Tue·Jul 15, 2025Tuesday·July 15, 2025

1. 01*

   Unveiling atomic electron motion effects in $e^{+}{e}^{-}$ high energy collisions at NA64

   Fernando Arias-Aragón🇮🇹 · Giovanni Grilli di Cortona🇮🇹 · Enrico Nardi🇮🇹

   Atomic electron motion is responsible for well-studied effects observed in low-energy (MeV-scale) processes. Recently, interest in this phenomenon has also emerged within the high-energy physics community, due to its potential to increase significantly the center-of-mass energy in fixed-target experiments. However, direct experimental evidence of this effect in high energy collisions has yet to be observed. We argue that a striking manifestation of atomic electron momenta could be revealed by the NA64 experiment at CERN during the proposed run with a 40 GeV positron beam. At this energy, ${\mu }^{+}{\mu }^{-}$ production via positron annihilation on electrons at rest is kinematically forbidden. The detection of ${\mu }^{+}{\mu }^{-}$ pairs from the annihilation channel would thus constitute direct evidence of an increase in the center-of-mass energy resulting from atomic electron motion. We also investigate the expected signatures for the proposed 60 GeV run, as well as for the data already collected at 70 GeV. Intriguingly, in both these cases, the predicted number of ${\mu }^{+}{\mu }^{-}$ pairs from positron annihilation is reduced compared to the electron-at-rest approximation.

   hep-phJHEP(2025)·4 citations
2. 02*

   Phase transition of hot dense QCD Matter from a refined holographic EMD model

   Zhibin Li🇨🇳 · Fei Wang🇨🇳

   In this study, we begin by delineating the Einstein-Maxwell-Dilaton (EMD) model within the holographic QCD framework and deriving the equation of state through holographic renormalization. Subsequently, we utilize the Wald method to determine the first law of thermodynamics for a five-dimensional black hole, thereby confirming the alignment of our EMD model with the thermodynamics of the grand canonical ensemble in the boundary field theory. By employing the $n-2$ form in the Wald method, we proceed to calculate the shear viscosity in Gauss-Bonnet gravity. The results we obtain demonstrate consistency with those from first-order metric perturbation. Furthermore, we construct a refined EMD model that attains quantitative agreement with the lattice QCD equation of state and baryon number susceptibility data at finite density. Using this enhanced model, we delve into the investigation of signals related to the QCD phase transition critical endpoint. At present, no non-monotonic changes in $\kappa {\sigma }^2$ have been observed within the 7$\sim$200 GeV collision energy range at STAR. However, our theoretical analysis suggests that if the chemical freeze-out line does not intersect the first-order phase transition line, a peak-like structure in $\kappa {\sigma }^2$ is anticipated within the 3$\sim$5 GeV range.

   hep-ph6 citations
3. 03*

   Production mechanism of doubly charmed exotic mesons $T_{cc}$

   Hee-Jin Kim🇰🇷 · Hyun-Chul Kim

   We investigate the production mechanism for doubly charmed tetraquark mesons within a coupled-channel formalism. The two-body Feynman kernel amplitudes are constructed using effective Lagrangians that respect heavy quark symmetry, chiral symmetry, SU(3) flavor symmetry, and hidden local symmetry. The fully off-shell coupled scattering equations are solved within the Blankenbecler-Sugar (BbS) reduction scheme. We find three positive-parity and one negative-parity tetraquark states with total spin $J=1$. Among them, two positive-parity states appear as bound states in the isoscalar and isovector $D{D}^{\ast }$ channels, while another appears as a resonance in the $D^{\ast }{D}^{\ast }$ channel. A negative-parity resonance is also predicted in the isoscalar channel. We analyze the coupling strengths of these tetraquark states to various channels. The dependence of the results on the reduced cutoff mass ${\Lambda }_0$ is examined. The most significant tetraquark state remains stable within the range of ${\Lambda }_0=(600-700)$ MeV.

   hep-phhep-exPRD(2025)·6 citations
4. 04*

   Enhancement of dark-photon haloscope sensitivity with degenerate modes: toward axion-level form factor and polarization determination

   Jose R. Navarro-Madrid🇪🇸 · José Reina-Valero🇪🇸 · Alejandro Díaz-Morcillo🇪🇸 · Benito Gimeno🇪🇸

   The dark photon has been postulated as a potential constituent of dark matter, exhibiting notable similarities to the axion. The primary distinction between the two particles lies in the nature of their respective fields: the dark photon field is a vector field with a polarization direction that remains undetermined. This work explores the prospect of utilizing three degenerate modes for scanning the three dimensions of space in order to mitigate the low form factor expected in the detection of the dark photon due to their unknown polarization. The employment of an haloscope with three orthogonal and degenerate modes in conjunction with the coherent sum of signals is demonstrated in this work in order to enhance the dark photon form factor up to the axion form factor, and to determine the direction of the dark photon polarization vector. We show in this manuscript that the maximum form factor is achieved in cavities of cubic, spherical, and cylindrical geometries, considering the introduction of tuning elements. To achieve this adequately, some conditions reviewed in this article must be fulfilled in the resonant cavity, leading to uncertainties in the final measurement. Finally, this technique can allow the simultaneous search for dark matter axions and dark photons, and to the knowledge of the authors, the method shown in this work is the most effective one for detecting dark photon with microwave resonant cavities.

   hep-phhep-exPRD(2025)·1 citation
5. 05*

   The Muon Magnetic Moment and Physics Beyond the Standard Model

   Peter Athron🇨🇳 · Kilian Möhling🇩🇪 · Dominik Stöckinger🇩🇪 · Hyejung Stöckinger-Kim🇩🇪

   We review the role of the anomalous magnetic moment of the muon a_\mu as a powerful probe of physics beyond the Standard Model (BSM), taking advantage of the final result of the Fermilab g-2 experiment and the recently updated Standard Model value. This review provides both a comprehensive summary of the current status, as well as an accessible entry point for phenomenologists with interests in dark matter, Higgs and electroweak or neutrino and flavour physics in the context of a wide range of BSM scenarios. It begins with a qualitative overview of the field and a collection of key properties and typical results. It then focuses on model-independent, generic formulas and classifies types of BSM scenarios with or without chiral enhancements. A strong emphasis of the review are the connections to a large number of other observables -- ranging from the muon mass and the muon--Higgs coupling and related dipole observables to dark matter, neutrino masses and high-energy collider observables. Finally, we survey a number of well-motivated BSM scenarios such as dark photons, axion-like particles, the two-Higgs doublet model, supersymmetric models and models with leptoquarks, vector-like leptons or neutrino mass models. We discuss the impact of the updated Standard Model value for a_\mu and of complementary constraints, exploring the phenomenology and identifying excluded and viable parameter regions.

   hep-phPPNP(2026)·29 citations
6. 06*

   Investigating QCD Dynamical Entropy in high-energy nuclear collisions

   G. S. Ramos🇧🇷 · L. S. Moriggi🇧🇷 · M.V. T. Machado🇧🇷

   In this work, the concept of QCD dynamical entropy is extended to heavy ion systems. This notion of entropy can be understood as a relative entropy and can also be used to estimate the initial entropy density in ultra-relativistic heavy ion collisions. The key quantity used to calculate this entropy is the nuclear unintegrated gluon distribution (nUGD), which provides a transverse momentum probability density. In the numerical analysis, both the geometric scaling phenomenon and the Glauber-Gribov approach have been used to evaluate realistic models for the nUGD. It is shown that the normalization procedure and the geometric scaling property make the dynamical entropy almost independent of the nucleus mass number $A$. Results are presented for the dynamical entropy density, $d{S}_D/dy$, in terms of the rapidity.

   hep-phhep-exnucl-thPLB(2025)·8 citations
7. 07*

   Rare Higgs Decay into a Photon and a Z Boson in Radiatively-Driven Natural Supersymmetry

   E. A. Reyes R.🇨🇴 · C. A. Lopez A.🇨🇴 · O. R. Torrijo G.🇨🇴 · D. G. Melo P🇨🇴

   In this article, we study the rare decay process in which a Higgs boson decays into a $Z$ boson and a photon. In the first part of the paper, we analyze the Standard Model (SM) contributions to the corresponding decay width, including the full leading-order result, two-loop $O({\alpha }_s)$ QCD corrections, and the recently reported two-loop $O(\alpha )$ electroweak corrections, evaluated under four different $\alpha$ renormalization schemes. The dependence on the Higgs boson mass is studied within the experimentally allowed range reported by the LHC. In the considered schemes, a non-negligible variation of about $4\%$ is found when the mass is varied within its current experimental uncertainty. In the second part of the paper, we analyze the leading-order contributions to the same process within the Minimal Supersymmetric Standard Model (MSSM). The spectrum of soft SUSY-breaking parameters and SUSY particle masses at the electroweak scale, which enter the computation of the one-loop amplitudes contributing to the decay width, is obtained by evolving the GUT-scale parameters of a Radiatively-Driven Natural Supersymmetry (RNS) model with non-universal Higgs boson masses. Variations of the RNS parameters can enhance the average SM prediction by up to $\sim 20\%$, reaching a value of $\sim 7.5$keV, while still satisfying the Higgs boson mass constraint. However, this comes at the cost of allowing a moderately large fine-tuning parameter, with values exceeding $100$, thereby placing the model outside its most natural parameter region. The predicted decay width in the RNS scenario is closer to the recent ATLAS RUN 2 + 3 combined measurement than the SM expectation.

   hep-phPRD(2025)·5 citations
8. 08*

   Production-Dependent Interpretation of the KLOE--MAMI $\eta \to {\pi }^0\gamma \gamma$ Tension via the Nucleon-Triggered Leptophobic Vector $V_{\mathcal{B}}$

   Yaroslav Balytskyi🇺🇸

   The recent KLOE measurement ${\mathrm{BR}}_{\text{KLOE}}^{\eta \to {\pi }^0\gamma \gamma }=(0.98\pm 0.11_{\text{stat}}\pm 0.14_{\text{syst}})\times 10^{-4}$ is less than half the current world average, $(2.55\pm 0.22)\times 10^{-4}$, dominated by MAMI photoproduction data. We show that this $\approx 5.5\sigma$ discrepancy can be resolved by the new leptophobic, nucleon-triggered vector particle $V_{\mathcal{B}}$ with \(1.5~\text{GeV}\lesssim m_{V_{\!\mathcal B}}\lesssim5~\text{GeV}\), coupled via the effective operator \(\bigl(\bar N N\bigr)\,\widetilde V_{\mathcal{B}}^{\mu\nu}F_{\mu\nu}P\). This interaction modifies the \(\eta^{(\prime)}\!\to\!\pi^{0}\left(\eta\right)\gamma\gamma\) decay rates \textit{only} in the processes involving an external nucleon current, \(\gamma p\!\to\!\eta^{(\prime)}p\) and \(\pi^-p\!\to\!\eta^{(\prime)}n\), but leaves purely leptonic production channels, such as \(e^+e^-\to \phi\to\eta^{(\prime)}\gamma\) at KLOE and \(e^+e^-\to J/\psi\to\gamma\eta^{(\prime)}\) at BESIII, Standard-Model-like. The same mechanism predicts a \(\approx 10\%\) nucleon-triggered enhancement of the \(\eta^\prime\!\to\!\pi^{0}\gamma\gamma\) decay rate and a negligible shift for \(\eta^\prime\!\to\!\eta\gamma\gamma\), together with an \(\rm{A}^{2}\)-scaling boost if produced on heavy nuclei instead of protons. $V_{\mathcal{B}}$ can be searched directly in $2\to 3$ photoproduction, for example, $\gamma p\to V_{\mathcal{B}}{\pi }^{0}p$. An integrated experimental program that compares ${\eta }^{(\prime )}\to {\pi }^0(\eta )\gamma \gamma$ in the presence of external nucleon currents with purely leptonic production, and conducts direct photoproduction searches for a GeV-scale vector, can decisively confirm or exclude our nucleon-rescaled, leptophobic-vector interpretation of the KLOE--MAMI discrepancy.

   hep-phJHEP(2026)·1 citation
9. 09*

   Off-shell modifications of the pion generalized parton distributions and transverse momentum dependent parton distributions

   Jin-Li Zhang🇨🇳

   The off-shell characteristics of pion generalized parton distributions (GPDs) and transverse momentum dependent parton distributions (TMDs) are examined within the framework of the Nambu-Jona-Lasinio model. In our previous papers, we separately investigated the properties of on-shell pion GPDs and light-front wave functions. It is particularly intriguing to compare the differences between on-shell and off-shell pion GPDs, which allows us to explore the effects associated with off-shellness. Due to the absence of crossing symmetry, the moments of GPDs also incorporate odd powers of the skewness parameter, resulting in new off-shell form factors. Through our calculations, we derived correction functions that account for modifications in pion GPDs due to off-shell effects. Unlike their on-shell counterparts, certain properties break down in the off-shell scenario; for instance, symmetry properties and polynomiality conditions may no longer hold. Additionally, we evaluate off-shell TMDs and compare them with their on-shell equivalents while also investigating their dependence on ${\mathbf{k}}_{\perp }$.

   hep-phnucl-thCPC(2026)·3 citations
10. 10*

    A Practical Guide to Unbinned Unfolding

    Florencia Canelli🇨🇭 · Kyle Cormier🇨🇭 · Andrew Cudd🇺🇸 · Dag Gillberg🇨🇦 · Roger G. Huang🇺🇸 · Weijie Jin🇨🇭 · Sookhyun Lee🇺🇸 · Vinicius Mikuni🇺🇸 · Laura Miller🇨🇦 · Benjamin Nachman🇺🇸 · Jingjing Pan🇺🇸 · Tanmay Pani🇺🇸 and 3 other authors

    Unfolding, in the context of high-energy particle physics, refers to the process of removing detector distortions in experimental data. The resulting unfolded measurements are straightforward to use for direct comparisons between experiments and a wide variety of theoretical predictions. For decades, popular unfolding strategies were designed to operate on data formatted as one or more binned histograms. In recent years, new strategies have emerged that use machine learning to unfold datasets in an unbinned manner, allowing for higher-dimensional analyses and more flexibility for current and future users of the unfolded data. This guide comprises recommendations and practical considerations from researchers across a number of major particle physics experiments who have recently put these techniques into practice on real data.

    hep-phhep-exphysics.data-anEPJC(2026)·15 citations
11. 11*

    The Multi-Messenger Astroparticle Physics: the First Constraint on Light Millicharged Dark Matter via Time-Delay Analysis of GRB GW170817A

    Wenxing Zhang🇨🇳 · Junle Pei🇨🇳 · Xin Zhang🇨🇳 · Tianjun Li🇨🇳

    The multi-messenger astroparticle physics provides a new approach to probe the new physics beyond the Standard Model. We propose to probe the light dark matter which can interact with electromagnetic interaction. To be concrete, we derive the new constraint on the millicharged dark matter from the multi-messenger observations of GW170817. In the neutron star merger event GW170817, the first detection of a gamma-ray burst (GRB) delayed by approximately 1.7 seconds relative to the gravitational wave emission was observed. Utilizing this delay, we constrain the parameter space of the millicharged dark matter within the large-scale structure of the Universe. For dark matter mass below $10^{-15}$ eV, the parameter $ϵ$ is constrained to be less than $10^{-14}$, representing the most stringent limits achieved to date.

    hep-phPRD(2026)·0 citations
12. 12*

    Chiral and flavor oscillations in quantum field theory

    Massimo Blasone🇮🇹 · Gennaro Zanfardino🇮🇹

    Massive fermions produced through weak charged interactions possess a definite chirality, which is not conserved during free propagation, leading to chiral oscillations. Neutrinos also exhibit flavor oscillations. These phenomena have been extensively studied - both individually and within a unified framework - using the first quantization approach, but only separately in the context of quantum field theory. In this work, we address this gap by developing a quantum field theory treatment of flavor-chiral oscillations. Focusing on the case of two-flavor mixing, we compute the expectation values of the (non-conserved) chiral-flavor charges and recover the same oscillation formulas obtained in the first quantization formalism. These charges are diagonalized via Bogoliubov transformations in both the chiral and flavor sectors. Such transformations reveal a non-trivial structure of the chiral-flavor vacuum, which consists of a condensate of particles with definite masses and helicities.

    hep-phhep-th2 citations
13. 13*

    Probing Right Handed Neutrino assisted Reheating with Gravitational Waves and Leptogenesis

    Arghyajit Datta🇰🇷 · Shaaban Khalil🇪🇬 · Rajat Kumar Mandal🇮🇳 · Arunansu Sil🇮🇳

    We investigate a non-instantaneous reheating period in the early Universe, where the inflaton field decays exclusively to right-handed neutrinos (RHNs). The subsequent decay of these RHNs into Standard Model particles not only drives the transition to a radiation-dominated era but also generates the baryon asymmetry of the Universe via leptogenesis. In this typical reheating scenario, gravitational waves (GWs) can be produced during inflaton decay, both through bremsstrahlung and inflaton scattering processes. While GW production via bremsstrahlung dominates near the end of the reheating phase, inflaton scattering leads to a non-negligible GW contribution near the maximum temperature of the Universe. The combined GW spectrum from both decay and scattering processes lies within the sensitivity range of proposed resonant cavity experiments. This framework thus offers a compelling and unified approach to addressing neutrino mass generation, the baryon asymmetry of the Universe via leptogenesis, and probing the dynamics of a non-instantaneous reheating era.

    hep-phastro-ph.HEhep-thJCAP(2026)·10 citations
14. 14*

    Fragmentation of fully heavy tetraquarks: The TQ4Q1.1 functions as a case study

    Francesco Giovanni Celiberto🇪🇸

    We extend the study of exotic matter formation via the TQ4Q1.1 set of collinear, variable-flavor-number-scheme fragmentation functions for fully charmed or bottomed tetraquarks in three quantum configurations: scalar ($J^{PC}=0^{++}$), axial vector ($J^{PC}=1^{+-}$), and tensor ($J^{PC}=2^{++}$). We adopt single-parton fragmentation at leading power and implement a nonrelativistic Quantum Chromodynamics (NRQCD) factorization scheme tailored to tetraquark Fock-state configurations. Short-distance inputs at the initial scale are modeled using updated calculations for both gluon- and heavy-quark-initiated channels. A threshold-consistent Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) evolution is then applied via the novel Heavy-flavor nonrelativistic-evolution (HF-NRevo) hybrid scheme. We provide the first systematic treatment of uncertainties from nonperturbative color-composite long-distance matrix elements (LDMEs), as well as from perturbative hard-scattering (H-MHOUs) and fragmentation-scale inputs (F-MHOUs), assessed separately and in combination. To support phenomenology, we compute NLL/NLO${}^{+}$ cross sections for tetraquark-jet systems at the HL-LHC and FCC within the hybrid collinear and high-energy factorization (HyF) as implemented in (sym)JETHAD, incorporating angular multiplicities as key observables sensitive to high-energy QCD dynamics. We also provide expected event yields based on realistic luminosity scenarios, offering a concrete benchmark for experimental searches. This work connects the investigation of exotic hadrons with state-of-the-art precision QCD.

    hep-phhep-exnucl-exnucl-thPRD(2025)·23 citations
15. 15*

    Structure of lightest nuclei in the visible Universe

    Satvir Kaur🇨🇳 · Chandan Mondal🇨🇳 · Xingbo Zhao🇨🇳 · Chueng-Ryong Ji🇺🇸

    The simplest atomic nucleus, deuteron, provides key insights into the strong nuclear interactions among quarks and gluons that shape the visible universe. We present the first attempt to calculate the internal structure of the deuteron by incorporating hidden-color degrees of freedom, modeling it as an effective mixture of singlet-singlet and octet-octet color clusters beyond the traditional proton-neutron picture. By employing the separation of variables for the light-front two-cluster bound-state equation, we explore how these hidden color correlations shape both its spin and electromagnetic structure. We incorporate the transverse and longitudinal dynamics by two Schrödinger-like equations, namely the light-front holography and the 't Hooft equation, respectively. Our predictions of the electromagnetic form factors and structure functions, including tensor-polarized function, align well with experimental data, offering insights into the partonic structure of the deuteron. Its tensor property could pave the way for a new era in spin physics, guiding future experimental investigations.

    hep-phPRD(2026)·6 citations
16. 16*

    Triply heavy baryon spectroscopy revisited

    Hao Zhou🇨🇳 · Si-Qiang Luo🇨🇳 · Xiang Liu🇨🇳

    We present a comprehensive study of triply heavy baryons (${\Omega }_{ccc}$, ${\Omega }_{bbb}$, ${\Omega }_{bcc}$, and ${\Omega }_{bbc}$) within the nonrelativistic quark model, employing the Gaussian expansion method to calculate mass spectra up to $D$-wave states. Our analysis represents the most complete treatment to date for this model, incorporating full angular momentum mixing effects. While our predictions for low-lying states agree well with lattice quantum chromodynamics (QCD) results, we find systematically lower masses for excited states compared to lattice calculations. Using the obtained wave functions, we estimate radiative decay widths up to $1D$ states, revealing significant differences from previous theoretical work. Additionally, we identify and resolve several misconceptions in prior treatments of triply heavy baryon spectroscopy, particularly symmetry constraint and wave function construction in three-quark systems. These results provide crucial information for future experimental searches and theoretical investigations of triply heavy baryon systems.

    hep-phhep-exPRD(2025)·15 citations
17. 17*

    Two loops, four tops and two ${\gamma }_5$ schemes: a renormalization story

    Stefano Di Noi🇩🇪 · Ramona Gröber🇮🇹

    We calculate the four-top quark operator contributions to the two-loop renormalization constants of the fermion and gluon fields, necessary to obtain the renormalization group equations for the fermion masses and the strong coupling constant. The computation has been carried out in the na\"ıve dimensional regularization scheme for the ${\gamma }_5$ matrix. We also discuss a strategy to translate the results into the Breitenlohner--Maison--'t~Hooft--Veltman scheme and present the corresponding beta functions in both schemes.

    hep-phPLB(2025)·20 citations
18. 18*

    No-group Scotogenic Model

    Takaaki Nomura🇨🇳 · Oleg Popov🇨🇳

    In the present work, the scotogenic model is constructed applying non invertible $Z_M$ symmetries. The stability of dark matter and the scotogenic structure of the neutrino mass matrix is achieved via the new non-group symmetry. The non-group Scotogenic model is given with minimalistic content giving a one-zero structure of the neutrino mass matrix, and numerical analysis of the lepton mixing angles and physics are presented. Other relevant constraints are also studied.

    hep-phhep-exhep-th19 citations
19. 19*

    Diffusion Monte Carlo calculation of compact $T_{cs0}$ and $T_{c\bar{s}0}$ tetraquarks

    M.C. Gordillo🇪🇸 · J. Segovia🇪🇸

    The LHCb collaboration amplitude analysis of the decays $B^{+}\to D^{+}{D}^{-}{K}^{+}$, $B^{+}\to D^{-}{D}_s^{+}{\pi }^{+}$, and $B^0\to {\bar{D}}^0{D}_s^{+}{\pi }^{-}$ suggested the existence of two new resonant $J^P=0^{+}$ states with minimum quark content $\bar{u}\bar{d}sc$ and $\bar{s}\bar{u}dc$/$\bar{s}\bar{d}uc$, named $T_{cs0}$ and $T_{c\bar{s}0}$, respectively. In this work, we used the diffusion Monte Carlo (DMC) method to compute the masses of those tetraquarks within the framework of the constituent quark model. We describe the systems as compact structures, not as diquark/antidiquark or meson/meson arrangements. In this context, compact means that we used directly the eigenvectors of the spin, color and flavor operators without any splitting and/or (re)combination of smaller units. This allows us to deduce the existence of two distinct bound configurations for each composition, corresponding to ground and excited flavor states. In both cases, the excited flavor states are the ones with masses comparable to the ones observed by LHCb. In addition, our analysis allows us to assign unambiguously an isospin value of $I$=1 to the experimentally obtained $T_{cs0}$ tetraquark.

    hep-phPLB(2025)·4 citations
20. 20*

    Quark model of nucleon based on an analogy with polaron

    S.S. Afonin🇷🇺 · A.V. Tulub🇷🇺

    We demonstrate that the polaron theory from solid state physics can serve as an interesting analogue model for non-perturbative QCD, at least in the description of nucleons and related low-energy physics of strong interactions. By drawing explicit analogies between polaron physics, arising for an electron moving in an ionic crystal, and physics of pion-nucleon interactions, certain rules for the "polaron/QCD correspondence" are proposed. In polaron theory, the effective fermion mass as a function of the coupling constant is known both in the weak and strong coupling limits. The conjectured "polaron/QCD correspondence" translates these results into strong interactions. It is then shown how application of these rules leads to unexpectedly good quantitative predictions for the nucleon mass and the pion-nucleon sigma term. The polaron approach also predicts that the quark degrees of freedom in the form of the constituent quark account for one-third of the nucleon mass, consistent with lattice predictions. We discuss possible physical reasons underlying the observed quantitative similarity between polaron physics and non-perturbative QCD.

    hep-phcond-mat.supr-conhep-latnucl-thEPJC(2025)·1 citation
21. 21*

    Waterfall phase in supersymmetric hybrid inflation

    Ahmad Moursy🇪🇬 · Qaisar Shafi🇺🇸

    We explore a class of realistic supersymmetric hybrid inflation models with a predicted scalar spectral index $n_s\approx 0.97-0.978$, which is in good agreement with the recent Atacama Cosmology Telescope (ACT) measurement. The waterfall field responsible for the gauge symmetry breaking in this scenario experiences some $e$-foldings during the inflationary epoch. The scalar perturbations associated with the waterfall field during this phase induce a stochastic gravitational wave spectrum that will be tested in the ongoing Pulsar Timing Array (PTA) measurements and in future experiments. In an $SU(5)$ setting an observable number density of the superheavy GUT monopole linked to the waterfall field can be realized.

    hep-phastro-ph.COJHEP(2026)·8 citations
22. 22*

    Generalized Beth-Uhlenbeck approach to the thermodynamics of quark-hadron matter

    David Blaschke🇵🇱 · Oleksii Ivanytskyi🇵🇱 · Gerd Röpke🇩🇪

    We present a unified approach to the transition from hadronic matter to quark matter where hadrons are treated as bound states of quarks which dissociate at high densities due to quark Pauli blocking. The newly developed approach makes use of a cluster virial expansion formulated in terms of a generalized $\Phi$-derivable approach to multi-quark correlations with bound and continuum states in their spectrum encoded in hadron phase shifts. Our model can be used to obtain thermodynamic functions not only at zero and small chemical potentials, where they are consistent with lattice QCD simulations, but also at large chemical potentials where lattice QCD simulations have the sign problem. By applying a reaction-kinetic criterion for the chemical freeze-out of multi-quark clusters in heavy-ion collisions, we demonstrate that the chemical freeze-out coincides with their Mott transition. The approach can be applied to study the effects of the QCD transition on primordial black hole formation in the early Universe and on hybrid neutron star formation in supernova explosions and binary neutron star mergers.

    hep-phnucl-thPoS(2025)·1 citation
23. 23*

    Signatures of Odd-Parity $s$-wave ${\Xi }^{\ast }$ States in Femtoscopic Correlation Functions

    Jia-Xin Lin🇨🇳 · Pablo Encarnación🇪🇸 · Miguel Albaladejo🇪🇸 · Albert Feijoo🇪🇸

    We investigate the ${\Xi }^{\ast }$ resonances within the molecular picture, where these states are dynamically generated as poles in the unitarized scattering amplitudes arising from the coupled-channel interactions of $K^{\ast -}\Lambda$, $K^{\ast -}{\Sigma }^0$, ${\rho }^{-}{\Xi }^0$, $\overline{K}{}^{\ast 0}{\Sigma }^{-}$, ${\rho }^0{\Xi }^{-}$, $\omega {\Xi }^{-}$, and $\varphi {\Xi }^{-}$. The interaction kernel is derived from the local hidden gauge formalism, while the unitarization procedure employs a hybrid method that combines cutoff and dimensional regularizations in the evaluation of the loop function. From a detailed spectroscopic analysis, we identify two $S=-2$ baryon states whose properties are compatible with some of the ${\Xi }^{\ast }$ resonances listed in the Review of Particle Physics. To explore their possible experimental signatures, we compute the femtoscopic correlation functions for all the vector-baryon pairs considered in the present study, using realistic estimates of production weights and varying source sizes $R=1,1.1,1.2,1.3,1.5$ fm.

    hep-phhep-exnucl-thPLB(2026)·5 citations
24. 24*

    Novel and Updated Bounds on Flavor-Violating Z Interactions in the Quark Sector

    Fayez Abu-Ajamieh (Indian Institute of Science, Bangalore)🇮🇳 · Amine Ahriche (University of Sharjah)🇦🇪 · Suman Kumbhakar (University of Calcutta)🇮🇳 · Nobuchika Okada (University of Alabama)🇺🇸

    We derive bounds on the flavor-violating (FV) couplings of the $Z$ boson to quarks and present future sensitivity projections. Our analysis shows that the current bounds on the FV couplings are $\mathcal{O}(10^{-9})$ for the $Z$ couplings to $cu$ and $sd$, $\mathcal{O}(10^{-7})$ for $bd$, $\mathcal{O}(10^{-6})$ for $bs$, and $\mathcal{O}(10^{-3})$ for $tu$ and $tc$. Overall, low-energy flavor experiments provide significantly stronger constraints on these FV couplings than current collider searches.

    hep-phhep-exInt.J.Mod.Phys.A(2026)·2 citations
25. 25*

    Asymgenesis

    Martin A. Mojahed🇩🇪 · Sascha Weber🇩🇪

    We present a framework based on the standard type-I seesaw model that relates the baryon asymmetry of the universe to the dark matter (DM) density. The framework, which we name "Asymgenesis", relies on the presence of primordial charge asymmetries seeded either in the dark sector or in the visible sector. A higher-dimensional portal operator reshuffles this initial asymmetry into both sectors, eventually resulting in a nonzero $B-L$ asymmetry and an asymmetric DM component. Compared to conventional asymmetric-dark-matter (ADM) schemes, our framework imposes far milder requirements on the portal interaction. In particular, the portal interaction need not violate $B-L$, and the temperature scales of efficient $B-L$ violation and efficient charge-transfer interaction mediated by the portal operator can be separated. We develop the formalism in detail and argue that the flexibility of our framework enlarges the model-building landscape for ADM.

    hep-phastro-ph.COhep-thPLB(2026)·2 citations
26. 26*

    Probing Non-Minimal Dark Sectors via the 21 cm Line at Cosmic Dawn

    Federico Cima🇺🇸 · Francesco D'Eramo🇮🇹

    Observations of the hydrogen hyperfine transition through the 21 cm line near the end of the cosmic dark ages provide unique opportunities to probe new physics. In this work, we investigate the potential of the sky-averaged 21 cm signal to constrain metastable particles produced in the early universe that decay at later times, thereby modifying the thermal and ionization history of the intergalactic medium. The study begins by extending previous analyses of decaying dark matter (DM), incorporating back-reaction effects and tightening photon decay constraints down to DM masses as low as 20.4 eV. The focus then shifts to non-minimal dark sectors with multiple interacting components. The analysis covers two key scenarios: a hybrid setup comprising a stable cold DM component alongside a metastable sub-component, and a two-component dark sector of nearly degenerate states with a metastable heavier partner. A general parameterization based on effective mass spectra and fractional densities allows for a model-independent study. The final part presents two explicit realizations: an axion-like particle coupled to photons, and pseudo-Dirac DM interacting via vector portals or electromagnetic dipoles. These scenarios illustrate how 21 cm cosmology can set leading bounds and probe otherwise inaccessible regions of parameter space.

    hep-phastro-ph.COJCAP(2026)·8 citations
27. 27*

    Exploring ultra-high energy neutrino experiments through the lens of the transport equation

    Stefano Palmisano🇮🇹 · Diego Redigolo🇮🇹 · Michele Tammaro🇮🇹 · Andrea Tesi🇮🇹

    We develop a first-principles formalism, based on the transport equation in the line-of-sight approximation, to link the expected number of muons at neutrino telescopes to the flux of neutrinos at the Earth's surface. We compute the distribution of muons inside Earth, arising from the up-scattering of neutrinos close to the detector, as well as from the decay of taus produced farther away. This framework allows one to account for systematic uncertainties, as well as to clarify the assumptions behind definitions commonly used in the literature, such as the effective area. We apply this formalism to analyze the high-energy muon event recorded by KM3NeT, with a reconstructed energy of $120_{-60}^{+110}\mathrm{PeV}$ and an elevation angle of ${\left(0.54\pm 2.4\right)}^{\circ }$, in comparison with the non-observation of similar events by IceCube. We find a $3.1\sigma$ tension between the two experiments, assuming a diffuse neutrino source with a power-law energy dependence. Combining both datasets leads to a preference for a very low number of expected events at KM3NeT, in stark contrast to the observed data. The tension increases both in the case of a diffuse source peaking at the KM3NeT energy and of a steady point source, whereas a transient source may reduce the tension down to $1.6\sigma$. The formalism allows one to treat potential beyond-the-Standard-Model sources of muons, and we speculate on this possibility to explain the tension.

    hep-phastro-ph.HEhep-exJHEP(2026)·9 citations
28. 28*

    Spacetime Grand Unified Theory

    Gonçalo M. Quinta🇵🇹

    The gauge symmetries and fermionic sector of the Standard Model are derived from the free Dirac Lagrangian in 8-dimensional spacetime. Motivated by second quantization, we embed the 4-dimensional Clifford algebra of the Dirac Lagrangian into that of 8-dimensional spacetime, showing this embedding carries a redundancy described by a complexified Pati-Salam group acting on field multiplets represented as Clifford algebra ideals, externally and internally via left and right multiplication. Invariance of the Dirac Lagrangian selects different real slices of the group: internal transformations follow $SU(4{)}_C\times SU(2{)}_L\times SU(2{)}_R$, external ones $SU(4{)}_F\times Spin(1,3)$, with $SU(4{)}_F$ acting on four particle families. Although $SU(4{)}_C$ and $SU(4{)}_F$ can be broken spontaneously and independently, we prove that fixing a triality in $C{\ell }_{8,0}$ simultaneously gives $SU(4{)}_C\to SU(3{)}_C\times U(1{)}_{B-L}$ and $SU(4{)}_F\to SU(3{)}_F\times U(1{)}_F$, originating a leptonic sector and a non-mixing fourth family whose stable neutrino is a potential dark matter candidate. Breaking $U(1{)}_F$ yields a hierarchy governed by a generalized Koide formula, with mass scales showing a modular nature. Most importantly, every quantity entering the Standard Model acquires a direct algebraic interpretation in higher dimensional spacetime.

    hep-phhep-th6 citations
29. 29*

    Constraints on the spread of nuclear masses in ultra-high-energy cosmic rays based on the Phase I hybrid data from the Pierre Auger Observatory

    Alexey Yushkov (for the Pierre Auger Collaboration)

    We present an analysis of the correlation between the depth of the maximum of air-shower profiles and the signal in water-Cherenkov stations in events registered simultaneously by the fluorescence and surface detectors of the Pierre Auger Observatory. The analysis enables us to place constraints on the spread of nuclear masses in ultra-high-energy cosmic rays with a minor impact from the experimental systematic uncertainties and uncertainties in air-shower simulations. Due to this unique feature, the correlation analysis has previously allowed us to exclude all pure and proton-helium compositions near the ankle in the cosmic-ray energy spectrum at 5$\sigma$ confidence level. The same property makes the correlation analysis an effective tool for testing the consistency of predictions of the post-LHC hadronic interaction models, including their latest versions such as EPOS LHC-R, QGSJet-III-01, Sibyll${}^{★}$ and Sibyll 2.3e. In this work, the correlation analysis using the Phase I hybrid data from the Pierre Auger Observatory is presented. The analysis uses the newest generation of hadronic interaction models and covers an extended energy range around the ankle in the cosmic-ray spectrum.

    ↳ astro-ph.HEhep-phPoS(2025)·1 citation
30. 30*

    Muon Signal Charge in the Underground Muon Detector of AugerPrime

    Marina Scornavacche (for the Pierre Auger Collaboration)

    The Underground Muon Detector of the Pierre Auger Observatory features a calorimetric detection mode that estimates the number of muons based on signal charge measurements. This contribution provides an overview of the calibration procedure, revisiting the previously published strategy and identifying a bias introduced by the triggers used to estimate the mean charge deposited by a vertical muon. We demonstrate that calibrating underground detectors requires careful consideration of the interactions of penetrating particles through matter. In devices based on plastic scintillators, energy deposition, and thus the recorded charge, is significantly affected by knock-on electron production in the surrounding ground as muons traverse the medium. To mitigate this effect, we propose a new calibration strategy that ensures an unbiased muon estimator. This approach is applied to data collected from 2019 to 2024.

    ↳ physics.ins-detastro-ph.IMhep-phPoS(2025)·1 citation
31. 31*

    Phenomenological Modeling of the ${}^{163}$Ho Calorimetric Electron Capture Spectrum from the HOLMES Experiment

    F. Ahrens🇮🇹 · B. K. Alpert🇺🇸 · D. T. Becker🇺🇸 · D. A. Bennett🇺🇸 · E. Bogoni🇮🇹 · M. Borghesi🇮🇹 · P. Campana🇮🇹 · R. Carobene🇮🇹 · A. Cattaneo🇮🇹 · A. Cian🇮🇹 · H. A. Corti🇮🇹 · N. Crescini🇮🇹 and 37 other authors

    We present a comprehensive phenomenological analysis of the calorimetric electron capture (EC) decay spectrum of ${}^{163}$Ho as measured by the HOLMES experiment. Using high-statistics data, we unfold the instrumental energy resolution from the measured spectrum and model it as a sum of Breit-Wigner resonances and shake-off continua, providing a complete set of parameters for each component. Our approach enables the identification and tentative interpretation of all observed spectral features, including weak and overlapping structures, in terms of atomic de-excitation processes. We compare our phenomenological model with recent ab initio theoretical calculations, finding good agreement for both the main peaks and the spectral tails, despite the limitations of current theoretical and experimental precision. The model delivers an accurate description of the endpoint region, which is crucial for neutrino mass determination, and allows for a realistic treatment of backgrounds such as pile-up and tails of low-energy components. Furthermore, our decomposition facilitates the generation of Monte Carlo toy spectra for sensitivity studies and provides a framework for investigating systematic uncertainties related to solid-state and detector effects. This work establishes a robust foundation for future calorimetric neutrino mass experiments employing ${}^{163}$Ho, supporting both data analysis and experimental design.

    ↳ nucl-exhep-phphysics.ins-detJHEP(2026)·4 citations
32. 32*

    The Giant Radio Array for Neutrino Detection (GRAND) Collaboration -- Contributions to the 39th International Cosmic Ray Conference (ICRC 2025)

    Jaime Álvarez-Muñiz · Rafael Alves Batista · Aurélien Benoit-Lévy · Teresa Bister · Martina Bohacova · Mauricio Bustamante · Washington Carvalho Jr. · Yiren Chen · LingMei Cheng · Simon Chiche · Jean-Marc Colley · Pablo Correa and 126 other authors

    The Giant Radio Array for Neutrino Detection (GRAND) is an envisioned observatory of ultra-high-energy particles of cosmic origin, with energies in excess of 100 PeV. GRAND uses large surface arrays of antennas to look for the radio emission from extensive air showers that are triggered by the interaction of ultra-high-energy cosmic rays, gamma rays, and neutrinos in the atmosphere or underground. In particular, for ultra-high-energy neutrinos, the future final phase of GRAND aims to be sensitive enough to detect them in spite of their plausibly tiny flux. Three prototype GRAND radio arrays have been in operation since 2023: GRANDProto300, in China, GRAND@Auger, in Argentina, and GRAND@Nançay, in France. Their goals are to field-test the GRAND detection units, understand the radio background to which they are exposed, and develop tools for diagnostic, data gathering, and data analysis. This list of contributions to the 39th International Cosmic Ray Conference (ICRC 2025) presents an overview of GRAND, in its present and future incarnations, and a first look at data collected by GRANDProto300 and GRAND@Auger, including the first cosmic-ray candidates detected by them.

    ↳ astro-ph.IMastro-ph.HEhep-exhep-ph+14 citations
33. 33*

    Novel Challenges in Tracking Self-Interacting Dark Matter Subhalos

    Demao Kong🇺🇸 · Hai-Bo Yu🇺🇸 · Ethan O. Nadler🇺🇸 · Philip Mansfield🇺🇸 · Andrew Benson🇺🇸

    Cosmological N-body simulations are among the primary tools for studying structure formation in the Universe. Analyses of these simulations critically depend on accurately identifying and tracking dark matter subhalos over time. In recent years, several new algorithms have been developed to improve the accuracy and consistency of subhalo tracking in cold dark matter simulations. These algorithms should be revisited in the context of new physics beyond gravity, which can modify the evolution and final properties of subhalo populations. In this work, we apply the particle-tracking-based subhalo finder Symfind to velocity-dependent self-interacting dark matter simulations with large cross section amplitudes to assess the performance of particle-tracking methods beyond the CDM paradigm. We find that the core-particle-tracking technique, which is key to the success of these algorithms in CDM, does not always yield accurate results in SIDM. The interplay between dark matter self-interactions and tidal stripping can cause the diffusion of core particles to larger radii, leading particle-tracking-based algorithms to prematurely lose track of SIDM subhalos. For massive core-expansion subhalos and core-collapse subhalos that experience close or repeated pericentric passages, a significant fraction of core particles can be lost, and particle-tracking-based finders such as Symfind offer no clear advantage over traditional methods that rely on identifying phase-space overdensities. On the other hand, for subhalos with large pericentric distances or fewer, more distant passages, Symfind tends to outperform. These differences depend sensitively on the cross section amplitude and turnover velocity of the underlying SIDM model. We therefore recommend a hybrid approach that leverages the strengths of both techniques to produce complete and robust catalogs of core-expansion and core-collapse SIDM subhalos.

    ↳ astro-ph.COastro-ph.GAhep-phJCAP(2025)·8 citations
34. 34*

    Update on testing of air-shower modelling using combined data of the Pierre Auger Observatory and phenomenological consequences

    Jakub Vícha (for the Pierre Auger Collaboration)

    The combined data of Fluorescence and Surface Detectors of the Pierre Auger Observatory has recently provided the strongest constraints on the validity of predictions from current models of hadronic interactions. The unmodified predictions of these models on the depth of shower maximum ($X_{\text{max}}$) and the hadronic part of the ground signal are unable to accurately describe the measured data at a level of more than 5$\sigma$ in the energy range 3-10 EeV. This inconsistency has been shown to originate not only from the predicted amount of muons at the ground level, but also from the predicted scale of $X_{\text{max}}$, which must be adjusted to better match the observed data. The resulting deeper $X_{\text{max}}$ scales of the models imply a heavier mass composition to be interpreted from the $X_{\text{max}}$ measurements. We show the results of the test with an updated data set of the Pierre Auger Observatory, studying also the energy evolution of the fitted modification parameters and new versions of the models of hadronic interactions. Additionally, we discuss the phenomenological consequences of the deeper $X_{\text{max}}$ scale of models on the interpretation of the features of the energy spectrum and the muon problem in air-shower modelling.

    ↳ astro-ph.HEhep-phPoS(2025)·5 citations
35. 35*

    Generalized Heisenberg Dynamics Revisited

    Yoshiharu Kawamura🇯🇵

    Taking as a model the fact that Heisenberg's matrix mechanics was derived from Hamiltonian mechanics using the correspondence principle, we explore a class of dynamical systems involving discrete variables, with Nambu mechanics as the starting point. Specifically, we reconstruct an extended version of matrix mechanics that describes dynamical systems possessing physical quantities expressed through generalized matrices. Furthermore, we reconfirm that a multiple commutator involving generalized matrices can serve as a discrete (quantized) version of the Nambu bracket or the Jacobian.

    ↳ quant-phhep-phhep-thmath-ph+1PTEP(2025)·0 citations
36. 36*

    Blandford-Znajek Effect and Neutrino Pair Annihilation as the Central Engines of Gamma Ray Bursts and Blazars

    Takeshi Fukuyama🇯🇵

    The central engine of gamma-ray burst is considered. Blandford-Znajek (BZ) process is reconsidered under the asymtotic magnetic condition $\mathbf{B}=B_0\hat{z}$ (rotation axis) at $r\gg r_H$. Another scenario of $\nu \overline{\nu }\to e^{+}{e}^{-}$ driven jet are combined to BZ process to compliment it.

    ↳ astro-ph.HEhep-phInt.J.Mod.Phys.A(2025)·0 citations
37. 37*

    Reciprocal relation of Schwinger pair production between ${\text{dS}}_2$ and ${\text{AdS}}_2$

    Chiang-Mei Chen🇹🇼 · Chun-Chih Huang🇹🇼 · Sang Pyo Kim🇰🇷 · Kuan-Yen Lin🇹🇼

    The Klein-Gordon and Dirac equation for a massive charged field in a uniform electric field has a symmetry of two-dimensional global de Sitter (dS) and anti-de Sitter (AdS) space. In the in-out formalism the mean numbers of spinors (spin-1/2 fermions) and scalars (spin-0 bosons) spontaneously produced by the uniform electric field are exactly found from the Bogoliubov relations both in the global and planar coordinates of (A)dS${}_2$ space. We show that the uniform electric field enhances the production of charged spinor and scalar pairs in the planar and global dS space while the AdS space reduces the pair production in which weak electric fields below the Breitenlohner-Freedman (BF) bound prohibits pair production. The leading Boltzmann factor in dS space can be written as the Gibbons-Hawking radiation or Schwinger effect enhanced by e-folding factors less than one that give the QED effect or the curvature effect. We observe that dS${}_2$ and AdS${}_2$ spaces are connected by QED, such as a reciprocal relation between the mean number of spinors and scalars provided that the spacetime curvature is analytically continued. The leading behavior of the mean numbers for spinors and scalars is explained as a residue sum of contour integrals of the frequency or momentum in the phase-integral formulation.

    ↳ hep-thgr-qchep-phPRD(2025)·4 citations
38. 38*

    Decoding Two-Particle States in QCD with Spatial Wavefunctions

    Yan Lyu🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Kotaro Murakami🇯🇵 · Takuya Sugiura🇯🇵

    A systematic framework for constructing optimized interpolating operators strongly coupled to QCD two-particle states is developed, which is achieved by incorporating inter-hadron spatial wavefunctions. To efficiently implement these operators in lattice QCD, a novel quark smearing technique utilizing noise vectors is proposed. Applied to the ${\Omega }_{ccc}{\Omega }_{ccc}$ system, these optimized operators prove superior to combinations of limited plane-wave operators, enabling the resolution of distinct eigenstates separated by only $\sim 5$ MeV near the threshold $2m_{{\Omega }_{ccc}}\simeq 9700$ MeV. This exceptional resolving power opens new possibilities for studies of a wide range of hadronic systems in QCD.

    ↳ hep-lathep-phnucl-thPRD(2026)·3 citations
39. 39*

    Wavefunction-based operator optimization for two-hadron systems in lattice QCD

    Yan Lyu🇯🇵 · Sinya Aoki🇯🇵 · Takumi Doi🇯🇵 · Tetsuo Hatsuda🇯🇵 · Kotaro Murakami🇯🇵 · Takuya Sugiura🇯🇵

    A systematic way to constructing optimized interpolating operators for two-hadron systems is developed by incorporating inter-hadron spatial wavefunctions. The wavefunctions can be obtained from an iterative process with an appropriate initial guess. To implement these operators, a novel quark smearing technique utilizing $Z_3$ noise vectors is proposed, which allows for effectively incorporating inter-hadron spatial wavefunctions at the source without using all-to-all quark propagators. Proof-of-principle application to the ${\Omega }_{ccc}{\Omega }_{ccc}$ system using physical-point lattice configurations with a large size $La\simeq 8.1$~fm demonstrates that optimized operators outperform combinations of limited plane-wave operators in the variational analysis, enabling clear identification of states around $2m_{{\Omega }_{ccc}}\simeq 9700$ MeV with the energy gap as narrow as $\sim 5$ MeV. A comparison on correlation functions, effective energies, and HAL QCD potentials between unoptimized operators and optimized operators is given, with a special emphasis on the effects from nearby elastic scattering states. Potential applicability of the optimized operator to various two-hadron systems and its relation to the variational method are also discussed.

    ↳ hep-lathep-phnucl-thPRD(2026)·4 citations
40. 40*

    Study of the $\Lambda \to p\ell {\bar{\nu }}_{\ell }$ semileptonic decay in lattice QCD

    Simone Bacchio🇨🇾 · Andreas Konstantinou🇨🇾

    We present the first lattice QCD determination of the $\Lambda \to N$ vector and axial-vector form factors, which are essential inputs for studying the semileptonic decay $\Lambda \to p\ell {\bar{\nu }}_{\ell }$. This channel provides a clean, theoretically controlled avenue for extracting the CKM matrix element $|V_{us}|$ from the baryon sector. Our analysis uses a gauge ensemble with physical light, strange, and charm quark masses and yields the most precise determination to date of the full set of transition form factors -- including second-class contributions -- as well as the associated couplings, radii, and the ratio of muon-to-electron decay rates, an observable sensitive to possible non-standard scalar and tensor interactions. We compare our non-perturbative results with next-to-next-to-leading order expansions in the small parameter $\delta =(m_{\Lambda }-m_N)/m_{\Lambda }\approx 0.16$. We find that the common phenomenological approximation of neglecting the $q^2$-dependence of the form factors leads to a $\sim 4\%$ deviation in the decay rate. This underscores the critical importance of precise, fully non-perturbative form factor inputs for achieving the sub-percent precision targets of upcoming experimental programs.

    ↳ hep-lathep-phPRL(2025)·17 citations
41. 41*

    Primordial Gravitational Wave Background as a Probe of the Primordial Black Holes

    Utkarsh Kumar🇨🇦

    We study the formation of primordial black holes (PBHs) from the collapse of density perturbations induced by primordial gravitational waves (PGWs). The PGWs' interpretation of the stochastic gravitational wave background (SGWB) detected by the Pulsar Timing Array (PTA) corresponds to PBHs formation in the mass range $[10^{-12}-10^{-3}]M_{\odot }$. Importantly, our analysis shows that PGWs' interpretation of recent PTA data remains viable, as it does not lead to PBH overproduction. We derive the amplitude of PGWs by leveraging existing constraints on the PBH abundance across a wide mass range. Notably, these constrained amplitudes predict SGWB signals that would be detectable by future gravitational wave observatories.

    ↳ gr-qcastro-ph.COhep-phhep-thPRD(2025)·11 citations
42. 42*

    CFT-approach to Rotating Field Lumps in Attractive Potential

    Yulia Galushkina🇷🇺 · Eduard Kim🇷🇺 · Emin Nugaev🇷🇺 · Yakov Shnir🇷🇺

    We demonstrate the importance of relativistic corrections for the study of the stability of $(2+1)$-dimensional non-topological solitons with quartic self-interaction in the low-energy limit. This result is explained by the restoration of conformal symmetry in the non-relativistic limit. Particularly, the corresponding cubic Gross-Pitaevskii equation supports scale-free non-topological solitons. An unbroken conformal symmetry provides the additional degeneration that allows for the exact result for the energy and angular momentum of the stationary classical solutions. We study the violation of conformal symmetry by relativistic corrections. The emergence of exponentially growing modes on the classical background is demonstrated using analytical approximations and numerical calculations.

    ↳ hep-thhep-phnlin.PSPRD(2025)·5 citations
43. 43*

    Prospects for joint multiband detection of intermediate-mass black holes by LGWA and the Einstein Telescope

    Yue-Yan Dong🇨🇳 · Ji-Yu Song🇺🇸 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    Gravitational-wave (GW) detection offers a novel approach to exploring intermediate-mass black holes (IMBHs). The GW signals from IMBH mergers mainly fall in the decihertz frequency band. The lunar-based GW detector, the Lunar Gravitational-Wave Antenna (LGWA), exhibits high sensitivity in this band, making it particularly well-suited for detecting IMBHs. However, for lower-mass IMBHs, the late inspiral and merger signals enter the sensitive frequency range of ground-based GW detectors. In this work, we aim to explore how multi-band observations with LGWA and the third-generation ground-based GW detector, the Einstein Telescope (ET), can contribute to detecting the population of IMBHs. We consider three population distribution cases of IMBHs, including two population models based on astrophysical motivations and a uniform distribution, and compute the signal-to-noise ratios for LGWA, ET, and their combination to directly compare their capabilities in detecting IMBH mergers. Our results suggest that LGWA possesses strong detection capability for high-mass IMBH mergers. At redshift $z=1$, LGWA's detection rate for IMBH binaries with primary masses above $5\times 10^4{M}_{\odot }$ is largely insensitive to orbital inclination and mass ratio. In contrast, ET is more suited for detecting IMBH binaries with primary masses below $10^3{M}_{\odot }$. The multi-band observation of LGWA and ET possesses strong detection capabilities across the full IMBH mass spectrum. Furthermore, we find that the multi-band detection can significantly and effectively recover the IMBH population distributions. In summary, we conclude that the multi-band observations of LGWA and ET will provide powerful detection capabilities for IMBHs and are expected to significantly enhance our understanding of this important yet still poorly observed class of black holes.

    ↳ gr-qcastro-ph.COhep-phJCAP(2026)·15 citations
44. 44*

    The multiplicity distributions of the high frequency gravitons

    Massimo Giovannini🇨🇭

    When the gravitons are created thanks to the variation of the space-time curvature the multiplicity distributions quantify the probability of producing a given number of species around the average occupation numbers of the underlying multiparticle states. The multiplicities of the relic gravitons are infinitely divisible and their analytical expressions encompass, in different regions of the physical parameters, the Poisson, Bose-Einstein, Gamma and Pascal probability distributions. Depending upon the post-inflationary timelines, the averaged multiplicities are controlled by the range of the comoving frequencies and they can be much larger in the GHz region than in the aHz domain where the temperature and polarization anisotropies of the microwave background set strict limits on the spectral energy density of the relic gravitons. Thanks to the absolute upper bound on the maximal frequency of the gravitons we can acknowledge that the averaged multiplicities are exponentially suppressed above the THz, where only few pairs of gravitons are independently created from the vacuum. The statistical properties of the produced particles can be finally interpreted in the light of the second-order interference effects and this perspective is quantitatively scrutinized by analyzing the associated quantum sensitivities. For putative instruments reaching spectral amplitudes $\mathcal{O}(10^{-35})/\sqrt{\mathrm{Hz}}$ in the MHz or GHz bands, the Bose-Einstein correlations could be used to probe the properties of cosmic gravitons and their super-Poissonian statistics. Both from the theoretical and observational viewpoint it is unjustified to require the same sensitivities (e.g. $\mathcal{O}(10^{-21})/\sqrt{\mathrm{Hz}}$) in the kHz and GHz domains.

    ↳ hep-thastro-ph.COgr-qchep-phNPB(2025)·3 citations
45. 45*

    Data production and Monte Carlo simulations for the Pierre Auger Observatory

    Paula Gina Isar (for the Pierre Auger Collaboration)

    The Pierre Auger Observatory consists of 1660 water-Cherenkov detectors (WCDs) and 27 fluorescence telescopes, covering a surface of 3000 km2 in the province of Mendoza, Argentina. After almost two decades, Auger Phase I has ended the data taking and has already delivered many outstanding physics results. The Auger Observatory is currently running in Phase II, with upgraded detectors for enhanced data of ultra-high-energy cosmic rays (UHECRs). During Phase I, several engineering detectors were developed and tested. Some of those developments led to new detectors, which are now part of the upgraded Observatory. For Phase II, the WCDs were upgraded with a surface-scintillator detector, a radio detector, a small photomultiplier, and an upgraded electronics board, facilitating mass-sensitive measurements for source identification of UHECRs. Moreover, an underground muon detector allows for a direct measurement of the muon content of air showers. The Offline framework is the main software for the event reconstruction and detector simulation at the Pierre Auger Observatory. It is continuously being developed to accommodate changes in the detector and new algorithms. It allows the running of various applications, which are made up of individual modules, either on raw data or simulations on an event-by-event basis. Large productions of shower and detector reference libraries are done with CORSIKA 7 and Offline on the European Grid Infrastructure (EGI) using the Virtual Organization Auger. Various air-shower geometries (up to 89 degrees in zenith) were considered, as well as several primary particles (from light to ultra-heavy nuclei, photons, and neutrinos), hadronic interaction models and detector configurations for Phase I and Phase II. In this contribution, we present the actual efforts and updates on software for data production and reference Monte Carlo simulations for Auger data analysis.

    ↳ astro-ph.HEastro-ph.IMhep-phPoS(2025)·1 citation
46. 46*

    Study of solar activity with AERA at the Pierre Auger Observatory

    R. M. de Almeida (for the Pierre Auger Collaboration)

    Solar activity events release vast amounts of energy, including radio waves, X-rays, ultraviolet radiation, and energetic particles, which interact with the ionosphere of the Earth and can disrupt radio wave propagation, affecting radio communications. They can either enhance reflections, improving long-distance terrestrial communications, or cause signal degradation and absorption, respectively, depending on whether the increased ionization affects the upper or lower layers of the ionosphere. In the first case, the solar cycle modulates the Maximum Usable Frequency (MUF), the highest frequency usable for radio communication between two Earth-based points. The Auger Engineering Radio Array (AERA) of the Pierre Auger Observatory was developed to measure the radio emission from extensive air showers in the $30-80$ MHz band. We examine the impact of solar activity on AERA data collected over approximately 11 years. We report the detection of different types of solar radio bursts and we investigate how increased solar radiation - particularly in the X-ray and extreme ultraviolet bands - also affects measurements in the AERA energy band. Our results show a remarkable correlation between the MUF and the broadband noise observed in the $30-40$ MHz frequency range. Radio blackouts are also observed in AERA spectrograms in coincidence with those reported by the National Oceanic and Atmospheric Administration (NOAA). Additionally, we performed a search for temporal coincidences between AERA data and independent observations of solar radio burst events from the e-CALLISTO network and the SWAVES instrument. These findings highlight the complex interplay between solar activity and radio wave propagation, which is also relevant for cosmic-ray detection.

    ↳ astro-ph.HEastro-ph.IMastro-ph.SRhep-phPoS(2025)·1 citation
47. 47*

    Oscillations of hypothetical strange stars as an efficient source ultra-high-energy particles

    Joanna Jałocha🇵🇱 · Łukasz Bratek🇵🇱

    We investigate the dynamical behavior of strange quark matter (SQM) objects, such as stars and planets, when subjected to radial oscillations induced by tidal interactions in stellar systems. Our study demonstrates that SQM objects can efficiently convert mechanical energy into hadronic energy due to the critical mass density at their surfaces of 4.7*10^{14} g/cm^3, below which SQM becomes unstable and decays into photons, hadrons, and leptons. We show that even small-amplitude radial oscillations, with a radius change of as little as 0.1%, can result in significant excitation energies near the surface of SQM stars. This excitation energy is rapidly converted into electromagnetic energy over short timescales approximately 1 ms, potentially leading to observable astrophysical phenomena. Higher amplitude oscillations may cause fragmentation or dissolution of SQM stars, which has important implications for the evolution of binary systems containing SQM objects and the emission of gravitational waves.

    ↳ astro-ph.HEastro-ph.SRhep-phnucl-thPoS(2025)·0 citations
48. 48*

    Lattice QCD Study of Positive Parity Dibaryons with Maximal Charm and Strangeness

    Navdeep Singh Dhindsa🇮🇳 · Nilmani Mathur🇮🇳 · M. Padmanath🇮🇳

    We present the ground-state energy spectra of dibaryons composed of single-flavor quarks, specifically systems with strangeness $\mathcal{S}=-6$ and charm $\mathcal{C}=6$. Our lattice QCD study is based on $N_f=2+1+1$ MILC ensembles with highly improved staggered quark (HISQ) sea quarks, spanning four lattice spacings and two spatial volumes. We employ valence quark propagators realized using a relativistic overlap action, evaluate correlation matrices with carefully designed operator bases, and extract reliable ground-state energy estimates in the $S=0$ and $S=2$ spin channels. We explore their binding characteristics and interaction dynamics by examining the energy separation between the dibaryon states and the corresponding two-baryon thresholds. These results contribute to a deeper understanding of single-flavor dibaryon states as a function of the quark masses. In the $S=0$ channel, the ${\Omega }_{ccc}$-${\Omega }_{ccc}$ system exhibits a clear signal of a bound state, while the $\Omega$-$\Omega$ system lies very close to the threshold, making it difficult to draw definitive conclusions. For $S=2$, both systems are found to be unbound.

    ↳ hep-lathep-exhep-phnucl-thPRD(2025)·5 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.