Mon·Oct 20, 2025Monday·October 20, 2025

1. 01*

   Effects of Radiative Corrections on Starobinsky Inflation

   John Ellis🇬🇧 · Tony Gherghetta🇺🇸 · Kunio Kaneta🇯🇵 · Wenqi Ke🇺🇸 · Keith A. Olive🇺🇸

   We analyze radiative corrections to the Starobinsky model of inflation arising from self-interactions of the inflaton, and from its Yukawa couplings, $y$, to matter fermions, and dimensionful trilinear couplings, $\kappa$, to scalar fields, which could be responsible for reheating the Universe after inflation. The inflaton self-interactions are found to be of higher order in the Hubble expansion rate during inflation, and hence unimportant for CMB observations. In contrast, matter couplings to the Starobinsky inflaton can have significant effects on the spectral index of scalar CMB perturbations, $n_s$, and on the tensor-to-scalar ratio, $r$. Using a renormalization-group improved analysis of the effective inflationary potential, we find that the Planck measurement of $n_s$ constrains the inflaton coupling to light fermions in the Einstein frame: $y<4.5\times 10^{-4}$, corresponding to an upper limit on the reheating temperature $T_{\mathrm{RH}}<2\times 10^{11}\mathrm{GeV}$, whereas the ACT DR6 measurement of $n_s$ corresponds to $3.8\times 10^{-4}<y<5.6\times 10^{-4}$ and $1.7\times 10^{11}\mathrm{GeV}<T_{\mathrm{RH}}<2.8\times 10^{11}\mathrm{GeV}$, while the upper limits on $r$ provide weaker constraints. Planck data also imply a constraint on a trilinear inflaton coupling to light scalars in the Einstein frame: $\kappa \le 4\times 10^{12}\mathrm{GeV}$, corresponding to $T_{\mathrm{RH}}\le 4.2\times 10^{13}\mathrm{GeV}$. We further present constraints on inflaton couplings to massive fermions and scalars, and analyze constraints on couplings in the Jordan frame.

   hep-phastro-ph.COgr-qchep-thPRD(2025)·22 citations
2. 02*

   Enhancing di-jet resonance searches via a final-state radiation jet tagging algorithm

   Bingxuan Liu🇨🇳 · Yuxuan Shen🇨🇳 · Yuanshunzi Sui🇨🇳

   In this article, we investigate the possibility of enhancing the di-jet resonance searches by tagging the final state radiation (FSR) jet, using an event-level deep neural network. It is found that solely relying on the 4-momenta of the leading three jets allows the algorithm to achieve good discriminating power that can identify the hardest FSR jet in signal, while rejecting other soft jets. Once the invariant mass is corrected with the tagged FSR jet, the mass resolution of the signal is greatly enhanced, and the sensitivity of the search is also improved by more than 10%. By crafting the input variables carefully, the algorithm introduces minimal mass sculpting for the background, and its applicability extends to a broad mass range. This work proves that FSR jet tagging can potentially enhance the di-jet resonance searches, suiting various stages of the physics programmes at the Large Hadron Collider (LHC) and High-Luminosity LHC (HL-LHC).

   hep-phCPC(2026)·0 citations
3. 03*

   Study of $P$ and $CP$ symmetries in ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ at electron-positron collider

   Yunlu Wang🇨🇳 · Yunlong Xiao🇨🇳 · Pengcheng Hong🇨🇳 · Ronggang Ping🇨🇳

   Symmetry studies represent one of the most promising frontiers in particle physics research. This investigation focuses on exploring $P$ and $CP$ symmetries in the charm system through the measurement of asymmetry decay parameters in the three-body decay of ${\Xi }_c^{+}$. Incorporating electron and positron beam polarization effects and utilizing the helicity formalism, we characterize the decay of ${\Xi }_c^{+}$ and its secondary hyperons through asymmetry decay parameters. The complete angular distribution formula for these decays has been systematically derived. Our study evaluates the sensitivity of the asymmetry parameters for the ${\Xi }_c^{+}\to {\Xi }^{-}{\pi }^{+}{\pi }^{+}$ decay channel under various data sample sizes and beam polarization scenarios. These findings establish a robust theoretical framework for future experimental studies at the STCF, providing valuable insights for symmetry investigations in the charm sector.

   hep-phCPC(2026)·0 citations
4. 04*

   The detection of cosmic neutrino background with helicity-changing decays

   Jihong Huang🇨🇳 · Shun Zhou🇨🇳

   In this talk, we present the investigation of the invisible decays of a heavy massive neutrino into a lighter neutrino and a massless Nambu-Goldstone boson, i.e., ${\nu }_i^{}\to {\nu }_j^{}+\varphi$. The total decay rates are calculated in the most general case, where the individual helicities of both parent and daughter neutrinos are specified. We then examine the evolution of the number densities of cosmological relic neutrinos throughout the expansion of the Universe, and explore the consequent impacts on the capture rates in PTOLEMY-like experiments. The total event rates can be significantly modified compared to those in the scenario of stable neutrinos, with helicity-changing decays playing an especially important role in the Dirac neutrino case.

   hep-ph0 citations
5. 05*

   Convergence of Heavy-Flavor PDFs at Small x and Its Impact on Future ep Colliders

   S. O. Kara🇹🇷

   We present the first quantitative demonstration of the statistical convergence of heavy-flavor parton distribution functions at small x across modern NNLO global fits. Using the latest NNPDF4.0, CT18, and MSHT20 sets, we find a maximal relative deviation of 16.8 percent at x = 1e-6 and Q = 100 GeV, corresponding to nearly a factor-of-two improvement over the approximately 30 percent spread in pre-2013 determinations. This convergence, stabilized by consistent alpha_s and scale treatments, marks a transition of the heavy-flavor sector into a statistically controlled regime of small-x QCD. We further show that this precision directly reduces PDF-driven uncertainties in heavy-quark electroproduction at future ep colliders (LHeC and FCC-eh) by about a factor of two and enhances the theoretical stability of leptophilic new-physics searches such as a neutral Z_l gauge boson. These findings establish a link between the precision frontier of QCD and the discovery potential of next-generation lepton-hadron facilities.

   hep-phPRD(2026)·0 citations
6. 06*

   The ${\gamma }^{\ast }\to \eta \gamma$ and ${\gamma }^{\ast }\to {\eta }^{\prime }\gamma$ form factors to NNLO accuracy in perturbative QCD

   V. M. Braun🇩🇪 · K. G. Chetyrkin🇩🇪 · A. N. Manashov🇩🇪

   We use conformal symmetry to calculate the NNLO anomalous dimension matrix (three loops) for flavor-singlet axial-vector QCD operators for spin $N\le 8$ from a set of gauge-invariant two-point correlation functions. Combining this result with the recent calculation of the two-loop coefficient functions, we carry out the calculation of the $\gamma {\gamma }^{\ast }\to \eta$ and $\gamma {\gamma }^{\ast }\to {\eta }^{\prime }$ form factors at large momentum transfers to the NNLO accuracy in perturbative QCD.

   hep-phPRD(2026)·1 citation
7. 07*

   Probing Composite Structure and Spin-Orbit Coupling with GPDs in ${}^4$He

   Antonio Garcia Vallejo🇺🇸 · Matthew D. Sievert🇺🇸

   In this work, we extend the Impulse Approximation for the generalized parton distributions (GPDs) of a spin-0 composite hadron with spin-$\frac{1}{2}$ constituents to manifestly incorporate the symmetries of the target wave function. The method utilizes a light-front Wigner function representation instead of a spectral density and a basis of Pauli matrices for the spin. It exploits the boost invariance of the light front and rotational invariance in the rest frame to parameterize the Wigner density in terms of only 3 structures. In addition to the isotropic term and a term describing $\vec{L}\cdot \vec{S}$ coupling previously observed for transverse momentum dependent parton distributions (TMDs), we also identify a novel coupling $\Delta \vec{L}\cdot \vec{S}$ to the angular momentum \textit{transfer} which is unique to the case of GPDs. We then apply the framework to a composite ${}^4$He target with simple phenomenological models to identify qualitative experimental signatures of composite-structure effects in light nuclei. The framework we have constructed here can be readily extended to the case of generalized TMDs (GTMDs), while the phenomenological framework is applicable both to analyses of light nucleus data and as training input for AI-assisted applications.

   hep-phnucl-thPRD(2026)·0 citations
8. 08*

   Diabatic Dynamical Diquark Model of Hidden-Strangeness Tetraquarks

   Shahriyar Jafarzade🇺🇸 · Richard F. Lebed🇺🇸

   We generalize our recent analysis of hidden-strangeness tetraquarks within the dynamical diquark model from its adiabatic form (in which each state is described solely by a diquark-antidiquark potential) to its diabatic form (which incorporates effects of di-hadron thresholds upon the states). We tabulate all relevant thresholds and compute the di-hadron content of each predicted state. Our results produce no particular hidden-strange tetraquark candidate whose structure is dominated by di-hadron structure, in contrast to the charm sector, where many exotic states are strongly associated with such thresholds: The hidden-strange states tend to remain compact and less influenced by di-hadron thresholds. Multiple states above 2~GeV with peculiar decay properties, including $\varphi (2170)$, $f_2(2340)$, and $\eta (2370)$, continue to serve as excellent hidden-strange tetraquark candidates.

   hep-phPRD(2025)·2 citations
9. 09*

   Neutrino Mass Induced $n$-$\overline{n}$ Oscillation

   Ilja Dorsner🇭🇷 · Svjetlana Fajfer🇸🇮 · Shaikh Saad🇸🇮

   The Georgi-Glashow model is the simplest possible attempt at grand unification. However, due to its particle content, the model preserves a global $U(1{)}_{B-L}$ symmetry, where $B$ and $L$ are baryon and lepton numbers, respectively. It thus leaves neutrinos massless just as the Standard Model does. The extensions of the Georgi-Glashow model that break lepton number by two units, i.e., scenarios with $|\Delta L|=2$ operator(s), naturally generate potentially viable Majorana neutrino masses. Since the dynamics that yields $|\Delta L|=2$ interactions unavoidably induces $|\Delta B|=2$ transitions via $B-L$ breaking, these extensions consequentially lead to intriguing processes such as neutron--antineutron ($n$--$\overline{n}$) oscillation. We investigate this intrinsic connection between neutrino mass generation and $n$--$\overline{n}$ oscillation within a number of representative extensions of the Georgi-Glashow model that can yield realistic neutrino masses and mixing parameters. These extensions include the tree-level seesaw mechanism realizations of the Type I, II, and III varieties, as well as the one-loop and two-loop radiative neutrino mass models.

   hep-phPLB(2026)·3 citations
10. 10*

    Characterizing Heavy Neutral Leptons: Measuring Parameters, Discriminating Majorana versus Dirac, and Using FASER2 as a Trigger for ATLAS

    Jonathan L. Feng🇺🇸 · Alec Hewitt🇺🇸 · Daniel La Rocco🇺🇸 · Daniel Whiteson🇺🇸

    This work explores the potential of the proposed FASER2 experiment at the LHC to determine the properties of a discovered heavy neutral lepton (HNL), including its mass, couplings, and whether it is a Majorana or Dirac fermion. We first consider a Majorana HNL with mass $m_N=1.84\mathrm{GeV}$ that is primarily produced through decays $D\to \mu N$ at the ATLAS interaction point. Such HNLs may travel macroscopic distances in the far-forward direction and then decay, yielding approximately 8600 $N\to \mu \pi$ decays in FASER2 at the High-Luminosity LHC. With FASER2 measurements alone, the HNL's mass and couplings can be measured to fractional uncertainties of approximately 0.1% and 3% at 95% CL, respectively, and the Dirac fermion hypothesis can be rejected at 99.8% CL. We then consider a second, more difficult, case of a Majorana HNL with mass $m_N=2.00\mathrm{GeV}$, yielding only 80 $N\to \mu \pi$ decays in FASER2. With FASER2 alone, measurements of HNL properties are still possible, but somewhat less precise. However, by using FASER2 as a trigger for ATLAS and measuring the charge of the muon produced in association with the HNL at ATLAS to search for lepton number violation, one can precisely measure the HNL's properties and reject the Dirac fermion hypothesis at 99.7% CL. These results show that FASER2, sometimes in coordination with ATLAS, can precisely determine HNL properties, with far-reaching implications for our understanding of neutrino masses, baryogenesis, and the fundamental symmetries of nature.

    hep-phhep-exPRD(2026)·2 citations
11. 11*

    Interactions of the deuteron with a hadronic medium

    L. M. Abreu🇧🇷 · R. Higa🇧🇷 · R. O. Magalhães🇧🇷 · F. S. Navarra🇧🇷

    We investigate the interactions of the deuteron with light mesons during the hadronic phase in heavy-ion collisions. We treat the deuteron as a weakly bound state and employ the quasi-free approximation to describe the $d\pi$ interaction. The underlying elementary $N\pi$ amplitudes are described by a hybrid effective model, combining the non-resonant background from chiral perturbation theory with resonant contributions via Breit-Wigner parameterizations. These amplitudes are used to calculate the vacuum and thermally-averaged cross-sections for deuteron dissociation and production, namely, $d+\pi \to N+N^{\prime }+\pi$ and the corresponding inverse reaction. We then use these cross sections in a rate equation to estimate the time evolution of the deuteron multiplicity. For the initial conditions we consider two models: the statistical hadronization model and the coalescence model, where the deuteron is treated as a hadronic molecule. Our findings suggest that the final deuteron yield does not retain a memory of its initial production mechanism.

    hep-phnucl-thPRD(2026)·0 citations
12. 12*

    Multi-species Dark Matter with Warmth and Randomness

    Mustafa A. Amin🇺🇸 · M. Sten Delos🇺🇸 · Kaixin Yang🇺🇸

    We present a general analytic framework for the evolution of cosmic structure in multi-species dark matter models that simultaneously incorporates finite velocity dispersion and Poisson fluctuations. Our approach accommodates arbitrary numbers of dark matter components with distinct mass fractions, velocity distributions, and number densities -- ranging from cold particles to warm species and sparse populations such as primordial black holes or solitons. The framework is based on solving a truncated BBGKY hierarchy, whose solution is obtained by solving Volterra integral equations. We provide an efficient algorithm to solve for the total, as well as inter- and intra-species power spectra. Worked examples with two-component mixtures illustrate how isocurvature (initially Poisson) and adiabatic spectra evolve differently depending on the properties of the warm or sparse fraction. This evolution is controlled by the free-streaming and Jeans scales, and the results match analytic estimates and $N$-body simulations.

    ↳ astro-ph.COhep-phJCAP(2026)·7 citations
13. 13*

    Exploring Ultra-Slow-Roll Inflation in Composite Pseudo-Nambu-Goldstone Boson Models: Implications for Primordial Black Holes and Gravitational Waves

    Marco Merchand🇯🇵

    We study inflation driven by a scalar potential arising from composite-sector dynamics, inspired by generalized composite Higgs models. The introduction of a non-minimal coupling, possessing the same functional form as the potential, induces a flattening at large field values that enables successful inflation. We analyze the conditions for ultra-slow-roll inflation, which leads to enhanced curvature perturbations, by combining analytical criteria near the inflection point with comprehensive numerical scans of the parameter space. The region consistent with Cosmic Microwave Background constraints and yielding approximately $N_e\approx 55\text{–}60$ e-folds also predicts primordial black holes with masses in the range $10^3\text{–}10^5\mathrm{g}$. Although such ultra-light primordial black holes are typically expected to have evaporated, recent proposals invoking evaporation suppression via memory-burden effects could allow their survival as viable dark matter candidates. Under this assumption, the predicted gravitational wave signal lies in a frequency range currently inaccessible to any existing or proposed detectors. Although no experimental proposals presently reach this frequency band, our results provide strong motivation to push the frontiers of gravitational wave detection towards these unexplored high-frequency regimes.

    ↳ astro-ph.COhep-phEPJC(2026)·6 citations
14. 14*

    New Elementary Operator for Kaon Photoproduction on the Nucleon and Nuclei

    Terry Mart🇮🇩 · Jovan Alfian Djaja🇮🇩

    A new elementary operator for kaon photoproduction on the nucleon and nuclei has been developed within a Feynman diagrammatic framework. By fitting the unknown coupling strengths at the electromagnetic and hadronic vertices of the baryon resonances to all available experimental data across the six isospin channels, the model achieves excellent agreement with the data. The operator includes 26 nucleon resonances in the $K\Lambda$ channels and 17 additional $\Delta$ resonances in the $K\Sigma$ channels. For applications to nuclear reactions, such as hypernuclear photoproduction, the operator is formulated in Pauli space, allowing a straightforward implementation of the nonrelativistic approximation. Several alternative forms for expressing the operator output are proposed. In one of them, the spin operators and photon polarization vectors are separated from the operator, since both are frame dependent, thereby enhancing its versatility in nuclear applications.

    ↳ nucl-thhep-phFew Body Syst.(2026)·2 citations
15. 15*

    Deconfinement-Higgs continuity in $\mathrm{SU}(2)$ adjoint Higgs model at finite temperature

    Yui Hayashi🇯🇵 · Masashi Kawahira🇯🇵 · Hiromasa Watanabe🇯🇵

    We study the finite-temperature phase structure of the four-dimensional $\mathrm{SU}(2)$ adjoint Higgs model, focusing on a possible \textit{deconfinement-Higgs continuity}: the conjecture that the high-temperature deconfined phase of Yang-Mills theory and the finite-temperature Higgs phase form a single thermodynamic phase. We first perform a global-symmetry analysis, showing that the Higgs and deconfined regimes are expected to share the same symmetry pattern, which is distinct from that of the confined phase. This suggests deconfinement-Higgs continuity, but does not exclude the possibility that the deconfined phase and the Higgs phase are separated by a phase transition not associated with the global symmetries. We then perform a deformation analysis, which yields an explicit continuous path between the ``deconfined symmetric'' and ``deconfined Higgs'' regions in a reduced three-dimensional lattice model. These results indicate that the Higgs and deconfined regimes can be continuously connected, while the confined phase remains distinct.

    ↳ hep-thhep-lathep-ph0 citations
16. 16*

    Relativistic tidal divergences in circular orbits and the dynamics of light rings

    Victor F. C. Vieira · Rafael P. Bernar · Caio F. B. Macedo🇧🇷

    Tidal forces acting on orbiting bodies arise from inhomogeneities in the gravitational field, generating stresses that can deform or even disrupt these objects. In this work, we analyze relativistic tidal forces associated with ultracompact objects described by static and spherically symmetric spacetimes, focusing on observers in circular geodesic motion. We show that, in contrast to the case of radial geodesics, tidal forces diverge as the orbit approaches null circular geodesics. As illustrative examples, we study two uniform-density stellar models: one isotropic and another supported purely by tangential stresses. We conjecture that the divergence of tidal forces near light rings may play a role in the nonlinear stability of ultracompact, horizonless objects.

    ↳ gr-qcastro-ph.HEhep-phhep-th2 citations
17. 17*

    Impact of neutrino decays on the Cosmic Neutrino Background anisotropies

    Nicola Terzaghi🇳🇱 · Guillermo Franco Abellán🇳🇱 · Fabian Zimmer🇳🇱 · Shin'ichiro Ando🇳🇱

    The anisotropies of the Cosmic Neutrino Background (C$\nu$B) offer an ideal tool to test non-standard neutrino interactions, since they directly trace the perturbations in the neutrino distribution function. Here, we study how invisible neutrino decays impact the C$\nu$B anisotropies, in a framework where neutrinos decay non-relativistically to dark radiation and lighter neutrinos in a manner consistent with the measured mass splittings. For this purpose, we perform the first implementation of such a late-time neutrino decay scenario within a linear Einstein-Boltzmann solver, and compute the C$\nu$B angular power spectra from the Boltzmann hierarchy solutions for a range of lifetimes and decay channels. We find that neutrino decays leave very strong signatures on the C$\nu$B angular spectra, about two orders of magnitude larger than on the CMB angular spectra, particularly for lifetimes comparable to the age of the Universe. We show that a future polarized tritium target run of the PTOLEMY experiment, with sufficient counting statistics to measure just the first $\sim 15$ multipoles of the neutrino sky map, could test neutrino decay models that remain undetectable with CMB data.

    ↳ astro-ph.COhep-ph2 citations
18. 18*

    Out-of-Equilibrium Dynamics in a U(1) Lattice Gauge Theory via Local Information Flows: Scattering and String Breaking

    Claudia Artiaco🇸🇪 · João Barata🇨🇭 · Enrique Rico🇨🇭

    We introduce local information flows as a diagnostic tool for characterizing out-of-equilibrium quantum dynamics in lattice gauge theories. We employ the information lattice framework, a local decomposition of total information into spatial- and scale-resolved contributions, to characterize the propagation and buildup of quantum correlations in real-time processes. Focusing on the Schwinger model, a canonical $(1+1)$-dimensional U(1) lattice gauge theory, we apply this framework to two scenarios. First, in the near-threshold scattering of two vector mesons, we demonstrate that the emergence of correlations at a longer length scale in the information lattice marks the production of heavier scalar mesons. Second, in the dynamics of electric field strings, we clearly distinguish between the confining regime, which evolves towards a steady state with a static correlation profile, and the string-breaking sector. The latter is characterized by dynamic correlation patterns that reflect the sequential formation and annihilation of strings. This information-centric approach provides a direct, quantitative, and interpretable visualization of complex many-body phenomena, offering a promising tool for analyzing dynamics in higher-dimensional gauge theories and experiments on quantum hardware.

    ↳ quant-phhep-lathep-ph18 citations
19. 19*

    First non-zero measurement of a nuclear electric dipole moment

    Gary Prézeau🇧🇷

    This paper reports the first non-zero measurement of a nuclear electric dipole moment using a novel method based on the rate of change of a supercurrent first proposed in 2016~\cite{https://doi.org/10.48550/arxiv.1604.02152} and fleshed out in this current paper. The theory, experimental concept and implementation are described in detail. The non-zero nuclear electric dipole moment measured with over 1000 hours of data was that of ${}^{181}$Ta producing a best value $|d_{\text{e}}^{\text{Ta}}|=(3.39\pm 0.31_{\text{stat}})\cdot 10^{-32}e\cdot \text{cm}$ and $|d_{\text{e}}^{\text{Ta}}|=(3.39\pm 3.18)\cdot 10^{-32}e\cdot \text{cm}>0$ at 99.985\%CL. There is an uncertainty on the value of overall multiplicative parameters such as the self-inductance of the superconducting circuit ($\pm 4\%$), the mutual inductance between the SQUID pickup coil and the sample wire ($\pm 15\%$), and the magnitude of the solenoid current ($\pm 5\%$). An upper-limit was estimated for the control element, ${}^{207}$Pb, $|d_{\text{e}}^{\text{Pb}}|\lesssim 1.2\cdot 10^{-31}e\cdot \text{cm}$ at 95\%CL.

    ↳ nucl-excond-mat.supr-conhep-phnucl-th+10 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.