arXiv subjects

X. -Q. Li

Publications and source records attributed to X. -Q. Li.

7 recordsLinked to original sources

arXiv2025

Evidence of mini-jet emission in a large emission zone from a magnetically-dominated gamma-ray burst jet

The second brightest GRB in history, GRB230307A, provides an ideal laboratory to study the mechanism of GRB prompt emission thanks to its extraordinarily high photon statistics and its single episode activity. Here we demonstrate that the rapidly variable components of its prompt emission compose an overall broad single pulse-like profile. Although these individual rapid components are aligned in time across all energy bands, this overall profile conspires to show a well-defined energy-dependent behavior which is typically seen in single GRB pulses. Such a feature demonstrates that the prompt emission of this burst is from many individual emitting units that are casually linked in a emission site at a large distance from the central engine. Such a scenario is in natural consistency with the internal-collision-induced magnetic reconnection and turbulence framework, which invokes many mini-jets due to local magnetic reconnection that constantly appear and disappear in a global magnetically-dominated jet.

astro-ph.HE↗

arXiv2024

Magnetar emergence in a peculiar gamma-ray burst from a compact star merger

The central engine that powers gamma-ray bursts (GRBs), the most powerful explosions in the universe, is still not identified. Besides hyper-accreting black holes, rapidly spinning and highly magnetized neutron stars, known as millisecond magnetars, have been suggested to power both long and short GRBs. The presence of a magnetar engine following compact star mergers is of particular interest as it would provide essential constraints on the poorly understood equation of state for neutron stars. Indirect indications of a magnetar engine in these merger sources have been observed in the form of plateau features present in the X-ray afterglow light curves of some short GRBs. Additionally, some X-ray transients lacking gamma-ray bursts (GRB-less) have been identified as potential magnetar candidates originating from compact star mergers. Nevertheless, smoking gun evidence is still lacking for a magnetar engine in short GRBs, and the associated theoretical challenges have been raised. Here we present a comprehensive analysis of the broad-band prompt emission data of a peculiar, very bright GRB 230307A. Despite its apparently long duration, the prompt emission and host galaxy properties are consistent with a compact star merger origin, as suggested by its association with a kilonova. Intriguingly, an extended X-ray emission component shows up as the $γ$-ray emission dies out, signifying the likely emergence of a magnetar central engine. We also identify an achromatic temporal break in the high-energy band during the prompt emission phase, which was never observed in previous bursts and reveals a narrow jet with half opening angle of approximately $\sim 3.4^\circ (R_{GRB}/10^{15}~{cm})^{-1/2}$, where $R_{GRB}$ is the GRB prompt emission radius.

astro-ph.HE↗

arXiv2005

Experimental Fault-Tolerant Quantum Cryptography in a Decoherence-Free Subspace

we experimentally implement a fault-tolerant quantum key distribution protocol with two photons in a decoherence-free subspace (DFS). It is demonstrated that our protocol can yield good key rate even with large bit-flip error rate caused by collective rotation, while the usual realization of BB84 protocol cannot produce any secure final key given the same channel. Since the experiment is performed in polarization space and does not need the calibration of reference frame, important applications in free-space quantum communication are expected. Moreover, our method can also be used to robustly transmit an arbitrary two-level quantum state in a type of DFS.

quant-ph↗

arXiv2003

SU(3) and Nonet Breaking Effects in $K_L \to γγ$ Induced by $s \to d + 2{gluon}$ due to Anomaly

In this paper we study the effects of $s\to d + 2{gluon}$ on $K_L \to γγ$ in the Standard Model. We find that this interaction can induce new sizeable SU(3) and U(3) nonet breaking effects in $K_L - η, η'$ transitions and therefore in $K_L\to γγ$ due to large matrix elements of $<η(η')|α_s G^a_{μν} \tilde G_a^{μν}|0>$ from QCD anomaly. These new effects play an important role in explaining the observed value. We also study the effects of this interaction on the contribution to $Δm_{K_L-K_S}$.

hep-ph↗

arXiv1999

Final State Interactions in $D^0 \to K^0 \bar{K^0}$

It is believed that the production rate of $D^0\to K^0\bar K^0$ is almost solely determined by final state interactions (FSI) and hence provides an ideal place to test FSI models. Here we examine model calculations of the contributions from s-channel resonance $f_J(1710)$ and t-channel exchange to the FSI effects in $D^0\to K^0\bar K^0$. The contribution from s-channel $f_0(1710)$ is sma$ For the t-channel FSI evaluation, we employ the one-particle-exchange (OPE) model and Regge model respecti$ The results from two methods are roughly consistent with each other and can reproduce the large rate of $D^0\to K^0\bar K^0$ reasonably well$

hep-ph↗

arXiv1997

The dissipative potential induced by QCD at finite temperature and density

In the framework of QCD at finite temperature we have obtained dissipative terms for the effective potential between $q$ and $\bar q$ which would partly explain the $J/ψ$ suppression in the Quark Gluon Plasma (QGP). The derivation of the dissipative potential for QGP is presented and the case for Hadron Matter (HM) is briefly discussed. The suppression effects are estimated based on simple approximations.

hep-ph↗

arXiv1997

Applications of the superflavor symmetry to heavy baryon-antibaryon pair production in electron-positron collision

The baryons containing two heavy quarks and a light quark are believed to have the diquark-quark structure and the diquark is composed of the two heavy quarks which is a spin-0 or spin-1 object. The superflavor symmetry can associate productions of such heavy baryon-antibaryon pair with the heavy meson productions. The whole scenario is presented in some details in this work, and the observation prospect in future experiments is discussed.

hep-ph↗