arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 451 records · Page 25Linked to original sources

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.

hep-ph↗

arXiv2017

A systematic study of mass spectra and strong decay of strange mesons

The mass spectrum of the kaon family is analyzed by the {modified} Godfrey-Isgur model with a color screening effect approximating the kaon as a heavy-light meson system. This analysis gives us the structure and possible assignments of the observed kaon candidates, which can be tested by comparing the theoretical results of their two-body strong decays with the experimental data. Additionally, prediction of some partial decay widths is made on the kaons still missing in experiment. This study is crucial to establishing the kaon family and searching for their higher excitations in the future.

hep-ph↗

arXiv2017

Prediction of triple-charm molecular pentaquarks

In a one-boson-exchange model, we study molecular states of double-charm baryon ($Ξ_{cc}(3621)$) and a charmed meson ($D$ and $D^*$). Our model indicates that there exist two possible triple-charm molecular pentaquarks, a $Ξ_{cc}D$ state with $I(J^P)=0(1/2^-)$ and a $Ξ_{cc}D^*$ state with $I(J^P)=0(3/2^-)$. In addition, we also extend our formula to explore $Ξ_{cc}\bar{B}^{(*)}$, $Ξ_{cc}\bar{D}^{(*)}$, and $Ξ_{cc}B^{(*)}$ systems, and find more possible heavy flavor molecular pentaquarks, a $Ξ_{cc}\bar{B}$ state with $I(J^P)=0(1/2^-)$, a $Ξ_{cc}\bar{B}^*$ state with $I(J^P)=0(3/2^-)$, and $Ξ_{cc}\bar{D}^*/Ξ_{cc}B^*$ states with $I(J^P)=0(1/2^-)$. Experimental search for these predicted triple-charm molecular pentaquarks is encouraged.

hep-ph↗

arXiv2017

New $Ω_c^0$ baryons discovered by LHCb as the members of $1P$ and $2S$ states

Inspired by the newly observed $Ω_c^0$ states at LHCb, we decode their properties by performing an analysis of mass spectrum and decay behavior. Our studies show that the five narrow states, i.e., $Ω_c(3000)^0$, $Ω_c(3050)^0$, $Ω_c(3066)^0$, $Ω_c(3090)^0$, and $Ω_c(3119)^0$, could be grouped into the $1P$ states with negative parity. Among them, the $Ω_c(3000)^0$ and $Ω_c(3090)^0$ states could be the $J^P=1/2^-$ candidates, while $Ω_c(3050)^0$ and $Ω_c(3119)^0$ are suggested as the $J^P=3/2^-$ states. $Ω_c(3066)^0$ could be regarded as a $J^P=5/2^-$ state. Since the the spin-parity, the electromagnetic transitions, and the possible hadronic decay channels $Ω_c^{(\ast)}π$ have not been measured yet, other explanations are also probable for these narrow $Ω_c^0$ states. Additionally, we discuss the possibility of the broad structure $Ω_c(3188)^0$ as a $2S$ state with $J^P=1/2^+$ or $J^P=3/2^+$. In our scheme, $Ω_c(3119)^0$ cannot be a $2S$ candidate.

hep-ph↗

arXiv2017

Production of the charmoniumlike state $Y(4220)$ through the $p\bar{p} \to Y(4220) π^0$ reaction

The $Y(4220)$ production in the process of $p\bar{p} \to Y(4220)π^0$ is studied within the effective Lagrangian approach. We first study the $e^+e^-\to Y(4220) \to p\bar{p}π^0$ reaction at center-of-mass energy $4.258$ GeV with the assumption that the $Y(4220)$ is a $ψ(4S)$ state. We show that the inclusion of nucleon and nucleon resonance leads to a quite good description of the experimental data of $π^0 p$ and $π^0 \bar{p}$ invariant mass distributions. Then, the total and angular distributions of the $p\bar{p} \to Y(4220)π^0$ reaction are investigated. It is shown that the nucleon pole is dominant but the contributions from excited nucleon resonances are non-negligible. The $p\bar{p} \to Y(4220)π^0$ reaction is useful for studying the property of $Y(4220)$ and our calculated results may be tested at the forthcoming $\overline{\mbox{P}}$ANDA experiments.

hep-ph↗

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.

hep-ph↗

arXiv2017

Exotic tetraquark states with the $qq\bar{Q}\bar{Q}$ configuration

In this work, we study systematically the mass splittings of the $qq\bar{Q}\bar{Q}$ ($q=u$, $d$, $s$ and $Q=c$, $b$) tetraquark states with the color-magnetic interaction by considering color mixing effects and estimate roughly their masses. We find that the color mixing effect is relatively important for the $J^P=0^+$ states and possible stable tetraquarks exist in the $nn\bar{Q}\bar{Q}$ ($n=u$, $d$) and $ns\bar{Q}\bar{Q}$ systems either with $J=0$ or with $J=1$. Possible decay patterns of the tetraquarks are briefly discussed.

hep-ph↗

arXiv2017

Modeling Collective Behavior of Posting Microblog by Stochastic Differential Equation with Jump

The characterization and understanding of online social network behavior is of importance from both the points of view of fundamental research and realistic utilization. In this manuscript, we propose a stochastic differential equation to describe the online microblogging behavior. Our analysis is based on the microblog data collected from Sina Weibo which is one of the most popular microblogging platforms in China. Especially, we focus on the collective nature of the microblogging behavior reflecting itself in the analyzed data as the characters of the periodic pattern, the stochastic fluctuation around the baseline, and the extraordinary jumps. Compared with existing works, we use in our model time dependent parameters to facilitate the periodic feature of the microblogging behavior and incorporate a compound Poisson process to describe the extraordinary spikes in the Sina Weibo volume. Such distinct merits lead to significant improvement in the prediction performance, thus justifying the validity of our model. This work may offer potential application in the future detection of the anomalous behavior in online social network platforms.

physics.soc-ph↗

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.

hep-ph↗

arXiv2017

Constructing new pseudoscalar meson nonets with the observed $X(2100)$, $X(2500)$, and $η(2225)$

Stimulated by the BESIII observation of $X(2100)$, $X(2500)$, and $η(2225)$, we try to pin down new pseudoscalar meson nonets including these states. The analysis of mass spectra and the study of strong decays indicate that $X(2120)$ and $η(2225)$ associated with $π(2070)$ and the predicted kaon $K(2150)$ may form a new pseudoscalar meson nonet. In addition, more experimental data for $X(2100)$ are necessary to determine its structure of nonets. Then, $X(2500)$, $X(2370)$, $π(2360)$, and the predicted kaon $K(2414)$ can be grouped into another new nonet. These assignments to the discussed pseudoscalar states can be further tested in experiment.

hep-ph↗

arXiv2017

Possible strange hidden-charm pentaquarks from $Σ_c^{()}\bar{D}_s^$ and $Ξ^{(',)}_c\bar{D}^$ interactions

Using the one-boson-exchange model, we investigate the $Λ_c\bar{D}_s^*$, $Σ_c\bar{D}_s^*$, $Σ_c^*\bar{D}_s^*$, $Ξ_c\bar{D}^*$, $Ξ_c'\bar{D}^*$, and $Ξ_c^*\bar{D}^*$ interactions by considering the one-eta-exchange and/or one-pion-exchange contributions. We further predict the existence of hidden-charm molecular pentaquarks. Promising candidates for hidden-charm molecular pentaquarks include a $Ξ_c'\bar{D}^*$ state with $0(\frac{1}{2}^-)$ and the $Ξ_c^*\bar{D}^*$ states with $0(\frac{1}{2}^-)$ and $0(\frac{3}{2}^-)$. Experimental searches for these predicted hidden-charm molecular pentaquarks are an interesting future research topic for experiments like LHCb.

hep-ph↗

arXiv2017

VLBA 24 and 43 GHz observations of massive binary black hole candidate PKS 1155+251

PKS 1155+251 is a radio-loud quasar source at z=0.203. Observations using very long baseline interferometry (VLBI) at ~2, 5, 8 and 15 GHz show that the structure of the radio source is quite complicated on parsec scales and that the outer hot spots are apparently undergoing a significant contraction. Because these results cannot be fully explained based on the compact symmetric object (CSO) scenario with a radio core located between the northern and southern complexes, we made observations with the Very Long Baseline Array (VLBA) at 24 and 43 GHz to search for compact substructures and alternative interpretations. The results show that the radio core revealed in the previous VLBI observations remains compact with a flat spectrum in our sub-milli-arcsecond--resolution images; the northern lobe emission becomes faint at 24 GHz and is mostly resolving out at 43 GHz; the southern complex is more bright but has been resolved into the brightest southern-end (S1) and jet or tail alike components westwards. Explaining the southern components aligned westward with a standard CSO scenario alone remains a challenge. As for the flatter spectral index of the southern-end component S1 between 24 and 43 GHz in our observations and the significant 15 GHz VLBA flux variability of S1, an alternative scenario is that the southern complex may be powered by a secondary black hole residing at S1. But more sensitive and high-resolution VLBI monitoring is required to discriminate the CSO and the binary black hole scenarios.

astro-ph.GA↗

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 $2^{++}$.

hep-ph↗

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.

hep-ph↗

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 $Ω_c(3119)$.

hep-ph↗

arXiv2017

Indoor Positioning using Similarity-based Sequence and Dead Reckoning without Training

For the traditional fingerprinting-based positioning approach, it is essential to collect measurements at known locations as reference fingerprints during a training phase, which can be time-consuming and labor-intensive. This paper proposes a novel approach to track a user in an indoor environment by integrating similarity-based sequence and dead reckoning. In particular, we represent the fingerprinting map as location sequences based on distance ranking of the APs (access points) whose positions are known. The fingerprint used for online positioning is represented by a ranked sequence of APs based on the measured Received Signal Strength (RSS), which is refereed to as RSS sequence in this paper. Embedded into a particle filter, we achieve the tracking of a mobile user by fusing the sequence-based similarity and dead reckoning. Extensive experiments are conducted to evaluate the proposed approach.

cs.NI↗

arXiv2017

A New Medical Diagnosis Method Based on Z-Numbers

How to handle uncertainty in medical diagnosis is an open issue. In this paper, a new decision making methodology based on Z-numbers is presented. Firstly, the experts' opinions are represented by Z-numbers. Z-number is an ordered pair of fuzzy numbers denoted as Z = (A, B). Then, a new method for ranking fuzzy numbers is proposed. And based on the proposed fuzzy number ranking method, a novel method is presented to transform the Z-numbers into Basic Probability Assignment (BPA). As a result, the information from different sources is combined by the Dempster' combination rule. The final decision making is more reasonable due to the advantage of information fusion. Finally, two experiments, risk analysis and medical diagnosis, are illustrated to show the efficiency of the proposed methodology.

cs.AI↗

arXiv2017

Newly observed $Λ_c(2860)^+$ at LHCb and its \emph{D}-wave partners $Λ_c(2880)^+$, $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$

New resonance $Λ_c(2860)^+$, reported by LHCb, is a key to establish \emph{D}-wave charmed and charmed-strange baryon families. In this work, we first carry out an analysis of mass spectra of the $λ$-mode excited charmed and charmed-strange baryon states, which may reveal the relation of $Λ_c(2860)^+$, $Λ_c(2880)^+$, $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$, $i.e.$, $Λ_c(2860)^+$ and $Λ_c(2880)^+$ can form a \emph{D}-wave doublet $[3/2^+,5/2^+]$ while $Ξ_c(3055)^+$ and $Ξ_c(3080)^+$ are the strange partners of $Λ_c(2860)^+$ and $Λ_c(2880)^+$, respectively. Further study of their two-body Okubo-Zweig-Iizuka-allowed decays supports $Λ_c(2860)^+$ and $Ξ_c(3055)^+$ as the \emph{D}-wave charmed and charmed-strange baryons, respectively, with $J^P=3/2^+$. For $Λ_c(2880)^+$ and $Ξ_c(3080)^+$, however, there exist some difficulties under the \emph{D}-wave assignment with $J^P=5/2^+$ since the experimental widths and some ratios of partial width of $Λ_c(2880)^+$ and $Ξ_c(3080)^+$ cannot be reproduced in our calculation.

hep-ph↗