Nuclear Theory·nucl-th

Tuesday·March 31, 2026

30 papers—12 primary·18 cross-listed

13
The Physics and Prospects of Super-Tau Charm Factories
Alexey A. Petrov🇺🇸 · Yangheng Zheng🇨🇳
The proposed Super tau-charm factories are a powerful new class of high-luminosity electron-positron colliders operating in the center-of-mass energy range between 2 and 7 GeV, a region that spans thresholds for tau leptons, open-charm hadrons, charmonium and charmonium-like states, hyperons, and light hadrons. With unprecedented data samples, threshold kinematics, and quantum-coherent production, these facilities offer unique opportunities to advance precision tests of the Standard Model and to search for physics beyond it. In this review, we examine the physics prospects of the Super Tau-Charm Facility, focusing on precision charm measurements, CP violation in mesons and baryons, tau lepton properties and rare decays, and nonperturbative QCD phenomena such as hadronization, spectroscopy, and time-like form factors. We also discuss the experimental landscape, technological challenges, and complementarity with existing and planned facilities. Together, these capabilities position super tau-charm factories at the forefront of the precision frontier in particle physics.
↳ hep-phhep-exnucl-exnucl-th2 citations
14
Dynamical tidal response of neutron stars as a probe of dense-matter properties
Abhishek Hegade K. R.🇺🇸 · Yumu Yang🇺🇸 · Mauricio Hippert🇧🇷 · Jacquelyn Noronha-Hostler🇺🇸 · Jorge Noronha🇺🇸 · Nicolás Yunes🇺🇸
Dynamical tidal deformations play a crucial role in the gravitational waves emitted by binary neutron star systems during their late inspiral. In this work, we systematically explore how relativistic (dynamical and dissipative) tidal deformations depend on the internal structure of a neutron star using two analytic classes of equations of state. The first class is a nucleonic model that is parameterized by nuclear physics observables, such as the symmetry energy coefficients and saturation properties. The second class is a toy model of quark matter, the MIT bag model. To model tidal dissipation, we self-consistently include contributions from weak-interaction-driven bulk-viscous effects while considering both the nucleonic and the quark-matter equations of state. The dissipative tide is sensitive to frequency and temperature, but its magnitude, as predicted by weak-interaction-driven bulk-viscous effects, is too small (within the equation-of-state models studied here) to be detectable by current or future observations. However, we find that the (conservative) dynamical tidal response function depends strongly on the slope of the symmetry energy and on higher-order coefficients of the symmetry energy. This indicates that the (conservative) dynamical tide is sensitive to higher-order coefficients, motivating a dedicated parameter-estimation study to assess how well they can be constrained.
↳ gr-qcastro-ph.HEnucl-thPRD(2026)·9 citations
15
Density screening effects in the NJL model: Chiral condensate, speed of sound, and the Critical End Point
Alejandro Rosas Díaz🇲🇽 · Alfredo Raya🇲🇽 · C. A. Vaquera Araujo🇲🇽 · S. Hernández-Ortiz🇲🇽
The phase diagram of Quantum Chromodynamics (QCD) remains a central topic in high-energy physics. At high temperature and low baryochemical potential, the chiral transition is experimentally observed and theoretically explored to be a smooth crossover, while at high densities, a first-order phase transition is theoretically expected in lack of direct experimental evidence. The search for the Critical End Point (CEP), where both regimes meet, is one of the main objectives of heavy-ion experiments at FAIR and NICA. In this work, we explore the QCD phase diagram structure using the Nambu--Jona-Lasinio (NJL) model, incorporating medium screening effects through an effective coupling $G (T, μ)$ for $μ ≫ T \sim 0$ . We apply a consistent regularization scheme and Sommerfeld expansion to include low thermal and large density corrections in the gap equation. Our numerical analysis focuses on the behavior of the chiral condensate, the dynamical quark mass, and the speed of sound. We find that screening effects shift the posible position of the CEP and modify the nature of the chiral transition. These findings provide theoretical support for ongoing experimental searches and may have implications for the physics of compact stars.
↳ hep-phhep-thnucl-th0 citations
16
Signatures from pion condensation and lepton flavor asymmetries in the cosmological gravitational wave background
Osvaldo Ferreira🇧🇷 · Eduardo S. Fraga🇧🇷 · Jürgen Schaffner-Bielich🇩🇪
Large lepton flavor asymmetries at the QCD epoch could generate a pion condensation phase in the early Universe. For large enough tau lepton flavor asymmetries, the speed of sound can exceed the conformal value, leaving a distinctive imprint on the low-frequency gravitational wave (GW) spectrum from causal sources. Beyond probing the formation of a pion condensation phase, the detection or non-detection of this signature in future Pulsar Timing Arrays (PTAs) datasets would provide a novel constraint on lepton asymmetries in the early Universe. We determine the corresponding GW spectrum and its tilt, comparing them with the standard case of vanishing lepton asymmetry. Finally, we discuss the implications for the stochastic GW background reported by PTAs, using the NANOGrav 15-year dataset.
↳ hep-phastro-ph.COnucl-th2 citations
17
Why Stellar Sequences Turn Over: Fixed Points, Instability, and Equation-of-State Universality
Isaac Legred🇺🇸 · Nicolas Yunes🇺🇸
We reformulate the stellar structure equations in the language of dynamical systems and show that the maximum mass of stellar sequences arises from the existence of a fixed point in the relativistic regime. In an appropriate representation of the Tolman-Oppenheimer-Volkoff equations, this fixed point becomes manifest and is directly associated with the turnover of the mass-radius curve. The existence of a fixed point implies an effective reduction in dimensionality near the onset of instability, which provides a simple explanation for several equation-of-state-insensitive relations and predicts new ones. In the weakly relativistic limit, we identify a complementary universal structure shared by stellar sequences at their maximum mass, which we term the "compressible limit," and derive distinct universal relations governing the maximum mass in the Newtonian and post-Newtonian regimes. Combining these theoretical results with current astrophysical constraints, we show that the J0740+6620 pulsar is unlikely to lie near the Tolman-Oppenheimer-Volkoff maximum mass unless the equation of state exhibits a strong first-order phase transition at densities just above its central density.
↳ astro-ph.HEgr-qcnucl-th1 citation
18
Late-time attractors in relativistic spin hydrodynamics in Gubser flow
Gen-Hui Li🇨🇳 · Xiang Ren🇨🇳 · Dong-Lin Wang🇨🇳 · Shi Pu🇨🇳
We investigate the late-time asymptotic solutions and attractor structure of the spin density in minimal causal spin hydrodynamics in Gubser flow. After deriving the differential equation governing the spin density, we obtain its late-time asymptotic solutions and identify both attractors and repellers in the corresponding numerical solutions. We then map these solutions back to flat Minkowski space and find parameter regions where the spin density exhibits a power-law decay. We further show that, when the characteristic length scale of the system is much larger than the proper time, several components of the spin density can decay as slowly as conventional thermodynamic variables in relativistic hydrodynamics. In this regime, the spin density behaves as a hydrodynamic mode governed by the late-time scaling laws of the flow.
↳ hep-phhep-thnucl-th2 citations
19
Vorticity-induced modifications of chemical freeze-out in heavy-ion collisions
Nandita Padhan🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Arghya Chatterjee🇮🇳 · Raghunath Sahoo🇮🇳
We investigate the influence of global rotation on the chemical freeze-out parameters in ultra-relativistic heavy-ion collisions. Within the framework of the hadron resonance gas (HRG) model, the freeze-out parameters are determined using commonly employed freeze-out criteria, namely the fixed energy per particle and the scaled entropy density, extended here to include rotational effects. We find that the presence of rotation leads to a systematic shift of the chemical freeze-out curve toward lower temperatures in the $T - μ_{B}$ phase diagram. The behavior of the electric charge and strangeness chemical potentials in the presence of rotation is also analyzed, providing the first systematic study of their rotational dependence within the HRG framework. Furthermore, we examine the impact of rotation on experimentally relevant observables, including hadron yield ratios and susceptibility ratios of conserved charges. Our results show that while particle yield ratios exhibit noticeable sensitivity to rotation, the conventional cumulant ratios remain comparatively less affected. This indicates that hadronic yield ratios may provide a more suitable observable for estimating the magnitude of rotational effects generated in heavy-ion collisions.
↳ hep-phhep-exhep-thnucl-ex+1PLB(2026)·3 citations
20
Probe charmonium-nucleon interactions in high energy proton-proton collisions
Jiaxing Zhao🇩🇪 · Taesoo Song🇩🇪 · Joerg Aichelin🇫🇷 · Elena Bratkovskaya🇩🇪 · Pol Bernard Gossiaux🇫🇷 · Klaus Werner🇫🇷
We investigate charmonium production and the charmonium-nucleon correlation function in pp collisions using the EPOS4+CATS framework. For the first time, the emission source of charmonium-proton pairs is dynamically generated and found to be non-Gaussian. This enables a femtoscopic extraction of the charmonium-proton interaction directly from experimental correlation functions. Both ground and excited charmonium states are included. We found that the excited states induce sizable uncertainties even negative in the observed prompt $J / ψ$ -proton correlation through feed-down effects, reflecting their stronger interactions.
↳ hep-phnucl-th1 citation
21
Isolation of photon-nuclear interaction backgrounds in the search for the chiral magnetic effect in relativistic heavy-ion collisions
Jing Gu🇨🇳 · Jinhui Chen🇨🇳 · Jie Zhao🇨🇳
The chiral magnetic effect (CME) in relativistic heavy-ion collisions originates from a chirality imbalance among quarks within metastable QCD vacuum domains and may be linked to $C P$ violation, which is believed to play a crucial role in the matter-antimatter asymmetry of the universe. Over the past two decades, extensive experimental efforts at RHIC and the LHC have been devoted to the search for evidence of the CME. Recent advances have greatly improved our understanding of background contributions that can mimic CME-like signals. In particular, analyses utilizing techniques designed to suppress flow-related backgrounds indicate that the CME signal at RHIC, if present, is small. To further investigate potential background sources, particularly those associated with strong electromagnetic fields, we estimate the contribution from coherent photon-nuclear interactions. These interactions are driven by intense electromagnetic fields produced in ultrarelativistic heavy-ion collisions, with cross sections that scale with the field strength. Notably, the polarization of the incident photons is aligned with the electric field, which is oriented along the impact parameter direction and perpendicular to the magnetic field. Consequently, such processes can generate charge-dependent correlations that mimic key features of the CME signal, yet originate from different physics mechanisms and are distinct from flow-induced backgrounds. In this study, we quantitatively assess the influence of these coherent photon-nuclear interactions on the precision measurement of the CME, aiming to improve the separation of the genuine CME signal from these background contributions.
↳ hep-phhep-exnucl-exnucl-thPRC(2026)·0 citations
22
Magnetic moments of open bottom--charm molecular pentaquark octets
Halil Mutuk🇹🇷 · Xian-Wei Kang🇨🇳
We present a comprehensive theoretical investigation of the magnetic moments of open heavy-flavor molecular pentaquarks with quark compositions $b c ˉ q q q$ and $c b ˉ q q q$ (where $q = u, d, s$ ). Employing a molecular picture in which the pentaquarks are treated as S-wave bound states of a heavy baryon and a meson, we systematically construct the complete spin--flavor wavefunctions for the two distinct SU(3) $_{f}$ octet representations, $8_{1 f}$ and $8_{2 f}$ , arising from symmetric and antisymmetric light-diquark configurations, respectively. Within the framework of the constituent quark model, we calculate the magnetic moments of spin-parity configurations, $J^{P} = \frac{1}{2}^{-} (\frac{1}{2}^{+} \otimes 0^{-})$ and $J^{P} = \frac{1}{2}^{-}, \frac{3}{2}^{-} (\frac{1}{2}^{+} \otimes 1^{-})$ , for each member of the $b c ˉ$ and $c b ˉ$ octets. Our results reveal a striking hierarchy: in the $8_{2 f}$ representation, the $\frac{1}{2}^{+} \otimes 0^{-}$ states exhibit near-universal magnetic moments ( $μ \approx - 0.062 μ_{N}$ for $b c ˉ q q q$ and $μ \approx + 0.362 μ_{N}$ for $c b ˉ q q q$ ), as a direct consequence of the spin-singlet light-diquark that suppresses light-quark contributions. In contrast, the $8_{1 f}$ representation shows a broad spectrum of values with frequent sign changes, reflecting the active role of the symmetric light-diquark. The clear differences between the $b c ˉ$ and $c b ˉ$ families demonstrate explicit heavy-quark flavor symmetry breaking in electromagnetic observables. These predictions provide a detailed set of electromagnetic benchmarks that can serve as discriminants for the internal flavor structure and spin configuration of future experimentally observed open heavy-flavor pentaquarks, offering valuable guidance for ongoing and future searches at facilities such as LHCb and Belle II.
↳ hep-phhep-exhep-latnucl-ex+1PLB(2026)·3 citations
23
Full energy fraction and angular dependence of medium-induced splittings in the large- $N_{c}$ limit
Carlota Andres🇫🇷 · Fabio Dominguez🇫🇷
Jets produced in relativistic heavy-ion collisions are modified by their interactions with the quark-gluon plasma (QGP), making jet substructure observables sensitive probes of QGP dynamics. A quantitative description of these modifications requires understanding how the medium affects elementary parton splittings with full dependence on both their energy fraction $z$ and splitting angle $θ$ , beyond the widely used soft emitted-gluon approximation. Here, we study medium-induced $1 \to 2$ splittings double-differential in $z$ and $θ$ , with full resummation of multiple scatterings, and show that in the large- $N_{c}$ limit and under the harmonic oscillator (HO) approximation, all path integrals can be evaluated analytically for any splitting channel, providing a computationally efficient semi-analytical result. We also revisit the semi-hard approximation (SHA), extending it to include leading corrections in inverse powers of the partons energies, which we denote the improved semi-hard approximation (ISHA), and assess its validity through a comparison with the large- $N_{c}$ -HO results. Our analysis shows that while the SHA is found to be unreliable across most of phase space, even for high-energy emitters, the ISHA provides a robust approximation for splittings where all partons are sufficiently energetic.
↳ hep-phnucl-th4 citations
24
Combined analysis of the data on cross sections and spin density matrix elements for $K^{*} Σ$ photoproduction reactions
Ai-Chao Wang🇨🇳 · Neng-Chang Wei🇨🇳 · Fei Huang🇨🇳
In our earlier work [Phys. Rev. C \textbf{98}, 045209 (2018)], we analyzed the differential cross-section data from the CLAS Collaboration for the reactions $γ p \to K^{*+} Σ^{0}$ and $γ p \to K^{* 0} Σ^{+}$ using an effective Lagrangian approach. We found that a satisfactory description of the data required the inclusion of the $s$ -channel $Δ (1905) 5/ 2^{+}$ resonance, in addition to $t$ -channel exchanges of $K$ , $κ$ , and $K^{*}$ , $s$ -channel contributions from nucleons ( $N$ ) and $Δ$ , $u$ -channel exchanges of $Λ$ , $Σ$ , and $Σ^{*}$ , and a generalized contact term. In the present work, we extend our analysis to incorporate the data on spin density matrix elements from the LEPS Collaboration for the $γ p \to K^{* 0} Σ^{+}$ reaction at photon energies $E_{γ} = 1.85$ -- $2.96$ GeV. Our goal is to impose more stringent constraints on the theoretical model and obtain a more reliable understanding of the reaction mechanisms. We obtain two fits that describe the experimental data equally well. In both fits, the $Δ (1905) 5/ 2^{+}$ resonance plays an important role. However, the contribution from $t$ -channel $κ$ exchange is significant in one fit but negligible in the other. This finding contradicts earlier claims in the literature that the LEPS parity spin asymmetry $P_{σ}$ data support a dominant role of $κ$ exchange in $γ p \to K^{* 0} Σ^{+}$ . We also present predictions for $P_{σ}$ at $E_{γ} = 8.5$ GeV, which may help clarify whether $κ$ exchange is indeed dominant in this reaction.
↳ hep-phnucl-thPRC(2026)·1 citation
25
The force of attraction between nucleons due to vacuum fluctuation
Anupam Ghosh🇮🇳
We investigate quantum vacuum interactions arising from the zero-point fluctuations of a spatially confined massive scalar field. Deriving analytical expressions for the planar interaction energy and vacuum pressure, we identify a fundamental transition from the canonical power-law scaling of massless fields to a distinct quantum saturation regime. We prove that in the macroscopic limit, where the boundary separation far exceeds the field's Compton wavelength ( $a ≫ λ_{c}$ ), the interaction energy does not vanish; instead, it asymptotes to a persistent constant, $- ℏ c / (24 π λ_{c}^{3})$ . This reveals a cohesive zero-point energy reservoir inherent to massive vacua. Applying this formalism to the femtometer scale of the deuteron ( $^{2}$ H) nuclei, we demonstrate that confining massive pion fluctuations generates an attractive force between nucleons.
↳ hep-phhep-thnucl-thquant-ph0 citations
26
Heavy-Flavor Fragmentation from HF-NRevo: Status, Prospects, and Intrinsic Charm
Francesco Giovanni Celiberto🇪🇸 · Francesca Lonigro🇪🇸
We report on recent developments of the Heavy-Flavor Non-Relativistic evolution (HF-NRevo) scheme, a framework designed to describe heavy-hadron formation through leading-power fragmentation at moderate and large transverse momentum. The approach combines short-distance inputs obtained from next-to-leading-order NRQCD calculations with collinear scale evolution in a variable-flavor-number scheme, ensuring a consistent treatment of heavy-flavor thresholds and partonic hierarchies. Within this setup we have constructed the NRFF1.0 family of fragmentation functions for $S$ -wave heavy quarkonia in their leading NRQCD Fock states. We discuss prospective applications of the HF-NRevo framework in the heavy-ion environment, where it can provide a perturbative baseline for investigating medium-induced modifications of heavy-flavor fragmentation. Its explicit treatment of partonic channels and heavy-flavor thresholds makes it particularly suitable for exploring jet-quenching sensitivity, energy-loss mechanisms, and the emergence of medium-modified fragmentation patterns in the quark-gluon plasma. The HF-NRevo scheme has also been extended to the exotic sector through the TQ4Q1.x and newly released TQ4Q2.0 fragmentation sets, which describe the formation of fully heavy tetraquarks in multiple quantum configurations. These developments open a novel pathway to study quarkoniumlike states and to probe the intrinsic charm content of the proton in forward hadron-collision environments. Altogether, this program broadens the phenomenological reach of heavy-flavor fragmentation studies at the HL-LHC and future collider facilities, opening access to previously unexplored aspects of QCD and potential portals to New Physics.
↳ hep-phhep-exhep-thnucl-ex+1PoS(2026)·4 citations
27
Probing excited-state quantum phase transitions with trapped cold ions
Marek Kuchař · Michal Macek
We propose concrete protocols to realize quantum criticality due to excited-state quantum phase transitions (ESQPTs) experimentally in presumably the simplest and most resilient system involving a single trapped ion oscillating in a radio-frequency Paul trap. We identify a specific class of excited states of the Extended Rabi Model (ERM) Hamiltonian, which occur between two critical ESQPT energies of the model in its (anti)Jaynes-Cummings superradiant phase. Properties of these states motivate the definition of several ESQPT witness observables. We study their critical scaling behaviors as well as various distinct state evolutions by driving the system across the quantum criticalities by changing the qubit-phonon coupling strength linearly in time at different finite rates. A mapping of the theoretical control parameters of the ERM to the experimental parameters of a trapped ion setup is provided, and simulations are performed for values referencing existing state-of-the-art setups, addressing both unitary state evolutions as well as relevant open-system corrections.
↳ quant-phcond-mat.stat-mechnucl-th0 citations
28
Hadron Structure from lattice QCD in the context of the Electron-Ion Collider
Constantia Alexandrou (University of Cyprus & The Cyprus Institute)🇨🇾
Hadron structure calculations using lattice Quantum Chromodynamics (QCD) have advanced significantly in recent years. Results for charges, form factors, and lower Mellin moments can be obtained to high precision, generalized parton distributions can now be computed either directly or reconstructed from moments, and transverse-momentum-dependent distributions can be accessed through direct lattice calculations. Together, these quantities provide detailed and complementary insights into the internal structure of hadrons. These theoretical developments are highly relevant to the experimental program of the Electron-Ion Collider (EIC) and of other facilities. We review the most pertinent lattice QCD results for hadron structure that inform the EIC scientific agenda, with particular emphasis on the pion, kaon, and nucleon.
↳ hep-lathep-phnucl-th5 citations
29
Hadron spectra and thermodynamics for all quark flavors from a universal Hagedorn temperature
Michał Marczenko🇵🇱 · Larry McLerran🇺🇸 · Krzysztof Redlich🇵🇱
We show that hadrons in QCD follow a spectrum determined by string dynamics characterized by a universal Hagedorn temperature linked to the string tension. While this behavior was recently established for light hadrons and glueballs, we demonstrate that the same dynamics describes the heavy-flavor sector. After separating the current quark masses, the resulting spectrum reproduces lattice QCD thermodynamics of charmed hadrons and the observed spectra of hadrons across quark flavors without additional parameters. These results reflect the universal confining dynamics of QCD through the string tension.
↳ hep-phnucl-th0 citations
30
Charge-Dependent Directed Flow in Symmetric Nuclear Collisions
Vipul Bairathi🇨🇱 · Kishora Nayak🇮🇳
The directed flow ( $v_{1}$ ) of identified hadrons ( $π^{\pm}, K^{\pm}, p, p ˉ, ϕ, Λ$ , and $Λ ˉ$ ) is studied in symmetric nuclear collisions (O+O, Cu+Cu, Ru+Ru, Au+Au, and U+U) at $s_{N N} = 200$ GeV using the string-melting version of a multiphase transport model with improved quark coalescence. The mid-rapidity $v_{1}$ -slope ( $d v_{1} / d y$ ) and its charge-dependent splitting ( $Δ d v_{1} / d y$ ) between particles and anti-particles are investigated as a function of nuclear mass number ( $A$ ) and collision centrality in both low- $p_{T}$ (0.2 $-$ 2.0 GeV/ $c$ ) and high- $p_{T}$ (2.0 $-$ 5.0 GeV/ $c$ ) regions. At low- $p_{T}$ , the $v_{1}$ -slope shows weak system-size dependence, while at high- $p_{T}$ strong system-size dependence is found and it becomes negative with nuclear mass number, reflecting the hard-soft asymmetry in particle production. The charge-dependent splitting $Δ d v_{1} / d y$ reveals a striking baryon-meson dichotomy: baryon pairs ( $p - p ˉ$ and $Λ - Λ ˉ$ ) exhibit significant splitting that grows with system size, whereas meson pairs ( $π^{+} - π^{-}$ and $K^{+} - K^{-}$ ) show minimal splitting. The effect of final state hadronic interactions on the $v_{1}$ -slope is found to be negligible confirming that it is primarily generated during the partonic phase and coalescence process. A comparison of the AMPT results with measurements from the STAR experiment at RHIC in Au+Au collisions establish the transported quark contribution as a baseline for the observed charge-dependent $v_{1}$ splitting, on top of which electromagnetic field effects must be considered.
↳ hep-phnucl-thJ.Phys.G(2026)·0 citations

Affiliations

first authorsco-authorsvia INSPIRE