Mon·Jul 28, 2025Monday·July 28, 2025

1. 01*

   Color-glass condensate beyond the Gaussian approximation

   Jani Penttala🇺🇸

   In the high-energy limit, perturbative calculations in QCD are conveniently done using the dipole picture which factorizes the scattering amplitude into a perturbative part and the nonperturbative scattering off the nuclear target, described using correlators of Wilson lines. These correlators can be computed in the color-glass condensate effective field theory by using a Gaussian model for the color density of the target. In this work, we generalize the Gaussian model to a generic function that is local in the transverse coordinates and the light-cone time, and show how to compute physical Wilson-line correlators in this model. We also consider a simple model for the color density based on stable probability distributions and show that the small-dipole behavior of the dipole amplitude is modified from quadratic to a power law, where the power is given by the stability parameter of the distribution. This generalization of the Gaussian model is suitable for numerical applications in the high-energy limit and can be used in future phenomenological studies of the nuclear structure.

   hep-phnucl-thJHEP(2026)·3 citations
2. 02*

   Axial-vector molecular structures $B_c^{\ast \pm }{B}_c^{\mp }$

   S. S. Agaev🇦🇿 · K. Azizi🇮🇷 · H. Sundu🇹🇷

   The axial-vector molecular structure ${\mathcal{M}}_{\mathrm{AV}}=(B_c^{\ast +}{B}_c^{-}+B_c^{\ast -}{B}_c^{+})/2$ is explored in QCD sum rule framework. The mass and current coupling of this compound are found by means of the two-point sum rule method. It turns out that the mass of ${\mathcal{M}}_{\mathrm{AV}}$ is equal to $m=(12770\pm 60)\mathrm{MeV}$ making possible its dissociations to pairs of $J/\psi {\eta }_b$, ${\rm Y}{\eta }_c$, $B_c^{\ast +}{B}_c^{-}$, and $B_c^{\ast -}{B}_c^{+}$ mesons. The partial widths of these decay modes contain the strong couplings at ${\mathcal{M}}_{\mathrm{AV}}$-meson-meson vertices which are calculated by utilizing the three-point sum rule method. The full decay width of the molecule ${\mathcal{M}}_{\mathrm{AV}}$ is formed due to these dominant processes and amounts to $\Gamma [{\mathcal{M}}_{\mathrm{AV}}]=(93\pm 14)\mathrm{MeV}$. Our results for parameters $m$ and $\Gamma [{\mathcal{M}}_{\mathrm{AV}}]$ of the hadronic molecule ${\mathcal{M}}_{\mathrm{AV}}$ are useful for experimental studies of various fully heavy four-quark mesons.

   hep-phhep-exhep-latPLB(2025)·7 citations
3. 03*

   Oscillation Baryogenesis via Ultraviolet Dark Matter Freeze-In

   Tian Dong🇺🇸 · Conor M. Floyd🇺🇸 · Antonia Hekster🇺🇸 · Derek J. Li🇺🇸 · Brian Shuve🇺🇸 · David Tucker-Smith🇺🇸

   We investigate baryogenesis from dark matter oscillations in the ultraviolet freeze-in regime. We find that the mechanism can simultaneously accommodate the observed abundances of baryons and dark matter for dark matter masses in the 10 keV to MeV range, provided the reheat temperature lies between the temperature of the electroweak phase transition and ~10 TeV. The mechanism predicts observable consequences due to the presence of a light dark matter component that is relativistic during structure formation, and X-ray bounds on decaying dark matter can set strong constraints depending on the operator mediating dark matter production.

   hep-phPRD(2025)·0 citations
4. 04*

   Return of the Lepton Number: Sterile Neutrino Dark Matter Production and the Revival of the Shi-Fuller Mechanism

   Cannon M. Vogel🇺🇸 · Helena García Escudero🇺🇸 · Julien Froustey🇺🇸 · Kevork N. Abazajian🇺🇸

   We explore resonant production of sterile neutrino dark matter via the Shi-Fuller (SF) mechanism, revisiting its cosmological viability in light of recent results demonstrating that lepton-number asymmetries $L_{\alpha }\gtrsim 1$ at temperatures $T>20\mathrm{MeV}$ are consistent with big bang nucleosynthesis (BBN). Using a quasiclassical Boltzmann transport calculation of the dark matter production, we compute the nonthermal phase space distributions of sterile neutrinos across a broad range of particle mass $m_s$ and mixing angle ${\sin }^2(2\theta )$ parameter space. We then evolve the resulting distributions through linear structure formation using CLASS and fit the resulting matter power spectra to thermal warm dark matter (WDM) transfer functions, enabling a direct mapping between SF models and equivalent thermal WDM particle masses $m_{\mathrm{th}}$. This allows us to reinterpret existing structure formation limits and Lyman-$\alpha$ forest preferences in the context of SF production. We find that lepton asymmetries $L\gtrsim 0.5$ at high temperatures open significant viable parameter space in the $m_s\gtrsim 10\mathrm{keV}$ and ${\sin }^2(2\theta )\lesssim 10^{-14}$ regime, compatible with both x-ray constraints from NuSTAR and INTEGRAL/SPI and recent Lyman-$\alpha$ inferences of $m_{\mathrm{th}}\approx 4.1\mathrm{keV}$. Following lepton number evolution below 20 MeV, we also specifically show that this lepton asymmetry parameter space is compatible with BBN and cosmic microwave background constraints. We present updated constraints, a refined $m_{\mathrm{th}}$ fitting function, and power-law approximations for $L$ across the parameter space. Our results motivate future x-ray observations targeting the $\sim 20\mathrm{keV}$ photon regime and testing of the $m_{\mathrm{th}}\gtrsim 10\mathrm{keV}$ WDM region.

   hep-phastro-ph.COPRD(2025)·10 citations
5. 05*

   Freezeout at constant energy density and spin polarization in heavy-ion collisions

   Andrea Palermo🇺🇸 · Masoud Shokri🇩🇪

   Using the local equilibrium density operator, we develop a geometry-informed linear response theory that takes into account the parameterization of the freezeout hypersurface before the gradient expansion is carried out. Assuming local equilibrium on an iso-energy density hypersurface, we study the $\Lambda$ hyperon spin polarization, and compute corrections to the isothermal case due to finite density. We argue that corrections to isothermal freezeout should be small, and that even in heavy ion collisions with energy as low as $\sqrt{s_{NN}}=11.5$ GeV they constitute at most a $10\%$ effect. They may, however, become relevant for local polarization observables.

   hep-phnucl-thPRD(2025)·2 citations
6. 06*

   Particle Correlations in Jets

   Wenbin Zhao🇺🇸 · Volker Koch🇺🇸 · Feng Yuan🇺🇸

   We study particle correlations in high energy jets by comparing the measured energy-energy correlator (EEC) with that constructed from two individual energy flows with respect to the jet axis. This comparison demonstrates that genuine correlations exists for small angle and moderate/large angle, indicating that they are coming from correlated splitting. This method will provide a unique tool to disentangle different physics, by comparing the genuine correlations in jet EEC between heavy ion collisions and proton-proton collisions. It will help to expose the medium modification of parton splitting in hot QCD medium. On the other hand, the medium responses are expected to be canceled out in the genuine correlations.

   hep-phnucl-exnucl-th8 citations
7. 07*

   Deep Neural Network Driven Simulation Based Inference Method for Pole Position Estimation under Model Misspecification

   Daniel Sadasivan🇨🇱 · Isaac Cordero🇨🇱 · Andrew Graham🇨🇱 · Cecilia Marsh🇨🇱 · Daniel Kupcho🇨🇱 · Melana Mourad🇨🇱 · Maxim Mai🇺🇸

   Simulation Based Inference (SBI) is shown to yield more accurate resonance parameter estimates than traditional chi-squared minimization in certain cases of model misspecification, demonstrated through a case study of pi-pi scattering and the rho(770) resonance. Models fit to some data sets using chi-squared minimization can predict inaccurate pole positions for the rho(770), while SBI provides more robust predictions across the same models and data. This result is significant both as a proof of concept that SBI can handle model misspecification, and because accurate modeling of pi-pi scattering is essential in the study of many contemporary physical systems (e.g., a1(1260), omega(782)). The method of Simulation Based Inference is shown to lead to a more accurate resonance parameter estimation than traditional chi-squared minimization in certain cases of model misspecification in a case-study of pi-pi scattering and the rho(770)-resonance. Models fit to certain data sets using chi-squared minimization can make inaccurate predictions for the pole position of the rho(770). SBI is shown to make a more robust predictions for the pole positions. This is significant, both as a proof of concept that the SBI method can be used in cases of model misspecification, and because models of pi-pi scattering are a crucial part to many physical systems of contemporary interest (e.g., a1(1260), omega(782)).

   hep-phnucl-thstat.APstat.MLPRD(2026)·7 citations
8. 08*

   Structure of heavy quarkonia in a strong magnetic field

   Ahmad Jafar Arifi🇯🇵 · Kei Suzuki🇯🇵

   We investigate the structural modifications of heavy quarkonia in the presence of strong magnetic fields using a constituent quark model. By incorporating the effects of spin mixing and quark Landau levels, we employ a nonrelativistic Hamiltonian that captures the essential features of quark dynamics in a magnetic field. The two-body Schrödinger equation is solved using the cylindrical Gaussian expansion method, which respects the cylindrical symmetry induced by a magnetic field. We extract the corresponding light-front wave function (LFWF) densities and analyze their transverse and longitudinal structures, revealing characteristic features such as transverse momentum broadening. While the longitudinal structure is only slightly modified within the nonrelativistic Hamiltonian, we discuss some corrections that can significantly affect its longitudinal structure. Furthermore, we discuss the structure modifications of excited states and find notable changes in the LFWF densities, and state reshuffling near avoided crossings. These results demonstrate the sensitivity of hadron structure to external magnetic fields and help bridge our understanding to relativistic approaches.

   hep-phhep-latnucl-thPRD(2025)·6 citations
9. 09*

   Effect of eigenstates on spectra in coupled-channel scattering with the chiral unitary model

   Takuma Nishibuchi🇯🇵 · Tetsuo Hyodo🇯🇵

   In recent years, as experimental data on the excited $\Xi (1620)$ and $\Xi (1690)$ states have accumulated, theoretical analyses based on chiral dynamics have also been actively pursued. In this study, we construct theoretical models within the chiral unitary approach to reproduce recent experimental data, and perform a model interpolation to examine the relationship between the poles appearing in different models. We then calculate the invariant mass spectra of the ${\pi }^{+}{\Xi }^{-}$ system in the ${\Xi }_c\to \pi \pi \Xi$ decay, using the scattering amplitudes obtained from each model, to investigate how the distinct pole structures influence the observable spectrum.

   hep-phnucl-thPoS(2026)·0 citations
10. 10*

    NRQCD Re-Confronts LHCb Data on Quarkonium Production within Jets

    Yunlu Wang🇨🇳 · Daekyoung Kang🇨🇳 · Hee Sok Chung🇰🇷

    We compare LHCb measurements of $J/\psi$ and $\psi (2S)$ transverse momentum distributions within jets with QCD calculations, which may be crucial in understanding the quarkonium production mechanism. Our theoretical calculations are based on the fragmenting jet function formalism, while the nonperturbative formation of quarkonia is described by the nonrelativistic QCD factorization formalism. We include the newest refinements in the perturbative calculation including resummation of threshold and DGLAP logarithms. We find that the $\psi (2S)$ data has the potential to discriminate between the different production mechanisms proposed in the literature.

    hep-phPRD(2025)·11 citations
11. 11*

    Determination of the sensitivity of $\Lambda$ and ${\Lambda }_c^{+}$ electric dipole moments using a full angular analysis

    R.T. Ovsiannikov🇺🇦 · A.Yu. Korchin🇺🇦 · E. Kou🇫🇷

    A search for a non-zero Electric Dipole Moment (EDM) of particles, which is a clear signal of a violation of CP symmetry, is one of the unique ways to discover physics beyond the Standard Model. In this paper, we discuss a method for determining the EDM of baryons from the full angular distribution of final particles in electron-positron pair annihilation processes. The question of how accurately the state-of-the-art experiments can determine EDM of $\Lambda$ and ${\Lambda }_c^{+}$ baryons is discussed in detail. Investigating the pseudo-statistics that corresponds to the BESIII experiment, the estimated sensitivity for $\Lambda$ EDM is obtained at the level of $10^{-18}$ $e$cm. The similar figure for the proposed Super Tau-Charm Facility (STCF) experiment is found to be of the order of $10^{-20}$ $e$cm. For the ${\Lambda }_c^{+}$ EDM, the calculated sensitivity for the STCF experiment is $10^{-16}$ $e$cm. The case of a polarized initial electron is considered separately as such an option is planned at the STCF experiment.

    hep-phEPJC(2025)·2 citations
12. 12*

    Polarization of the $\varphi$ meson in the hadronic phase with nucleon scatterings and a viscous hydrodynamic background

    Eduardo Grossi🇮🇹 · Andrea Palermo🇺🇸 · Ismail Zahed🇺🇸

    We extend our previous work on the spin alignment of the $\varphi$ vector meson in the hadronic phase of the Quark Gluon Plasma, by including effects of nucleon scatterings. The emission rates are calculated in a realistic hydrodynamic background simulated with the code Fluid$u$m, for different beam energies. We find that all the effects taken into account cannot explain the out-of-plane spin alignment of the $\varphi$ meson observed experimentally.

    hep-phnucl-thPRC(2025)·4 citations
13. 13*

    Revisiting the ${\Lambda }_c^{+}\to {\bar{K}}^0\eta p$ reaction: the role of $N^{\ast }(1535),N^{\ast }(1650)$ and $\Sigma (1620)$

    Jing Song🇨🇳 · Melahat Bayar🇪🇸 · Yi-Yao Li🇨🇳 · Eulogio Oset🇪🇸

    We perform a theoretical study of the weak decay ${\Lambda }_c^{+}\to {\bar{K}}^0\eta p$ using a coupled-channel chiral unitary approach that incorporates both pseudoscalar-baryon and vector-baryon interactions. Our framework includes contributions from both internal and external weak emission mechanisms, as well as strong final state interactions. We assume that the $N^{\ast }(1535)$ and $N^{\ast }(1650)$ resonances are dynamically generated through meson-baryon scattering and they appear as distinct structures in the $\eta p$ invariant mass distributions. {A clear peak also appears in the ${\bar{K}}^{0}p$ invariant mass distribution around 1620~MeV, associated with the dynamically generated $\Sigma (1620)$ resonance.} Notably, this work provides the first theoretical description of the simultaneous observation of these two related $N^{\ast }$ resonances in the same meson-baryon final state. Our results highlight the crucial role of final state interaction and the interplay between different weak decay topologies in shaping the resonance patterns. These findings offer new insights into the nature of nucleon excitations and support the interpretation of $N^{\ast }(1535)$ and $N^{\ast }(1650)$ as dynamically generated states. {Moreover, the identification of the $\Sigma (1620)$ further supports the picture of hadronic molecular structures emerging from meson-baryon interactions in the non-perturbative QCD regime.}

    hep-phEPJC(2025)·3 citations
14. 14*

    Quark models: What can they teach us?

    Alexey Nefediev🇩🇪

    Quark models have a more than 60-year history and through this time they served as a powerful investigation and prediction tool in hadronic physics. In recent years, a lot of new experimental information has been arriving on hadrons that do not qualify as simple quark model states. Yet, quark models remain the cornerstone of the classification scheme for hadrons, provide valuable insights into various phenomena inherent in QCD, and facilitate gaining a clear and physically transparent picture of the underlying physics. In the spotlight of this review is a chiral quark model inspired by quantum field theory approach to confined quarks. The model is well suited for studies of spontaneous breaking of chiral symmetry in the vacuum of QCD as well as its implications in the spectrum of hadrons. It can also be employed to investigate chiral restoration at finite temperatures.

    hep-phhep-latInt.J.Mod.Phys.A(2025)·4 citations
15. 15*

    Is flavor discrete?

    Alexei Y Smirnov🇩🇪

    Relevance of the discrete symmetries for explanation of the observed flavor structures in the leptonic sector is considered. Achievements of the "traditional'' discrete symmetry approach and the modular symmetry approach are confronted. Minimal models with small number of parameters do not work. Complication of symmetry prescriptions allow to introduce new free parameters and thus describe the data but simultaneously bring two connected problems: (i) problem of "missing" representations, and (ii) problem of selection of certain point in huge discrete parameter space formed by possible charge assignments. Both problems must be addressed in complete model. Alternatively, one can keep minimal symmetry prescription but extend models introducing new physics unrelated to the original flavor symmetry. The low energy predictions can be "polluted" by additional physics such as effects of coupling to hidden sector, RGE running, decoupling of heavy degrees of freedom, mixing with sterile neutrinos, {\it etc.} The set up with discrete symmetries in the Hidden sector which communicates to the visible one via the neutrino portal and the basis fixing symmetry still looks promising.

    hep-ph1 citation
16. 16*

    EVAluation of the Equivalent Vector Boson Approximation at highest energy colliders

    Benjamin Dahlén🇸🇪 · Maximilian Löschner🇩🇪 · Krzysztof Mękała🇩🇪 · Jürgen Reuter🇩🇪 · Panagiotis Stylianou🇩🇪

    Collider processes at the highest available partonic center-of-mass energies - 10 TeV and above - exhibit a new regime of electroweak interactions where electroweak gauge bosons mostly act as quasi-massless partons in vector boson fusion processes. We scrutinize these processes using the Equivalent Vector boson Approximation (EVA) based on its implementation in the Monte Carlo generator framework Whizard. Using a variety of important physics processes, including top pairs, Higgs pairs, neutrino pairs, and vector boson pairs, we study the behavior of processes initiated by transverse and longitudinal vector bosons, both $W$ and $Z$ induced. By considering several distributions for each process, we conclude that: there is no universal, process-independent prescription which minimizes the discrepancies between EVA- and matrix-element-based predictions; even by resorting to process-by-process prescriptions, we typically observe significant observable-dependent effects; the uncertainties associated with parameter dependencies in the EVA can be as large as $\mathcal{O}$(100%), and can only possibly be reduced by careful process-dependent kinematical selections.

    hep-phhep-exJHEP(2025)·5 citations
17. 17*

    Determination of the $\varphi$-meson production process and its absorption cross section via directed flow

    Jan Steinheimer🇩🇪 · Tom Reichert🇩🇪 · Marcus Bleicher🇩🇪

    We show that the directed flow of $\varphi$-mesons in Au+Au collisions at $\sqrt{s_{NN}}=3$ GeV, is sensitive on production and the absorption cross section of the $\varphi$ in a nuclear medium. This provides a new observable to constrain the in-medium properties of the $\varphi$ which is independent of its absolute production rate. It is shown that the STAR data disfavor any significant $\varphi$-N absorption in dense nuclear matter and are consistent with a very small cross section of the $\varphi$ comparable to the vacuum cross section. The similarity of the $\varphi$-meson and proton directed flow also indicates that the $\varphi$ is produced in conjunction with a baryon.

    hep-phnucl-thPLB(2025)·6 citations
18. 18*

    An analytic result for the $0\to ggHHH$ amplitude

    John M. Campbell🇺🇸 · Giuseppe De Laurentis🇬🇧 · R. Keith Ellis🇬🇧

    We present a fully analytic calculation of the leading-order one-loop amplitude for triple Higgs production via gluon fusion, $gg\to HHH$, retaining full dependence on the mass of the heavy quark circulating in the loop. This amplitude provides a direct probe of the triple and quartic Higgs self-couplings, the measurement of which is a central goal of current and future colliders. The amplitude can be presented in compact form thanks to the use of analytic reconstruction techniques, based on finite-field and $p$-adic evaluations, partial fraction decompositions, and primary decompositions to identify common numerator factors. Our results provide a compact and efficient representation of the matrix element for this process, enabling evaluations that are more than an order of magnitude faster than existing numerical alternatives.

    hep-phJHEP(2026)·2 citations
19. 19*

    Pushing the hybrid approach to low beam energies with dynamic initial conditions from hadronic transport

    Renan Góes-Hirayama🇩🇪 · Joscha Egger🇩🇪 · Zuzana Paulínyová🇸🇰 · Iurii Karpenko🇨🇿 · Hannah Elfner🇩🇪

    While hybrid approaches of relativistic hydrodynamics+transport have been well established for the dynamical description of heavy-ion collisions at high beam energies, moving to lower beam energies is challenging. In this work, we propose dynamic initial conditions for the viscous hydrodynamic evolution in heavy-ion collisions at low to intermediate beam energies. They are comprised of core hadrons based on the local energy density during the pre-equilibrium hadronic evolution. The SMASH-vHLLE hybrid approach is then applied to lower beam energies, achieving good agreement with measured bulk observables between $\sqrt{s_{\mathrm{NN}}}=3$ and $9.1\mathrm{GeV}$, thus providing guidance for measurements in STAR-BES and CBM at FAIR.

    hep-phhep-exnucl-thPRC(2026)·9 citations
20. 20*

    Left-Handed Physics is not right for EDMs

    Marco Ardu🇪🇸 · Sacha Davidson🇫🇷 · Nicola Valori🇪🇸

    Heavy New Physics models with lepton flavour-changing interactions are motivated by neutrino masses, and generically induce dipole interactions for leptons, which can be flavour-changing ($l_j\to l_i\gamma$) or flavour-diagonal (magnetic and electric dipole moments(edms)). We focus on models with complex couplings, and where the singlet Standard Model leptons ($\{e_R^i\}$) do not interact with the New Physics. In such models, edms are calculated to arise at two loops, despite that complex amplitudes for $l_j\to l_i\gamma$ appear at one loop. We explore whether the extra loop suppression of edms survives flavour basis rotations that could be induced by flavour-changing NP contributions to the charged lepton mass matrix. We show that one-loop edms vanish in both the mass and Yukawa eigenstate bases.

    hep-phEPJC(2025)·2 citations
21. 21*

    Initial conditions and bulk viscosity effects on $\Lambda$ polarization in high-energy heavy ion collisions

    Andrea Palermo🇺🇸

    The $\Lambda$ spin polarization is a crucial probe of the gradients of velocity and temperature in the quark-gluon plasma generated in heavy-ion collisions. However, it is still not systematically used to tune hydrodynamic models. In this work, we investigate the influence of different initial conditions and parametrization of the bulk viscosity on $\Lambda$ polarization, showing that they affect the local polarization significantly. These results highlight the impact that the use of local polarization can have on refining theoretical models. Finally, we compare our results, including feed-down corrections, with experimental data from high-energy heavy-ion collisions at STAR and ALICE, and demonstrate the crucial role of bulk viscosity in generating the correct sign of longitudinal polarization at LHC energies.

    hep-phnucl-thEPJ Web Conf.(2026)·0 citations
22. 22*

    Comprehensive ALP Searches in Meson Decays

    Jorge Alda🇮🇹 · Marta Fuentes Zamoro🇪🇸 · Luca Merlo🇪🇸 · Xavier Ponce Díaz🇨🇭 · Stefano Rigolin🇮🇹

    We present a comprehensive study of axion-like particles (ALPs) in meson decays, combining effective field theory and ultraviolet models within the open-source tool ALPaca. The analysis accounts for running and matching effects across energy scales, including non-perturbative QCD corrections via chiral perturbation theory. We discuss several benchmark models, both flavour-universal and non-universal, using the most up-to-date theoretical computations for ALP decays and branching ratios. Experimental signatures such as prompt, displaced, and invisible decays are included. A dedicated analysis of the Belle II anomaly in the decay $B^{+}\to K^{+}\nu \bar{\nu }$ is performed. Our results highlight the power of flavour observables in constraining ALPs and provide a versatile foundation for future searches.

    hep-phhep-ex21 citations
23. 23*

    Relativistic scalar dark matter drag forces on a black hole binary

    Shuo Xin🇺🇸 · Elias R. Most🇺🇸

    Dark matter around black holes can induce drag forces through dynamical friction and accretion, potentially affecting the orbital evolution and gravitational wave emission of binary systems. While dynamical friction from scalar field dark matter has been studied in the relativistic regime for single black holes, the case of a binary black hole (BBH) has remained unexplored. As a first step, we present a series of two-dimensional general-relativistic simulations of BBH in a wind tunnel for an asymptotically homogeneous scalar field background. We extract the drag forces, torque, mass and charge accretion acting on the binary, and analyze their dependence on the binary separation, velocity and the scalar field parameters. We find that the binary's drag is not a simple superposition of two isolated black holes; the presence of a companion modifies the gravitational wake and yields significant nonlinearities. This additional force and torque can (in principle) modify the inspiral and induce a dephasing of the gravitational wave signal.

    ↳ gr-qcastro-ph.HEhep-phPRD(2026)·4 citations
24. 24*

    Classification of flavor dependence of Chiral Magnetic Effect with Deep Neural Network using multiple correlators

    Somdeep Dey🇮🇳 · Abhisek Saha🇨🇳 · Soma Sanyal🇮🇳

    We study the flavor dependence of the Chiral Magnetic Effect (CME) by analyzing two key charge-separation correlators used to characterize the charge separation effect: the conventional $\Delta \gamma$ and the recently proposed $R_{{\psi }_2}$. Using the AMPT (A Multiphase Transport) model with an initial-state centrality-dependent charge separation, we evaluate the sensitivity of these correlators to 2-flavor ($u,d$) and 3-flavor ($u,d,s$) quark scenarios. While both correlators exhibit modest flavor dependence in mid-central (30-50\%) collisions, their discriminative power varies significantly with centrality and transverse momentum ($p_T$), limiting their utility disentangling the flavor dependent scenarios. To overcome these limitations, we develop a neural network classifier trained on final-state hadronic observables (e.g., $d{N}_{ch}/d\eta$, $p_T$ spectra). The model achieves $>90\%$ accuracy in flavor classification by leveraging multi-observable correlations, with $p_T$-differential features proving particularly discriminative. Crucially, by incorporating background contributions directly into the training data, our approach provides more reliable flavor estimates than correlator-only methods.

    ↳ nucl-thhep-phnucl-exPRC(2026)·2 citations
25. 25*

    Constraining the origin of the highest-energy cosmic-ray events detected by the Pierre Auger Observatory: a three-dimensional approach

    Marta Bianciotto (for the Pierre Auger Collaboration)

    Unveiling the sources of ultra-high-energy cosmic rays remains one of the main challenges of high-energy astrophysics. Measurements of anisotropies in their arrival directions are key to identifying their sources, yet magnetic deflections obscure direct associations. In this work, we reconstruct the sky regions of possible origin of the highest-energy cosmic-ray events detected by the Pierre Auger Observatory by tracing their trajectories through Galactic magnetic fields using up-to-date models, while fully accounting for energy and directional uncertainties. A mixed composition at injection is assumed to model the detected charge distributions of such events. Different classes of astrophysical sources are investigated and tested for a correlation with the inferred regions of origin of the events. By incorporating constraints on the maximum propagation distances, we also allow for a three-dimensional localization of the possible source regions. Our findings provide new constraints on the sources of the highest-energy cosmic particles and offer fresh insights into the role of Galactic magnetic fields in shaping the observed ultra-high-energy cosmic-ray sky.

    ↳ astro-ph.HEhep-phPoS(2025)·5 citations
26. 26*

    Large-scale anisotropies of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory

    Marta Bianciotto (for the Pierre Auger Collaboration)🇮🇹

    Measurements of anisotropies in the arrival directions of ultra-high-energy cosmic rays are crucial to pinpoint their sources, which are yet to be discovered. A dipolar anisotropy in right ascension above 8~EeV has been detected by the Pierre Auger Observatory with a significance of $6.8\sigma$. The direction of the dipole suggests an extragalactic origin of ultra-high-energy cosmic rays above those energies. In this contribution, we provide an overview of the studies on large-scale anisotropies in the arrival directions of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory with energy thresholds from $\sim 0.03$~EeV up to $32$~EeV and we present and discuss the recent results achieved with the latest available dataset, which includes 19 years of operations -- resulting in a total exposure of 123,000~km${}^2$~sr~yr and nearly 50,000 events above 8~EeV.

    ↳ astro-ph.HEhep-phEPJ Web Conf.(2025)·1 citation
27. 27*

    Measurement of the Inelastic Proton-Proton Cross-Section at $\sqrt{s}\ge 40$ TeV Using the Hybrid Data of the Pierre Auger Observatory

    Olena Tkachenko (for the Pierre Auger Collaboration)🇨🇿

    Measuring proton-proton interaction cross-sections at center-of-mass energies above 40 TeV remains a significant challenge in particle physics. The Pierre Auger Observatory provides a unique opportunity to study the interactions at the highest energies through the distribution of the depth of maximum shower development ($X_{\max }$) observed by its Fluorescence Detector. In previous studies, the determination of the interaction cross-section at ultrahigh energies has relied on the assumption that the tail of the $X_{\max }$ distribution is proton-dominated, which restricts the analysis to a limited energy range below the ankle and introduces related systematic uncertainties. In this contribution, we adopt a novel method for the simultaneous estimation of the proton-proton interaction cross-section and the primary cosmic-ray mass composition using data from the Pierre Auger Observatory, avoiding assumptions about one quantity to infer the other and thus improving the accuracy and robustness of our analysis. In addition, a systematic shift in the $X_{\max }$ scale is fitted to account for both experimental uncertainties and theoretical constraints on the modeling of particle interactions. The obtained results are consistent with previous analyses and provide additional constraints on hadronic interaction models. The measured proton-proton inelastic cross-section at ultra-high energies agrees well with extrapolations of accelerator data. The inferred cosmic-ray composition and the $X_{\max }$-scale shift are also compatible with previous estimates.

    ↳ astro-ph.HEhep-ph2 citations
28. 28*

    Jet Quenching in Holographic QCD as an Indicator of Phase Transitions in Anisotropic Regimes

    Irina Ya. Aref'eva🇷🇺 · Ali Hajilou🇷🇺 · Alexander Nikolaev🇷🇺 · Pavel Slepov🇷🇺

    In this paper, we employ the gauge/gravity duality to study jet quenching (JQ) phenomena in the quark-gluon plasma. For this purpose, we implement holographic QCD models constructed from an Einstein-Maxwell-dilaton gravity at finite temperature and finite chemical potential for light and heavy quarks. The models capture both the confinement and deconfinement phases of QCD and the first-order phase transitions. We calculate the JQ parameter in different models and compare them with the experimental data obtained in heavy-ions studies. In particular, we investigate how JQ, as a function of temperature $T$, chemical potential $\mu$, and magnetic field $c_B$, serves as a probe for identifying first-order phase transitions within the $(T,\mu ,c_B)$ parameter space of holographic QCD. Particular attention is paid to the dependence of JQ on the parameter $\nu$, which characterizes longitudinal versus transverse anisotropy relative to the heavy-ion collision axis. By analyzing the dependence of the JQ parameters on these thermodynamic variables, we map critical regions associated with phase boundaries. We compare our findings to earlier studies of the running coupling constant's behavior within the gauge-gravity duality framework. This approach provides new insights into the interplay between non-perturbative dynamics and phase structure in strongly coupled systems.

    ↳ hep-thhep-phPRD(2025)·7 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.