arXiv subjects

Chang-Zheng Yuan

Publications and source records attributed to Chang-Zheng Yuan.

At least 19 recordsLinked to original sources

arXiv2026

HepScript: A Dual-Use DSL for Human-AI Collaborative Data Analysis Workflows in High-Energy Physics

The escalating data scale in High-Energy Physics (HEP) fuels a growing aspiration for higher analytical efficiency. While Large Language Models (LLMs) offer a path toward automation via agentic AI, they struggle with complex scientific workflows that require deep domain knowledge and are tightly coupled to experiment-specific codebases. To address this, we introduce a methodology centered on HepScript, a dual-use Domain-Specific Language (DSL) for HEP data analysis workflows. HepScript serves as a shared formal interface, abstracting HEP analysis logic into a constrained syntax that is both intuitive for human experts and reliably generable by AI agents. First developed for the Beijing Spectrometer III (BESIII) experiment, HepScript hides the complexity of the underlying software stack, translating high-level analysis intent into low-level, production-ready code. In our case studies, this abstraction reduces the required human-written code by 93\%. Crucially, HepScript's constrained grammar defines a tractable action space, enabling AI agents to autonomously generate executable specifications for core analysis stages directly from published literature with a 95\% success rate. Our work demonstrates a scalable pathway toward human-AI collaborative systems, where a formally specified DSL acts as an unambiguous translation layer between human expertise, AI automation, and production environment, rendering previously intractable automation problems solvable.

hep-ex↗

arXiv2026

Precision $YN$ and $\bar{n}N$ measurements with an LH$_2$/LD$_2$ target in the BESIII detector

Located at the BEPCII $e^{+}e^{-}$ collider, the BESIII experiment provides a robust platform for investigating (anti)hyperon-nucleon ($YN$) and antineutron-nucleon ($\bar{n}N$) interactions. This is made possible by the high production cross-sections of $J/ψ$ and $ψ(3686)$ resonances and their substantial decay branches into these baryons. Although previous studies using the beam pipe as a target demonstrated feasibility, statistical precision remains constrained by the limited material budget. To address this, we propose installing a dedicated liquid hydrogen or liquid deuterium target between the beam pipe and the Cylindrical Gas Electron Multiplier Inner Tracker. Monte Carlo simulations confirm that the added material has a negligible effect on charged particle tracking. This upgrade is expected to enhance the effective luminosity for scattering on free protons by a factor of 10--30 for $Λ$, $Σ^{+}$, $Ξ$, and $\bar{n}$ beams, enabling high-precision measurements of $YN$ and $\bar{n}N$ interactions that will significantly advance our knowledge of non-perturbative strong interactions.

hep-ex↗

arXiv2026

Unraveling the Hyperon Puzzle in Neutron Stars via Novel, High-Precision Hyperon Factories

The strong forces between nucleons ($N$=$p$, $n$) are fundamental to the visible universe. The interactions between hyperons (baryons with strange quarks) and nucleons are essential for the intrinsic properties of neutron stars. Whereas the interactions between nucleons ($pp$, $pn$, $nn$) have been extensively studied, the interactions between nucleons and hyperons ($NΛ$, $NΣ$, $NΞ$, $NΩ$, ...) are not well understood, due to the small amount of relevant data, limited by the scarcity of suitable hyperon sources. Here we point out and investigate a new high-quality source: hyperons produced in $pp$ collisions, such as $pp\to pK^+Λ$, $pKΣ$, $pKπΣ$, $pKKΞ$, $pKKKΩ$. At a fixed target experiment using proton beam with known momentum and liquid hydrogen target, $pp\to pK^+Λ$ can be produced copiously. By tagging $p$ and $K^+$, the flux and momentum of the $Λ$ can be determined precisely. By placing an additional target around the primary one, these $Λ$-s serve as an ideal source, enabling an unprecedentedly precise study of $Λ$ interactions with a wide range of targets. Similar methods can be used to obtain high-quality sources of other hyperons, such as $Σ$, $Ξ$ and $Ω$. These novel, high-statistics sources of hyperons with precisely known kinematics present new opportunities for applications in particle and nuclear physics, particularly in understanding the hyperon puzzle of neutron stars. We propose a new high-luminosity experiment with two nested concentric targets, optimized for such measurements. This concept can also be incorporated into existing experiments, such as HADES and CBM at FAIR, as well as proposed experiments, such as H-NS and HHaS at HIAF, by adding a second target without significant modification of the current detectors.

nucl-ex↗

arXiv2025

Discovery of XYZ particles at the BESIII Experiment

Charmonium is a bound state of a charmed quark and a charmed antiquark, and a charmoniumlike state is a resonant structure that contains at least a charmed quark-antiquark pair but has properties that are incompatible with a conventional charmonium state. The charmoniumlike states are also called XYZ particles to indicate their underlying nature is still unclear. The BESIII experiment has contributed significantly in the study of the XYZ particles, and here we review the discoveries of the Zc(3900), Zc(4020), and Zcs(3985) tetraquark states and the observations of several new vector charmoniumlike states at the BESIII experiment.

hep-ex↗

arXiv2025

Heavy quarkonia and new hadrons with two heavy quarks

We give a pedagogical introduction to heavy quarkonia -- bound states of a heavy quark and its antiquark (e.g., charmonium $c\bar{c}$, bottomonium $b\bar{b}$) -- as well as to the exotic hadrons containing two heavy quarks that have been discovered since 2003. The review covers the foundational discoveries ($J/ψ$ and $Υ$), basic properties, spectroscopy interpreted via potential models, production mechanisms at colliders, and decay modes. A significant focus is placed on the so-called ``$XYZ$" states -- particles like the $X(3872)$, $Y(4260/4230)$, $Z_c(3900)$, and $P_c$ -- whose properties defy conventional quark model expectations. These states, considered candidates for hybrids, multi-quark states, hadronic molecules, or hadroquarkonia, provide unprecedented probes of non-perturbative QCD and challenge our understanding of quark confinement and hadron formation. The chapter summarizes the current experimental landscape and highlights key open questions driving future research in hadron spectroscopy.

hep-ex↗

arXiv2024

Novel method for identifying the heaviest QED atom

The bound state of a $τ^+τ^-$ pair by the electromagnetic force is the heaviest and smallest QED atom. Since the discovery of the two lightest QED atoms more than 60 years ago, no evidence for the third one has been found. We demonstrate that the $J_τ$ ($τ^+τ^-$ atom with $J^{PC}=1^{--}$) resonance signal can be observed with a significance larger than $5σ$ including both statistical and systematic uncertainties, via the process $e^+e^-\to X^+ Y^- \slashed{E}$ ($X,\,Y=e$, $μ$, $π$, $K$, or $ρ$, and $\slashed{E}$ is the missing energy) with $1.5~{\rm ab^{-1}}$ data taken around the $τ$ pair production threshold. The $τ$ lepton mass can be measured in a precision of 2 keV with the same data sample. This is within one year's running time of the proposed super tau-charm factory or super charm-tau factory.

hep-ph↗

arXiv2024

Poles and Poltergeists in $e^+ e^- \to D \bar D$ Data

A recent report of $e^+ e^- \to D\bar D$ events by the BESIII Collaboration suggests the presence of a structure $R$ at 3900~MeV\@. We argue that this structure, called $G(3900)$ in the past, is not in fact due to a new $c\bar c$ resonance, but rather naturally emerges as a threshold enhancement due to the opening of the $D^*\bar D$ channel. We further find that the appearance of this structure does not require suppression because of a radial node in the $ψ(4040)$ wave function, although a node improves fit quality. The measured $e^+ e^-$ coupling of $ψ(4040)$ is found to be substantially smaller than previously estimated. In addition, we report new corrections to the measured cross section $σ(e^+ e^- \to D\bar D)$ at energies near $ψ(3770)$.

hep-ph↗

arXiv2023

New approach to finding invisible states in $e^+e^-$ annihilation and application to BESIII data

We compare precision $e^+e^-$ to $μ^+μ^-$ cross section measurements by BESIII in the E_cm =3.8-4.6 GeV range, to predictions based on measured R_had data. The consistency is poor (p-value <0.012). Allowing for resonance contributions not seen in R_had gives an excellent fit, with the state at 4421 MeV ( 4.6 sigma) giving insight into the psi(4415) and the 3.1 sigma structure at 4211 MeV, if confirmed, being a new, very narrow resonance. This analysis shows the power of precision $e^+e^-$ to $μ^+μ^-$ measurements to uncover or probe otherwise difficult to access states.

hep-ex↗

arXiv2023

Heavy Flavour Spectroscopy

The discovery of hadronic states beyond the conventional two-quark meson and three-quark baryon picture in the last two decades is one of the most amazing accomplishments in fundamental physics research. We review the experimental progress on the study of the exotic states (also known as the XYZ particles) beyond the conventional quark model. We give a general review and then focus on the lineshape measurement of the X(3872), observation of new decay modes of the Y(4230) and new vector charmoniumlike states Y(4500) and Y(4790), evidence for the neutral isospin partners of the charged charmoniumlike $Z_{cs}$ states, discoveries of the tetraquark state candidates with four different flavours or two-pairs of charm-anticharm quarks and the pentaquark states.

hep-ex↗

arXiv2022

Exotic states in the quarkonium sector

The discovery of hadronic states beyond the conventional two-quark meson and three-quark baryon picture in the last two decades is one of the most amazing accomplishments in fundamental physics research. Many experiments contributed to this field despite of the original goals of the design. We review the experimental progress on the study of the quarkoniumlike states -- states with at least one heavy quark-antiquark pair and possible light quarks, also known as XYZ states. We give a general review and then focus on the new experimental results on the X(3872) and its bottom-quark partner X_b, the X(3960), the Y(4260), Y(4500), Y(4660), and Y(10750), and the charged charmoniumlike Z_c and Z_{cs} states. The observations suggest that we did observe hadronic molecules and we also observed hadronic states with some other quark configurations. Possible further studies at the existing and future facilities are briefly discussed.

hep-ph↗

arXiv2022

Improved description of e^+e^- \to p\bar{p}π^0 cross section line shape and more stringent constraints on ψ(3770) and ψ(4230) \to p\bar{p}π^0

By using the cross sections of e^+e^- \to p\bar{p}π^0 measured at the center-of-mass energies from 3.65 to 4.60 GeV, we find that the line shape well agrees with pure continuum production parametrized by a power law function and the significance of both ψ(3770) and ψ(4230) \to p\bar{p}π^0 is less than 0.4σ. We set more stringent constraints on the charmless decays of the charmonium state, ψ(3770), and the charmoniumlike state, ψ(4230), to p\bar{p}π^0 than in previous measurements. The data are also used to estimate the cross sections of p\bar{p} \to π^0ψ(3770) and p\bar{p} \to π^0ψ(4230) that are essential for planning the data taking of the PANDA experiment.

hep-ph↗

arXiv2022

New puzzle in charmonium decays

By analyzing existing data on pseudoscalar charmonium decays, we obtain the ratio of the branching fractions of $η_c(2S)$ and $η_c$ decays into ten different final states with light hadrons. For the first time, we test the two existing theoretical predictions of these decays, and find that the experimental data are significantly different from both of them. The lack of observation of any decay mode with higher rate in $η_c(2S)$ than in $η_c$ decays suggests very unusual decay dynamics in pseudoscalar charmonium decays to be identified. We also report the first model-independent evaluation of the partial width of $η_c(2S)\to γγ$ ($2.21_{-0.64}^{+0.88}$ keV) and improved determination of that of $η_c\to γγ$ ($5.43_{-0.38}^{+0.41}$ keV). The latter shows a tension with the most recent lattice QCD calculation.

hep-ph↗

arXiv2021

New experimental results on light and heavy hadrons

We review the experimental progress on the study of light and heavy hadrons and focus on recent discoveries of the XYZ states, pentaquark states, $T_{cs}$ and $T_{cc}$ states in the heavy hadron sector, and on the $π_1(1600)$ and the states close to the $p\bar{p}$ threshold in the light hadron sector. The observations suggest that we did observe hadronic molecules and we also observed hadronic states with some other quark configurations.

hep-ex↗

arXiv2021

A cornucopia of antineutrons and hyperons from super J/psi factory for next-generation nuclear and particle physics high-precision experiments

In order to study the interactions and structure of various types of matter one typically needs to carry out scattering experiments utilizing many different particles as projectiles. Whereas beams of $e^\pm$, $μ^\pm$, $π^\pm$, $K^\pm$, proton, antiproton, and of various heavy ions have been produced and have enabled many scientific breakthroughs, beams of antineutrons, hyperons ($Λ$, $Σ$ and $Ξ$) and their antiparticles are typically not easy to obtain. Here we point out and investigate a new high-quality source of these particles: a super $J/ψ$ factory with capability of accumulating trillions of $J/ψ$ decays each year. In the relevant $J/ψ$ decays the desired particle is produced together with other final state particles that can be tagged. This allows accurate determination of the flux and momentum of the projectile, enabling unprecedented precision-study of the corresponding interactions with a broad range of targets. These novel high-statistics sources of baryons and antibaryons with precisely known kinematics open fresh opportunities for applications in particle and nuclear physics, including antinucleon-nucleon interaction, nonvalence $s\bar{s}$ component of the nucleon, (anti)hyperon-nucleon interaction, OZI violation, (multi-strange) hypernuclei, exotic light hadron spectroscopy and many others, as well as calibration of Monte Carlo simulation for hadronic and medical physics.

hep-ex↗

arXiv2021

Charmonium and Charmoniumlike States at the BESIII Experiment

Charmonium is a bound state of a charmed quark and a charmed antiquark, and a charmoniumlike state is a resonant structure that contains a charmed quark and antiquark pair but has properties that are incompatible with a conventional charmonium state. While operating at center-of-mass energies from 2 to 4.9 GeV, the BESIII experiment can access a wide mass range of charmonium and charmoniumlike states, and has contributed significantly in this field. We review BESIII results involving conventional charmonium states, including the first observation of M1 transition $ψ(3686) \to γη_c(2S)$ and the discovery of the $ψ_2(3823)$; and report on studies of charmoniumlike states, including the discoveries of the $Z_c(3900)$ and $Z_c(4020)$ tetraquark candidates, the resolution of the fine structure of the $Y(4260)$, the discovery of the new production process $e^+e^-\to γX(3872)$, and the uncovering of strong evidence for the commonality among the $X(3872)$, $Y(4260)$, and $Z_c(3900)$ states. The prospects for further research at BESIII and proposed future facilities are also presented.

hep-ex↗

arXiv2020

Hadronic cross section of $e^+e^-$ annihilation at bottomonium energy region

The Born cross section and dressed cross section of $e^+e^-$ to $b\bar{b}$ and the total hadronic cross section in $e^+e^-$ annihilation in the bottomonium energy region are calculated based on the Rb values measured by the BaBar and Belle experiments. The data are used to calculate the vacuum polarization factors in the bottomonium energy region, and to determine the resonant parameters of the vector bottomonium(-like) states, the Y(10750), Upsilon(5S), and Upsilon(6S).

hep-ph↗

arXiv2020

The $XYZ$ states: experimental and theoretical status and perspectives

The quark model was formulated in 1964 to classify mesons as bound states made of a quark-antiquark pair, and baryons as bound states made of three quarks. For a long time all known mesons and baryons could be classified within this scheme. Quantum Chromodynamics (QCD), however, in principle also allows the existence of more complex structures, generically called exotic hadrons or simply exotics. These include four-quark hadrons (tetraquarks and hadronic molecules), five-quark hadrons (pentaquarks) and states with active gluonic degrees of freedom (hybrids), and even states of pure glue (glueballs). Exotic hadrons have been systematically searched for in numerous experiments for many years. Remarkably, in the past fifteen years, many new hadrons that do not exhibit the expected properties of ordinary (not exotic) hadrons have been discovered in the quarkonium spectrum. These hadrons are collectively known as $XYZ$ states. Some of them, like the charged states, are undoubtedly exotic. Parallel to the experimental progress, the last decades have also witnessed an enormous theoretical effort to reach a theoretical understanding of the $XYZ$ states. Theoretical approaches include not only phenomenological extensions of the quark model to exotics, but also modern non-relativistic effective field theories and lattice QCD calculations. The present work aims at reviewing the rapid progress in the field of exotic $XYZ$ hadrons over the past few years both in experiments and theory. It concludes with a summary on future prospects and challenges.

hep-ex↗

arXiv2020

The BESIII Physics Programme

The standard model of particle physics is a well-tested theoretical framework, but there are still a number of issues that deserve further experimental and theoretical investigation. For quark physics, such questions include: the nature of quark confinement, the mechanism that connects the quarks and gluons of the standard model theory to the strongly interacting particles; and the weak decays of quarks, which may provide insights into new physics mechanisms responsible for the matter-antimatter asymmetry of the Universe. These issues are addressed by the Beijing Spectrometer III (BESIII) experiment at the Beijing Electron-Positron Collider II (BEPCII) storage ring, which for the past decade has been studying particles produced in electron-positron collisions in the tau-charm energy-threshold region, and has by now accumulated the world's largest datasets that enables searches for nonstandard hadrons, weak decays of the charmed particles, and new physics phenomena beyond the standard model. Here, we review the contributions of BESIII to such studies and discuss future prospects for BESIII and other experiments.

hep-ex↗