Nuclear Theory·nucl-th

Wednesday·August 12, 2026

13 papers—2 primary·11 cross-listed

01
Nucleon electromagnetic form-factors in a minimal Gari-Krümpelmann model including the explicit two-pion continuum
Wulf Krümpelmann🇩🇪 · Yong-Hui Lin🇨🇳 · Ulf-G. Meißner🇩🇪
The Gari--Krümpelmann (GK) model provided one of the first semiphenomenological descriptions of the electromagnetic nucleon form-factors over a wide range of momentum transfer. It combined vector-meson dominance at low and intermediate momentum transfer with perturbative-QCD constraints at large momentum transfer. The present work extends this framework by including the dispersive two-pion continuum explicitly in the isovector channel. The two-pion contribution is taken from modern dispersive analyses and embedded into the intrinsic high- $Q^{2}$ structure of the GK ansatz. The physical $ρ$ dynamics is then interpreted as part of the correlated two-pion spectral function. The direct coupling terms remain essential for the transition to the asymptotic regime. This gives a cleaner separation between long-range continuum dynamics, coherent vector-meson contributions, and direct quark-current dynamics. With just 5 parameters, we can describe the large body on form-factor data and differential cross sections from electron-proton scattering in the space-like region.
nucl-thhep-exhep-phnucl-ex0 citations
02
Laser spectroscopy illuminates the $N = 32$ shell closure
Tim E. Lellinger🇩🇪 · Liss V. Rodriguez🇩🇪 · Patrick Muller🇩🇪 · Osama Ahmad🇧🇪 · Mark L. Bissell🇨🇭 · Klaus Blaum🇩🇪 · Emily Burbach🇩🇪 · Bradley Cheal🇬🇧 · Till Fabritz🇩🇪 · Ronald F. Garcia Ruiz🇺🇸 · Matthias Heinz🇺🇸 · Jack Hughes🇬🇧 and 20 other authors
Atomic nuclei are strongly correlated quantum many-body systems, and how their shell structure evolves with increasing neutron excess remains a central open question in nuclear physics. Calcium isotopes are an ideal testing ground: alongside the traditional magic numbers $N = 20, 28$ , new shell closures have been proposed at $N = 32, 34$ ( $^{52, 54} Ca$ ). While the charge radius rises rapidly towards $N = 32$ , further moments and radii in the isotopic chain have remained inaccessible due to the low production yield of a few ions per second. Here we apply a highly sensitive collinear laser spectroscopy technique, which reveals a strikingly simple behaviour: adding one neutron to $^{52} Ca$ yields a pure single-particle magnetic dipole moment in $^{53} Ca$ , while the charge-radius slope towards $^{54} Ca$ exceeds that towards $^{52} Ca$ . This provides strong evidence for a robust $N = 32$ shell closure and stringently constrains nuclear structure models.
nucl-thphysics.atom-ph1 citation
03
Ground-State Energy Estimation of HeH $^{+}$ , ArH $^{+}$ , and H $_{2}$ O via Sample-Based Quantum Diagonalization
Jubin Park🇰🇷 · Chae-Hyun Yoon🇰🇷 · Minkyu Lee🇰🇷 · Myung-Ki Cheoun🇰🇷
Accurate ground-state energies are essential for understanding molecular structure, chemical bonding, and reaction energetics in quantum chemistry. In this work, we investigate the ground-state properties of the molecular systems HeH $^{+}$ , ArH $^{+}$ , and H $_{2}$ O using Sample-Based Quantum Diagonalization (SQD), a hybrid quantum-classical framework designed for near-term quantum devices. Unlike variational approaches such as VQE, which require deep parameterized circuits and repeated expectation-value measurements, SQD reconstructs a low-energy determinant subspace directly from measured bitstrings. For the present calculations, bitstrings were generated on IBM quantum hardware using shallow local unitary cluster Jastrow (LUCJ) circuits whose parameters were constructed from the $t_{1}$ and $t_{2}$ amplitudes of coupled-cluster singles and doubles (CCSD) calculations based on restricted Hartree--Fock (RHF) references. From these samples, we compute ground-state potential-energy curves of HeH $^{+}$ , ArH $^{+}$ , and H $_{2}$ O with the 6-31G and cc-pVDZ basis sets. For all three systems, the SQD results obtained with the cc-pVDZ basis closely follow the corresponding same-basis CCSD energies and reproduce the equilibrium-region trends of the potential-energy curves. HeH $^{+}$ and ArH $^{+}$ were chosen as simple yet astrophysically important molecular-ion benchmarks, while H $_{2}$ O was included as a representative polyatomic molecule to assess the applicability of SQD beyond diatomic ionic systems. At the adopted equilibrium geometries, the deviations from the same-active-space CASCI references are 0.00, 2.51, and 6.34 mHa for HeH $^{+}$ , ArH $^{+}$ , and H $_{2}$ O, respectively. These results demonstrate the feasibility of hardware-assisted SQD for the present benchmark systems and motivate further studies of its accuracy and computational scaling for larger molecular active spaces.
↳ physics.chem-phnucl-th0 citations
04
Extraction of baryon number susceptibilities at finite density from heavy-ion collisions
Grégoire Pihan🇺🇸 · Roman Poberezhniuk🇺🇸 · Volodymyr A. Kuznietsov🇺🇸 · Volodymyr Vovchenko🇺🇸
We present, to our knowledge, the first Bayesian extraction of baryon number susceptibilities of QCD matter at finite baryon density from heavy-ion collision data on proton number cumulants. The framework embeds arbitrary equation-of-state susceptibilities $χ_{n}^{B}$ into realistic hydrodynamic particlization hypersurfaces through maximum-entropy freeze-out, maps the resulting (anti)baryon fluctuations onto protons, applies the experimental kinematic acceptance, and accounts for exact baryon number conservation. Applying the framework to measurements of (net-)proton number fluctuations in 0--5\% central Au-Au collisions from the RHIC Beam Energy Scan in the collider mode, we extract, at each collision energy, the second-order susceptibility normalized by the hadron resonance gas value, $χ_{2}^{B} / χ ˉ_{2}^{B}$ , and the higher-order susceptibility ratios $χ_{3}^{B} / χ_{1}^{B}$ and $χ_{4}^{B} / χ_{2}^{B}$ . We obtain tight constraints on $χ_{2}^{B}$ , with extracted values in quantitative agreement with lattice QCD based estimates along the chemical freeze-out line for $μ_{B} ≲ 300$ ~MeV. At larger $μ_{B}$ , the extracted values indicate an enhancement of baryon number fluctuations relative to the noncritical lattice-based extrapolation and HRG baseline considered here. The third- and fourth-order susceptibilities are only weakly constrained. In particular, we find that the observed nonmonotonic collision-energy dependence of the proton factorial cumulant ratio $C^_{3} / C^_{1}$ can be described without irreducible three- or four-baryon correlations. This behavior emerges from the interplay between the energy dependence of $χ_{2}^{B}$ and exact baryon number conservation.
↳ hep-phnucl-exnucl-th0 citations
05
Event-by-event analysis of chiral charge separation in $p^{↑} +$ Au collisions within an improved AMPT model
Chen Gao🇨🇳 · Gui-Zhen Wu🇨🇳 · Yi Xu🇨🇳 · Wei-Tian Deng🇨🇳
We study the charge separation induced by chiral magnetic effect (CME) in $p^{↑}$ +Au collisions at $s_{N N} = 200$ GeV event-by-event with an improved string-melting AMPT model. In this model, an impact-parameter-dependent formation-time delay is introduced to reduce the peak Bjorken energy density from $\sim$ 2 to $\sim$ 0.3 GeV/fm $^{3}$ and reproduces the illiptic flow $v_{2} (p_{T})$ measured by PHENIX in $p +$ Au simultaneously. The event-by-event CME source, whose quark momentum-exchange fraction scales with $∣ B ∣_{event} /∣ B ∣_{max}$ and is capped at the 7\% value from Au+Au, transmits the field geometry directly to the observable. We find that the initial correlator shows a clear scheme hierarchy tracking $B^{2}$ . The parton cascade preserves $\sim$ 80--90\% of the signal, while coalescence and ART hadronic rescattering dissipate the bulk, leaving $\sim$ 10--30\% in the final state. The $γ_{O S} / γ_{S S}$ splitting remains visible. These results support the use of the inter-scheme difference $Δ γ_{IV} - Δ γ_{II}$ as an essentially background-free CME observable as we proposed in previous work.
↳ hep-phnucl-th0 citations
06
Probing vorticity and fluctuations in a rotating hadron resonance gas at LHC energy
S. Ipsita Sahoo🇮🇳 · Sanjeebani Biswal🇮🇳 · D. Dutta🇮🇳 · D. K. Mishra🇮🇳
A large vorticity produced in non-central ultra-relativistic heavy-ion collisions induces an effective chemical potential in both partonic and hadronic matter, thereby influencing the quark-hadron transition and its associated properties. In this work, we investigate the influence of rotation on hadron yields within the framework of Hadron Resonance Gas (HRG) model. Our results show that vorticity significantly modifies hadron yields and their ratios. Most notably, rotation enhances the $p / π^{+}$ ratio while suppressing the $K^{+} / π^{+}$ ratio, suggesting that these observables may serve as sensitive probes of the rotational properties of the medium created in heavy-ion collisions. To quantify the effect of rotation, the calculated dependence of the $p / π^{+}$ ratio on vorticity is compared with the centrality dependence of the $p / π$ ratio measured by the ALICE collaboration in Pb+Pb collisions at $s_{_{N N}}$ = 5.02 TeV. From this comparison, we estimate the maximum vorticity produced at freeze-out for different collision centralities. In case of peripheral collisions, the freeze-out vorticity ( $ω$ ) is found to reach an upper bound value of approximately 0.088 GeV, whereas for central collisions it is about 0.028 GeV. Furthermore, we investigate the effect of rotation on fluctuations of conserved quantities and their correlations. This study provides a quantitative framework for assessing the role of rotation in the thermodynamics of hadronic matter and its phenomenological consequences for heavy-ion collisions.
↳ hep-phnucl-exnucl-th0 citations
07
Probing Gluon Linear Polarization with Dihadron Fragmentation in $χ_{b}$ Decays
Zhi-Guo He🇨🇳 · Guanghui Li🇨🇳 · Yang Liu🇨🇳 · Yu-Jie Tian🇨🇳 · Xin-Kai Wen🇨🇳 · Bin Yan🇨🇳
The dihadron fragmentation function (DiFF) of a linearly polarized gluon has not yet been accessed experimentally, leaving an important aspect of spin-dependent gluon hadronization unexplored. We show that, at leading order, the color-singlet decay channel of the $P$ -wave bottomonium state $χ_{b 0}$ produces two energetic gluons with correlated linear polarizations. Within collinear factorization, their fragmentation into separate dihadron pairs generates an Artru--Collins-type angular correlation that provides the first direct probe of the linearly polarized gluon DiFF, while the corresponding semi-inclusive decay rate constrains the unpolarized gluon DiFF. A spectator-model benchmark indicates percent-level asymmetries, potentially within reach of existing Belle data. A dedicated Belle~II data set would substantially improve the statistical precision, enabling more stringent constraints on the kinematic dependence of the linearly polarized gluon DiFF.
↳ hep-phhep-exnucl-exnucl-th1 citation
08
Scaling of soft QGP signatures in relativistic lead, xenon and oxygen collisions in EPOS4
Salman Khurshid Malik🇮🇳 · Fakhar Ul Haider🇮🇳 · Pratibha Bhagat🇮🇳 · Anju Bhasin🇮🇳 · Ramni Gupta🇮🇳
The collective expansion and hydrodynamic evolution in heavy-ion collisions is well-established. However, whether femtometer-scale droplets of QGP are produced in small systems at high energies remains a fundamental open question. Analysis of Pb $-$ Pb collisions at $s_{NN}$ = 5.02 TeV, Xe $-$ Xe at $s_{NN}$ = 5.44 TeV and O $-$ O collisions at $s_{NN}$ = 5.36 TeV using EPOS4 is reported to make predictions and postdictions. The results are compared with ALICE data for Pb $-$ Pb and Xe $-$ Xe collisions. Charged particle multiplicity (d $N_{ch}$ /d $η$ ), transverse-momentum ( $p_{T}$ ) spectra for pions ( $π^{\pm}$ ), kaons ( $K^{\pm}$ ), and protons ( $p (p)$ ) are studied. The inclusion of hadronic afterburner, UrQMD (Ultra-relativistic Quantum Molecular Dynamics) is found to be necessary to correctly describe baryon yields. $p_{T}$ -fluctuations are also studied via normalized $p_{T}$ correlator, $⟨⟨ Δ p_{T, i} Δ p_{T, j} ⟩⟩ / ⟨⟨ p_{T} ⟩⟩$ . Lastly, anisotropic flow harmonics ( $v_{2} {2}$ , $v_{3} {2}$ ) are computed as a function of $p_{T}$ and centrality. Since EPOS4 has not been extensively studied for flow observables, this study thereby provides a non-trivial assessment of its collective dynamics. The results are compared with experiment wherever data is available. Taken together, this study provides a unified description of soft observables from Pb $-$ Pb through Xe $-$ Xe down to O $-$ O and offer quantitative guidance on how such collisions may inform of the properties of the QGP.
↳ hep-phnucl-thPRC(2026)·0 citations
09
Evolution of the underlying event and non-extensive thermodynamics in pp collisions from RHIC to LHC energies
Suraj Prasad🇭🇺 · Aditya Nath Mishra🇮🇳 · Guy Paić🇭🇺 · Gergely Gábor Barnaföldi🇭🇺
We investigate the geometrical and thermodynamical aspects of particle production in pp collisions over a broad center-of-mass energy, ranging from $s = 62.4$ GeV to 13 TeV using PYTHIA8. We study the azimuthal dependence of charged-particle production relative to the leading particle. This includes the study of the Tsallis--Pareto parameters extracted from the charged-particle transverse-momentum spectra in fixed $Δ ϕ$ intervals relative to the leading charged particle. The simultaneous analysis of charged-particle multiplicity and event topology demonstrates that the underlying event (UE) dominated region can be extended beyond the conventional transverse side region across RHIC and LHC energies. To further disentangle effects from soft and hard particle production mechanisms, the study is performed in different transverse spherocity and charged-particle flattenicity classes. We demonstrate that the UE region extends beyond the conventional transverse region, validating an enlarged angular interval of $4 0^{\circ} ≲ ∣Δ ϕ ∣ ≲ 14 0^{\circ}$ from RHIC to LHC energies. Event-shape selections reveal that jetty events consistently exhibit larger $q$ and lower $T_{s}$ than isotropic events. The $Δ ϕ$ profiles of charged-particle multiplicity and transverse spherocity remain universal in shape across collision energies despite the strong increase in overall event activity, whereas the Tsallis parameters retain a residual, leading-particle-driven energy dependence in the near- and away-side regions.
↳ hep-phhep-exhep-thnucl-ex+10 citations
10
Monsters and neutron stars
Sourendu Gupta🇮🇳
Using dimensional arguments and other simple estimates, it is pointed out that a branch of nuclei with mass number A>10^7 could be metastable if they have close to maximal isospin. This branch is continuous with neutron stars. The fastest decay mode of these hypothetical metastable nuclei (which we call monsters) is through neutron evaporation. We present an estimate of the lifetime and show it could be more than 100 ps for A>10^{39}. We speculate about their creation in binary neutron star mergers, where we argue that their lifetimes could be extended further, and their presence could be detectable in gravity wave experiments of the near future.
↳ hep-phnucl-th0 citations
11
Gluonic nucleon energy correlators and fracture functions for Color Glass Condensate
Heikki Mäntysaari🇫🇮 · Yu Shi🇨🇳 · Yossathorn Tawabutr🇹🇭 · Xuan-Bo Tong🇫🇮
Nucleon energy correlators (NECs) and fracture functions provide novel tools for probing nucleon and nuclear structure at small $x$ through measurements in the target fragmentation region (TFR) of deep inelastic scattering (DIS). We investigate gluonic NECs and fracture functions using the Color Glass Condensate effective theory at eikonal accuracy. We find that only the unpolarized and linearly polarized gluon components in an unpolarized target are nonvanishing at this order, and that both are determined by the adjoint dipole $S$ -matrix. Furthermore, we show that the linearly polarized gluonic NEC $h_{1}^{t, g}$ generates a characteristic $cos 2 ϕ$ azimuthal asymmetry in the DIS energy pattern in the TFR. Unlike analogous observables in the current fragmentation region, this asymmetry is governed by the ratio of the linearly polarized gluon NEC $h_{1}^{t, g}$ to the unpolarized quark NEC $f_{1}^{q}$ , making it particularly sensitive to the saturation scale. Our numerical analysis shows that this asymmetry exhibits substantial nuclear suppression, providing a novel window into the onset of gluon saturation at the future Electron-Ion Collider.
↳ hep-phnucl-th0 citations
12
Moment of Inertia of an Interacting Bose Gas
Aleksandar Gecic🇷🇴 · Victor E. Ambrus🇷🇴 · Kenji Fukushima🇷🇴
The response of many-body quantum systems to rotation can be characterized by the moment of inertia. For a classical gas, the moment of inertia can be expressed as the integral of the enthalpy density multiplied by the squared radial distance from the rotation axis. In quantum field theory, the finite rotation in the grand canonical ensemble demands the causality bound. This constraint imposes technical challenges in treating transverse momenta discretized with the Bessel function zeros. However, we define the moment of inertia in the limit of zero angular velocity, in which the causality constraint is irrelevant and ordinary quantum field theoretical techniques can be applied. We evaluate the moment of inertia in the $ϕ^{4}$ theory and find that, surprisingly, the interacting effects including the ring-diagram resummation are consistent with the classical expectation and the moment of inertia density remains proportional to the enthalpy density.
↳ hep-thnucl-th0 citations
13
QCD Vacuum in an Inhomogeneous Magnetic Field
Prabal Adhikari🇺🇸 · Brian C. Tiburzi🇺🇸
The effect of an inhomogeneous magnetic field on the QCD vacuum is addressed using the framework of chiral perturbation theory. The magnetic field is chosen to be localized along one spatial direction, with a profile for which the underlying quantum mechanical problem is exactly solvable. Particular attention is paid to regularization and renormalization using dimensional regularization. While the non-vanishing gradient of the magnetic field requires additional operators in chiral perturbation theory, their effect occurs at next-to-next-to-leading order in the chiral expansion. Consequently, the magnetic field dependence of equilibrium vacuum observables can be determined at next-to-leading order without undetermined parameters. We compute the zero-temperature free energy and chiral condensate for the inhomogeneous background, both as integrated quantities as well as spatially resolved local observables. Comparison with locally constant approximations enables a direct probe of the spatial response and nonlocal structure of the magnetized QCD vacuum. We additionally derive the induced vacuum current associated with the inhomogeneity of the magnetic field.
↳ hep-phhep-latnucl-th0 citations

Affiliations

first authorsco-authorsvia INSPIRE