arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 325 records · Page 18Linked to original sources

arXiv2022

$b$-hadron spectroscopy study based on the similarity of double bottom baryon and bottom meson

The dynamical similarity which exists between the $λ$-mode excited $bbq$ baryons ($q$ refers to the $u$, $d$, and $s$ quarks) and the $\bar{b}q$ mesons inspires us to carry out a combined study of their spectroscopy. In this work, the masses and strong decays of these low-lying $b\bar{q}$ and $bbq$ states are studied by the same theoretical methods, and the dynamical similarity which is implied in their mass spectra and strong decays are also discussed. The recent discovered $\bar{b}q$ states, including the $B_J(5840)$, $B_J(5970)$, $B_{sJ}(6064)$, and $B_{sJ}(6114)$, are analyzed. According to our result, the $B_J(5840)$ could be assigned as a 2$S$ state, while the $B_J(5970)$ could be regarded as a member of the $1D(2^-,~3^-)_{j_q=5/2}$ doublet. The $B_{sJ}(6064)$ and $B_{sJ}(6114)$ are probably the $D$-wave states. Especially, they could be explained as the members of the $1D(1^-,~2^-)_{j_q=3/2}$ and $1D(2^-,~3^-)_{j_q=5/2}$ doublets, respectively. The predicted masses and decay properties of other unknown $\bar{b}q/bbq$ states may provide useful clues to the future experiment.

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arXiv2022

$\mathbf{Υ(10753)\toΥ(nS)π^+π^-}$ decays induced by hadronic loop mechanism

In this work, we investigate the $Υ(10753)\toΥ(nS)π^+π^-$ ($n=1,2,3$) processes by considering the hadronic loop mechanism, where $Υ(10753)$ is assigned to a conventional bottomonium in the $4S$-$3D$ mixing scheme. Our results of the concerned processes own considerable branching ratios, which can reach up to the order of magnitude of $10^{-4}-10^{-3}$. We should indicate that the measured $Γ_{e^+e^-}\times\mathcal{B}[Υ(10753)\toΥ(nS)π^+π^-]$ values given by Belle can be reproduced well. This fact supports the former bottomonium assignment to the $Υ(10753)$ in the $4S$-$3D$ mixing scheme. Obviously, it is a good opportunity for the ongoing Belle II experiment if the predicted result in this work can be tested further.

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arXiv2022

Manifestly exotic pentaquarks with a single heavy quark

Inspired by the observed $X(2900)$, we study systematically the mass spectra of the ground pentaquark states with the $qqqq\bar{Q}$ ($Q=c,b$; $q=n,s$; $n=u,d$) configuration in the framework of the Chromomagnetic Interaction model. We present a detailed analysis of their stabilities and decay behaviors. Our results indicate that there may exist narrow states or even stable states. We hope that the present study may inspire experimentalist's interest in searching for such a type of the exotic pentaquark state.

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arXiv2022

The quasi-fission phenomeonon of double charm $T_{cc}^+$ induced by nucleon

In this work, we study the reaction of a nucleon and a doubly charmed state $T_{cc}$. Under the assumption of the $T_{cc}$ as a molecular state of $D^{*}D$, the reaction of the nucleon and $T_{cc}$ is mediated by exchanges of $π$, $η$, $ρ$, and $ω$ meson, which results in split of $T_{cc}$ state with two $D$ mesons in final state. With the help of the effective Lagrangians, the cross section of $p+T^+_{cc}\to p+D^++D^0$ process is calculated, and a very large cross section can be obtained with very small incoming momentum of proton. It decrease rapidly with the increase of the momentum to about 10 mb at momenta of order of GeV. Such large cross section suggests that induced by a proton the $T_{cc}^+$ state is very easy to decay and transit to two $D$ mesons. In the rest frame of the $T_{cc}^+$ state, an obvious accumulation of final $D$ meson at small momentum region can be observed in predicted Dalitz plot, which is due to the molecular state interpretation of $T_{cc}$ state. This novel quasi-fission phenomenon of double charm molecular $T_{cc}^+$ state induced by a proton can be accessible at the forthcoming PANDA experiment.

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arXiv2022

Where are the hidden-charm hexaquarks?

In this work, we carry out the study of hidden-charm hexaquark states with the typical configurations $qqc\bar{q}\bar{q}\bar{c}$ ($q=u, d, s$). The mass spectra of hidden-charm hexaquark states are obtained within the chromo-magnetic interaction model. In addition to the mass spectra analysis, we further illustrate their two-body strong decay behaviors. There exist some compact bound states which cannot decay through the strong interaction. Hopefully our results will help to search for such types of the exotic states in the future experiments.

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arXiv2022

Light unflavor vector meson spectroscopy around the mass range of $2.4\sim 3$ GeV and possible experimental evidence

In this work, we predict the spectroscopy behavior of these light unflavored vector mesons with masses at the range of $2.4\sim 3$ GeV, which are still missing in the experiment. By presenting their mass spectrum and studying their two-body Okubo-Zweig-lizuka allowed decay widths, we discuss the possible experimental evidences of these discussed states combining with the present experimental data. Especially, we strongly suggest that our experimental colleagues carry out the exploration of these higher states via the $e^+e^-$ annihilation into light mesons. It is obvious that BESIII and Belle II will be potential experiments to achieve this target.

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arXiv2022

Mass behavior of hidden-charm pentaquarks with open-strange inspired by these established $P_c$ molecular states

Stimulated by the meson-baryon molecular interpretations of the $P_c$ states ($P_c(4312)/P_c(4440)/P_c(4457)$), we systematically study the interactions between an $S-$wave charm-strange baryon $Ξ_c^{(\prime,*)}$ and an anti-charmed meson $\bar{D}^{(*)}$ in a coupled channel analysis. Effective potentials for the $Ξ_c^{(\prime,*)}\bar{D}^{(*)}$ interactions in a one-boson-exchange model can be related to those in the $Σ_c^{(*)}\bar{D}^{(*)}$ systems by using the $SU(3)$ flavor symmetry and heavy quark symmetry. Our results can predict several promising hidden-charm molecular pentaquarks with strangeness $|S|=1$, which include the $Ξ_c^{\prime}\bar{D}$ states with $I(J^P)=0,1(1/2^-)$, the $Ξ_c^*\bar{D}$ states with $0,1(3/2^-)$, the $Ξ_c^{\prime}\bar{D}^*$ states with $0(1/2^-)$ and $0,1(3/2^-)$, and the $Ξ_c^*\bar{D}^*$ states with $0(1/2^-,3/2^-,5/2^-)$.

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arXiv2022

Production of charmed baryon $Λ_c(2860)$ via low energy antiproton-proton interaction

In the present work, we study the production problem of the charmed baryon $Λ_c(2860)^+$ at $\overline{\mbox{P}}$ANDA. With the $J^P=\frac{3}{2}^+$ assignment to $Λ_c(2860)^+$, an effective Lagrangian approach is adopted to calculate the cross section of $p\bar{p} \to Λ_c^-Λ_c(2860)^+$. The Dalitz plot analysis and the $D^0p$ invariant mass spectrum distribution are also given for the $p\bar{p} \to Λ_c^-Λ_c(2860)^+ \to Λ_c^-pD^0$ process. The numerical results show that the total cross section may reach up to about 10 $ μ$b. With the designed luminosity of $\overline{\mbox{P}}$ANDA ($2\times10^{32}~\mbox{cm}^{-2}\mbox{s}^{-1}$), about $ 10^8 $ $Λ_c(2860)$ events can be expected per day by reconstructing the final $ pD^0 $.

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arXiv2022

Restudy of the color-allowed two-body nonleptonic decay of bottom baryons ${Ξ_b}$ and ${Ω_b}$ supported by hadron spectroscopy

In this work, we calculate the branching ratios of the color-allowed two-body nonleptonic decays of the bottom baryons, which include the $Ξ_b\to Ξ_c^{(*)}$ and $Ω_b\to Ω_c^{(*)}$ weak transitions by emitting a pseudoscalar meson ($π^{-}$, $K^{-}$, $D^{-}$, and $D_s^{-}$) or a vector meson ($ρ^{-}$, $K^{*-}$, $D^{*-}$, and $D_s^{*-}$). For achieving this aim, we adopt the three-body light-front quark model with the support of hadron spectroscopy, where the spatial wave functions of these heavy baryons involved in these weak decays are obtained by a semirelativistic potential model associated with the Gaussian expansion method. Our results show that these decays with the $π^-$, $ρ^-$, and $D_s^{(*)-}$-emitted mode have considerable widths, which could be accessible at the ongoing LHCb and Belle II experiments.

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arXiv2021

Predicting another doubly charmed molecular resonance $T_{cc}^{\prime+}(3876)$

The isospin breaking effect plays an essential role in generating hadronic molecular states with a very tiny binding energy. Very recently, the LHCb Collaboration observed a very narrow doubly charmed tetraquark $T_{cc}^+$ in the $D^0D^0π$ mass spectrum, which lies just below the $D^0D^{*+}$ threshold around 273 keV. In this work, we study the $D^0D^{*+}/D^+D^{*0}$ interactions with the one-boson-exchange effective potentials and consider the isospin breaking effect carefully. We not only reproduce the mass of the newly observed $T_{cc}^+$ very well in the doubly charmed molecular tetraquark scenario, but also predict the other doubly charmed partner resonance $T_{cc}^{\prime+}$ with $m=3876~\text{MeV}$, and $Γ= 412~\text{keV}$. The prime decay modes of the $T_{cc}^{\prime+}$ are $D^0D^+γ$ and $D^+D^0π^0$. The peculiar characteristic mass spectrum of the $D^0D^{*+}/D^+D^{*0}$ molecular systems can be applied to identify the doubly charmed molecular states.

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arXiv2021

Evidence supporting the existence of $P_c(4380)^{\pm}$ from the recent measurements of $B_s \to J/ψp\bar{p}$

Very recently, the LHCb collaboration released the newest measurements of $B_s \to J/ψp\bar{p}$, where an enhancement structure near 4.34 GeV was observed in the invariant mass spectrum of $J/ψp$ with the statistical significance of $3.1-3.7$ $σ$. In this work, by performing a combined analysis for the three invariant mass spectra of $B_s \to J/ψp\bar{p}$, we find that this $J/ψp$ structure near 4.34 GeV can correspond to the contributions from the $P_c(4380)^+$ state with the assumption of $J^{P}=3/2^{-}$ together with the reflections of $B_s \to (f_2^{*} \to p\bar{p})J/ψ$. Here, $P_c(4380)$ was first observed in $Λ_b \to J/ψp K$ but not confirmed in the updated LHCb data in 2019, and $f_2^{*}$ means the exciting light isoscalar tensor meson around 2.0 GeV. Thus, this provides a possible evidence to support the existence of the pentaquark $P_c(4380)$. Specifically, the assumed spin parity $J^{P}=3/2^{-}$ of $P_c(4380)$ is consistent with a prediction of the theoretical explanation of an $S$-wave $\bar{D}Σ_c^*$ molecular bound state.

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arXiv2021

Magic mixing angles for doubly heavy baryons

We study the so-called magic mixing angles for doubly heavy baryons. Defining that a magic mixing angle rotates states with definite $^{2S+1}(l_λ)_J$ to make them heavy-quark symmetric states, we derive the magic mixing angle only in the case $L_ρ=0$ between the heavy quark symmetric states with quantum numbers $\left(J, j_\ell\right)$ and the states with $\left(J, s_q+j_ρ\right)=\left(J, \{^4l_λ/^2l_λ\}\right)$ for a doubly heavy baryon in the standard $ρ-λ$ configuration, where $\vec j_\ell=\vec l_λ+\vec s_q$, $\vec s_ρ=\vec s_{Q1}+\vec s_{Q2}$, and $\vec j_ρ=\vec s_ρ+\vec L_ρ$. We discuss how this mixing angle affects model building for a doubly heavy baryon.

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arXiv2021

$D D^{*}$ potentials in chiral perturbation theory and possible molecular states

The $DD^{*}$ potentials are studied within the framework of heavy meson chiral effective field theory. We obtain the effective potentials of the $DD^{*}$ system up to $O(ε^2)$ at the one-loop level. In addition to the one-pion exchange contribution, the contact and two-pion exchange interactions are also investigated in detail. Furthermore, we search for the possible molecular states by solving the Schrödinger equation with the potentials. We notice that the contact and two-pion exchange potentials are numerically non-negligible and important for the existence of a bound state. In our results, no bound state is found in the $I=1$ channel within a wide range of cutoff parameter, while there exists a bound state in the $I=0$ channel as the cutoff is near $m_ρ$ in our approach.

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arXiv2021

Detection of a Parsec-Scale Jet in a Radio-Quiet Narrow-Line Seyfert 1 Galaxy with Highly Accreting Supermassive Black Hole

The jet in active galactic nuclei (AGN) is a key ingredient in understanding the co-evolution of galaxies and their central supermassive black holes (SMBHs). Unfortunately, the mechanism of jet launching and collimation is still elusive. The observational evidence of decreasing radio loudness with increasing Eddington ratio implies that the jet should be coupled with the accretion process. To further explore the relationship between the jet and accretion, it is necessary to extend our knowledge of the jet to an extreme end of the Eddington ratio distribution of AGN. Using Very Long Baseline Array (VLBA), we report the detection of the parsec-scale radio structure in Mrk 335, a radio-quiet narrow-line Seyfert 1 galaxy with an Eddington ratio close to/above unity. The VLBA image at 1.5 GHz reveals an elongated structure extending $\sim20$ parsec in north-south direction with a peak flux density of $1.98\pm0.05$ mJy/beam and radio brightness temperatures as high as $6\times10^{7}$ K. This feature provides a strong evidence of a parsec-scale (bipolar) jet launched from a highly accreting SMBH. We discuss the result by comparing Mrk 335 with other highly accreting systems, e.g. Galactic black holes and tidal disruption events, and recall the discovery of collimated corona in the vicinity of SMBH in Mrk 335 by previous X-ray observations, whose relation to the parsec-scale radio jet should be explored by future simultaneous X-ray spectroscopy and high resolution radio observations.

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arXiv2021

Correlation of the hidden-charm molecular tetraquarks and the charmoniumlike structures existing in the $B\to XYZ+K$

The molecular assignments to the three $P_c$ states and the similar production mechanism between the $Λ_b\to P_c+K$ and $B\to XYZ+K$ convince us the $B$ decaying to a charmonium state plus light mesons could be the appropriate production process to search for the charmoniumlike molecular tetraquarks. In this work, we systematically study the interactions between a charmed (charmed-strange) meson and an anti-charmed (anti-charm-strange) meson, which include the $D^{(*)}\bar{D}^{(*)}$, $\bar{D}^{(*)}\bar{D}_1$, $D^{(*)}\bar{D}_2^*$, $D_s^{(*)}\bar{D}_s^{(*)}$, ${D}_s^{(*)}\bar{D}_{s0}^*$, $D_s^{(*)}\bar{D}_{s1}^{\prime}$, ${D}_s^{(*)}\bar{D}_{s1}$, $D_s^{(*)}\bar{D}_{s2}^*$ systems. After adopting the one-boson-exchange effective potentials, our numerical results indicate that, on one hand, there can exist a serial of isoscalar charmoniumlike $\mathcal{D}\bar{\mathcal{D}}$ and $\mathcal{D}_s\bar{\mathcal{D}}_s$ molecular states, on the other hand, we can fully exclude the charged charmoniumlike states as the isovector charmoniumlike molecules. Meanwhile, we discuss the two-body hidden-charm decay channels for the obtained $\mathcal{D}\bar{\mathcal{D}}$ and $\mathcal{D}_s\bar{\mathcal{D}}_s$ molecules, especially the $D^{*}\bar{D}^{*}$ molecular tetraquarks. By analyzing the experimental data collected from the $B\to XYZ+K$ and the mass spectrum and two-body hidden-charm decay channels for the obtained $\mathcal{D}\bar{\mathcal{D}}$ and $\mathcal{D}_s\bar{\mathcal{D}}_s$ molecules, we find several possible hints of the existence of the charmoniumlike molecular tetraquarks, i.e., a peculiar characteristic mass spectrum of the isoscalar $D^*\bar{D}^*$ molecular systems can be applied to identify the charmoniumlike molecule. We look forward to the future experiments like the LHCb, Belle II, and BESIII Collaborations can test our results with more precise experimental data.

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arXiv2021

The Origin of Radio Emission in Black Hole X-ray Binaries

We studied the relation of accretion-jet power and disk luminosity, especially the jet efficiencies and disk radiative efficiencies for different accretion disks as well as black hole (BH) spin, in order to explore the origin of radio emission in black hole X-ray binaries (BHXBs). We found that jet efficiency increases more rapidly (efficient) than the nearly constant disk radiative efficiency for thin disk component in high accretion regime, which could account for the steep track ($μ>1$) in the observed radio and X-ray luminosity relations ($L_{\rm R}\propto L_{\rm X}^μ$), but the thin disk component may not be able to explain the standard track ($μ\approx 0.6$) in the BHXBs. For hot accretion flows (HAF), the resulting jet efficiency changes along with the large range of accretions from quiescent state to nearly Eddington state, which could account for the standard track in the BHXBs. The BH spin-jet is discussed for the magnetic arrested disk (MAD) state; in this state, the spin-jet power might contribute to a linear correlation between jet power and mass accretion rate for a given source. More accurate observations are required to test the results.

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arXiv2021

Charmonium decays into $Λ_c\barΛ_c$ pair governed by the hadronic loop mechanism

In this work, we investigate the open-charm decay process $ψ\toΛ_c\barΛ_c$ via the hadronic loop mechanism for vector charmonia above $Λ_c\barΛ_c$ threshold. The branching ratios of these vector charmonium states to $Λ_c\barΛ_c$ are estimated. The charmonium explanation of the $Y(4630)$ observed in $e^+e^- \to Λ_c\barΛ_c$ is tested. Furthermore, for the predicted higher vector charmonia above 4.7 GeV, the branching ratios $\mathcal{B}[ψ(nS)\toΛ_c\barΛ_c]$ with $n=7,8,9$ are found to be of the order of magnitude of $10^{-4}-10^{-3}$ while $\mathcal{B}[ψ(mD)\toΛ_c\barΛ_c]$ with $m=6,7,8$ are of the order of magnitude of $10^{-3}-10^{-2}$. The experimental signals of these missing charmonium states are discussed. The search for them may be an interesting topic in the future BESIII and Belle II experiments.

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arXiv2021

Where are $3P$ and higher $P-$wave states in the charmonium family?

How to hunt for higher $P$-wave states of charmonium is still an open topic when $2P$ charmonia were identified. {In this work, we present an unquenched quark model calculation to illustrate the spectroscopy behavior of these $3P$, $4P$ and $5P$ states in charmonium family.} For the $3P$ charmonia, the predicted masses are around 4.2 GeV and their two-body open-charm decay behaviors were given, by which we propose that searching for these $3P$ states via their open-charm decay channels from $γγ$ fusion and $B$ decay can be accessible at future experiment like LHCb and Belle II. We continue to calculate the masses of these $4P$ and $5P$ charmonia. Combing with these calculated results of higher $P$-wave states of charmonium, we find that the coupled-channel effect becomes more obvious with increasing the radial quantum number, which can be understood well by the modified Godfrey-Isgur model with screened potential.

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