Nuclear Theory·nucl-th

Tuesday·February 25, 2025

21 papers—6 primary·15 cross-listed

07
Comment on "QCD factorization with multihadron fragmentation functions"
D. Pitonyak🇺🇸 · C. Cocuzza🇺🇸 · A. Metz🇺🇸 · A. Prokudin🇺🇸 · N. Sato🇺🇸
We make several comments on the recent work in Ref.~\cite{Rogers:2024nhb} while also reaffirming and adding to the work in Ref.~\cite{Pitonyak:2023gjx}. We show that the factorization formula for $e^{+} e^{-} \to (h_{1} \dots h_{n}) X$ in Ref.~\cite{Rogers:2024nhb} is equivalent to a version one can derive using the definition of a $n$ -hadron fragmentation function (FF) introduced in Ref.~\cite{Pitonyak:2023gjx}. In addition, we scrutinize how to generalize the number density definition of a single-hadron FF to a $n$ -hadron FF, arguing that the definition given in Ref.~\cite{Pitonyak:2023gjx} should be considered the standard one. We also emphasize that the evolution equations for dihadron FFs~(DiFFs) in Ref.~\cite{Pitonyak:2023gjx} have the same splitting functions as those for single-hadron FFs. Therefore, the DiFF (and $n$ -hadron FF) definitions in Ref.~\cite{Pitonyak:2023gjx} have a natural number density interpretation and are consistent with collinear factorization using the standard hard factors and evolution kernels. Moreover, we make clear that the operator definition for the DiFF $D_{1}^{h_{1} h_{2}} (ξ, M_{h})$ written down in Ref.~\cite{Rogers:2024nhb} agrees exactly with the one in Ref.~\cite{Pitonyak:2023gjx}. Contrary to what is implied in Ref.~\cite{Rogers:2024nhb}, this definition did not appear in the literature prior to the work in Ref.~\cite{Pitonyak:2023gjx}. There also seem to be inconsistencies in how $D_{1}^{h_{1} h_{2}} (ξ, M_{h})$ appears in previous unpolarized cross section formulas in the literature.
↳ hep-phnucl-thPRD(2026)·11 citations
08
Physics motivated models of pulsar X-ray hotspots: off-center dipole configurations
Chun Huang · Alexander Y. Chen
Recently, it was proposed that an off-center dipole magnetic configuration, together with a non-trivial temperature profile, may be the best model to explain the X-ray light curve of PSR J0030+0451 observed by the Neutron Star Interior Composition Explorer (\emph{NICER}). Using a theoretical model for the electric current density in a force-free pulsar magnetosphere, we compute from first principles the distribution of electric current over the polar cap associated with an off-center magnetic dipole. We then use a simple prescription to compute the resulting temperature distribution, which allows us to derive the observed X-ray light curve. We investigate the role of the volumetric return current region in the polar cap and find that although it does not make a big difference in an aligned dipole case, the difference can be bigger in the case of an off-center dipole. Finally, we apply Markov Chain Monte Carlo (MCMC) fitting to the X-ray light curves of pulsars PSR J0030+0451 and PSR J0437--4715 with and without the volumetric return current, and find that our model can reasonably recover the observed X-ray light curves.
↳ astro-ph.HEastro-ph.SRgr-qcnucl-thApJ(2025)·13 citations
09
Perturbative Corrections to Quark TMDPDFs in the Background-Field Method: Gauge Invariance, Equations of Motion, and Multiple Interactions
Swagato Mukherjee🇺🇸 · Vladimir V. Skokov🇺🇸 · Andrey Tarasov🇺🇸 · Shaswat Tiwari🇺🇸
We calculate the perturbative corrections in the strong coupling to the unpolarized quark transverse-momentum dependent parton distribution function (TMDPDF) operator within a background-field framework, extending the approach of Ref. [1]. We focus on ensuring gauge invariance, identifying two key components needed: a gauge-invariant TMDPDF operator with a transverse gauge link at spatial infinity, and accounting of the equations of motion (EoM) of the background fields. We go beyond next-to-leading order in strong coupling expansion, considering multiple interactions with the background field at all orders of strong coupling. By examining the interplay between quark and gluon contributions, we show that spurious singularities, proportional to EoM, can be misinterpreted as genuine divergences in QCD factorization unless properly identified and removed.
↳ hep-phhep-lathep-thnucl-thPRD(2025)·5 citations
10
Yu-Shiba-Rusinov states in color superconducting quark matter
Virgil V. Baran🇷🇴 · Jens Paaske🇩🇰
The high-density region of the QCD phase diagram displays an intricate competition between color superconductivity and the QCD Kondo effect due to color exchange in quark matter containing a single heavy quark impurity. We explore the characteristic impurity-induced superconducting subgap states arising in such systems by generalizing the surrogate model solver, recently considered in the context of condensed matter physics [Phys. Rev. B 108, L220506 (2023)]. The method consists of approximating the full superconducting bulk by only a small number of effective levels whose parameters are chosen so as to best reproduce the Matsubara frequency dependence of the impurity-bulk hybridization function. We numerically solve a surrogate QCD Kondo model describing a quantum impurity color-exchange coupled to a two-color two-flavor superconducting bulk. The results directly indicate the presence of multiple phase transitions as the coupling of the impurity to the bulk is increased, due to the interplay between various overscreened states. The methods introduced here are straightforward enough to be extended to more realistic QCD scenarios.
↳ hep-phcond-mat.str-elcond-mat.supr-connucl-thPRD(2025)·1 citation
11
Electromagnetic Form Factors and the Proton Radius Puzzle: A Critical Review of Extraction Methods via Electron-Proton Scattering
Gerome A. Paterez🇺🇸 · Jade C. Jusoy🇺🇸 · Edmar Pantohan🇺🇸 · Eulogio Auxtero Jr🇺🇸
The study of protons, fundamental constituents of atomic nuclei, is crucial for understanding nuclear physics and fundamental forces. This review examines advancements in extracting electromagnetic form factors, essential for probing proton structure. Electron-proton scattering experiments, particularly at Jefferson Lab (JLab) and Mainz Microtron (MAMI), have played a key role [arXiv:2009.10510, arXiv:1912.03881]. Various methodologies, such as Rosenbluth separation and polarization transfer, are discussed, highlighting their evolution and challenges, including systematic uncertainties and theoretical ambiguities [arXiv:1706.00696]. Literature indicates the Rosenbluth method yields a proton radius of approximately 0.8 fm, consistent with early measurements but differing from recent polarization transfer results, which suggest a smaller radius [arXiv:1912.03881]. The polarization transfer technique has become a preferred approach, offering precise measurements of the electric-to-magnetic form factor ratio, especially at high momentum transfer [arXiv:1706.00696, arXiv:1912.03881]. Alternative methods, such as cross-section ratios, extend form factor studies but still face residual uncertainties [arXiv:2009.10510]. While significant progress has been made, discrepancies persist, particularly in proton radius extraction. Future research must address systematic uncertainties to refine our understanding of proton electromagnetic properties and advance particle physics [arXiv:1912.03881, arXiv:1706.00696].
↳ nucl-exnucl-th0 citations
12
Calorimetric analysis for long-baseline neutrino experiments
Kai Gallmeister🇩🇪 · Ulrich Mosel🇩🇪
In neutrino long-baseline experiments the energy of the incoming neutrino must be reconstructed from observations of the final state. We first discuss the problems that arise for energy conservation during the final-state interactions in a momentum-dependent potential. We then show, for the example of the Deep Underground Neutrino Experiment, that the presence of such a potential is necessarily connected with a large uncertainty in the reconstructed energy. This same uncertainty also affects the determination of energy- and four-momentum-transfers in neutrino-nucleus reactions. We analyze the origins of these uncertainties using transport theory for the description of the evolution of the final state of the reaction. We show that the spectral functions of target nuclei play an essential role not only for the initial neutrino-nucleus interaction but also for the final state evolution.
↳ hep-exhep-phnucl-exnucl-thPRD(2025)·4 citations
13
Ultra fast, event-by-event heavy-ion simulations for next generation experiments
Manjunath Omana Kuttan🇩🇪 · Kai Zhou🇩🇪 · Jan Steinheimer🇩🇪 · Horst Stoecker🇩🇪
We present a novel deep generative framework that uses probabilistic diffusion models for ultra fast, event-by-event simulations of heavy-ion collision output. This new framework is trained on UrQMD cascade data to generate a full collision event output containing 26 distinct hadron species. The output is represented as a point cloud, where each point is defined by a particle's momentum vector and its corresponding species information (ID). Our architecture integrates a normalizing flow-based condition generator that encodes global event features into a latent vector, and a diffusion model that synthesizes a point cloud of particles based on this condition. A detailed description of the model and an in-depth analysis of its performance is provided. The conditional point cloud diffusion model learns to generate realistic output particles of collision events which successfully reproduce the UrQMD distributions for multiplicity, momentum and rapidity of each hadron type. The flexible point cloud representation of the event output preserves full event-level granularity, enabling direct application to inverse problems and parameter estimation tasks while also making it easily adaptable for accelerating any event-by-event model calculation or detector simulation.
↳ hep-phhep-exhep-thnucl-ex+1PRC(2025)·6 citations
14
Limiting fragmentation in the dilute Glasma
Andreas Ipp🇦🇹 · Markus Leuthner🇦🇹 · David I. Müller🇦🇹 · Sören Schlichting🇩🇪 · Kayran Schmidt🇦🇹 · Pragya Singh🇫🇮
We discuss the local longitudinal scaling behavior of the dilute Glasma. We gain insight into how the fragmentation region is dominated by the longitudinal structure of one of the two colliding nuclei in heavy-ion collisions and study the effect of the correlation scales of the nuclear color charge distributions. We compare with results from the full dilute Glasma framework and analyze the rapidity limits of the fragmentation region. From our findings, it follows that all scalar observables that can be constructed out of the dilute Glasma field strength tensor show limiting fragmentation behavior and the field strength tensor itself transforms locally via Lorentz boosts when changing the collision energy.
↳ hep-phnucl-thPoS(2025)·1 citation
15
Proton spin from small- $x$ with constraints from the valence quark model
Daniel Adamiak🇺🇸 · Heikki Mäntysaari🇫🇮 · Yossathorn Tawabutr🇫🇮
We apply the valence quark model recently calculated for polarized proton to constrain the non-perturbative initial condition for the small- $x$ helicity evolution. The remaining free parameters are constrained by performing a global analysis to the available polarized small- $x$ deep inelastic scattering data. A good description of the world data is obtained with only 8 free parameters. The model parameters are tightly constrained by the data, allowing us to predict the proton polarized structure function $g_{1}^{p}$ to be negative at small $x$ . Furthermore, we obtain the small- $x$ quark and gluon spins to give a contribution $\int_{1 0^{- 5}}^{0.1} d x (\frac{1}{2} ΔΣ + Δ G) = 0.76 \pm 0.13$ or $1.70 \pm 0.20$ to the proton spin, depending on the applied running coupling prescription.
↳ hep-phnucl-thPLB(2025)·4 citations
16
Feasibility of Dark Matter in Neutron Stars: A Quantitative Analysis
Prashant Thakur🇮🇳
This thesis investigates the impact of dark matter on neutron star properties, focusing on mass, radius, and tidal deformability. Using two-fluid and single-fluid models, dark matter is incorporated into the equation of state (EOS) via a Relativistic Mean Field (RMF) approach. The study finds that increasing dark matter content reduces the maximum mass, radius, and tidal deformability. Bayesian inference, supported by LIGO-Virgo gravitational wave data and NICER mass-radius measurements, refines these models. Despite dark matter's influence, the semi-universal C-Love relation remains valid. Machine learning techniques effectively classify dark matter-admixed neutron stars. The thesis also explores a sigma-cut potential in the EOS, which stiffens the EOS at high densities, favoring larger radii and lower f-mode frequencies. The study of non-radial oscillations, particularly f- and p-modes, highlights their sensitivity to neutron star composition and EOS. These findings enhance our understanding of neutron star interiors and dark matter's role, emphasizing the need for further observational and theoretical advancements.
↳ astro-ph.HEhep-phnucl-th0 citations
17
Mechanical properties of proton using flavor-decomposed gravitational form factors
Zeinab Dehghan🇮🇷 · F. Almaksusi🇮🇷 · K. Azizi🇮🇷
We investigate the mechanical properties of the proton by extracting its flavor-decomposed gravitational form factors (GFFs) using Light-Cone QCD sum rules (LCSR). These form factors encode critical information about the internal dynamics and spatial distribution of energy, momentum, and internal forces within the proton. The flavor decomposition of the quark sector indicates the role of each flavor in the proton's pressure and shear force distributions. Our results show that the up quark contributes more significantly compared to the down quark in the three conserved proton GFFs, as well as in the energy and shear force distributions. Additionally, we define the non-conserved form factor $c ˉ^{q} (t)$ , which takes part in the distributions of energy and pressure; the latter is essential for maintaining proton stability. Furthermore, we determine the proton's mass and mechanical radii, providing valuable insight into its internal structure and dynamics.
↳ hep-phhep-exhep-latnucl-thJHEP(2025)·29 citations
18
The charmonium-like exotic hadron productions in $e^{+} e^{-}$ collisions at the BESIII energy with the PACIAE model
Jian Cao🇨🇳 · Wen-Chao Zhang🇨🇳 · Zhi-Lei She🇨🇳 · An-Ke Lei🇨🇳 · Jin-Peng Zhang🇨🇳 · Hua Zheng🇨🇳 · Dai-Mei Zhou🇨🇳 · Yu-Liang Yan🇨🇳 · Zhong-Qi Wang🇨🇳 · Ben-Hao Sa🇨🇳
Inspired by the BESIII observation of exotic hadron $G$ (3900) in $e^{+} e^{-} \to D D ˉ$ process [PRL 133(2024)081901], we use the parton and hadron cascade model PACIAE to simulate the productions of charmonium-like exotic hadrons including $X (3872)$ , $Z_{c} (3900)^{0}$ and $G (3900)$ in the $e^{+} e^{-}$ annihilations at $s$ =4.95 GeV. The charmonium-like candidates are recombined by Dynamically Constrained Phase-space Coalescence model using component mesons $D D ˉ$ (for $G (3900)$ ) or $D D ˉ^{*} / D ˉ D^{*}$ (for $X (3872)$ , $Z_{c} (3900)^{0}$ and $G (3900)$ ) in the PACIAE simulated final hadronic state. We then calculate, for the first time, the charmonium-like candidate's orbital angular momentum quantum number in its rest frame and perform the spectral classification for each of the above candidates. For $G (3900)$ , as its $J^{P C}$ is $1^{--}$ , it is identified as the $P$ -wave $D D ˉ$ or $D D ˉ^{*} / D ˉ D^{*}$ state. Meanwhile, for $X (3872)$ and $Z_{c} (3900)^{0}$ , as their $J^{P C}$ s are, respectively, $1^{++}$ and $1^{+-}$ , they are identified as the $S$ -wave $D D ˉ^{*} / D ˉ D^{*}$ candidates. It is observed that the yield of the $P$ -wave $G (3900)$ composed of $D D ˉ^{*} / D ˉ D^{*}$ is significantly larger than that composed of $D D ˉ$ . Moreover, in the $D D ˉ^{*} / D ˉ D^{*}$ channel, the yield of the $P$ -wave $G (3900)$ is around three times as large as the yield of the $S$ -wave $Z_{c} (3900)^{0}$ , and it is around two orders of magnitude as large as the yield of the $S$ -wave $X (3872)$ . Finally, significant discrepancies are observed in the transverse momentum spectra and the rapidity distributions among the $X (3872)$ , $Z_{c} (3900)^{0}$ and $G (3900)$ states. These discrepancies are proposed as valuable criteria for identifying the different charmonium-like exotic hadrons from each other.
↳ hep-phnucl-thPRD(2025)·8 citations
19
Thermoelectric effects of an interacting hadron gas in the presence of an external magnetic field
Kamaljeet Singh🇮🇳 · Kshitish Kumar Pradhan🇮🇳 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳
The hot and dense hadronic medium formed during the heavy-ion collisions at the Relativistic Heavy Ion Collider and Large Hadron Collider energies can show thermoelectric effects in the presence of temperature gradients and nonzero baryon chemical potential. In this article, we study the thermoelectric coefficients of an interacting hot and dense hadron gas using the relativistic Boltzmann transport equation under the relaxation time approximation. We discuss the thermoelectric properties within different frameworks of hardon resonance gas models. In the presence of an external magnetic field, the thermoelectric coefficients become anisotropic, which leads to Hall-like thermoelectric coefficients, namely Nernst coefficients, along with the magneto-Seebeck coefficients. For the first time, we also estimate the Thomson coefficient of the medium, which comes into the picture due to the temperature dependence of the Seebeck coefficient of the medium. In the context of studying the thermoelectric generator performance, we calculate the values of the thermoelectric figure of merit of the medium.
↳ hep-phhep-exhep-thnucl-ex+1PRD(2025)·9 citations
20
Stability conditions for bound states in antiprotonic atoms
Fredrik Parnefjord Gustafsson🇨🇭 · Daniel Pęcak🇵🇱 · Tomasz Sowiński🇵🇱
We study the stability of bound antiprotons in close proximity to the atomic nucleus. Using experimental data from X-ray spectroscopy measurements of antiprotonic atom transitions, we tune a minimal theoretical framework and estimate parameter ranges where the strong or electromagnetic decay channels govern the stability of the deepest bound states. In this way, we present an overview of the dominant decay mechanism of antiprotonic orbits for a given principle quantum number, to assist future spectroscopic experiments on antiprotonic atoms.
↳ physics.atom-phnucl-thPRC(2025)·3 citations
21
Studying Effects of Evolution on Charge Separation in Small Collision System with A MultiPhase Transport model
Yi Xu🇨🇳 · Chen Gao🇨🇳 · Shi-Xue Zhang🇨🇳 · Wei-Tian Deng🇨🇳
In relativistic high energy heavy-ion collisions, Chiral Magnetic Effect (CME) could produce a charge separation in QGP. The charge separation could survive into final hadron system during evolution, observed as correlator $Δ γ$ . This physics procedure could also occurs in small collision system if CME emerge in the QGP droplet. In this paper, we study the effects of QGP droplet evolution on charge separation in small collision system, based on AMPT model. Our calculation indicates that, with given initial charge separation, the effects of parton level evolution and hadron level evolution weaken the charge separation indeed, but there is still enough signals could remained. Furthermore, we found that, the contribution of background to $Δ γ$ is negligible in small collision system. So, we propose the small collision system being a good place to confirm contribution of CME.
↳ hep-phnucl-thPRC(2025)·2 citations

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