Nuclear Theory·nucl-th

Monday·August 31, 2026

24 papers—7 primary·17 cross-listed

08
CGC and saturation approach: Impact-parameter dependent model of perturbative QCD and combined HERA data
Michael Roa · José Garrido🇨🇱 · Miguel Guevara
In this paper we confront the CGC/saturation approach of Ref.~\cite{CLMS} with the experimental combined HERA data and obtain its parameters. The model includes two features that are in accordance with our theoretical knowledge of deep inelastic scattering. These consist of: \textit{i}) the use of analytical solution for the non-linear Balitsky-Kovchegov (BK) evolution equation and \textit{ii}) the exponential behavior of the saturation momentum on the impact parameter $b$ -dependence, characterized by $Q_{s}$ $\propto exp (- mb)$ which reproduces the correct behavior of the scattering amplitude at large $b$ in accord with Froissart theorem. The model results are then compared to data at small- $x$ for the structure-function of the proton $F_{2}$ , the longitudinal structure function $F_{L}$ , the charm structure function $F_{2}^{c c ˉ}$ , the exclusive vector meson ( $J / ψ, ϕ, ρ$ ) production and Deeply Virtual Compton Scattering (DVCS). We obtain a good agreement for the processes in a wide kinematic range of $Q^{2}$ at small- $x$ . Our results provide a strong guide for finding an approach, based on Color Glass Condensate/saturation effective theory for high energy QCD, to make reliable predictions from first principles and for forthcoming experiments like the Electron-Ion Collider and the LHeC.
↳ hep-phhep-exnucl-exnucl-thPRD(2024)·5 citations
09
Modified homotopy approach for diffractive production in the saturation region
Carlos Contreras🇨🇱 · José Garrido🇨🇱 · Eugene Levin🇮🇱 · Rodrigo Meneses🇨🇱
In this paper we continue to develop the homotopy method for solving of the non linear evolution equation for the diffractive production in deep inelastic scattering(DIS). We introduce part of the nonlinear corrections as a first step of this approach. This simplified nonlinear evolution equation is solved analytically taking into account the initial and boundary conditions for the process. At the second step of our approach we demonstrated that the perturbative procedure can be used for the remaining parts of the non-linear corrections. It turns out that these corrections are small and can be estimated in the regular iterative procedure.
↳ hep-phnucl-thPRD(2024)·4 citations
10
Modified Homotopic approach for diffractive production
Carlos Contreras🇨🇱 · José Garrido🇨🇱 · Eugene Levin🇮🇱 · Rodrigo Meneses🇨🇱
We review the recent developments of the use of the homotopy method for solving the non-linear evolution equation for the diffractive production in deep inelastic scattering. We introduce part of the non-linear corrections in the linear term. This simplified non-linear evolution equation is solved analytically taking into account the initial and boundary conditions for the process. It turns out that these corrections are rather small and can be estimated in the regular iterative procedure.
↳ hep-phnucl-thActa Phys.Polon.Supp.(2025)·0 citations
11
Homotopy approach for scattering amplitude for running QCD coupling
Carlos Contreras🇨🇱 · José Garrido🇨🇱 · Eugene Levin🇮🇱
In this paper we proposed the homotopy approach for solving the nonlinear Balitsky-Kovchegov (BK) evolution equation with running QCD coupling. The approach consists of two steps. First, is the analytic solution to the nonlinear evolution equation for the simplified, leading twist kernel. Second, is the iteration procedure that allow us to calculate corrections analytically or semi-numerically. For the leading twist kernel it is shown that the first iteration leads to $\leq 1%$ accuracy. The $ζ = - \frac{4 N _{c}}{b _{0}} Y ln \Lb \bas (1/ Q_{s}^{2} (Y)) / \bas \Lb r^{2} \Rb \Rb$ ( $r$ is the dipole size, $Q_{s}$ is the saturation scale) and geometric scaling behaviour of the scattering amplitude are discussed as well as the dependence on the value of the infrared cutoff.
↳ hep-phnucl-thPRD(2025)·3 citations
12
Multiplicity distribution of produced gluons in deep inelastic scattering: main equations and their homotopy solutions for heavy nuclei
Carlos Contreras🇨🇱 · Jose Garrido🇨🇱 · Eugene Levin🇮🇱
In this paper we discuss the multiplicity distribution in the deep inelastic processes in the frame work of high energy QCD. We obtained three results. First, we get the new derivation of the equations for the cross sections of productions of $n$ -cut Pomerons in the final states ( $σ_{n}$ ). These equations coincide with the equations that have been derived using the Abramovsky, Gribov and Kancheli (AGK) cutting rules but based on the dipole approach to QCD. Second, we developed the homotopy approach for finding the solutions to these equations. It consists with the analytic solution for the first iteration and the converge procedure of calculating the next iterations using computing. Third, we found the analytical solution for $σ_{n}$ at large $n ≳ N (z) = 2 N_{0} z exp (z^{2} / (2 κ))$ with $z = ln (r^{2} Q_{s}^{2})$ . Using this solution we calculate the entropy of the produced gluons at large $z$ : $S_{E} = ln (N (z))$ , where the saturation momentum $Q_{s}$ and all constants are discussed in the text.
↳ hep-phnucl-thPRD(2026)·2 citations
13
Tidal effects on radiation in gravitational shockwave collisions
Isabelle Blackstad🇺🇸 · Himanshu Raj🇺🇸 · Raju Venugopalan🇺🇸
We compute high frequency gravitational wave radiation in shockwave collisions of a light mass compact object with energy $μ_{L}$ off a heavy compact object (black hole) with energy $μ_{H} ≫ μ_{L}$ . A formal solution is obtained in terms of shockwave propagators that provide snapshots of $O (μ_{L} μ_{H}^{n})$ tidal response functions sensitive to classical and potentially semi-classical dynamics of black hole formation. In a perturbative expansion, the first nontrivial contribution of $O (μ_{L} μ_{H})$ is the emission of a graviton from the Lipatov vertex generated by the fusion of two reggeized gravitons. For graviton frequencies $ω \to 0$ , the Lipatov amplitude reduces to the ultrarelativistic limit of the single-graviton exchange Weinberg amplitude. At $O (μ_{L} μ_{H}^{2})$ , the Lipatov amplitude includes a piece accounting for the rescattering of the graviton off a reggeized graviton and another, corresponding to graviton emission from a vertex fusing three reggeized gravitons. These nontrivial contributions again simplify to the Weinberg radiative amplitude for two-graviton exchange in the soft limit. We highlight throughout double copy structures to gluon radiation in dilute-dense collisions of Yang-Mills shockwaves. We relate our shockwave results to the eikonal multiple scattering framework of Veneziano et al.
↳ hep-thgr-qchep-phnucl-th0 citations
14
A doubly critical point in the color-superconducting regime of the RG-consistent NJL model
Hosein Gholami🇩🇪 · Marco Hofmann🇩🇪 · Michael Buballa🇩🇪
Nambu--Jona-Lasinio (NJL) models of color-superconducting quark matter suffer from cutoff artifacts once temperature or quark chemical potential become comparable to the model cutoff. These artifacts can be removed employing a renormalization-group (RG) consistent regularization scheme. In this article we perform a systematic study of neutral beta-equilibrated quark matter within the three-flavor NJL model with RG consistent regularization. Varying the coupling constant in the scalar diquark channel, we map out the phase diagram in the plane of chemical potential and temperature, and identify the gapless domains. We particularly focus on the melting pattern of the color-flavor locked (CFL) phase. At larger couplings the CFL phase melts through a so-called $d$ SC phase, as expected from leading-order Ginzburg--Landau analyses. Lowering the coupling, the phase structure becomes markedly richer: While at large densities the CFL phase still melts through a $d S C$ phase, we find a $u S C$ phase at lower chemical potential. These phases, $u S C$ and $d S C$ meet at a doubly critical point whose existence had been anticipated long ago but was never demonstrated explicitly in a model.
↳ hep-phhep-thnucl-th0 citations
15
Constraining Light and Strange Flavor Equilibration in Relativistic Heavy-Ion Collisions
Andrew Gordeev🇺🇸
Relativistic heavy-ion collisions are the only known means of creating the quark-gluon plasma, a deconfined state of QCD matter. Hydrodynamic modeling has established that this medium behaves as a strongly coupled, low-viscosity fluid, but typically assumes that its quark and gluon composition reaches chemical equilibrium by the onset of the hydrodynamic phase. This assumption remains uncertain: gluon-dominated initial states suggest that quark production continues well into the hydrodynamic stage, with potentially different rates for light and strange quarks. This dissertation develops a dynamical framework for light and strange quark chemical equilibration. Incomplete equilibration of each flavor is described through time-dependent quark fugacities that modify both the equation of state and the particlization of the medium. Implemented within a multistage framework of fluctuating initial conditions, viscous hydrodynamics, particlization, and hadronic transport, the model is used to study the effects of equilibration on the hydrodynamic evolution and on hadronic and electromagnetic observables. The framework is embedded within a Bayesian analysis in which Gaussian process emulators trained on the model calculations infer the initial light and strange quark fugacities, their equilibration timescales, and selected transport coefficients from Au+Au collision data at RHIC. The strange sector is found to begin substantially undersaturated, more suppressed than the light sector; the data further favor a slower approach to equilibrium for strangeness, though the timescales themselves remain weakly constrained. These results favor a quark-gluon plasma whose flavor composition is still approaching chemical equilibrium during the hydrodynamic phase rather than fixed at its outset, and motivate extensions to collision systems of differing size and energy.
↳ hep-phnucl-th0 citations
16
Magnetic Moments and Radiative Transitions of the $T_{cc} (3875)^{+}$ and its partner states
Jing Wu🇨🇳 · Yi-Kun Wang🇨🇳 · Kai-Bao Chen🇨🇳 · Yan-Rui Liu🇨🇳 · Jian-Bo Cheng🇨🇳 · Wei-Hua Yang🇨🇳
We systematically investigate the magnetic moments (MMs) and radiative decay widths of S-wave doubly heavy tetraquark states based on chromomagnetic interaction (CMI). They provide a complementary probe to distinguish compact from molecule structures in addition to the mass spectrum and strong decay properties. Using the CMI eigenvectors, we compute the MMs and M1 transition rates for the tetraquarks in the compact configuration. We predict the MM of the observed $T_{cc} (3875)^{+}$ with $I (J^{P}) = 0 (1^{+})$ to be 0.45 $μ_{N}$ when treating it as a compact tetraquark state, whereas the MM of the $0 (1^{+})$ $D D^{*}$ molecule is about $- 0.07 μ_{N}$ . Five radiative transition channels related to the $T_{cc} (3875)^{+}$ are identified with widths ranging from $6.07$ keV to $306.37$ keV. Our results show that the MMs of the $J^{P} = 1^{+}$ $b c q ˉ q ˉ^{'}$ ( $q / q^{'} = u, d, s$ ) and $J^{P} = 1^{+}$ $QQ n ˉ s ˉ$ ( $Q = b, c; n = u, d$ ) states are influenced by the diquark-spin mixing. Through the analyses of radiative transitions between different tetraquark states, we find that such processes in the $QQ n ˉ n ˉ^{'}$ , $QQ s ˉ s ˉ$ , and $b c n ˉ s ˉ$ cases may serve to reveal the tetraquark structures of the initial or final states. We also define the magnetic coupling matrices characterizing the MMs of the tetraquark system with $J^{P} = 1^{+}$ , with which the range of MM can be constrained. The present study provides a valuable reference point for the search of exotic states in future particle physics experiments.
↳ hep-phhep-exhep-latnucl-ex+10 citations
17
Hyperon bulk viscosity effects in neutron-star inspirals
Elena M. Kantor🇷🇺 · Mikhail E. Gusakov🇷🇺 · Kirill Y. Kraav🇷🇺
The paper revisits the role of hyperon bulk viscosity during neutron-star inspiral. We find that hyperon bulk viscosity exerts only a minor influence on the gravitational-wave phase, causing a phase shift of $\sim 1 0^{- 3} rad$ . This shift is too small to be detected by existing gravitational-wave observatories, and it seems unlikely that next-generation detectors will be able to isolate this effect from other factors. However, our analysis indicates that hyperon bulk viscosity can significantly heat the hyperon core of a neutron star, raising its temperature to approximately $5 \times 1 0^{8} K$ .
↳ astro-ph.HEgr-qcnucl-th0 citations
18
Doppler-shift attenuation method (DSAM) lifetimes in $^{54}$ Cr - a re-evaluation
Andrew E. Stuchbery
Background: Contemporary stopping powers for fp-shell nuclei slowing in tantalum can differ by a factor of two from the 1963 Lindhard, Scharff and Schiøtt (LSS) theory [Mat. Fys. Medd. Dan. Vid. Selsk. 33 no. 14, (1963)] used in Doppler-shift attenuation method (DSAM) lifetime measurements dating back to the 1970s. In recent work [Phys. Rev. C 113, 044306 (2026)], it was found that anomalously high collectivity in the $4_{1}^{+} \to 2_{1}^{+}$ transition of 58Fe given in the literature [Nucl. Data Sheets 111, 897 (2010)] could be traced back as due to the use of these historical stopping powers in the Doppler-shift lifetime measurements. Satisfactory agreement with shell-model calculations was obtained from a re-analysis of the measurement of Bolotin et al. [Nucl. Phys. A 311, 75 (1978)] once the stopping powers were replaced by up-to-date values. Purpose: The DSAM measurement on 54Cr by the same group [Nucl. Phys. A 337, 1 (1980)], which used the same experimental methods and procedures, is re-examined. Method: The computer code used in the original DSAM analysis has been rebuilt and upgraded with the capacity to use contemporary stopping powers. E2 transition strengths derived from the revised lifetimes are compared with shell-model calculations. Results: The lifetimes increase by 16% to 27%, with the larger increase generally corresponding to shorter lifetimes where electronic stopping dominates. Conclusions: Revised lifetimes, based on current stopping powers, imply E2 transition rates between states up to the 6 $_{1}^{+}$ state in 54Cr that compare well with shell-model calculations. The lifetime data together with branching ratios and the shell-model calculations strongly suggest revision of the spins assigned to the levels at 3.786 (currently (4) $^{+}$ ) and 4.043 MeV (currently 5 $^{+}$ ). These levels are suggested to be the 5 $_{1}^{+}$ and 6 $_{2}^{+}$ states, respectively.
↳ nucl-exnucl-th0 citations
19
Expansion attractor in classical Yang-Mills theory
Clemens Werthmann🇧🇪
Applications of the concept of a hydrodynamic attractor have been mostly constrained to the context of hydrodynamization in heavy ion collisions. Deepening the understanding of the general phenomenon requires generalizing it to other contexts in order to see which facettes are truly universal and not a peculiarity of equilibrating conformal Bjorken flow. As part of this endeavor, this work aims to study the behaviour in a system that does not hydrodynamize, but nevertheless loses memory through expansion. We find that the system goes through three stages. At early times, expansion drives the ratio $P_{L} / ϵ$ to converge to $- 1$ as $τ^{- 2}$ . This memory loss is partially restored at intermediate times, when interaction dominated degrees of freedom through expansion dominated evolution grow quadraticallly in time. At late times, interactions shuffle of information in state space without significant memory loss or restoration.
↳ hep-phhep-thnucl-th0 citations
20
System-size dependence of strangeness production from p+p to Pb+Pb: quantitative tests of the $K^{+} / π^{+}$ horn
Neeraj🇮🇳 · Amal Sarkar🇮🇳
The pronounced maximum ("horn") in the $K^{+} / π^{+}$ excitation function observed in central Pb+Pb collisions is well established feature of collision-energy dependence, but its dependence on system size remains poorly understood. We confront hadronic (SMASH) and partonic (PHSD) transport, Glauber core-corona, canonical-ensemble suppression, and the two-phase statistical model of the early stage (SMES) with $K^{+} / π^{+}$ data spanning the complete NA61/SHINE system-size ladder (p+p, Be+Be, Ar+Sc, Xe+La) together with NA49 Pb+Pb and STAR Au+Au, quantifying every comparison by $χ^{2}$ . No single framework describes the full range: core-corona is preferred for intermediate systems, SMES with canonical strangeness conservation for heavy systems, and none reproduces the small-system data. Neither transport model generates the horn, with or without partonic degrees of freedom. The data exhibit a step-like enhancement of $K^{+} / π^{+}$ between Be+Be and Ar+Sc, quantified within the core-corona framework by a step from $\fcore \approx 0.22$ (Be+Be) to $\fcore \approx 0.58$ (Ar+Sc). The strangeness saturation factor $\gs$ rises in two distinct steps, separating geometric core formation from thermodynamic equilibration. The $(K^{+} / π^{+}) / (K^{-} / π^{-})$ double ratio, which at fixed $\sqrts$ cancels the system-independent $μ_{B}$ contribution, shows a step between light and heavy systems at a global significance of $3.7 σ$ , providing evidence for genuine strangeness enhancement beyond the pair-production baseline. Preliminary Xe+La data favor core-corona ( $\chindf = 5.8$ ) over SMASH ( $\chindf = 23.3$ ); finalized spectra will sharpen the CC/SMES discrimination at the $27%$ level.
↳ hep-phnucl-th0 citations
21
Lifetime measurements in neutron-rich odd-A yttrium isotopes ( $^{93 - 99}$ Y): Investigation of shape coexistence and the intertwined quantum phase transition
A. Pfeil · N. Gavrielov · U. Köster · Y. H. Kim · N. Cieplicka-Oryńczak · J. Dudouet · A. Esmaylzadeh · Ł. W. Iskra · M. Ley · J.-M. Régis · D. Reygadas · J. Jolie
Lifetimes of 16 excited states in the neutron-rich odd- $A$ nuclei $^{93 - 99}$ Y were measured using fast-timing $γ$ - $γ$ coincidence spectroscopy with fast scintillation detectors at the LOHENGRIN recoil separator. Particular attention is given to the region around $N \approx 59$ , where rapid changes in nuclear deformation and shape coexistence occur. The lifetimes, determined using the generalized centroid difference method, are compared with interacting boson-fermion model calculations with configuration mixing, in which the odd- $A$ yttrium isotopes are described as a proton coupled to a bosonic core containing normal and intruder configurations. The results provide new constraints on theoretical descriptions of shape coexistence and structural evolution in neutron-rich nuclei near $A \approx 100$ , particularly for odd- $A$ systems where experimental information remains limited.
↳ nucl-exnucl-th0 citations
22
Color screening versus thermal decay as the mechanism of $Υ$ suppression in high energy nuclear collisions
Yida Yang🇨🇳 · Baoyi Chen🇨🇳 · Jiaxing Zhao🇩🇪 · Pengfei Zhuang🇨🇳
To clearly identify the mechanism behind the suppression of heavy quarkonium in relativistic heavy-ion collisions, we study $Υ$ production at RHIC energies by solving its transport equation driven solely by the suppression rates. By calculating the nuclear modification factor and comparing it with experimental data, we find that the sudden suppression governed by the color-screening temperature cannot simultaneously describe both the ground and excited states of the $Υ$ , whereas the continuous suppression induced by thermal decay successfully reproduces all the $Υ$ measurements. This provides strong evidence that inelastic scatterings with thermal partons, rather than color screening, dominate quarkonium suppression in heavy-ion collisions.
↳ hep-phnucl-th0 citations
23
Investigation of S-wave tetraquark bound and resonant states with all Jacobi coordinates
Xin-He Zheng🇨🇳 · Yao Ma🇩🇪 · Liang-Zhen Wen🇨🇳 · Shi-Lin Zhu🇨🇳
We systematically explore the $S$ -wave tetraquark systems $Q s n ˉ n ˉ$ , $QQ n ˉ n ˉ$ , $QQ Q ˉ Q ˉ$ , and $ss s ˉ s ˉ$ ( $Q = c, b$ ; $n = u, d$ ) within the constituent quark potential model. We incorporate all K-type Jacobi coordinates in addition to the conventional H-type configurations, optimize the basis expansion via a stochastic parameter generation strategy, and apply the complex scaling method to identify bound and resonant states. Our calculations demonstrate that while conventional H-type configurations suffice for low-lying states such as the $T_{cc} (3875)^{+}$ molecular candidate, the inclusion of K-type configurations becomes important for extracting highly excited resonances, allowing higher-energy resonances absent in H-only calculations to be identified. Furthermore, we identify resonance candidates for the $T_{cs 0} (2900)$ , $X (6900)$ , and $X (7200)$ , whereas the absence of fully-strange compact poles below 2.6 GeV challenges the interpretation of $ϕ (2170)$ and $X (2370)$ as $S$ -wave compact $ss s ˉ s ˉ$ tetraquarks.
↳ hep-phhep-exnucl-th0 citations
24
Effect of Thermal Broadening on Light Hadron Production in Heavy-Ion Collisions
Q'inich Coc🇩🇪 · Oscar Garcia-Montero🇪🇸 · Aleksas Mazeliauskas🇩🇪
The measured hadron yields in heavy-ion collisions are well described by thermal particle production at temperatures close to the QCD pseudo-critical transition. However, if particles are produced in thermal equilibrium, then the in-medium effects, e.g., broadening of their spectral functions, must be taken into account. In this work, we study for the first time the effect of the thermal broadening of the light vector-meson spectral functions on light hadron production in heavy-ion collisions. We generalize the efficient resonance decay framework FastReso to resonances with finite-width spectral functions. We then compute the pion, kaon and proton spectra from the decays of hadron resonances for in-medium and vacuum spectral functions. We perform a simultaneous blast-wave fit with decay feed-down to measured particle spectra in central Pb-Pb and Xe-Xe collisions at the LHC. We find an increase in pion spectra at low momenta, from including thermally broadened $ρ$ and $ω$ mesons. Additional pion yield from finite-resonance widths reduces the commonly observed discrepancy between models and data, but does not completely resolve the soft pion puzzle in heavy-ion collisions.
↳ hep-phnucl-exnucl-th0 citations

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