arXiv subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 307 records · Page 17Linked to original sources

arXiv2022

What can we learn from the electromagnetic properties of hidden-charm molecular pentaquarks with single strangeness?

Inspired by the observation of the $P_{cs}(4459)$ and $P_{ψs}^Λ(4338)$, we systematically investigate the magnetic moments, the transition magnetic moments, and the radiative decay behaviors of the $S$-wave isoscalar $Ξ_c^{(\prime)}\bar D^{(*)}$ molecular pentaquark states in this work. Our quantitative investigation shows that their electromagnetic properties can provide important hint to decode the inner structure of these discussed isoscalar $Ξ_c^{(\prime)}\bar D^{*}$ molecular pentaquarks. As the potential research issue, we suggest future experiment to focus on the electromagnetic properties of these isoscalar $Ξ_c^{(\prime)}\bar D^{(*)}$ molecular pentaquarks, which are a typical hidden-charm molecular pentaquark system with single strangeness.

hep-ph↗

arXiv2022

Probing the electromagnetic properties of the $Σ_c^{()}D^{()}$-type doubly charmed molecular pentaquarks

In this work, we discuss the electromagnetic properties of the $S$-wave $Σ_c^{(*)}D^{(*)}$-type doubly charmed molecular pentaquarks, which have close relation to their inner structures. Both the $S$-$D$ wave mixing effect and the coupled channel effect are taken into account. We analyze the magnetic moments for the $S$-wave $Σ_c^{(*)}D^{(*)}$ molecular states, and extend our theoretical framework to study the transition magnetic moments and the radiative decay widths between the $S$-wave $Σ_c^{(*)}D^{(*)}$ molecules. We discuss the relations between the magnetic moments and the transition magnetic moments for the $S$-wave $Σ_c^{(*)}D^{(*)}$-type doubly charmed molecular pentaquarks, which can be regarded as an indirect way to measure their magnetic moments experimentally. The present study may inspire experimentalist's interest in measuring the electromagnetic properties of the hadronic molecular states.

hep-ph↗

arXiv2022

The role of the $ω(4S)$ and $ω(3D)$ states in mediating the $e^+e^-\to ωη$ and $ωπ^0π^0$ processes

The $e^+e^-\to ωη$ and $e^+e^-\toωπ^0π^0$ processes are ideal platforms to search for higher $ω$ states. Focusing on the observations of two enhancement structures around 2.2 GeV existing in $e^+e^-\to ωη$ and $e^+e^-\toωπ^0π^0$ at BESIII, we analyze how the $ω(4S)$ and $ω(3D)$ states play the role in the $e^+e^-\to ωη$ and $e^+e^-\toωπ^0π^0$ processes. The present study is supported by theoretical $ω$ mesonic spectroscopy. For reproducing the data of the cross sections of $e^+e^-\toωη$ and $ωπ^0π^0$, the intermediate $ω(4S)$ and $ω(3D)$ should be introduced, which indicates that the enhancement structures around 2.2 GeV existing in $e^+e^-\toωη$ and $ωπ^0π^0$ contain the $ω(4S)$ and $ω(3D)$ signals. Nonetheless, in the process $e^+e^-\toωη$, the $ω(4S)$ plays a dominant role, while the $ω(4S)$ and $ω(3D)$ have similar sizable contributions in the process of $e^+e^-\toωπ^0π^0$, which leads to a difference in the line shape of enhancement structure in the cross sections under the interference effect. Thus, we find a solution to alleviate the puzzling difference of resonance parameter of two reported enhancement structures around 2.2 GeV existing in $e^+e^-\to ωη$ and $e^+e^-\toωπ^0π^0$ at BESIII. The present study provides valuable information to construct $ω$ meson family, which can be accessible at future experiment like BESIII.

hep-ph↗

arXiv2022

AoI-Constrained Bandit: Information Gathering over Unreliable Channels with Age Guarantees

Age-of-Information (AoI) is an application layer metric that has been widely adopted to quantify the information freshness of each information source. However, few works address the impact of probabilistic transmission failures on satisfying the harsh AoI requirement of each source, which is of critical importance in a great number of wireless-powered real-time applications. In this paper, we investigate the transmission scheduling problem of maximizing throughput over wireless channels under different time-average AoI requirements for heterogeneous information sources. When the channel reliability for each source is known as prior, the global optimal transmission scheduling policy is proposed. Moreover, when channel reliabilities are unknown, it is modeled as an AoI-constrained Multi-Armed Bandit (MAB) problem. Then a learning algorithm that meets the AoI requirement with probability 1 and incurs up to O(K\sqrt{T\log T}) accumulated regret is proposed, where K is the number of arms/information sources, and T is the time horizon. Numerical results show that the accumulated regret of our learning algorithm is strictly bounded by K\sqrt{T\log T} and outperforms the AoI-constraint-aware baseline, and the AoI requirement of every source is robustly satisfied.

cs.IT↗

arXiv2022

Production of the $η_{1}(1855)$ through kaon induced reactions under the assumptions that it is a molecular or a hybrid state

By the reaction of kaon interacting with a proton, we investigate the production of the newly observed $η_{1}(1855)$ predicted in the picture of the $K\bar{K}_1(1400)$ molecular state and hybrid state. The total and differential cross sections of the concrete $K^{-}p\toη_{1}(1855)Λ$ reaction are calculated. Taking the partial decay width of the $η_{1}$ to $K\bar{K}^{\ast }$ as 0.9 MeV and 98.1 MeV, the minimum cross section of the $η_{1}(1855)$ production via the $K^{-}p$ reaction can reach up 0.59 $nb$ and 63.8 $nb$ at the center of mass energies $W\simeq 3.5$ GeV, respectively. The differential cross sections for the $η_{1}(1855)$ production at the different center of mass energies are also available. Furthermore, we present the Dalitz processes of $2\rightarrow 3$ and $2\rightarrow 4$, and initially discuss the feasibility of finding out the $η_{1}(1855)$ in experiments like J-PARC.

hep-ph↗

arXiv2022

Induced fission-like process of hadronic molecular states

In this work, we predict a new physical phenomenon, induced fission-like process and chain reaction of hadronic molecular states. As a molecular state, if induced by a $D$ meson, the $X(3872)$ can split into $D\bar{D}$ final state which is forbidden due to the spin-parity conservation. The breeding of the $D$ meson of the reaction, such as $D^0X(3872)\to D^0\bar{D}^0D^0$, makes the chain reaction of $X(3872)$ matter possible. We estimate the cross section of the $D$ meson induced fission-like process of $X(3872)$ into two $D$ mesons. With very small $D^0$ beam momentum of 1 eV, the total cross section reaches an order of 1000 b, and decreases rapidly with the increasing of beam momentum. With the transition of $D^*$ meson in molecular states to a $D$ meson, the $X(3872)$ can release large energy, which is acquired by the final mesons. The momentum distributions of the final $D$ mesons are analyzed. In the laboratory frame, the spectator $D$ meson in molecular state concentrates in the low momentum area. The energy from the transition frim $D^*$ to $D$ meson is mainly acquired by two scattered $D$ mesons. The results suggest that the $D$ meson environment will lead to the induced fission-like process and chain reaction of the $X(3827)$. Such phenomenon can be extended to other hadronic molecular states.

hep-ph↗

arXiv2022

Double-charm heptaquark states composed of two charmed mesons and one nucleon

Inspired by the experimental discoveries of $T_{cc}$, $Σ_c(2800)$, and $Λ_c(2940)$ and the theoretical picture where they are $DD^*$, $DN$, and $D^*N$ molecular candidates, we investigate the double charm heptaquark system of $DD^*N$. We employ the one-boson-exchange model to deduce the pairwise $D$-$D^*$, $D$-$N$, and $D^*$-$N$ potentials and then study the $DD^*N$ system with the Gaussian expansion method. We find two good hadronic molecular candidates with $I(J^P)=\frac{1}{2}(\frac{1}{2}^-)$ and $\frac{1}{2}(\frac{3}{2}^-)$ $DD^*N$ with only $s$-wave pairwise interactions. The conclusion remains unchanged even taking into account the $S$-$D$ mixing and coupled channel effects. In addition to providing the binding energies, we also calculate the root-mean-square radii of the $DD^*N$ system, which further support the molecular nature of the predicted states. They can be searched for at the upcoming LHC run 3 and run 4.

hep-ph↗

arXiv2022

Comparing Unit Trains versus Manifest Trains for the Risk of Rail Transport of Hazardous Materials -- Part I: Risk Analysis Methodology

Transporting hazardous materials (hazmats) using tank cars has more significant economic benefits than other transportation modes. Although railway transportation is roughly four times more fuel-efficient than roadway transportation, a train derailment has greater potential to cause more disastrous consequences than a truck incident. Train types, such as unit train or manifest train (also called mixed train), can influence transport risks in several ways. For example, unit trains only experience risks on mainlines and when arriving at or departing from terminals, while manifest trains experience additional switching risks in yards. Based on prior studies and various data sources covering the years 1996-2018, this paper constructs event chains for line-haul risks on mainlines (for both unit trains and manifest trains), arrival/departure risks in terminals (for unit trains) and yards (for manifest trains), and yard switching risks for manifest trains using various probabilistic models, and finally determines expected casualties as the consequences of a potential train derailment and release incident. This is the first analysis to quantify the total risks a train may encounter throughout the shipment process, either on mainlines or in yards/terminals, distinguishing train types. It provides a methodology applicable to any train to calculate the expected risks (quantified as expected casualties in this paper) from an origin to a destination.

stat.AP↗

arXiv2022

Comparing Unit Trains versus Manifest Trains for the Risk of Rail Transport of Hazardous Materials -- Part II: Application and Case Study

Built upon the risk analysis methodology (presented in the part I paper), this part II paper focuses on applying this methodology. Five illustrative scenarios were used to analyze the best or worst cases and compare the transportation risk differences between service options using unit trains and manifest trains. The comparison results indicate that if all tank cars are placed at the positions with the lowest probability of derailing and if switching tank cars alone in classification yards, it could provide the lowest risk estimate given the same transportation demand (i.e., number of tank cars to transport). This paper also shows that based on the data and parameters in the case study, risks during arrival/departure events and yard switching events could be as significant as risks that on mainlines. This paper provides a way to use the risk analysis methodology for rail safety decisions. The methodology and its application can be tailored to specific infrastructure and rolling stock characteristics.

stat.AP↗

arXiv2022

Identification and simulation of surface alpha events on passivated surfaces of germanium detectors and the influence of metalisation

Events from alpha interactions on the surfaces of germanium detectors are a major contribution to the background in germanium-based searches for neutrinoless double-beta decay. Surface events are subject to charge trapping, affecting their pulse shape and reconstructed energy. A study of alpha events on the passivated end-plate of a segmented true-coaxial n-type high-purity germanium detector is presented. Charge trapping is analysed in detail and an existing pulse-shape analysis technique to identify alpha events is verified with mirror pulses observed in the non-collecting channels of the segmented test detector. The observed radial dependence of charge trapping confirms previous results. A dependence of the probability of charge trapping on the crystal axes is observed for the first time. A first model to describe charge trapping effects within the framework of the simulation software SolidStateDetectors$.$jl is introduced. The influence of metalisation on events from low-energy gamma interactions close to the passivated surface is also presented.

physics.ins-det↗

arXiv2022

Investigating the $\mathbf{Υ(10753)\to Υ(1^3D_J)η}$ transitions

In this work, we investigate the $Υ(10753)\toΥ(1^3D_J)η$ ($J=1,2,3$) processes, where the $Υ(10753)$ is assigned as a conventional bottomonium under the $4S$-$3D$ mixing scheme. Our result shows that the concerned processes have considerable branching ratios, {\it i.e.}, branching ratios $\mathcal{B}[Υ(10753)\toΥ(1^3D_{1})η]$ and $\mathcal{B}[Υ(10753)\toΥ(1^3D_{2})η]$ can reach up to the order of magnitude of $10^{-4}-10^{-3}$, while $\mathcal{B}[Υ(10753)\toΥ(1^3D_{3})η]$ is around $10^{-6}-10^{-5}$. With the running of Belle II, it is a good opportunity for finding out the concerned hidden-bottom hadronic decays.

hep-ph↗

arXiv2022

Neutrino Rocket Jet Model: An Explanation of High-velocity Pulsars and their Spin-down Evolution

The fact that the spatial velocity of pulsars is generally higher than that of their progenitor stars has bothered astronomers for nearly 50 years. It has been extensively argued that the high pulsar velocity should be acquired during a natal kick process on a timescale of 100ms - 10s in the supernova explosion, in which some asymmetrical dynamical mechanism plays a key role. However, a satisfactory picture generally is still lacking. In this study, it is argued that the neutrino rocket model can well account for the high speed as well as the long-term evolution behaviors of pulsars. The neutrinos are emitted from superfluid vortex neutrons through the neutrino cyclotron radiation mechanism. The unique characters of left-handed neutrinos and right-handed antineutrinos resulting from the nonconservation of parity in weak interactions play a major role in the spatial asymmetry. The continuous acceleration of pulsars can be naturally explained by this model, which yields a maximum velocity surpassing 1000 km s$^{-1}$. The alignment between the spinning axis and the direction of motion observed for the Crab pulsar (PSR 0531) and the Vela pulsar (PSR 0833) can be well accounted for. The observed correlation between the spin-down rate and the period of long-period pulsars with $P \gtrsim 0.5$s can also be satisfactorily explained.

astro-ph.HE↗

arXiv2022

DiVAE: Photorealistic Images Synthesis with Denoising Diffusion Decoder

Recently most successful image synthesis models are multi stage process to combine the advantages of different methods, which always includes a VAE-like model for faithfully reconstructing embedding to image and a prior model to generate image embedding. At the same time, diffusion models have shown be capacity to generate high-quality synthetic images. Our work proposes a VQ-VAE architecture model with a diffusion decoder (DiVAE) to work as the reconstructing component in image synthesis. We explore how to input image embedding into diffusion model for excellent performance and find that simple modification on diffusion's UNet can achieve it. Training on ImageNet, Our model achieves state-of-the-art results and generates more photorealistic images specifically. In addition, we apply the DiVAE with an Auto-regressive generator on conditional synthesis tasks to perform more human-feeling and detailed samples.

cs.CV↗

arXiv2022

Newly observed $a_0(1817)$ as the scaling point of constructing the scalar meson spectroscopy

Stimulated by the newly observed $a_0(1817)$ by the BESIII Collaboration, we find a perfect Regge trajectory composed of the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$, which leads us to categorize the $a_0(980)$, $a_0(1450)$, and $a_0(1817)$ into the isovector scalar meson family. This scenario is supported by their two-body Okubo-Zweig-Iizuka allowed strong decay behaviors. In this scheme, we also predict the third radial excitation of the $a_0(980)$, which is denoted as the $a_0(2115)$, accessible at future experiment as a direct test of this assignment. We find another Regge trajectory which contains three isoscalar scalar states $f_0(980)$, $X(1812)$, and $f_0(2100)$. We investigate their two-body Okubo-Zweig-Iizuka allowed strong decay patterns, which are roughly consistent with the experimental data. The $f_0(980)$, $X(1812)$, and $f_0(2100)$ can be well grouped into the isoscalar scalar meson family. We want to emphasize that these two Regge trajectories have a similar slope. In summary, the present work provides a scheme of constructing the scalar meson family based on these reported scalar states. The possibility of the $f_0(1710)$ as the candidate of the scalar glueball cannot be excluded by the observation of the $a_0(1817)$ since the $a_0(1817)$ is more suitable as the isovector partner of the $X(1812)$.

hep-ph↗

arXiv2022

Predicted $Λ\barΛ$ and $Ξ^-\barΞ^+$ decay modes of the charmoniumlike $Y(4230)$

In this work, we predict the light hadronic decay channels $Y(4230)\toΛ\barΛ$ and $Ξ^-\barΞ^+$ when treating the $Y(4230)$ as a vector charmonium state. By the hadronic loop mechanism, the branching ratios of the $Y(4230)\toΛ\barΛ$ and $Ξ^-\barΞ^+$ processes are calculated. In addition, we discuss the possibility of carrying out the search for the signal of the $Y(4230)$ through $Λ\barΛ$ and $Ξ^-\barΞ^+$ channels from the $e^+e^-$ annihilation. Assuming $Y(4230)$ exist in $Λ\barΛ$ and $Ξ^-\barΞ^+$ channel, we also present the time-like electromagnetic form factors (EMFFs) at $\sqrt{s}=m_{Y(4230)}$.

hep-ph↗

arXiv2022

Fully heavy pentaquark states in constituent quark model

The LHCb collaboration reported a fully charmed tetraquark state X(6900) in the invariant mass spectrum of $J/ψ$ pairs in 2020. This discovery inspires us to further study the fully heavy pentaquark system. In this work, we investigate systematically all possible configurations for ground fully heavy pentaquark system via the variational method in the constituent quark model. According to our calculations, we further analyze the relative lengths between quarks and the contributions to the pentaquark masses from different terms of the Hamiltonian. We think no stable states exist in fully heavy pentaquark system. We hope that our study will be helpful to explore for fully heavy pentaquark states.

hep-ph↗

arXiv2022

Identifying the contribution of higher $ρ$ mesons around 2 GeV in the $e^+ e^- \to ωπ^0$ and $e^+ e^- \to ρη^{\prime}$ processes

The properties of the light vector meson states around 2.0 GeV have been poorly understood for a long time, which has become a barrier to the expansion to higher light vector meson spectrum. Recently, the BESIII collaboration released the measurements of the $e^+ e^- \to ωπ^0$ and $e^+ e^- \to ρη^{\prime}$ reactions above 2.0 GeV, both of which are ideal processes to study the isovector $ρ$ meson family. In this work, through carrying out a combined analysis of the Born cross section data for the above two processes with the theoretical support on mass spectrum, and production and strong decay behaviors of the $ρ$ meson family around 2.0 GeV, we identify the enhancement structure near 2034 MeV observed in $e^+e^-\toωπ^0$ to be the interference contribution from two resonances $ρ(1900)$ and $ρ(2150)$, and another enhancement structure at 2111 MeV reported in $e^+e^-\toρη^{\prime}$ to be the contributions from $ρ(2000)$ and $ρ(2150)$. This conclusion means that the $e^+e^-\toωπ^0$ and $e^+e^-\toρη^{\prime}$ are the excellent golden channels to establish $ρ(1900)$ and $ρ(2000)$, especially for a $D$-wave state $ρ(2000)$, whose experimental search in the $e^+e^-$ collision should be quite challenging. The relevant cross section measurements with higher precision are expected in the future BESIII and Belle II experiments.

hep-ph↗

arXiv2022

Triple-charm molecular states composed of $D^D^D$ and $D^D^D^*$

Inspired by the newly observed $T_{cc}^+$ state, we systematically investigate the $S$-wave triple-charm molecular states composed of $D^*D^*D$ and $D^*D^*D^*$. We employ the one-boson-exchange model to derive the interactions between $D(D^*)$ and $D^*$ and solve the three-body Schrödinger equations with the Gaussian expansion method. The $S$-$D$ mixing and coupled channel effects are carefully assessed in our study. Our results show that the $I(J^P)=\frac{1}{2}(0^-,1^-,2^-)$ $D^*D^*D$ and $I(J^P)=\frac{1}{2}(0^-,1^-,2^-,3^-)$ $D^*D^*D^*$ systems could form bound states, which can be viewed as three-body hadronic molecules. We present not only the binding energies of the three-body bound states, but also the root-mean-square radii of $D $-$D^*$ and $D^*$-$D^*$, which further corroborate the molecular nature of these states. These predictions could be tested in the future at LHC or HL-LHC.

hep-ph↗