Wed·Jan 7, 2026Wednesday·January 7, 2026

1. 01*

   Dark matter and scalar sector in a novel two-loop scotogenic neutrino mass model

   A. E. Cárcamo Hernández🇨🇱 · Catalina Espinoza🇲🇽 · Juan Carlos Gómez-Izquierdo🇲🇽 · Juan Marchant González · Myriam Mondragón🇲🇽

   We propose an extended $3+1$ Higgs doublet model where the Standard Model (SM) gauge structure is enhanced by the discrete symmetry $Q_6\times Z_2\times Z_4$, and the fermion content is extended with right-handed Majorana neutrinos. The scalar sector, besides four $SU(2)$ doublets, incorporates multiple gauge-singlet scalars. In our model, the tiny active neutrino masses arise from a novel radiative seesaw mechanism at two-loop level and the leptonic mixing features the cobimaximal mixing pattern compatible with neutrino oscillation experimental data. Along with this, the proposed model is consistent with SM quark masses and mixings as well as with the constraints arising from dark matter relic density and dark matter direct detection. Our analysis reveals that the best-fit point satisfying dark matter constraints yields a non-SM scalar with mass near $95$ GeV, which could be a possible candidate for the observed $95$ GeV diphoton excess. We further obtain other non SM scalars with masses at the subTeV scale which are within the LHC reach, while successfully complying with the experimental bounds arising from collider searches.

   hep-ph2 citations
2. 02*

   Helicity Dependent Distribution Functions of the Proton and $\Lambda$ and ${\Sigma }^0$ Baryons

   Yang Yu🇨🇳 · Peng Cheng🇨🇳 · Hui-Yu Xing🇨🇳 · Daniele Binosi🇮🇹 · Craig D. Roberts🇨🇳

   Using continuum Schwinger function methods, a coherent set of predictions for proton, $\Lambda$ and ${\Sigma }^0$ distribution functions (DFs) has been made available -- both helicity dependent and unpolarised. The results and comparisons between them reveal impacts of diquark correlations and SU$(3)$-flavour symmetry breaking, some of which are highlighted in this contribution. For instance: in-proton ratios of helicity-dependent/unpolarised valence-quark DFs are presented; it is highlighted that, were it not for the presence of axialvector diquarks in the ${\Sigma }^0$, the valence strange quark would carry none of the ${\Sigma }^0$ spin; and the sign and size of polarised gluon DFs is discussed -- at a scale typical of modern measurements, gluon partons carry roughly 40% of each octet baryon's spin.

   hep-phhep-exhep-latnucl-ex+10 citations
3. 03*

   Higgs boson decays $h\to Z\gamma$ and $h\to m_{V}Z$ in the $U(1{)}_X$VLFM

   Rong-Zhi Sun🇨🇳 · Shu-Min Zhao🇨🇳 · Yue-Tong Liu🇨🇳 · Xing-Xing Dong🇨🇳

   We study the Higgs boson decays $h\to Z\gamma$ and $h\to m_{V}Z$ in a model with vectorlike fermions and $U(1{)}_X$ symmetry ($U(1{)}_X$VLFM), where $m_V$ is a vector meson ($\rho ,\omega ,\varphi ,J/\psi ,{\rm Y}$). The exotic Yukawa interactions in this model generate mixing between Standard Model (SM) fermions and vectorlike fermions, and this mixing affects the Higgs boson mass and Higgs couplings. The corrections to the CP-even and CP-odd $h\gamma Z$ couplings come from loop diagrams that involve the new particles, and these corrections have a clear impact on the decay rates of $h\to Z\gamma$ and $h\to m_{V}Z$. In suitable regions of the parameter space, the model can produce non-negligible deviations in ${\Gamma }_{\mathrm{NP}}(h\to Z\gamma )/{\Gamma }_{\mathrm{SM}}(h\to Z\gamma )$ and ${\Gamma }_{\mathrm{NP}}(h\to m_{V}Z)/{\Gamma }_{\mathrm{SM}}(h\to m_{V}Z)$, providing possible signals of new physics (NP) beyond the SM.

   hep-phEPJC(2026)·0 citations
4. 04*

   The Future of Higgs Boson Physics

   Michael E. Peskin🇺🇸

   In this lecture, I discuss measurements of the properties of the Higgs boson and related observables in the era of Higgs factories. This highly motivated experimental program is the challenge for the next generation of particle physicists.

   hep-phhep-exphysics.acc-phEur.Phys.J.Plus(2026)·0 citations
5. 05*

   Partial $\mu -\tau$ symmetry from kinetic normalization

   N. Chamoun🇸🇾 · C. Hamzaoui · M. Toharia🇨🇦

   We consider models with broken $\mu$-$\tau$ permutation symmetry through higher dimensional operators renormalizing the lepton kinetic terms in the action. We study the consequences on the structure of the neutrino mass matrix and find in particular that the allowed region for the lightest mass in the normal hierarchy plotted as a function of the atmospheric mixing element $|V_{\mu 3}|$ is very restricted with the atmospheric mixing angle ${\theta }_{23}$ to lie in the second octant. On the other hand, the corresponding allowed region in the inverted hierarchy regime is less restrictive.

   hep-phPHEP(2025)·0 citations
6. 06*

   Two Higgs doublet model with a complex singlet scalar and Multi-critical Point Principle

   Gi-Chol Cho🇯🇵 · Chikako Idegawa🇨🇳 · Chiaki Nose🇯🇵

   We study a two Higgs doublet model extended by a complex singlet scalar, in which the imaginary part of the singlet serves as a dark matter (DM) candidate. In this model, degenerate masses of the three neutral Higgs bosons are crucial for achieving consistency with current constraints from DM direct-detection experiments and Higgs searches. This is called the degenerate scalar scenario. To provide a theoretical motivation for such a degenerate Higgs spectrum, we impose the tree-level Multiple Point Principle (MPP), which requires the electroweak and singlet vacua to be degenerate, and analyze its implications for the scalar potential, DM phenomenology, and the electroweak phase transition. We show that the tree-level MPP favors large SU(2)${}_L$ doublet-singlet mixing parameters, which compete with the degenerate scalar scenario. Nevertheless, we demonstrate that viable parameter regions still exist in which the observed DM constraints are satisfied. Furthermore, although the tree-level MPP forbids a tree-level-driven first-order electroweak phase transition, we show that thermal loop effects can induce a strong first-order transition compatible with electroweak baryogenesis.

   hep-phPTEP(2026)·0 citations
7. 07*

   Study of $CP$ violation in ${\Lambda }_b^0\to N^{\ast }M$ decays with the final-state rescattering mechanism

   Hui-Qiang Shang🇨🇳 · Tian-Liang Feng🇨🇳 · Jing Gao🇩🇪 · Qin Qin🇨🇳 · Fu-Sheng Yu🇨🇳

   In this work, we investigate the charmless non-leptonic two-body ${\Lambda }_b$ decays within the framework of final-state rescattering mechanism. In contrast to the Cutkosky cutting method, we compute both the absorptive and dispersive parts of the hadronic rescattering triangle diagrams. Based on the established formalism, we analyze the ${\Lambda }_b\to N^{\ast }(1535,1520)M$ decay processes with $M=K_S,K_0^{\ast }(700)$, $f_0(500,980),\rho (770),{\bar{K}}^{\ast 0}$, $\varphi$, and predict various physical observables, such as their branching ratios, direct and partial-wave $CP$ asymmetries, as well as decay asymmetry parameters. These two-body decay processes are expected to contribute primarily to the subsequent four-body decay channels, such as ${\Lambda }_b^0\to p{\pi }^{-}{\pi }^{+}{\pi }^{-}$, whose $CP$ asymmetry measurements will be accessible at the LHCb experiment.

   hep-ph5 citations
8. 08*

   Single-quark electromagnetic form factors of charmonium up to $J=2$

   Jian Huang🇨🇳 · Muyang Chen🇨🇳 · Xian-Hui Zhong🇨🇳

   We calculate the single-quark electromagnetic form factors of a broad subset of charmonium, including ${\eta }_c(1S)$, ${\eta }_c(2S)$, ${\chi }_{c0}(1P)$, ${\chi }_{c0}(2P)$, $J/\psi (1S)$, $J/\psi (2S)$, ${\chi }_{c1}(1P)$, ${\chi }_{c1}(2P)$, $h_c(1P)$, $h_c(2P)$, ${\chi }_{c2}(1P)$ and ${\chi }_{c2}(2P)$, via a relativized quark model. The reference frame dependence of the results is estimated as the computational error. We compare our results with those of the lattice quantum chromodynamics (LQCD), the Dyson-Schwinger equation (DSE) and the basis light front quantization (BLFQ) approaches where available and we find that most of our results agree with the other results. We also predict the single-quark electromagnetic form factors of ${\chi }_{c0}(2P)$, ${\chi }_{c1}(2P)$, $h_c(1P)$, $h_c(2P)$, ${\chi }_{c2}(1P)$ and ${\chi }_{c2}(2P)$, where no direct comparisons are available.

   hep-ph0 citations
9. 09*

   Heavy-quark initiated charged-current deep-inelastic scattering coefficient functions through $\mathcal{O}({\alpha }_s^2)$

   Kirill Kudashkin🇨🇳

   We compute the coefficient functions for heavy-quark initiated charged-current deep-inelastic scattering through $\mathcal{O}({\alpha }_s^2)$, retaining full mass dependence for a single heavy-quark flavor. The calculation employs a cut-based approach to isolate individual diagram contributions and to derive differential equations for the relevant master integrals, which are solved analytically in terms of generalized polylogarithms. The results are presented in the decoupling scheme for $n_L$ light active flavors, facilitating their direct implementation in variable-flavor number schemes such as ACOT and FONLL.

   hep-phJHEP(2026)·1 citation
10. 10*

    Solutions to axion electrodynamics with electric-magnetic duality in supersymmetric Seiberg-Witten theory

    Tong Li🇨🇳 · Rui-Jia Zhang🇨🇳

    Axion and magnetic monopole are among the most fascinating candidates for physics beyond the Standard Model. The potential connection between axion and magnetic monopole stems from the Witten effect and is revealed by non-standard axion electrodynamics. Non-standard axion electrodynamics under electric-magnetic duality modifies conventional axion Maxwell equations and motivates intriguing axion-photon phenomenology. A calculable ultraviolet model of Peccei-Quinn axion coupled to magnetic monopoles and electric charges was proposed based on $\mathcal{N}=2$ supersymmetric Seiberg-Witten (SW) theory with manifest electric-magnetic duality. In this work, we aim to investigate the solutions to the non-linear axion electrodynamics from SW axion model and propose relevant detection strategies for non-trivial axion-photon couplings. Based on the infrared Lagrangian of SW axion, we derive the electromagetic (EM) equations of motion. We also analyze the moduli space coordinate in SW theory and find out the reliabe parameter space. We then solve the resultant axion Maxwell equations with an external EM field. The observable axion-induced EM fields are obtained analytically and then numerically computed. Finally, we propose the detection strategy with an LC circuit and show the prospective sensitivity to SW axion-photon couplings.

    hep-ph0 citations
11. 11*

    Inflation in Extra-Dimensions with one or two branes

    Nicolás Bernal🇦🇪 · Catarina Cosme🇪🇸 · Andrea Donini🇪🇸 · Nuria Rius🇪🇸

    In this paper, we study two inflationary models, namely, monomial inflation and the simplest $\alpha$-attractor inflation, within extra-dimensional frameworks. We consider three extra-dimensional setups: Dark Dimension, which embeds one flat extra-dimension to explain the observed smallness of the 4D cosmological constant ${\Lambda }_4$; and the two Randall-Sundrum scenarios with one warped extra-dimension, namely RS1 with two branes and RS2 with one brane. We derive the corresponding Friedmann equations, compute the slow-roll parameters in each case, and we fit the experimental data for ($n_s-1$, $\alpha$, ${\Delta }_s^2$, $r$), using Planck, BICEP, and ACT data. We find that monomial inflation is strongly disfavored in all scenarios, while $\alpha$-attractor inflation provides an excellent fit to current observations, with extra-dimensional setups offering additional flexibility compared to the standard 4D case.

    hep-phastro-ph.COhep-th1 citation
12. 12*

    Hyperon neutrinoless double beta decays in chiral perturbation theory

    Zi-Ying Zhao🇨🇳 · Ze-Rui Liang🇨🇳 · Feng-Kun Guo🇨🇳 · Li-Ping He🇨🇳 · De-Liang Yao🇨🇳

    We study the neutrinoless double beta decays of spin-1/2 hyperons, $B_1^{-}\to B_2^{+}{\ell }^{-}{\ell }^{-}$ with $B_1^{-}\in \{{\Sigma }^{-},{\Xi }^{-}\}$ and $B_2^{+}\in \{p,{\Sigma }^{+}\}$, which violate lepton number by two units. The decay amplitudes are computed within covariant baryon chiral perturbation theory at the one-loop level. Dalitz plots of the squared amplitude for six physical decay processes are presented in this proceeding, while a detailed numerical analysis will be presented in a forthcoming publication.

    hep-phEPJ Web Conf.(2026)·1 citation
13. 13*

    Sommerfeld Effect and Bound State Formation for Dark Matter Models with Colored Mediators with SE+BSF4DM

    Mathias Becker🇮🇹 · Emanuele Copello🇩🇪 · Julia Harz🇩🇪 · Martin Napetschnig🇩🇪

    In the universal framework of simplified $t$-channel dark matter models, the calculation of the relic abundance can be dominated by mediator annihilation when the dark matter and mediator masses are almost degenerate. We analyze four representative models with scalar and fermionic mediators, confront them with direct detection limits and highlight the differences and common features between them. The mediator annihilations are considerably enhanced by the Sommerfeld effect and bound state formation. Albeit their effect is subdominant in the coannihilation regime, excited bound state levels are included as well. We find that Sommerfeld and bound-state effects can lead to order one corrections to the constraints on the DM mass in the coannihilating regime, with the precise magnitude depending on the specific model realization. In addition we provide SE+BSF4DM, an intuitive and easy to use add-on to micrOMEGAs, allowing for an automated inclusion of these effects for a generic $t$-channel Dark Matter Model, which is publicly available on Github.

    hep-ph5 citations
14. 14*

    Anatomy of Roper Resonance

    Igor Strakovsky (GWU)🇺🇸

    Sixty years ago, the first excited state of a proton/neutron was ``born.'' During this time, we learned a lot about it, specifically - how unique this case is: a single resonance with two pole positions on different Riemann sheets. Let me present a brief history to remind readers how development progressed. Sure, history is sometimes something that never happened, described by those who were never there...

    hep-phhep-exnucl-exnucl-thActa Phys.Polon.B(2026)·0 citations
15. 15*

    Searches for extra-dimensional excitations in light-by-light scattering

    Malak Ait Tamlihat (1)🇲🇦 · Ghizlane Ez-Zobayr (2)🇲🇦 · Laurent Schoeffel (3)🇫🇷 · Yahya Tayalati (1,2) ((1) Mohammed V University, (2) Mohammed VI Polytechnic University, (3) CEA Saclay)🇲🇦

    We present a comprehensive phenomenological analysis of the Radion in the Randall-Sundrum model, focusing on its production via light-by-light scattering in ultra-peripheral proton-proton collisions at the LHC. We provide a consistent derivation of the effective couplings to Standard Model fields, clarifying the normalization of the trace anomaly-induced coupling to photons and the role of kinetic mixing with the Higgs boson. We demonstrate that while the pure gravitational coupling is loop-suppressed relative to Axion-Like Particles (ALPs), making the unmixed Radion elusive, the non-minimal mixing with the Higgs sector can induce constructive interference that enhances the signal by orders of magnitude. Using forward proton tagging to select exclusive high-mass events, we reinterpret recent experimental limits on ALPs to derive the first exclusion contours for the Radion in the $({\Lambda }_r,\xi )$ plane, showing that mixing scenarios are beginning to be constrained by current LHC data.

    hep-phJHEP(2026)·1 citation
16. 16*

    Study of sub-GeV Dipolar Dark States at SND@LHC within Invisible Bounds on Meson Decays

    Debajyoti Biswas🇮🇳

    Electromagnetic form factors constitute a natural portal for accessing states beyond the Standard Model. In particular, dimension-5 magnetic and electric dipole moment operators offer a minimal and predictive framework for Feebly Interacting Particles (FIPs). In this work, we perform a study of the sensitivity reach of the Scattering and Neutrino Detector (SND@LHC) in the detection of dipolar dark states through photon-mediated interactions with the Standard Model particles. The far-forward region of the LHC provides FIPs with large momenta that scatter off electrons and nuclei inside the target. Production of dark states from meson decays is constrained by invisible decay widths, while the Drell-Yan process offers a production channel in the GeV range. We present sensitivity plots for magnetic and electric dipole moment interactions at SND@LHC and compare them with constraints from direct detection, beam dump, fixed-target, and collider experiments. The validity of the effective theory that describes the dipole model is also studied by considering conservative bounds on the couplings.

    hep-phEPJC(2026)·1 citation
17. 17*

    Standard Model Higgs Peaks: a Note on the Vacuum Instability during Inflation

    G. Franciolini🇮🇹 · A. Kehagias🇬🇷 · A. Riotto🇨🇭

    In the Standard Model, the Higgs potential develops an instability at high field values when the quartic self-coupling runs negative. Large quantum fluctuations during cosmic inflation could drive the Higgs field beyond the potential barrier, creating regions that would be catastrophic for our observable universe. We point out that the extreme-value statistics describing the peaks (maxima) of the Higgs values is the correct statistics to infer the condition to avoid vacuum instability. Even if this statistics delivers a bound on the Hubble rate during inflation which is only a factor $\sqrt{2}$ stronger than the one commonly adopted in the literature, it is qualitatively distinct and we believe worthwhile communicating it.

    hep-phastro-ph.COgr-qchep-thJCAP(2026)·3 citations
18. 18*

    Cavity Multimodes as an Array for High-Frequency Gravitational Waves

    Diego Blas🇪🇸 · Yifan Chen🇨🇳 · Yuxin Liu🇨🇳 · Yanfei Shang🇨🇳 · Jing Shu🇨🇳

    Microwave cavities operated in the presence of a background magnetic field provide a promising avenue for detecting high-frequency gravitational waves (HFGWs). We demonstrate for the first time that the distinct antenna patterns of multiple electromagnetic modes within a single cavity enable localization and reconstruction of key properties of an incoming HFGW signal, including its polarization ratio and frequency drift rate. Using a 9-cell cavity commonly employed in particle accelerators as a representative example, we analyze the time-domain response of 18 nearly degenerate modes, which can be sequentially excited by a frequency-drifting signal. The sensitivity is further enhanced by the number of available modes, in close analogy to the scaling achieved by a network of independent detectors, enabling sensitivity to astrophysically plausible binary sources.

    hep-phastro-ph.HEastro-ph.IMgr-qc+13 citations
19. 19*

    Flavor physics at the EIC with b-jet tagging

    Shaouly Bar-Shalom🇮🇱 · Jose Wudka🇺🇸

    We employ an approximate conserved quantum number (defined as "$b$-Parity" in [1]) of the Standard Model (SM): $b_P=(-1{)}^n$, where $n$ is the number of produced $b$-jets in the reaction $e+p/A\to n\cdot j_b+X$, to explore new TeV-scale flavor-changing interactions involving the 3rd generation quarks at the EIC; simply by counting the number of $b$-jets in the final state. In particular, the SM single and di-jet production at the EIC which occur through charge current interactions, $e+p/A\to j+/E_T$ and $e+p/A\to 2\cdot j+/E_T$, are $b_P$-even since the $b_P$-violating (i.e, $b_P=-1$) SM signals for these processes are necessarily CKM suppressed and, therefore, have a vanishingly small production rate. In contrast, new flavor physics can generate $b_P=-1$ signals at the EIC whose only significant SM background is due to $b$-jet misidentification. We thus show that $b_P$ can be used as a simple and sensitive probe of new flavor violating physics; specifically, we find that counting single $b$-jet events in $e+p/A\to j+/E_T$ at the EIC with a center-of-mass (CM) energy of $\sqrt{s}\sim 140$ GeV, can probe scales of new physics up to $\Lambda \sim \mathcal{O}(5)$ TeV for a certain type of new chiral flavor-changing physics in 3rd generation interactions. This is remarkably more than 30 times larger than the assumed EIC CM energy and it critically depends on the $b$-tagging efficiency and purity as well as the feasibility of electron-beam polarization. The sensitivity of the di-jet process, $e+p/A\to 2j+/E_T$, to these type of new physics is reduced compared to the single-jet channel.

    hep-phhep-exPRD(2026)·3 citations
20. 20*

    Sterile Neutrino Dark Matter as a Probe of Inflationary Reheating

    James M. Cline🇨🇦 · Yong Xu🇨🇦

    Sterile neutrinos offer a minimal and testable explanation for dark matter (DM), with their radiative decay actively searched for in X-ray observations. We show that cold sterile neutrino DM can be efficiently produced during reheating from inflaton decays with a small branching ratio, $\mathrm{BR}\lesssim 10^{-4}$. This production mechanism opens regions of parameter space where the active-sterile mixing is small enough to evade current X-ray constraints while reproducing the observed DM abundance. We systematically map the viable parameter space in terms of the sterile neutrino mass, mixing angle, inflaton mass, reheating temperature, and branching ratio. We further demonstrate that sterile neutrino DM can serve as a probe of inflationary reheating, with future X-ray observations capable of yielding information on the inflaton mass and the reheating-temperature ratio $m_{\varphi }/T_{\mathrm{rh}}$. For a given inflationary model in which the inflaton mass is known, this leads to a lower bound on the reheating temperature that is several orders of magnitude stronger than the existing bound from Big Bang Nucleosynthesis.

    hep-phastro-ph.COJCAP(2026)·4 citations
21. 21*

    Optomechanical platform for high-frequency gravitational wave and vector dark matter detection

    David Rousso🇩🇪 · Moritz Bjoern Kristiansson Kunze · Christoph Reinhardt

    We present a proposal for a nanomechanical membrane resonator integrated into a moderate-finesse ($\mathcal{F}\sim 10$) optical cavity as a versatile platform for detecting high-frequency gravitational waves and vector dark matter. Gravitational-wave sensitivity arises from cavity-length modulation, which resonantly drives membrane motion via the radiation-pressure force. This force also enables in situ tuning of the membrane's resonance frequency by nearly a factor of two, allowing a frequency coverage from 0.5 to 40 kHz using six membranes. The detector achieves a peak strain sensitivity of $2\times 10^{-23}/\sqrt{\text{Hz}}$ at 40 kHz. Using a silicon membrane positioned near a gallium-arsenide input mirror additionally provides sensitivity to vector dark matter via differential acceleration from their differing atomic-to-mass number ratios. The projected reach surpasses the existing limits in the range of $2\times 10^{-12}$ to $2\times 10^{-10}$ $\text{eV}/c^2$ for a one-year measurement. Consequently, the proposed detector offers a unified approach to searching for physics beyond the Standard Model, probing both high-frequency gravitational waves and vector dark matter.

    ↳ astro-ph.IMhep-phphysics.ins-det2 citations
22. 22*

    Orchestral AI: A Framework for Agent Orchestration

    Alexander Roman🇺🇸 · Jacob Roman

    The rapid proliferation of LLM agent frameworks has forced developers to choose between vendor lock-in through provider-specific SDKs and complex multi-package ecosystems that obscure control flow and hinder reproducibility. Integrating tool calling across multiple LLM providers remains a core engineering challenge due to fragmented APIs, incompatible message formats, and inconsistent streaming and tool-calling behavior, making it difficult to build portable, reliable agent systems. We introduce Orchestral, a lightweight Python framework that provides a unified, type-safe interface for building LLM agents across major providers while preserving the simplicity required for scientific computing and production deployment. Orchestral defines a single universal representation for messages, tools, and LLM usage that operates seamlessly across providers, eliminating manual format translation and reducing framework-induced complexity. Automatic tool schema generation from Python type hints removes the need for handwritten descriptors while maintaining type safety across provider boundaries. A synchronous execution model with streaming support enables deterministic behavior, straightforward debugging, and real-time interaction without introducing server dependencies. The framework's modular architecture cleanly separates provider integration, tool execution, conversation orchestration, and user-facing interfaces, enabling extensibility without architectural entanglement. Orchestral supports advanced agent capabilities found in larger frameworks, including rich tool calling, context compaction, workspace sandboxing, user approval workflows, sub-agents, memory management, and MCP integration.

    ↳ cs.AIastro-ph.IMhep-ph2 citations
23. 23*

    The Nucleon Axial Form Factor from Averaging Lattice QCD Results

    Aaron S. Meyer🇺🇸

    Flagship neutrino oscillation experiments depend on precise and accurate theoretical knowledge of neutrino-nucleon cross sections across a variety of energies and interaction mechanisms. Key ingredients to the amplitudes that make up these cross sections are parameterized form factors. The axial form factor describing a weak interaction with a nucleon is part of one of the primary neutrino-nucleon interaction mechanisms, quasielastic scattering, yet this form factor is uncertain and its precision is limited by the availability of data for a neutrino scattering with nucleons or small nuclear targets. Lattice Quantum Chromodynamics (LQCD) now offers another approach for obtaining mathematically rigorous constraints of the axial form factor from theoretical calculations with complete systematic error budgets. In this work, strategies for averaging LQCD results are explored, including both a random sampling of form factor values across momentum transfers as well as an averaging strategy based on analytic calculations of form factor derivatives. Fits to z expansion parameterizations are reported and compared against neutrino-hydrogen and neutrino-deuterium scattering data.

    ↳ hep-lathep-exhep-ph16 citations
24. 24*

    An Effective Upper Bound on the Pressure-to-Energy Density Ratio in Neutron Stars

    Bao-Jun Cai🇨🇳 · Bao-An Li🇺🇸 · Yu-Gang Ma🇨🇳

    The equation-of-state (EOS) parameter $\varphi \equiv P/\epsilon$, defined as the ratio of pressure to energy density, encapsulates the fundamental response of matter under extreme compression. Its value at the center of the most massive neutron star (NS), $\text{x}\equiv P_{\mathrm{c}}/{\epsilon }_{\mathrm{c}}$, provides an upper bound on the maximum attainable central EOS parameter of cold visible matter. Remarkably, owing to the intrinsically nonlinear structure of the EOS in General Relativity (GR), this bound lies far below the naive Special Relativity (SR) limit of unity. In this work, we refine the theoretical upper bound on $\text{x}$ in a self-consistent manner by incorporating, in addition to the causality constraint from SR, the mass-sphere stability condition associated with the mass evolution pattern in the vicinity of the NS center. This condition is formulated within the intrinsic and perturbative analysis of the dimensionless Tolman--Oppenheimer--Volkoff equations (IPAD-TOV) framework. The combined constraints yield an improved bound, $\text{x}\lesssim 0.385$, which is slightly above but fully consistent with the previously derived causal-only limit, $\text{x}\lesssim 0.374$. We further derive an improved scaling relation for NS compactness and demonstrate its robustness across a broad set of 284 realistic EOSs, including models with first-order phase transitions, exotic degrees of freedom, continuous crossover behavior, and deconfined quark cores. Within the IPAD-TOV framework, the resulting bound on $\text{x}$ provides a new EOS-insensitive probe of the microphysics of cold superdense matter compressed by strong-field gravity in GR.

    ↳ nucl-thastro-ph.HEgr-qchep-ph+1PRD(2026)·3 citations
25. 25*

    Bounce Inflation with Dynamical Dark Energy in Light of DESI DR2

    Xin-zhe Zhang🇨🇳 · Hao-Hao Li🇨🇳 · Taotao Qiu🇨🇳

    Recently, the Dark Energy Spectroscopic Instrument Data Release 2 (DESI DR2) suggests that the dark energy in our universe might be evolving, favoring the Chevallier-Polarski-Linder (CPL) parameterization and a lower Hubble constant. In our previous work, it has been reported that cosmological model with the non-singular bounce inflation (BI) scenario and $\Lambda$CDM might alleviate the Hubble tension into 3$\sigma$ confidence. In this paper, we study the cosmological model of BI with a dynamical dark energy. We find that individual consideration of the CPL parameterization and the data \texttt{DESI DR2} tend to larger Hubble constants for both BI and power law (PL) case with cosmic microwave background (CMB) data. Employing BI with combined CPL parameterization and \texttt{DESI DR2}, we obtain the Hubble constant $H_0=65.2_{-2.2}^{+1.8}\mathrm{km}\cdot {\mathrm{s}}^{-1}\cdot {\mathrm{Mpc}}^{-1}$, which is larger than $H_0=64.0\pm 2.1\mathrm{km}\cdot {\mathrm{s}}^{-1}\cdot {\mathrm{Mpc}}^{-1}$ for the PL case. After considering nontrivial weak lensing effect and spatial curvature as well as adding \texttt{Pantheon+}, BI fits 3.1$\sigma$ confidence of $\Lambda$CDM with $w_0=-0.919\pm 0.038$ and $w_{\mathrm{a}}=-0.37\pm 0.12$, and it prefers evolving dark energy than the PL case with $w_0=-0.960\pm 0.074$ and $w_{\mathrm{a}}=-0.15_{-0.25}^{+0.28}$.

    ↳ astro-ph.COgr-qchep-phhep-th3 citations
26. 26*

    First comments on a descoped/staged FCC-ee

    Alain Blondel🇫🇷 · Christophe Grojean🇩🇪 · Patrick Janot🇨🇭 · Guy Wilkinson🇬🇧

    In response to its remit, the European Strategy Group (ESG) recommended the electron-positron Future Circular Collider (FCC-ee) as the preferred option for the next flagship collider at CERN; and a descoped FCC-ee as the preferred alternative option (with reduced synchrotron radiation (SR) power, without a run at the $\mathrm{t}\bar{\mathrm{t}}$ threshold, and with only two interaction regions) in the event that the preferred option turns out not to be feasible. Upon request of the ESG, a basic comparison of the physics potential of the descoped option with that of the baseline version is presented in this short note. Our first observations about the alternative proposal of a descoped FCC-ee are that (i) the same performance as the baseline, apart from $\mathrm{t}\bar{\mathrm{t}}$-run related, is achieved with the longer proposed period of operation; and (ii) the top run remains essential, but can be staged at a later date. The full appraisal of the consequences of descoping and a proposal for the best way to integrate possible staging wherever feasible, and possible improvements, will need further joint studies by the physics and accelerator groups.

    ↳ hep-exhep-phphysics.acc-ph1 citation

* 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.