arXiv subjects

Qiang Zhao

Publications and source records attributed to Qiang Zhao.

At least 37 records · Page 2Linked to original sources

arXiv2025

A unified approach for the hadronic weak decays of $Λ$ and $Σ^{\pm}\to Nπ$

We provide a unified approach for the two-body hadronic weak decays of hyperons with $S=-1$, i.e. $Λ$ and $Σ^\pm$, in the framework of the non-relativistic constitute quark model (NRCQM). A combined analysis shows that the branching ratios and asymmetry parameters of the decay channels $Λ\to pπ^-$ and $Σ^\pm\to Nπ$ can be well described in the same framework with the direct pion emission, color suppressed internal $W$ emission, and pole terms included. However, the channel $Λ\to nπ^0$ indicates significant deviations from the experimental data based on these mentioned transition mechanism. We demonstrate that the final state interactions (FSIs) via the coupled-channel rescatterings play a crucial role in $Λ\to nπ^0$. Namely, the dominant decay channel of $Λ\to pπ^-$ can contribute to $Λ\to nπ^0$ via the $pπ^-\to nπ^0$ rescatterings. This is a leading correction effect for $Λ\to nπ^0$ at the one-loop level. We find that such FSIs only become the leading effects in $Λ\to nπ^0$, but contribute as subleading contributions in other channels. We also demonstrate that the pole terms are indispensable in these hyperon decays. In particular, for $Σ^-\to nπ^-$ and $Σ^+\to nπ^+$, it shows that $Λ(1405)$ as the intermediate state in the pole term amplitude is necessary for reproducing the experimental data. We also find that a dynamic selection rule forbids the radial excitation state $N(1710)$ of the quark model multiplet $|70, ^28,2,0^+,1/2^+\rangle$ from contribution. To some extent, the hyperon hadronic weak decays serve as a special probe for the underlying transition mechanisms and can provide some constraints on the intermediate $J^P=1/2^\pm$ baryon resonances.

hep-ph↗

arXiv2025

Huizhou Hadron Spectrometer -- a Proposed High-rate Experimental Setup at the High Intensity Heavy-ion Accelerator Facility

The High-Intensity Heavy-Ion Accelerator Facility (HIAF), currently under construction in Huizhou, Guangdong Province, China, is projected to be completed by 2025. This facility will be capable of producing proton and heavy-ion beams with energies reaching several GeV, thereby offering a versatile platform for advanced fundamental physics research. Key scientific objectives include exploring physics beyond the Standard Model through the search for novel particles and interactions, testing fundamental symmetries, investigating exotic hadronic states such as di-baryons, pentaquark states and multi-strange hypernuclei, conducting precise measurements of hadron and hypernucleus properties, and probing the phase boundary and critical point of nuclear matter. To facilitate these investigations, we propose the development of a dedicated experimental apparatus at HIAF - the Huizhou Hadron Spectrometer (HHaS). This paper presents the conceptual design of HHaS, comprising a solenoid magnet, a five-dimensional silicon pixel tracker, a Low-Gain Avalanche Detector (LGAD) for time-of-flight measurements, and a Cherenkov-scintillation dual-readout electromagnetic calorimeter. The design anticipates an unprecedented event rate of 1-100 MHz, extensive particle acceptance, a track momentum resolution at 1% level, an electromagnetic energy resolution of ~3% @ 1 GeV and multi-particle identification capabilities. Such capabilities position HHaS as a powerful instrument for advancing experimental studies in particle and nuclear physics. The successful realization of HHaS is expected to significantly bolster the development of medium- and high-energy physics research within China.

hep-ex↗

arXiv2025

Decoding spin-parity quantum numbers and decay widths of double $J/ψ$ exotic states

We derive helicity amplitudes for the fully charmed tetraquark states decays into vector meson pair under two types of models, where the one is from quark model and the other one is from diquark model. The decay angular distributions have been given by the cascade decays $T_{4c}\to J/ψ(D_{(s)}^*)+J/ψ(\bar{D}_{(s)}^*)$ along with $J/ψ\to μ^++μ^-$ or $D_{(s)}^*\to D_{(s)}+π$, showing that spin-0 and spin-2 states can be distinguished. We also find that the spin-0 state decay to $J/ψ$-pair exhibits a higher degree of quantum entanglement than that in spin-2 state decays. These findings will assist in experimentally differentiating various spin-parity states, determining decay widths and unveiling undiscovered hadronic states within existing structures, thereby shedding light on the internal properties of double $J/ψ$ exotic states.

hep-ph↗

arXiv2025

Threshold effects as the origin of $Y(4500)$ observed in $e^+e^-\to J/ψK^+K^-$

The BESIII collaboration has recently observed a resonant structure $Y(4500)$ in $e^{+}e^{-}\to J/ψK^{+}K^{-}$, whose origin remains unresolved. In this study, we analyze the cross section line shape of $e^{+}e^{-}\to J/ψK^{+}K^{-}$ by taking into account the $ψ(4415)$ state and intermediate charmed meson loops. By treating $ψ(4415)$ as both a pure $S$-wave state and $S$-$D$ mixed states, and introducing the $Z_{cs}^{(\prime)}$ resonance, we find that the $Y(4500)$ peak at $\sqrt{s}=4.5~\text{GeV}$ arises from the triangle singularity mechanism in the $Z_{cs}^{(\prime)}$-mediated rescattering processes, supporting its interpretation as a threshold effect rather than a conventional resonance.

hep-ph↗

arXiv2025

A short review of the vector charmonium-like state $ψ(4230)$

We present a concise review of the vector charmonium state $ψ(4230)$, which was originally labelled as $Y(4260)$ in the literature. As one of the earliest candidates for a QCD exotic states, its interpretation has initiated various ideas about possible manifestations of non-perturbative mechanisms in the charmonium mass regime. In this short article we briefly review the experimental status of $ψ(4230)$ and discuss possible theoretical interpretations. We will focus on four broadly investigated scenarios, i.e. tetraquark, hybrid, hadro-quarkonium, and hadronic molecule, and highlight the key issues based on these approaches. Crucial experimental observables, e.g. mass position, lineshapes, di-lepton decay width $Γ_{ee}$, production rates in $B$ meson decays, dominant hadronic decay patterns, and the potential $1^{-+}$ and $0^{--}$ exotic partners, are assessed, which can provide crucial structure information for understanding this mysterious state.

hep-ph↗

arXiv2025

Predictions for the isospin-violating decays of $B_{c}(1P)^{+}\to B_{c}^{(*)+}π^{0}$

In this work we study the isospin-violating decays of $B_{c}(1P)^{+}\to B_{c}^{(*)+}π^{0}$, which may provide additional information for the determination of the properties of the first orbital excitation states of $B_{c}(1P)^{+}$. By assuming a dual relation between the U(1) anomaly soft-gluon coupling for $B_{c}(1P)^{+}\to B_{c}^{(*)+}π^{0}$ and the intermediate meson loop transitions, we can quantify the isospin-violating decay effects for these four $P$-wave states. We find that the partial decay width of $B_{c0}^{*+}\to B_{c}^{+}π^{0}$ is about three orders of magnitude larger than that for $B_{c2}^{*+}\to B_{c}^{+}π^{0}$. It implies that $B_{c0}^{*+}$ can be established in the $B_{c}^{+}π^{0}$ decay channel as a single state. Meanwhile, the two axial-vector states $B_{c1}^{+}/B_{c1}'^{+}$ can be possibly identified in $B_{c1}^{+}/B_{c1}'^{+}\to B_{c}^{*+}π^{0}$ with comparable strengths. Although these isospin-violating decays turn out to be small, the theoretical predictions should be useful for guiding future experimental efforts.

hep-ph↗

arXiv2025

Equation of state of spin-polarized nuclear matter in the relativistic Hartree-Fock method

We calculate the equation of state (EOS) of spin-polarized nuclear matter in the relativistic Hartree-Fock method. To this end, we employ the relativistic point-coupling model, with which the Fock terms are considerably simplified, reducing them to the same form as the Hartree terms. In analogy to the slope parameter $L$ of the isospin-symmetry energy for spin-unpolarized matter, we evaluate the spin slope parameter $L_s$ of the corresponding spin-symmetry energy for spin-polarized matter. We find that the slope parameter $L$ and the spin slope parameter $L_s$ have a negative correlation in the case of isoscalar polarization, where neutrons and protons are spin-polarized in the same direction. On the other hand, the spin slope parameter is nearly independent of the slope parameter in the case of isovector polarization, where neutrons are spin-polarized along the opposite direction to protons. We show that these correlations are a natural consequence of the relativistic point coupling model which we employ.

nucl-th↗

arXiv2025

Revisit the diquark of $Λ_c$ in the $Λ_c\to ΛK^+$ and $Λ_c\to Σ^0 K^+$ processes

The spatial distributions of $[ud]$ diquark and heavy-light diquark of the SU(3)-flavor antitriplet charmed baryons are investigated by the two singly Cabibbo-suppressed hadronic weak decays, $Λ_c\to ΛK^+$ and $Λ_c\to Σ^0 K^+$ within the nonrelativistic constituent quark model. The above two spatial distributions are reflected by the two parameters $α_ρ$ and $α_λ$, which are the harmonic oscillator strength parameters of the charmed baryons. These two parameters obtain strong constraints from the decay widths of $Λ_c\to ΛK^+$ and $Λ_c\to Σ^0 K^+$. The larger the harmonic oscillator parameter is, the more compact the spatial distribution will become. The current $α_ρ$ and $α_λ$ indicate that neither the light diquark nor the heavy-light diquark turns out to favor a compact structure. In addition, some selection rules, including the ``$Λ$ selection rule'', can be useful for the search of excited baryons in the heavy-flavor baryon hadronic weak decays.

hep-ph↗

arXiv2025

Understanding the non-trivial isoscalar pseudoscalar structures in the $K_S K_Sπ^0$ spectra in the $J/ψ$ radiative decay

Initiated by the recent observation of a flattened lineshape of $IJ^{PC}=00^{-+}$ around $1.4\sim 1.5$ GeV in the $K_S K_S π^0$ invariant mass spectrum by BESIII, we make a systematic partial wave analysis of $J/ψ\toγη_X\to γK\bar{K}π$ based on an isobaric approach. We demonstrate that in the scenario of the first radial excitations of the isoscalar pseudoscalar from the $K\bar{K}π$ threshold to about 1.6 GeV the non-trivial $K_S K_S π^0$ invariant mass spectrum can be explained by the coupled-channel effects with the presence of the triangle singularity mechanism. It shows that a combined fit of the Dalitz plots, three-body and two-body spectra can be achieved which suggests that the one-state solution around $1.4\sim 1.5$ GeV proposed before still holds well. In particular, we show that the coupled-channel effects between the three important quasi-two-body decay channels, $K^*\bar{K}+c.c.$, $κ\bar{K}+c.c.$ and $a_0(980)π$, can be well described by taking into account the one-loop corrections in the isobaric approach. This is because the isoscalar pseudoscalar states are coupled to the $K^*\bar{K}+c.c.$ and $a_0(980)π$ ($κ\bar{K}+c.c.$) channels via the $P$ and $S$ waves, respectively. As a consequence, the coupled-channel effects can be largely absorbed into the redefinition of the tree-level effective couplings with the transition amplitudes computed to the order of one-loop corrections. Then, the coupled-channel effects can be estimated by the contributions from the one-loop rescattering amplitudes in comparison with the tree-level ones, where we find that the rescattering contributions from the $P$-wave into the $S$-wave, or vice verse, are apparently suppressed in the kinematic region near threshold.

hep-ph↗

arXiv2025

An effective finite-range Gogny-type interaction for the quantum molecular dynamics like model

In this work, we propose an effective finite-range Gogny-type interaction that can be directly used in the quantum molecular dynamics (QMD) like model. Two methods for determining the parameters of the effective interaction are discussed. The first method establishes an approach to connect the conventional Gogny interaction in nuclear structure to that in heavy-ion collisions, the second method allows for the description of the symmetry energy varying from the supersoft to stiff, as well as the momentum-dependent symmetry potential, exhibiting behaviors ranging from monotonic to non-monotonic variations. This effective interaction opens up opportunities for a deeper understanding of finite-range interactions and non-monotonic momentum-dependent symmetry potentials in future studies.

nucl-th↗

arXiv2025

Combined study of the isospin-violating decay $D^{}_{s}\to D_{s} π^0$ and radiative decay $D^_s\to D_sγ$ with intermediate meson loops

We carry out a combined study of the isospin-violating decay $D_{s}^{*} \to D_{s} π^{0}$ and radiative decay $D^*_s\to D_sγ$ in an effective Lagrangian approach by taking into account the corrections from the one-loop transitions. By distinguishing the transition mechanisms of the long-distance interactions through the intermediate meson loops from the short-distance interactions through the $η-π^{0}$ mixing at the tree level the isospin-violating decay $D_{s}^{*} \to D_{s} π^{0}$ can be well constrained. In our approach the higher order corrections to the isospin-violating effects can involve the intermediate $D^{(*)}$ and $K^{(*)}$ scatterings. We find that the contributions from the destructive interference of intermediate meson loops via $D^{(*)0}(c\bar{u}){K}^{(*)+}(u\bar{s})$ and $D^{(*)+}(c\bar{d}){K}^{(*)0}(d\bar{s})$ rescatterings are significant. Within the commonly accepted ultra-violet (UV) cutoff range we obtain the partial decay width $Γ[D_{s}^{*} \to D_{s} π^{0}] = 9.92^{+0.76}_{-0.66}\,\mathrm{eV}$. This approach allows us to describe the $D_s^*$ radiative decay in the same framework via the vector meson dominance (VMD) model. We demonstrate that both the tree-level and one-loop transitions can be self-consistently determined if we adopt the experimental data for the branching ratio fraction of $D_{s}^{*} \to D_{s} π^{0}$ to $D^*_s\to D_sγ$. It then leads to a reliable estimate of the total decay width of $D_s^*$, i.e. $Γ_{\text{total}}(D_s^{*+})=170^{+ 13}_{-12}\,\mathrm{eV}$.

hep-ph↗

arXiv2025

Spontaneous rotational symmetry breaking induced by electronic instability in the normal state of La_{1-x} Sr_{x} NiO_{2}

The spontaneous rotational symmetry breaking (RSB), a hallmark phenomenon in cuprate and iron-based high-temperature superconductors, is believed to intimately connected to superconductivity, both of which originate from interactions among different degrees of freedoms and competing quantum states. Understanding RSB is pivotal for unraveling the microscopic origin of unconventional superconductivity. Although infinite-layer nickelates (ILNs) share similar crystalline structure and the same nominal 3d-electron configurations with cuprates, they have significant differences in Fermi surface topology, electronic band characteristics, and charge order. These distinctions make ILNs an ideal platform for studying RSB in unconventional superconductors. Through angular-resolved resistivity measurements within a large temperature and doping range, we identify pronounced RSB signatures near doping concentrations x=0.05 and 0.25. Based on the strongly correlated electronic structures from combined density functional theory and dynamical mean field theory calculations, we find that the calculated electronic susceptibility has a peak structure at the corresponding doping concentration, indicating pronounced electronic instabilities which drive RSB. Detailed analysis of the electronic susceptibility demonstrates that the van Hove singularity at the Fermi level significantly contributes to the electronic instability at 0.05 Sr doping. Our findings reveal the important role of electronic correlation, Van Hove singularity, and Fermi surface nesting in the emergence of RSB. Our work not only deepens the understanding of electronic behavior in ILNs, but also provides new ideas and methods for exploring RSB in other unconventional superconductors.

cond-mat.supr-con↗

arXiv2025

Status and prospect of weak radiative hyperon decays

Weak radiative hyperon decays represent a rich interplay between weak interactions and the internal structure of baryons, offering profound insights into Quantum Chromodynamics and weak interactions. Recent experimental observations, particularly from BESIII, have revealed deviations from theoretical predictions. These deviations could signal new physics or the need for refined theoretical models incorporating intermediate resonance effects. This review discusses recent theoretical advancements and key experimental findings, focusing on recent measurements from BESIII and their implications for strong interactions and baryon structure.

hep-ph↗

arXiv2025

A Novel Low-Background Photomultiplier Tube Developed for Xenon Based Detectors

Photomultiplier tubes (PMTs) are essential in xenon detectors like PandaX, LZ, and XENON experiments for dark matter searches and neutrino properties measurement. To minimize PMT-induced backgrounds, stringent requirements on PMT radioactivity are crucial. A novel 2-inch low-background R12699 PMT has been developed through a collaboration between the PandaX team and Hamamatsu Photonics K.K. corporation. Radioactivity measurements conducted with a high-purity germanium detector show levels of approximately 0.08 mBq/PMT for $\rm^{60}Co$ and 0.06~mBq/PMT for the $\rm^{238}U$ late chain, achieving a 15-fold reduction compared to R11410 PMT used in PandaX-4T. The radon emanation rate is below 3.2 $\rm μ$Bq/PMT (@90\% confidence level), while the surface $\rm^{210}Po$ activity is less than 18.4 $μ$Bq/cm$^2$. The electrical performance of these PMTs at cryogenic temperature was evaluated. With an optimized readout base, the gain was enhanced by 30\%, achieving an average gain of $4.23 \times 10^6$ at -1000~V and -100~$^{\circ}$C. The dark count rate averaged 2.5~Hz per channel. Compactness, low radioactivity, and robust electrical performance in the cryogenic temperature make the R12699 PMT ideal for next-generation liquid xenon detectors and other rare event searches.

physics.ins-det↗

arXiv2025

The Cabibbo-favored hadronic weak decays of the $Ξ_c$ in the quark model

The Cabibbo-favored hadronic weak decay of the $Ξ_c^+\to Ξ^0π^+$, $Ξ_c^0\to Ξ^-π^+$, $Ξ_c^0\to Ξ^0π^0$, $Ξ_c^0\to Ξ^0η^{(')}$ and $Ξ_c^0\to Ξ^+K^-$ are studied in the non-relativistic constituent quark model. By analyzing their decay mechanisms at the quark level we show that the pole terms are essential for understanding the transition dynamics in addition to the usually considered direct meson emission process and color suppressed process in the charmed baryon hadronic weak decays. The experimentally measurable asymmetry parameters are also predicted in order to further pin down the decay mechanism.

hep-ph↗

arXiv2025

Improving key rates by tighter information reconciliation leakage estimation for quantum key distribution

Previous research has aimed to precisely estimate information leakage to improve the secure key rate (SKR) and maximum transmission distance in quantum key distribution (QKD). However, existing methods repeatedly considerd the information of the multi-photon pulses known to Eve before and after information reconciliation, resulting in an overestimation of the leakage amount. We propose a novel approach that considers the quantum part's effect on post-processing, providing a more accurate estimation of information reconciliation leakage to improve the SKR. Theoretical analysis shows that our method more accurately estimates the information reconciliation leakage, significantly improving the SKR at any distance as well as the maximum transmission distance. It is worth mentioning that previous studies treat information leakage of the error correction as Shannon bound $Nh(e)$, and our method can estimate it more tightly. Simulation results for decoy-BB84 and measurement-device-independent (MDI) protocols using Cascade are consistent with the theoretical analysis. The farther the transmission distance, the greater the growth rate of SKR. When the error rate is 33%, compared with the original method, the SKR growth rate of decoy-BB84 at 100KM is 100.4%, and the transmission distance of MDI increases by 22KM.

quant-ph↗

arXiv2024

Revealing the mystery of the double charm tetraquark in $pp$ collision

A novel approach is proposed to probe the nature of the double charm tetraquark through the prompt production asymmetry between $T_{\bar{c}\bar{c}}^-$ and $T_{cc}^+$ in $pp$ collisions. When comparing two theoretical pictures, i.e. the compact tetraquark and hadronic molecular pictures, we find that the former one exhibits a significantly larger production asymmetry, enabling the unambiguous determination of the tetraquark's internal structure. Additionally, distinctive differences in the transverse momentum and rapidity distributions of $T_{\bar{c}\bar{c}}^-$ and $T_{cc}^+$ cross sections emerge, particularly at $p_\mathrm{T}\approx 2~\mathrm{GeV}$ and $y\approx \pm 6$ at a center-of-mass energy of 14$~\mathrm{TeV}$. The insignificant asymmetry in hadronic molecular picture is because that hadronic molecules are produced in hadronic phase, where the phase space of their constituents needs to be taken into account rigorously. Our work can be extended to the exploration of other double heavy tetraquark candidates, offering a versatile approach to advance our understanding of exotic hadrons.

hep-ph↗

arXiv2024

Exact-exchange relativistic density functional theory in three-dimensional coordinate space

The exact-exchange relativistic density functional theory (Ex-RDFT) of atomic nuclei has been solved in three-dimensional lattice space for the first time. The exchange energy is treated within the framework of the orbital-dependent relativistic Kohn-Sham density functional theory, wherein the local Lorentz scalar and vector potentials are derived using the relativistic optimized effective potential method. The solutions of binding energies, charge radii, and density distributions are benchmarked against the traditional relativistic Hartree-Fock approach for spherical and axially deformed nuclei. Furthermore, the triaxial neutron-rich $^{104-120}\text{Ru}$ isotopes are investigated with the exchange correlations, which is beyond the current capacity of the traditional relativistic Hartree-Fock approach. The results notably indicate the $γ$-softness of these neutron-rich nuclei, which is consistent with experimental observations. This novel approach establishes a foundation for the study of nuclei without imposing any symmetry restrictions employing relativistic density functional with exchange correlations.

nucl-th↗