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Qiang Zhao

Publications and source records attributed to Qiang Zhao.

At least 127 records · Page 7Linked to original sources
arXiv2018

Strong decays of higher charmonium states into open-charm meson pairs

The open-charm strong decays of higher charmonium states up to the mass of the $6P$ multiplet are systematically studied in the $^3P_0$ model. The wave functions of the initial charmonium states are calculated in the linear potential (LP) and screened potential (SP) quark model. The decay widths for most of the well-established charmonium states above the open-charm thresholds can be reasonably described. By comparing our quark model calculations with the experimental observations we also discuss the nature of some of the newly observed charmonium-like states. It is found that (i) the $ψ(4415)$ may favor the $ψ(4S)$ or $ψ_1(3D)$ assignment. There may exist two highly overlapping vector charmonium states around 4.4 GeV; (ii) In the LP model the $J^{PC}=1^{--}$ $Y(4660)$ resonance and the $J^{PC}=0^{++}$ $X(4500)$ resonance may be assigned as the $ψ(5S)$ and $χ_{c0}(4P)$, respectively; (iii) The newly observed state $X^*(3860)$ can be assigned as the $χ_{c0}(2P)$ state with a narrow width of about $30$ MeV; (iv) It seems to be difficult to accommodate the $X(4140)$ and $X(4274)$ states in the same potential model as excited $χ_{c1}$ states. (v) The $X(3940)$ resonance can be assigned as the $η_c(3S)$ state; (vi) The vector charmonium-like states $Y(4230/4260,4360)$ and scalar $X(4700)$ cannot be described by any conventional charmonium states self-consistently in our model.

hep-ph↗
arXiv2018

Branching ratios and $CP$ asymmetries of $B\rightarrow χ_{c1}K(π)$ decays

We investigate the exclusive nonleptonic decays $B\rightarrow χ_{c1}K(π)$ in the conventional perturbative QCD (PQCD) formalism. The predictions of branching ratios and $CP$ asymmetries are given in detail. We compare our results with available experimental data as well as predictions of other theoretical studies existing in the literature. It seems that the branching ratios of $B\rightarrow χ_{c1} K$ are more consistent with data than the earlier analyses. For the Cabibbo-suppressed $B_s$ decay, the branching ratio can reach the order of $10^{-5}$, which would be straight forward for experimental observations. The numerical results show that the direct $CP$ asymmetries of the concerned decays are rather small. The mixing-induced $CP$ asymmetry in the $B^0\rightarrow χ_{c1}K_S$ is very close to $\sin{2β}$, which suggests that this channel offer an alternative method for measuring the Cabbibo-Kobayashi-Maskawa (CKM) angle $β$. The obtained results in the present work could be tested by further experiments in the LHCb and forthcoming Belle II.

hep-ph↗
arXiv2018

Revisiting the pseudoscalar meson and glueball mixing and key issues in the search for pseudscalar glueball state

We revisit the mixing mechanism for pesudscalar mesons and glueball which is introduced by the axial vector anomaly. We demonstrate that the physical mass of the pseudoscalar glueball does not favor to be lower than 1.8 GeV if all the parameters are reasonably constrained. This conclusion, on the one hand, can accommodate the pseudoscalar glueball mass calculated by Lattice QCD, and on the other hand, is consistent with the high-statistics analyses at BESIII that all the available measurements do not support the presence of two closely overlapping pseudoscalar states in any exclusive channel. Such a result is in agreement with the recent claim that the slightly shifted peak positions for two possible states $η(1405)$ and $η(1475)$ observed in different channels are actually originated from one single state with the triangle singularity interferences. By resolving this long-standing paradox, one should pay more attention to higher mass region for the purpose of searching for the pseudoscalar glueball candidate.

hep-ph↗
arXiv2018

Disentangling the role of the $Y(4260)$ in $e^+e^-\to D^*\bar{D}^*$ and $D_s^*\bar{D}_s^*$ via line shape studies

Whether the $Y(4260)$ can couple to open charm channels has been a crucial issue for understanding its nature. The available experimental data suggest that the cross section line shapes of exclusive processes in $e^+e^-$ annihilations have nontrivial structures around the mass region of the $Y(4260)$. As part of a series of studies of the $Y(4260)$ as mainly a $\bar{D}D_1(2420)+c.c.$ molecular state, we show that the partial widths of the $Y(4260)$ to the two-body open charm channels of $e^+e^-\to D^*\bar{D}^*$ and $D_s^*\bar{D}_s^*$ are much smaller than that to $\bar{D}D^*π+c.c.$. The line shapes measured by the Belle Collaboration for these two channels can be well described by the vector charmonium states $ψ(4040)$, $ψ(4160)$ and $ψ(4415)$ together with the $Y(4260)$. It turns out that the interference of the $Y(4260)$ with the other charmonia produces a dip around 4.22~GeV in the $e^+e^-\to D^*\bar{D}^*$ cross section line shape. The data also show an evidence for the strong coupling of the $Y(4260)$ to the $D\bar D_1(2420)$, in line with the expectation in the hadronic molecular scenario for the $Y(4260)$.

hep-ph↗
arXiv2018

Strong and radiative decays of the low-lying $S$- and $P$-wave singly heavy baryons

The strong and radiative decays of the low-lying $S$- and $P$-wave $Λ_{c(b)}$, $Σ_{c(b)}$, $Ξ_{c(b)}$, $Ξ_{c(b)}'$ and $Ω_{c(b)}$ baryons are systematically studied in a constituent quark model. We find that the radiative decay mode $Λ_b^0γ$ could be very useful for us to establish the missing neutral states $Σ_b^{0}$ and $Σ_b^{*0}$. Our calculation shows that most of those missing $λ$-mode $P$-wave singly heavy baryons have relatively narrow decay width of less than 30 MeV. Their dominant strong and radiative decay channels can be ideal for searching for their signals in future experiment. Configuration mixings between the $J^P=1/2^-$ states $|^2P_λ \frac{1}{2}^- \rangle$ and $|^4P_λ \frac{1}{2}^- \rangle$ of the $\mathbf{6}_F$ multiplet are discussed. The $Ξ_c(2930)^0$ state seems to favor the mixed state $|Ξ_c'~ P_λ\frac{1}{2}^-\rangle_2$ with $J^P=1/2^-$. The $Σ_c(2800)$ resonance may be assigned to $|Σ_c~ ^2P_λ \frac{3}{2}^- \rangle$ with $J^P=3/2^-$ or $|Σ_c~ ^4P_λ \frac{5}{2}^- \rangle$ with $J^P=5/2^-$. In general, the excitations of $|^2P_λ \frac{3}{2}^- \rangle$ and $|^4P_λ \frac{5}{2}^- \rangle$ of the $\mathbf{6}_F$ multiplet have similar strong decay properties. In order to to identify them, angular distributions of their decays in either strong decay modes or radiative transitions should be needed.

hep-ph↗
arXiv2017

360 Panorama Cloning on Sphere

In this paper, we address a novel problem of cloning a patch of the source spherical panoramic image to the target spherical panoramic image, which we call 360 panorama cloning. Considering the sphere geometry constraint embedded in spherical panoramic images, we develop a coordinate-based method that directly clones in the spherical domain. Our method neither differentiates the polar regions and equatorial regions, nor identifies the boundaries in the unrolled planar-formatted panorama. We discuss in depth two unique issues in panorama cloning, i.e. preserving the patch's orientation, and handling the large-patch cloning (covering over 180 field of view) which may suffer from discoloration artifacts. As experimental results demonstrate, our method is able to get visually pleasing cloning results and achieve real time cloning performance.

cs.GR↗
arXiv2017

First-principles study on various point defects formed by hydrogen and helium atoms in tungsten

The different point defects formed by two hydrogen atoms or two helium atoms in tungsten were investigated through first-principles calculation. The energetically favorable site for a hydrogen atom is tetrahedral interstitial site while substitutional site is the most preferred site for a helium atom. The formation energies of two hydrogen or helium atoms are determined by their positions, and there are not a multiple of a single atom's. After relaxation, two adjacent hydrogen atoms are away from each other while helium atoms are close to. The reasons for the interaction between two hydrogen or helium atoms are also discussed.

cond-mat.mtrl-sci↗
arXiv2017

Understanding the newly observed $Ω_c$ states through their decays

The strong and radiative decay properties of the low-lying $Ω_c$ states are studied in a constituent quark model. We find that the newly observed $Ω_c$ states by the LHCb Collaboration can fit in well the decay patterns. Thus, their spin-parity can be possibly assigned as the following: (i) The $Ω_c(3000)$ has $J^P=1/2^-$ and corresponds to the narrow $1P$ mixed state $|1^2P_λ\frac{1}{2}^-\rangle_1$, its partner $|1^2P_λ\frac{1}{2}^-\rangle_2$ should be a broad state with a width of $\sim 100$ MeV. (ii) The $Ω_c(3050)$ and $Ω_c(3066)$ can be assigned to be two $J^P=3/2^-$ states, $|1^4P_λ\frac{3}{2}^-\rangle$ and $|1^2P_λ\frac{3}{2}^-\rangle$, respectively. (iii) The $Ω_c(3090)$ can be assigned as the $|1^4P_λ\frac{5}{2}^-\rangle$ state with $J^P=5/2^-$. (iv) The $Ω_c(3119)$ might correspond to one of the two $2S$ states of the first radial excitations, i.e. $|2^2S_{λλ}\frac{1}{2}^+\rangle$ or $|2^4S_{λλ}\frac{3}{2}^+\rangle$.

hep-ph↗
arXiv2017

Flexible and Actuating Nanoporous Poly(ionic liquids)- paper based Hybrid Membranes

Porous and flexible actuating materials are important in the development of smart systems. We report here a facile method to prepare scalable, flexible actuating porous membranes based on a poly(ionic liquid)-modified tissue paper. The targeted membrane property profile was based on a synergy of a gradient porous structure of poly(ionic liquid) network and the flexibility of tissue paper. The gradient porous structure was built up through ammonia-triggered electrostatic complexation of a poly(ionic liquid) with poly(acrylic acid) (PAA) that were previously impregnated inside the tissue paper. As a result, these porous membranes undergo bending deformation in response to organic solvents in vapor or liquid phase and can recover their shape back in air, which was demonstrated to be able to serve as solvent sensors. Besides, they show enhanced mechanical properties due to the introduction of mechanically flexible tissue paper that allows the membranes to be designed as new responsive textiles and contractile actuators.

physics.app-ph↗
arXiv2017

Cross section line shape of $e^+e^-\toχ_{c0}ω$ around the $Y(4260)$ mass region

We demonstrate that the recent measurement of the cross section line shapes of $e^+e^-\to χ_{c0}ω$ can be naturally explained by the molecular picture for $Y(4260)$ where the $Y(4260)$ is treated as a hadronic molecule dominated by $\bar{D}D_1(2420)+c.c.$ This result is consistent with properties extracted for $Y(4260)$ as the $\bar{D}D_1(2420)+c.c.$ molecular state in other reactions such as $e^+e^-\to J/ψππ$, $h_cππ$, $\bar D D^*π+c.c.$, and $γX(3872)$.

hep-ph↗
arXiv2016

Open charm contributions to the E1 transitions of $ψ(3686)$ and $ψ(3770)\to γχ_{cJ}$

The E1 transitions of $ψ(3686)$ and $ψ(3770)\to γχ_{cJ}$ are investigated in a non-relativistic effective field theory (NREFT) where the open charm effects are included systematically as the leading corrections. It also allows a self-consistent inclusion of the $S$-$D$ mixing in the same framework. We are able to show that the open charm contributions are essential for understanding the significant discrepancies between the non-relativistic leading order calculations and the experimental data.

hep-ph↗
arXiv2016

Production of $Y(4260)$ as a hadronic molecule state of $\bar{D}D_1 +c.c.$ in $e^+e^-$ annihilations

We study the $Y(4260)$ production mechanism in $e^+e^-$ annihilations in the framework of hadronic molecules and investigate the consequence of such a picture in different decay channels. In the hadronic molecule picture the $Y(4260)$ is described as a mixture state composed of a long-ranged $\bar{D}D_1(2420)+c.c.$ molecule state and a compact $c\bar{c}$ component. We show that the compositeness relation can still provide a reasonable constraint on the wavefunction renormalization parameter due to the dominance of the molecular component. Such a mechanism can be regarded as a natural consequence of the heavy quark spin symmetry (HQSS) breaking. This study elaborates the molecular picture for the $Y(4260)$ in the $e^+e^-$ annihilations and affirms that the cross section lineshape of $e^+e^-\to \bar{D}D^*π+c.c.$ in the vicinity of the $Y(4260)$ should have a nontrivial behavior. In this framework we predict that the upper limit of the $Y(4260)$ leptonic decay width is about 500 eV. We also investigate the coupling for $D_1(2420)\to D^*π$ in the $^3P_0$ quark model and examine the possible HQSS breaking effects due to the deviation from the $|^1P_1\rangle$ and $|^3P_1\rangle$ ideal mixing. This will in turn provide a constraint on the HQSS breaking coupling for the $Y(4260)$ to $\bar{D}D_1(2420)+c.c.$ via its $c\bar{c}$ component.

hep-ph↗
arXiv2016

Sensing solvents with ultra-sensitive porous poly(ionic liquid) actuators

We introduced a new concept for fabricating solvent stimulus polymer actuators with unprecedented sensitivity and accuracy. This was accomplished by integrating porous architectures and electrostatic complexation gradients in a poly(ionic liquid) membrane that bears ionic liquid species for solvent sorption. In contact with 1.5 mol% of acetone molecules in water, the actuator membrane (1 mm x 20 mm x 30 um) bent into a closed loop. While the interaction between solvents and the polymer drives the actuation, the continuous gradient in complexation degree combined with the porous architecture optimizes the actuation, giving it a high sensitivity and even the ability to discriminate butanol solvent isomers. The membrane is also capable of cooperative actuation. The design concept is easy to implement and applicable to other polyelectrolyte systems, which substantially underpins their potentials in smart and sensitive signaling microrobotics/devices.

cond-mat.soft↗
arXiv2016

Monitoring method for neutron flux for a spallation target in an accelerator driven sub-critical system

In this paper, we study a monitoring method for neutron flux for the spallation target used in an accelerator driven sub-critical (ADS) system, where a spallation target located vertically at the centre of a sub-critical core is bombarded vertically by high-energy protons from an accelerator. First, by considering the characteristics in the spatial variation of neutron flux from the spallation target, we propose a multi-point measurement technique, i.e. the spallation neutron flux should be measured at multiple vertical locations. To explain why the flux should be measured at multiple locations, we have studied neutron production from a tungsten target bombarded by a 250 MeV-proton beam with Geant4-based Monte Carlo simulations. The simulation results indicate that the neutron flux at the central location is up to three orders of magnitude higher than the flux at lower locations. Secondly, we have developed an effective technique in order to measure the spallation neutron flux with a fission chamber (FC), by establishing the relation between the fission rate measured by FC and the spallation neutron flux. Since this relation is linear for a FC, a constant calibration factor is used to derive the neutron flux from the measured fission rate. This calibration factor can be extracted from the energy spectra of spallation neutrons. Finally, we have evaluated the proposed calibration method for a FC in the environment of an ADS system. The results indicate that the proposed method functions very well.

physics.ins-det↗
arXiv2016

Understanding the newly observed heavy pentaquark candidates

We find that several thresholds can contribute to the enhancements of the newly observed heavy pentaquark candidates $P_c^+(4380)$ and $P_c^+(4450)$ via the anomalous triangle singularity (ATS) transitions in the specific kinematics of $Λ_b\to J/ψK^- p$. Apart from the observed two peaks we find that another peaks around 4.5 GeV can also be produced by the ATS. We also show that the $Σ_c^{(*)}$ can be produced at leading order in $Λ_b$ decay. This process is different from the triangle diagram and its threshold enhancement only appears as CUSP effects if there is no pole structure or the ATS involved. The threshold interaction associated with the presence of the ATS turns out to be a general phenomenon and plays a crucial role in the understanding of candidates for exotic states.

hep-ph↗
arXiv2015

Searching for observable effects induced by anomalous triangle singularities

We investigate the anomalous triangle singularity (ATS) and its possible manifestations in various processes. We show that the ATS should have important impact on our understanding of the nature of some newly observed threshold states. Discussions on how to distinguish the ATS phenomena from genuine dynamic pole structures are presented.

hep-ph↗
arXiv2015

Study of the rare decay $J/ψ\rightarrow e^+e^- ϕ$

We study the decay process of $J/ψ\rightarrow e^+e^- ϕ$ where the relatively clean electromagnetic (EM) transitions appear at leading order at tree level while the hadronic contributions only emerge via hadronic loop transitions. We include the low-lying scalar $f_0(980)$ and pseudoscalar $η/η'$ as the dominant contributions in the evaluation of the hadronic loop contributions. It is found that the hadronic effects are negligible comparing with the EM contributions. The decay width of $J/ψ\rightarrow e^+e^- ϕ$ is determined to be about $2.12\times 10^{-6}$ keV if there is no any other leading mechanism contributing, and this result will be tested by the BESIII experiment with a large data sample of $J/ψ$.

hep-ph↗