = 1^+$, also with opposite color structures. However, the extracted masses and these suggested assignments to these $X$ states do depend on these running quark masses where $m_s (2 \mbox{ GeV}) = 95 \pm 5$ MeV and $m_c (m_c) = 1.23 \pm 0.09$ GeV. As a byproduct, the masses of the hidden-bottom partner states of the $X(4500)$ and $X(4700)$ are extracted to be both around 10.64 GeV, which can be searched for in the $Υϕ$ invariant mass distribution.

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arXiv2017

A review of the open charm and open bottom systems

Since the discovery of the first charmed meson in 1976, many open-charm and open-bottom hadrons were observed. In 2003 two narrow charm-strange states $D_{s0}^*(2317)$ and $D_{s1}(2460)$ were discovered by the BaBar and CLEO Collaborations, respectively. After that, more excited heavy hadrons were reported. In this work, we review the experimental and theoretical progress in this field.

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arXiv2017

The hidden-charm multiquark states

Since 2003 many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states cannot be accommodated within the naive quark model, which are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. In 2015, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this talk, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.

hep-ph↗
arXiv2016

D-wave charmed and bottomed baryons from QCD sum rules

We study the $D$-wave charmed baryons of $SU(3)$ flavor $\mathbf{\bar3}_F$ using the method of QCD sum rule in the framework of heavy quark effective theory (HQET). We find that the $Λ_c(2880)$, $Ξ_c(3055)$ and $Ξ_c(3080)$ can be well described by the $D$-wave $SU(3)$ $\mathbf{\bar 3}_F$ charmed baryon multiplets of $J^P=3/2^+$ and $5/2^+$, which contain two $λ$-mode orbital excitations, i.e., the $Λ_c(2880)$ has $J^P=5/2^+$, and the $Ξ_c(3055)$ and $Ξ_c(3080)$ have $J^P = 3/2^+$ and $5/2^+$, respectively. Our results also suggest that the $Λ_c(2880)$ has a partner state, the $Λ_c(3/2^+)$ of $J^P=3/2^+$. Its mass is around $2.81 ^{+0.33}_{-0.18}$ GeV, and the mass difference between it and the $Λ_c(2880)$ is $28^{+45}_{-24}$ MeV. We also evaluate the masses of their bottom partners.

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arXiv2016

Searching for hidden-charm baryonium signals in QCD sum rules

We give an explicit QCD sum rule investigation to hidden-charm baryonium states with the quark content $u\bar u d\bar d c\bar c$, spin $J=0/1/2/3$, and of both positive and negative parities. We systematically construct the relevant local hidden-charm baryonium interpolating currents, which can actually couple to various structures, including hidden-charm baryonium states, charmonium states plus two pions, and hidden-charm tetraquark states plus one pion, etc. We do not know which structure these currents couple to at the beginning, but after sum rule analyses we can obtain some information. We find some of them can couple to hidden-charm baryonium states, using which we evaluate the masses of the lowest-lying hidden-charm baryonium states with quantum numbers $J^P=2^-/3^-/0^+/1^+/2^+$ to be around 5.0 GeV. We suggest to search for hidden-charm baryonium states, especially the one of $J=3^-$, in the $D$-wave $J/ψππ$ and $P$-wave $J/ψρ$ and $J/ψω$ channels in this energy region.

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arXiv2016

QCD sum rule study of hidden-charm pentaquarks

We study the mass spectra of hidden-charm pentaquarks having spin $J = {1\over2}/{3\over2}/{5\over2}$ and quark contents $uud c \bar c$. We systematically construct all the relevant local hidden-charm pentaquark currents, and select some of them to perform QCD sum rule analyses. We find that the $P_c(4380)$ and $P_c(4450)$ can be identified as hidden-charm pentaquark states composed of an anti-charmed meson and a charmed baryon. Besides them, we also find a) the lowest-lying hidden-charm pentaquark state of $J^P = 1/2^-$ has the mass $4.33^{+0.17}_{-0.13}$ GeV, while the one of $J^P = 1/2^+$ is significantly higher, that is around $4.7-4.9$ GeV; b) the lowest-lying hidden-charm pentaquark state of $J^P = 3/2^-$ has the mass $4.37^{+0.18}_{-0.13}$ GeV, consistent with the $P_c(4380)$ of $J^P = 3/2^-$, while the one of $J^P = 3/2^+$ is also significantly higher, that is above $4.6$ GeV; c) the hidden-charm pentaquark state of $J^P = 5/2^-$ has a mass around $4.5-4.6$ GeV, slightly larger than the $P_c(4450)$ of $J^P = 5/2^+$.

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arXiv2016

Decoding the $X(5568)$ as a fully open-flavor $su\bar b\bar d$ tetraquark state

We investigate the recent evidence for a charged $X(5568)$ meson as an exotic open-flavor tetraquark state $su\bar b\bar d$ with $J^P=0^+/1^+$ in the framework of QCD sum rules. We use the color antisymmetric $[\mathbf{\bar 3_c}]_{su} \otimes [\mathbf{3_c}]_{\bar{b}\bar d}$ tetraquark currents in both scalar and axial-vector channels to perform evaluations and numerical analyses. Our results imply that the $X(5568)$ can be interpreted as both the scalar $su\bar b\bar d$ tetraquark state and the axial-vector one, which are in good agreement with the experimental measurement. We also discuss the possible decay patterns of the $X(5568)$ and suggest to search for its neutral partner in the radiative decay into $B_s^0 γ$ and $B_s^* γ$, which can be used to determine its spin-parity quantum numbers. Moreover, we predict its charmed partner state around $2.55$ GeV with the quark content $su\bar c\bar d$ and $J^P=0^+/1^+$.

hep-ph↗
arXiv2016

The hidden-charm pentaquark and tetraquark states

In the past decade many charmonium-like states were observed experimentally. Especially those charged charmonium-like $Z_c$ states and bottomonium-like $Z_b$ states can not be accommodated within the naive quark model. These charged $Z_c$ states are good candidates of either the hidden-charm tetraquark states or molecules composed of a pair of charmed mesons. Recently, the LHCb Collaboration discovered two hidden-charm pentaquark states, which are also beyond the quark model. In this work, we review the current experimental progress and investigate various theoretical interpretations of these candidates of the multiquark states. We list the puzzles and theoretical challenges of these models when confronted with the experimental data. We also discuss possible future measurements which may distinguish the theoretical schemes on the underlying structures of the hidden-charm multiquark states.

hep-ph↗
arXiv2016

A hidden-charm pentaquark state in $Λ^0_b \to J/ψp π^-$ decay

We study here the $Λ_b^0 \to J/ψp π^-$ reaction in analogy to the $Λ^0_b \to J/ψp K^-$ one, and we note that in both decays there is a sharp structure (dip or peak) in the $J/ψp$ mass distribution around $4450$ MeV, which is associated in the $Λ^0_b \to J/ψp K^-$ experiment to an exotic pentaquark baryonic state, although in $Λ_b^0 \to J/ψp π^-$ it shows up with relatively low statistics. We analyze the $Λ^0_b \to J/ψp π^-$ interaction along the same lines as the $Λ^0_b \to J/ψp K^-$ one, with the main difference stemming from the reduced Cabibbo strength in the former and the consideration of the $π^-p$ final state interaction instead of the $K^-p$ one. We find that with a minimal input, introducing the $π^-p$ and $J/ψp$ interaction in $S$-wave with realistic interactions, and the empirical $P$-wave and $D$-wave contributions, one can accomplish a qualitative description of the $π^-p$ and $J/ψp$ mass distributions. More importantly, the peak structure followed by a dip of the experimental $J/ψp$ mass distribution is reproduced with the same input as used to describe the data of $Λ^0_b\rightarrow J/ψp K^-$ reaction. The repercussion for the triangular singularity mechanism, invoked in some works to explain the pentaquark peak, is discussed.

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