Motivated by the observation of the doubly charmed tetraquark $ T_{cc}(3875)^+ $ , we present a systematic study of doubly heavy tetraquarks ( $ T_{QQ'\bar{q}\bar{q}'} $ ) using heavy antiquark-diquark symmetry (HADS) within a constituent quark model. By calibrating model parameters to known hadron spectra and incorporating the effective mass formula, we predict the masses for 38 ground-state tetraquarks with $ cc $ , $ bb $ , and $ bc $ heavy quark pairs, including the non-strange, single-strange, and double-strange configurations with quantum numbers $ J^P = 0^+, 1^+ $ and $ 2^+ $ . Notably, we identify several stable states below the relevant meson-meson thresholds, particularly in the $ bb\bar{q}\bar{q}' $ sector. The explicit connection between the doubly heavy tetraquark and the heavy baryon spectra through HADS reduces model dependence and reveals the fundamental systematics in the heavy-quark hadron landscape.

China

Liu-Yu Zhang

Tian-Wei Wu

Yong-Liang Ma

Bridging doubly heavy tetraquark mass spectrum with heavy baryons utilizing heavy antiquark-diquark symmetry * The work of Tian-Wei Wu is supported by the National Natural Science Foundation of China (12405108). Yong-Liang Ma is supported in part by the National Science Foundation of China (NSFC) (12347103) and Gusu Talent Innovation Program (ZXL2024363)

The search for the Chiral Vortical Effect (CVE) in relativistic heavy-ion collisions is carried out by measuring azimuthal correlators for baryon pairs such as Λ and protons. Experimental results from the ALICE collaboration show significant separations in these correlator observables between baryon-baryon and baryon-antibaryon, however, the interpretation remains unclear. It is believed that background contributions from baryon production mechanisms play an important role. Using three phenomenological models, the Blast Wave, AMPT, and AVFD+UrQMD, we systematically investigate the background effects in Pb–Pb collisions at <math altimg='si3.svg'><msqrt><msub><mi>s</mi><mrow><mrow><mi mathvariant='normal'>N</mi></mrow><mi>N</mi></mrow></msub></msqrt></math> = 5.02 TeV. We demonstrate that local baryon conservation, as well as hadronic annihilation processes, can significantly influence the correlators. The feed-down contribution from secondary protons is also estimated. Our study provides a foundation for disentangling background mechanisms and further facilitates the search for the CVE.

Chunzheng Wang

Jie Wan

United States

Jinfeng Liao

Yugang Ma

Shuzhe Shi

Qiye Shou

Zhengqing Wang

Kegang Xiong

Song Zhang

Liang Zheng

Assessing background effects in search of the chiral vortical effect in relativistic heavy-ion collisions

In high-energy proton-proton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math>) collisions at the LHC, nonprompt charm hadrons, originating from beauty hadron decays, provide a valuable probe for beauty quark dynamics, particularly at low transverse momentum where direct beauty measurements are challenging. We employ a multiphase transport (AMPT) model of string melting version coupled with pythia8 initial conditions to study the beauty hadron and nonprompt charm hadron productions in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>. In this work, the beauty quark mass during the generation stage has been increased to reproduce the measured <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math> cross section, and a beauty flavor-specific coalescence parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msubsup><mrow><mi>r</mi></mrow><mrow><mi>B</mi><mi>M</mi></mrow><mrow><mi>b</mi></mrow></msubsup></mrow></math> is introduced to match LHCb measurements of beauty baryon-to-meson ratios. With these refinements, the AMPT model achieves a reasonable agreement with experimental data on beauty hadron yields and nonprompt charm hadron production from ALICE and LHCb. We present the transverse momentum and multiplicity dependence of nonprompt-to-prompt charm hadron ratios, providing new insights into the interplay between beauty quark production and the hadronization process. We emphasize that the multiplicity dependence of the nonprompt to prompt charm hadron productions can be useful to constrain the flavor dependences of the coalescence dynamics. This work establishes a unified framework for future studies of heavy quark transport and collective flow behavior in small collision systems.

Jialin He

Xinye Peng

Xiaoming Zhang

Studies of beauty hadron and nonprompt charm hadron production in pp collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msqrt><mrow><mi>s</mi></mrow></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math> within a transport model approach

Event shape measurements are crucial for understanding the underlying event and multiple-parton interactions (MPIs) in high energy proton-proton (pp) collisions. In this study, the Tsallis blast-wave model with independent non-extensive parameters for mesons and baryons was applied to analyze the transverse momentum spectra of charged pions, kaons, and protons in pp collision events at $ \sqrt{s}=13 $ TeV classified by event shape estimators such as relative transverse event activity, unweighted transverse spherocity, and flattenicity. Our analysis reveals consistent trends in the kinetic freeze-out temperature and non-extensive parameter across different collision systems and event shape classes. The use of diverse event-shape observables in pp collisions has significantly expanded the accessible freeze-out parameter space, enabling a more comprehensive exploration of its boundaries. Among these event shape classifiers, flattenicity emerges as a unique observable for disentangling hard process contributions from additive MPI effects, which helps isolate collective motion effects encoded by the radial flow velocity. Through the analysis of the interplay between event-shape measurements and kinetic freeze-out properties, we gain deeper insights into mechanisms responsible for flow-like signatures in pp collisions.

Zhongbao Yin

Extracting the kinetic freeze-out properties of high energy pp collisions at the LHC with event shape classifiers * Supported by the National Key Research and Development Program of China (2024YFA1610800), the National Natural Science Foundation of China (12205259, 12147101, 12275103, 12061141008), the Fundamental Research Funds for the Central Universities, China University of Geosciences(Wuhan) with G1323523064 and the Innovation Fund of Key Laboratory of Quark and Lepton Physics QLPL2025P01

In this work, we systematically investigate the jet associated identified hadron productions of pions, kaons, and protons based on the event topological separation method in proton-proton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math>) collisions at <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>13</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math> employing a multiphase transport model with pythia8 initial conditions. Enabling relative transverse event activity classifier <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi>T</mi></msub></math>, we analyze the transverse momentum (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math>) spectra and particle ratios in the jet aligned toward region and the underlying event contributions sensitive transverse region varying with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi>T</mi></msub></math>. The results indicate that a multi-phase transport model, incorporating both partonic and hadronic final-state interactions, provides a satisfactory description to the experimental data of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math> differential yields, particle ratios, and average transverse momentum of identified particles in both the toward and transverse regions across different event activity classes. By subtracting the underlying event contribution from the toward region using the transverse region hadron yield, we introduce the in-jet hadron productions to analyze the modifications to the jet itself. We find that the in-jet baryon to meson ratios reveal a sensitive dependence on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>R</mi><mi>T</mi></msub></math> driven by final-state interactions, leading to a unique crossing pattern at intermediate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>p</mi><mi>T</mi></msub></math>. This behavior can be regarded as a novel signature for probing jet medium interactions and energy loss effects in small collision systems.

Yuhao Peng

Yan Wu

Investigating jet-induced identified hadron production from the relative transverse activity classifier in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi><mi>p</mi></math> collisions at the LHC

In this work, we investigate the collective flow development in high energy proton proton (pp) collisions with a multiphase transport model (AMPT) based on PYTHIA8 initial conditions with a sub-nucleon structure. It is found that the PYTHIA8 based AMPT model can reasonably describe both the charged hadron productions and elliptic flow experimental data measured in pp collisions at $$\sqrt{s}=13$$ <math> <mrow> <msqrt> <mi>s</mi> </msqrt> <mo>=</mo> <mn>13</mn> </mrow> </math> TeV. By turning on the parton and hadron rescatterings in AMPT separately, we find that the observed collective flow in pp collisions is largely developed during the parton evolution, while no significant flow effect can be generated with the pure hadronic rescatterings. It is also shown that the parton escape mechanism is important for describing both the magnitude of the two-particle cumulant and the sign of the four-particle cumulants. We emphasize that the strong mass ordering of the elliptic flow results from the coalescence process in the transport model and can thus be regarded as unique evidence related to the creation of deconfined parton matter in high energy pp collisions.

Lian Liu

Zi-Wei Lin

Qi-Ye Shou

Zhong-Bao Yin

Disentangling the development of collective flow in high energy proton proton collisions with a multiphase transport model

We study the production of $$D^0$$ <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math> meson in p+p and p-Pb collisions using the improved AMPT model considering both coalescence and independent fragmentation of charm quarks after the Cronin broadening is included. After a detailed discussion of the improvements implemented in the AMPT model for heavy quark production, we show that the modified AMPT model can provide a good description of $$D^0$$ <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math> meson spectra in p-Pb collisions, the $$Q_{\textrm{pPb}}$$ <math> <msub> <mi>Q</mi> <mtext>pPb</mtext> </msub> </math> data at different centralities and $$R_{\textrm{pPb}}$$ <math> <msub> <mi>R</mi> <mtext>pPb</mtext> </msub> </math> data in both mid- and forward (backward) rapidities. We also studied the effects of nuclear shadowing and parton cascade on the rapidity dependence of $$D^{0}$$ <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math> meson production and $$R_{\textrm{pPb}}$$ <math> <msub> <mi>R</mi> <mtext>pPb</mtext> </msub> </math> . Our results indicate that using the same strength of the Cronin effect (i.e $$\delta $$ <math> <mi>δ</mi> </math> value) as that obtained from the mid-rapidity data leads to a considerable overestimation of the $$D^0$$ <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math> meson spectra and $$R_{\textrm{pPb}}$$ <math> <msub> <mi>R</mi> <mtext>pPb</mtext> </msub> </math> data at high $$p_{\textrm{T}}$$ <math> <msub> <mi>p</mi> <mtext>T</mtext> </msub> </math> in the backward rapidity. As a result, the $$\delta $$ <math> <mi>δ</mi> </math> is determined via a $$\chi ^2$$ <math> <msup> <mi>χ</mi> <mn>2</mn> </msup> </math> fitting of the $$R_{\textrm{pPb}}$$ <math> <msub> <mi>R</mi> <mtext>pPb</mtext> </msub> </math> data across various rapidities. This work lays the foundation for a better understanding of cold-nuclear-matter (CNM) effects in relativistic heavy-ion collisions.

Chao Zhang

Shusu Shi

Investigating $$D^0$$ <math> <msup> <mi>D</mi> <mn>0</mn> </msup> </math> meson production in p-Pb collisions at 5.02 TeV with a multi-phase transport model

The production of exotic hadron <math><mrow><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></mrow></math> in <math><mrow><mi>p</mi><mi>p</mi></mrow></math> collisions at <math><mrow><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>2.76</mn><mspace width="0.16em"></mspace><mi>TeV</mi></mrow></math> is investigated by the parton and hadron cascade model PACIAE in this work. In the simulation the final partonic state (quark matter, QM) and the final hadronic state (hadron matter, HM) are continuously processed and recorded. The <math><mrow><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></mrow></math> compact tetraquark state and loose molecular state are, respectively, coalesced and recombined in the QM and HM with the quantum statistical mechanics inspired dynamically constrained phase-space coalescence model. The formation time, velocity, and temperature of QM (tetraquark state) and HM (molecular state) are proposed as identifying criteria between the two states. Our results in transverse momentum spectrum and rapidity distribution, etc. show a significant discrepancy between the two states and confirm that they are also valuable criteria identifying the <math><mrow><mi>X</mi><mo>(</mo><mn>3872</mn><mo>)</mo></mrow></math> compact tetraquark state or molecular state.

Zhi-Lei She

An-Ke Lei

Yu-Liang Yan

Dai-Mei Zhou

Wen-Chao Zhang

Hua Zheng

Yi-Long Xie

Gang Chen

Ben-Hao Sa

Identifying an <math><mtext>X(3872)</mtext></math> tetraquark state versus a molecular state by formation time, velocity, and temperature in relativistic nuclear collisions

We develop a parton and hadron cascade model paciae 3.0 based on pythia 6.428 and the paciae 2.2 program series for nuclear collisions. The original simulation framework composed of the initial partonic state, the partonic rescattering stage, hadronization stage, and the hadronic rescattering stage, is renamed a C-simulation framework for high-energy (<math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>≥</mo><mn>3</mn></mrow></math> GeV) nuclear collisions. A B-simulation framework without partonic rescattering is designed for the high-energy nuclear collisions, too. In addition, an A-simulation framework is introduced for the low-energy (<math><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo>&lt;</mo><mn>3</mn></mrow></math> GeV) nuclear collisions, which is developed in the hadronic degree of freedom only. In the C-simulation framework, the parton-parton inelastic-scattering processes are implemented, the single-string structure and multiple-string interaction mechanisms are proposed to investigate the strangeness enhancement, and the phenomenological coalescence hadronization model is modified. With the model, the particle yield, transverse momentum distribution, and rapidity distribution resulted from A-simulation framework well reproduce the data measured at the FOPI and E895 experiments, and the results from B- and C-simulation frameworks are well consistent with the data measured at the energies of the BNL Relativistic Heavy Ion Collider and the Large Hadron Collider.

Gao-Chan Yong

Xiao-Mei Li

Xu Cai

Introduction to the parton and hadron cascade model PACIAE 3.0

It has been a challenge to understand the experimental data on both the nuclear modification factor and elliptic flow of <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> mesons in p−Pb collisions at LHC energies. In this work, we study these collisions with an improved multi-phase transport model. By including the independent fragmentation and a significant Cronin effect (i.e., transverse momentum broadening) for charm quarks, we provide the first simultaneous description of the <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> meson <math><msub><mrow><mi>R</mi></mrow><mrow><mi>pA</mi></mrow></msub></math> and <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math> data at <math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub><mo>≤</mo><mn>8</mn></math> GeV/c. The model also reasonably describes the <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> meson <math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> spectra and the low-<math><msub><mrow><mi>p</mi></mrow><mrow><mi>T</mi></mrow></msub></math> charged hadron spectra, <math><msub><mrow><mi>R</mi></mrow><mrow><mi>pA</mi></mrow></msub></math> and <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math>. Our results show that both parton interactions and the Cronin effect are important for the <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> meson <math><msub><mrow><mi>R</mi></mrow><mrow><mi>pA</mi></mrow></msub></math>, while parton interactions are mostly responsible for the <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> meson <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math>. It is thus essential to include the Cronin effect for the simultaneous description of the <math><msup><mrow><mi>D</mi></mrow><mrow><mn>0</mn></mrow></msup></math> meson <math><msub><mrow><mi>R</mi></mrow><mrow><mi>pA</mi></mrow></msub></math> and <math><msub><mrow><mi>v</mi></mrow><mrow><mn>2</mn></mrow></msub></math>. This work implies that the Cronin effect could also be important for heavy hadrons in large systems.

Resolving the And Puzzle of Mesons in −Pb collisions at the LHC