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Register a new userAnalysis of the vector hidden-charm tetraquark states without explicit P-waves via the QCD sum rules
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Zhi-Gang Wang
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In the present work, we take the scalar, pseudoscalar, axialvector, vector and tensor (anti)diquark operators as the elementary constituents to construct vector four-quark currents without introducing explicit P-waves, and explore the mass spectrum of the vector hidden-charm tetraquark states via the QCD sum rules comprehensively, and revisit the assignments of the $Y$ states in the scenario of tetraquark states. The predicted vector hidden-charm tetraquark states can be confronted to the experimental data in the future.
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In this article, we study the masses and pole residues of the pseudoscalar-diquark-pseudoscalar-antidiquark type and vector-diquark-vector-antidiquark type scalar hidden-charm $cubar{c}bar{d}$ ($cubar{c}bar{s}$) tetraquark states with QCD sum rules by taking into account the contributions of the vacuum condensates up to dimension-10 in the operator product expansion. The predicted masses can be confronted with the experimental data in the future. Possible decays of those tetraquark states are also discussed.
In the present work, we investigate the axialvector doubly-charmed tetraquark molecular states without strange, with strange and with doubly-strange via the QCD sum rules, and try to make assignment of the $T^+_{cc}$ from the LHCb collaboration in the scenario of molecular states. The predictions favor assigning the $T^+_{cc}$ to be the heavier $DD^{*}$ molecular state with the spin-parity $J^P=1^+$, while the lighter $DD^{*}$ molecular state with the spin-parity $J^P=1^+$ still escapes experimental detections. All the predicted doubly-charmed tetraquark molecular states can be confronted to the experimental data in the future.
The purpose of the present study is to explore the mass spectrum of the hidden charm tetraquark states within a diquark model. Proposing that a tetraquark state is composed of a diquark and an antidiquark, the masses of all possible $[qc][bar{q}bar{c}]$, $[sc][bar{s}bar{c}]$, and $[qc][bar{s}bar{c}]$ $left([sc][bar{q}bar{c}]right)$ hidden charm tetraquark states are systematically calculated by use of an effective Hamiltonian, which contains color, spin, and flavor dependent interactions. Apart from the $X(3872)$, $Z(3900)$, $chi_{c2}(3930)$, and $X(4350)$ which are taken as input to fix the model parameters, the calculated results support that the $chi_{c0}(3860)$, $X(4020)$, $X(4050)$ are $[qc][bar{q}bar{c}]$ states with $I^GJ^{PC}=0^+0^{++}$, $1^+1^{+-}$, and $1^-2^{++}$, respectively, the $chi_{c1}(4274)$ is an $[sc][bar{s}bar{c}]$ state with $I^GJ^{PC}=0^+1^{++}$, the $X(3940)$ is a $[qc][bar{q}bar{c}]$ state with $I^GJ^{PC}=1^-0^{++}$ or $1^-1^{++}$, the $Z_{cs}(3985)^-$ is an $[sc][bar{q}bar{c}]$ state with $J^{P}=0^{+}$ or $1^+$, and the $Z_{cs}(4000)^+$ and $Z_{cs}(4220)^+$ are $[qc][bar{s}bar{c}]$ states with $J^{P}=1^{+}$. Predictions for other possible tetraquark states are also given.
We review the calculations of form factors and coupling constants in vertices with charm mesons in the framework of QCD sum rules. We first discuss the motivation for this work, describing possible applications of these form factors to heavy ion collisions and to B decays. We then present an introduction to the method of QCD sum rules and describe how to work with the three-point function. We give special attention to the procedure employed to extrapolate results obtained in the deep euclidean region to the poles of the particles, located in the time-like region. We present a table of ready-to-use parametrizations of all the form factors, which are relevant for the processes mentioned in the introduction. We discuss the uncertainties in our results. We also give the coupling constants and compare them with estimates obtained with other methods. Finally we apply our results to the calculation of the cross section of the reaction $J/psi + pi rightarrow D + bar{D^*}$.
Using the QCD sum rule approach we investigate the possible four-quark structure of the recently observed charmed scalar mesons $D_0^{0}(2308)$ (BELLE) and $D_0^{0,+}(2405)$ (FOCUS) and also of the very narrow $D_{sJ}^{+}(2317)$, firstly observed by BABAR. We use diquak-antidiquark currents and work to the order of $m_s$ in full QCD, without relying on $1/m_c$ expansion. Our results indicate that a four-quark structure is acceptable for the resonances observed by BELLE and BABAR: $D_0^{0}(2308)$ and $D_{sJ}^{+}(2317)$ respectively, but not for the resonances observed by FOCUS: $D_0^{0,+}(2405)$.
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