arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 523 records · Page 29Linked to original sources

arXiv2015

Combined study of $2S$ and $1D$ open-charm mesons with natural spin-parity

In this paper, we perform a combined study of $2S$ and $1D$ open-charm mesons with natural spin-parity. Our results indicate that $D^*_1(2600)/D^*_{s1}(2700)$ and $D^*_1(2760)/D^*_{s1}(2860)$ are predominantly the $2^3S_1$ and $1^3D_1$ charmed/charmed-strange mesons, respectively, while $D_3^*(2760)/D_{s3}^*(2860)$ can be regarded as the $1^3D_3$ charmed/charmed-strange mesons. In addition, some typical ratios of partial widths of the discussed natural states are predicted, by which future experiments can test these assignments, especially for the $2S$-$1D$ mixing scheme existing in $D^*_1(2600)/D^*_1(2760)$ and $D^*_{s1}(2700)/D^*_{s1}(2860)$.

hep-ph↗

arXiv2015

High-spin mesons below 3 GeV

In this work, we study the high-spin states with masses below 3 GeV observed in experiments and we perform analysis of mass spectrum and investigation of strong decay behaviors of the high-spin states. Comparing our results with the experimental data, we can reveal the underlying properties of these high-spin states; more importantly, we also predict their abundant decay features, which can provide valuable information for experimental exploration of these high-spin states.

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arXiv2015

The masses and axial currents of the doubly charmed baryons

The chiral dynamics of the doubly heavy baryons is solely governed by the light quark. In this work, We have derived the chiral corrections to the mass of the doubly heavy baryons up to N$^3$LO. The mass splitting of $Ξ_{cc}$ and $Ω_{cc}$ at the N$^2$LO depends on one unknown low energy constant $c_7$. With the experimental mass of $Ξ_{cc}(3520)$ as the input, we estimate the mass of $Ω_{cc}$ to be around 3.678 GeV. Moreover, we have also performed a systematical analysis of the chiral corrections to the axial currents and axial charges of the doubly heavy baryons. The chiral structure and analytical expressions will be very useful to the chiral extrapolations of the future lattice QCD simulations of the doubly heavy baryons.

hep-ph↗

arXiv2015

$a_1(1420)$ resonance as a tetraquark state and its isospin partner

We systematically construct tetraquark currents of $I^GJ^{PC}=1^-1^{++}$ and classify them into types $\mathbf{A}$ (antisymmetric), $\mathbf{S}$ (symmetric) and $\mathbf{M}$ (mixed), based on flavor symmetries of diquarks and antidiquarks composing the tetra quark currents. We use tetraquark currents of type $\mathbf{M}$ to perform QCD sum rule analyses, and find a tetraquark current $η^M_{5μ}$ with quark contents $q s\bar q \bar s$($q=u$ or $d$) leading to a mass of $1.44 \pm 0.08$ GeV consistent with the $a_1(1420)$ state recently observed by the COMPASS collaboration. Our results support tetraquark explanations for both $a_1(1420)$ and $f_1(1420)$, assuming that they are isospin partners. We also study their possible decay patterns. As tetraquark candidates, the possible decay modes of $a_1(1420)$ are $S$-wave $a_1(1420) \rightarrow K^*(892)K$ and $P$-wave $a_1(1420)\rightarrow f_0(980) π$ while the possible decay patterns of $f_1(1420)$ are $S$-wave $f_1(1420) \rightarrow K^*(892)K$ and $P$-wave $f_1(1420) \rightarrow a_0(980) π$. We speculate that $a_1(1420)$ is partly responsible for the large isospin violation in the $η(1405)\to f_0(980)π_0$ decay mode which is reported by BESIII collaboration in the $J/ψ\toγ3π$ process.

hep-ph↗

arXiv2015

Observation of $e^+e^-\to χ_{c0}ω$ and missing higher charmonium $ψ(4S)$

Stimulated by the recent BESIII observation of a new resonance in $e^+ e^- \to ωχ_{c0}$ and by the fact that this state is consistent with our predicted $ψ(4S)$, in this work we estimate the meson loop contribution to $ψ(4S) \to ωχ_{c0}$. The evaluation indicates that our theoretical estimate can overlap with the experimental data in a reasonable parameter range. This fact shows that introduction of the missing higher charmonium $ψ(4S)$ provides a possible explanation to the recent BESIII observation. The upper limit of a branching ratio of $ψ(4S) \to ηJ/ψ$ is also predicted as $1.9 \times 10^{-3}$, which can be further tested by BESIII, Belle and forthcoming BelleII.

hep-ph↗

arXiv2015

Light axial vector mesons

Inspired by the abundant experimental observation of axial-vector states, we study whether the observed axial-vector states can be categorized into the conventional axial-vector meson family. In this paper we carry out an analysis based on the mass spectra and two-body Okubo-Zweig-Iizuka-allowed decays. Besides testing the possible axial-vector meson assignments, we also predict abundant information for their decays and the properties of some missing axial-vector mesons, which are valuable for further experimental exploration of the observed and predicted axial-vector mesons.

hep-ph↗

arXiv2015

Hidden-charm decays of $X(3915)$ and $Z(3930)$ as the P-wave charmonia

In this work, we investigate the $X(3915)$ and $Z(3930)$ decays into $J/ψω$ with the $χ_{c0}^\prime(2P)$ and $χ_{c2}^\prime (2P)$ assignments to $X(3915)$ and $Z(3930)$, respectively. The results show that the decay width of $Z(3930)\to J/ψω$ is at least one order smaller than that of $X(3915)\to J/ψω$. This observation explains why only one structure $X(3915)$ has been observed in the $J/ψω$ invariant mass spectrum for the process $γγ\to J/ψω$.

hep-ph↗

arXiv2015

P-wave charmed baryons from QCD sum rules

We study the P-wave charmed baryons using the method of QCD sum rule in the framework of heavy quark effective theory (HQET). We consider systematically all possible baryon currents with a derivative for internal rho- and lambda-mode excitations. We have found a good working window for the currents corresponding to the rho-mode excitations for Lambda_c(2595), Lambda_c(2625), Xi_c(2790) and Xi_c(2815) which complete two SU(3) 3F_bar multiplets of J(P)=1/2(-) and 3/2(-), while the currents corresponding to the lambda-mode excitations seem also consistent with the data. Our results also suggest that there are two Sigma_c(2800) states of J(P)=1/2(-) and 3/2(-) whose mass splitting is 14 \pm 7 MeV, and two Xi_c(2980) states whose mass splitting is 12 \pm 7 MeV. They have two Omega_c partners of J(P) = 1/2(-) and 3/2(-), whose masses are around 3.25 \pm 0.20 GeV with mass splitting 10 \pm 6 MeV. All of them together complete two SU(3) 6F multiplets of J(P)=1/2(-) and 3/2(-). They may also have J(P)=5/2(-) partners. Xi_c(3080) may be one of them, and the other two are Sigma_c(5/2(-)) and Omega_c(5/2(-)), whose masses are 85 \pm 23 and 50 \pm 27 MeV larger.

hep-ph↗

arXiv2015

Exploration of charmed pentaquarks

In this work, we explore the charmed pentaquarks, where the relativistic five-quark equations are obtained by the dispersion relation technique. By solving these equations with the method based on the extraction of the leading singularities of the amplitudes, we predict the mass spectrum of charmed pentaquarks with $J^P=1/2^{\pm}$ and $3/2^{\pm}$, which is valuable to further experimental study of charmed pentaquark.

hep-ph↗

arXiv2015

Charmed-strange mesons revisited: mass spectra and strong decays

Inspired by the present experimental status of charmed-strange mesons, we perform a systematic study of the charmed-strange meson family, in which we calculate the mass spectra of the charmed-strange meson family by taking a screening effect into account in the Godfrey-Isgur model and investigate the corresponding strong decays via the quark pair creation model. These phenomenological analyses of charmed-strange mesons not only shed light on the features of the observed charmed-strange states, but also provide important information on future experimental search for the missing higher radial and orbital excitations in the charmed-strange meson family, which will be valuable task in LHCb, forthcoming BelleII and PANDA.

hep-ph↗

arXiv2015

Charged charmonium-like structures and the initial single chiral particle emission mechanism

This paper summarizes what we have done so far to explain charged charmonium/bottomonium-like structures using a hadronic triangle diagram which we call the initial single chiral particle emission mechanism. We discuss processes like $A\to A'+P+P'$ in which two chiral particles $P$ and $P'$ are emitted from $A$. In the intermediate we consider a hadronic one-loop diagram in which $D^{(*)}/D_s^{(*)}/B^{(*)}/B_s^{(*)}$ are included to explain some enhancements experimentally observed. Using this mechanism we explain some of the exotic enhancements and predict a couple of enhancement structures.

hep-ph↗

arXiv2015

Pseudotensor meson family

The pseudoscalar tensor states, $π_2$, $η_2$, and $K_2$, are systematically studied through the Okubo-Zweig-Iizuka- allowed two-body strong decays, including both the observed states reported by the Particle Data Group and the predicted states. Phenomenological analysis combined with the experimental data not only can test the assignments to these discussed states, but it can also predict more abundant information {on} their partial decay widths, which is helpful in the experimental study of these observed and predicted pseudotensor states.

hep-ph↗

arXiv2015

How to detect super-massive binary black holes at parsec scales

It is difficult to find or identifying the binary black holes in parsec scales, since the dual AGN may be merged quickly. It is required to explore more possibilities to identifying binary black holes in parsec scales, we give some discussions, especially with the VLBI methods.

astro-ph.GA↗

arXiv2014

The D-wave heavy-light mesons from QCD sum rules

We study the D-wave c_bar s heavy meson doublets (1^-,2^-) and (2^-,3^-) using the method of QCD sum rule in the framework of heavy quark effective theory. Choosing the same threshold values omega_c around 2.7 Gev, we calculate the masses of the 1^- and 3^- states. They are m_{D*_{s1}} = 2.81 \pm 0.10 GeV and m_{D*_{s3}} = 2.85 \pm 0.08 GeV, consistent with the newly observed D*_{s1}(2860) and D*_{s3}(2860) states by LHCb. The masses of their 2^- partners are calculated to be 2.82 \pm 0.10 and 2.81 \pm 0.08 GeV. The mass splittings within the same doublet are calculated to be m_{D_{s2}} - m_{D*_{s1}} = 0.016 \pm 0.007 GeV and m_{D*_{s3}} - m_{D'_{s2}} = 0.039 \pm 0.014 GeV.

hep-ph↗

arXiv2014

4.8 GHz Intra-Day Variability of FSRQ 0507+179

As one of targets of many flux monitoring campaigns, the FSRQ 0507+179 shows various flux variation properties at almost all observing wavelengths, from radio to $γ$-ray. With Urumqi 25-m telescope, our study on this object is focusing on its radio flux variability, especially the Intra-Day Variability (IDV). We carried out a total of six epochs of IDV observations on 0507+179 at 4.8 GHz since Mar. 2010, found clearly IDV behaviors in all observing sessions and consider it is likely a type I IDV source by analyzing the characteristics and the timescales of the light curves. Additionally, we found 0507+179 exhibited some different IDV behaviors after an optical flare.

astro-ph.HE↗

arXiv2014

Prediction of a missing higher charmonium around 4.26 GeV in $J/ψ$ family

Inspired by the similarity of mass gaps of $J/ψ$ and $Υ$ families, the prediction of missing higher charmonium with mass $4263$ MeV and very narrow width is made. In addition, the properties of two charmonium-like states, $X(3940)$ and $X(4160)$, and charmonium $ψ(4415)$ are discussed. Here, $X(3940)$ as $η_c(3S)$ is established while the explanation of $X(4160)$ to be $η_c(4S)$ is fully excluded and $η_c(4S)$ is typically a very narrow state. These predictions can be accessible at BESIII, Belle and BelleII in near future.

hep-ph↗

arXiv2014

A possible global group structure for exotic states

Based on the fact that the long expected pentaquark which possesses the exotic quantum numbers of $B=1$ and $S=1$ was not experimentally found, although exotic states of $XYZ$ have been observed recently, we conjecture that the heavy flavors may play an important role in stabilizing the hadronic structures beyond the traditional $q\bar q$ and $qqq$ composites.

hep-ph↗

arXiv2014

Numerical analysis of the production of $D^{(*)}(3000)$, $D_{sJ}(3040)$ and their partners through the semileptonic decays of $B_{(s)}$ mesons in terms of the light-front quark model

Inspired by the newly observed $D^{(*)}(3000)$, and $D_{sJ}(3040)$ states, in this work we study the production of $D^{(*)}(3000)$, $D_{sJ}(3040)$ and their partners through the semileptonic decays of $B_{(s)}$ mesons, where the light-front Quark model is applied to the whole calculation. Our numerical results indicate that the $B_{(s)}$ semileptonic decays into the $2P$ states of the charmed or charmed-strange meson family have considerable branching ratios, which shows that these semileptonic decays can be accessible at future experiments, especially LHCb and the forthcoming Belle II.

hep-ph↗