Tue·Jan 13, 2026Tuesday·January 13, 2026

1. 01*

   Exploring Invisible New Physics with Exotic Pion Decays

   Wolfgang Altmannshofer🇺🇸 · Jeff A. Dror🇺🇸 · Pierce Giffin🇺🇸 · Stefania Gori🇺🇸 · Ollie Jackson🇺🇸 · Khai Luong🇺🇸 · Patrick Schwendimann🇺🇸 · Se Rang Seo🇺🇸

   We study the sensitivity of past and future stopped-pion experiments to light, invisible dark sector particles produced in exotic pion decays. We consider two-body decays involving sterile neutrinos, ${\pi }^{+}\to {\ell }^{+}N$, as well as three-body decays ${\pi }^{+}\to {\ell }^{+}{\nu }_{\ell }X$, with $X$ an invisible scalar, axion-like particle, or dark vector. We recast existing limits from the PIENU experiment and project the reach of the planned PIONEER experiment using detailed simulations based on the current detector design. We find that PIONEER can improve bounds on exotic pion branching ratios by at least one order of magnitude below current limits. We compare the projected sensitivities with complementary constraints from lepton anomalous magnetic moments, mono-photon searches, and beam-dump experiments, identifying weak-violating axion-like particles as a particularly well-motivated benchmark. Our results establish PIONEER as a powerful and complementary probe of light, invisible dark sectors.

   hep-ph9 citations
2. 02*

   Temperature-Dependent CPT Violation: Constraints from Big Bang Nucleosynthesis

   Gabriela Barenboim🇪🇸 · Anne-Katherine Burns🇪🇸

   In this study, we explore temperature-dependent CPT violation during Big Bang Nucleosynthesis (BBN) through electron-positron mass asymmetries parametrized by $b_0(T)=\alpha T^2$. The $T^2$ scaling naturally evades stringent laboratory bounds at zero temperature while allowing for significant CPT violation at MeV scales in the early universe \cite{ParticleDataGroup:2024cfk}. Using a modified version of the BBN code \faGithub \href{https://github.com/vallima/PRyMordial}{\,\texttt{PRyMordial}} with dynamically-solved chemical potentials and appropriate finite-mass corrections, we constrain electron-positron mass differences from observed abundances of Helium-4, Deuterium, and $N_{\mathrm{eff}}$. We find that $\alpha$ must be greater than or approximately equal to $10^{-6}$ GeV${}^{-1}$ for keV-scale mass differences at BBN. All three observables show no simultaneous $1\sigma$ overlap, though pairwise combinations allow for constrained regions of parameter space. We present three toy models demonstrating how $b_0(T)\propto T^2$ arises from field-theoretic mechanisms, including temperature-driven phase transitions. These results provide the most stringent constraints on early-universe CPT violation in this regime, probing parameter space inaccessible to laboratory experiments.

   hep-phastro-ph.COPRD(2026)·1 citation
3. 03*

   Baryogenesis from the Thermodynamic Arrow of Time: a Transfer-Function Bound and an Entropy-Clock Mechanism

   Yakov Mandel

   We formulate a transfer test for baryogenesis driven by time-dependent derivative sources. A zero-mean oscillatory chemical potential convolved with a smooth finite-time kernel is low-pass filtered. For a one-sided exponential effective kernel, the signed response is $I_{\phi }(x)=(\cos \phi -x\sin \phi )/(1+x^2)$ and the phase-optimized envelope is $F_{\mathrm{amp}}(x)=1/\sqrt{1+x^2}$, with $x=\omega {\tau }_{\mathrm{off}}$. Its sharp onset gives a $1/x$ high-frequency tail; smoother turn-ons can suppress more strongly. An integration-by-parts bound shows that rapidly sign-changing sources are controlled by their residual low-frequency component. We then study an entropy-clock ansatz, ${\theta }_X={ϵ}_X\ln (S/S_0)$, giving ${\mu }_X={ϵ}_{X}d\ln S/dt$ during entropy-producing reheating; the yield equation includes entropy dilution. During perturbative matter-dominated reheating, $S\propto a^{15/8}$ and $\Pi =d\ln S/d\ln a=15/8$ before completion. Successful freeze-out requires overlap between entropy production and charge violation. In a Weinberg-operator $B-L$ benchmark this selects $T_R=\mathcal{O}(T_F)$, with $T_F\sim 10^{12}$--$10^{13}\mathrm{GeV}(0.05\mathrm{eV}/{\bar{m}}_{\nu }{)}^2$. If $T_R\gg T_F$, the source ends before freeze-out and is washed out; if $T_R\ll T_F$, the interaction is never efficient during reheating. For a direct baryon source, $|{ϵ}_X{\Pi }_{\mathrm{eff}}|\simeq 3.2\times 10^{-3}(10^{12}\mathrm{GeV}/T_{\mathrm{ov}})$; sphaleron reprocessing of a $B-L$ source increases this by $79/28$. With $\Pi =15/8$, this gives $|{ϵ}_X|\zeta \simeq 1.7\times 10^{-3}$ and $4.8\times 10^{-3}$, respectively, at $T_{\mathrm{ov}}=10^{12}\mathrm{GeV}$. The entropy-clock source is phenomenological; a UV completion must explain why the charge-biasing variable tracks $\ln S$ or an equivalent monotonic dissipative variable.

   hep-ph1 citation
4. 04*

   Analysis of the semileptonic decays of ${\Xi }_{cc}$ and ${\Omega }_{cc}$ baryons in QCD sum rules

   Guo-Liang Yu🇨🇳 · Zhi-Gang Wang🇨🇳 · Jie Lu🇨🇳 · Bin Wu🇨🇳 · Peng Yang🇨🇳 · Ze Zhou🇨🇳

   We firstly carry out a systematic analysis on the spin ${\frac{1}{2}}^{+}\to {\frac{3}{2}}^{+}$ weak transition process in the framework of three-point QCD sum rules, where the initial and final states are doubly and singly charmed baryons. In the phenomenological side, all possible couplings of interpolating current to hadronic states are considered. In doing operator production expansion at QCD side, the contributions of the perturbative part, vacuum condensate terms of $⟨\bar{q}q⟩$, $⟨g_s^{2}GG⟩$, $⟨\bar{q}{g}_s\sigma Gq⟩$ and $g_s^2⟨\bar{q}q{⟩}^2$ are all considered. After the form factors in space-like region ($Q^2>0$) are obtained, the numerical results are extrapolated into time-like region ($Q^2<0$) by a fitting function. Using the predicted form factors, we finally analyze the semileptonic decays of ${\Xi }_{cc}^{++}\to {\Sigma }_c^{\ast +}{l}^{+}{\nu }_l$, ${\Xi }_{cc}^{++}\to {\Xi }_c^{\prime \ast +}{l}^{+}{\nu }_l$, ${\Omega }_{cc}^{+}\to {\Xi }_c^{\prime \ast 0}{l}^{+}{\nu }_l$ and ${\Omega }_{cc}^{+}\to {\Omega }_c^{\ast 0}{l}^{+}{\nu }_l$ with $l=e,\mu$. The predictions in this work can deepen our understanding of the dynamics in the decay processes of doubly heavy baryons and provide useful information to explore the possibility of new physics in heavy baryonic decay channels.

   hep-phPRD(2026)·4 citations
5. 05*

   Dark-Portal Leptogenesis in a Non-Holomorphic Modular Scoto-Seesaw Model

   Salah Nasri🇦🇪 · Labh Singh🇮🇳 · Tapender🇮🇳 · Surender Verma🇮🇳

   This work explores the neutrino phenomenology of the scotoseesaw model under non-holomorphic $A_4$ modular flavor symmetry providing a non-SUSY framework for realization of the modular symmetry. To prevent mixing between the beyond standard model fields associated with the tree and loop-level neutrino mass contributions, we assign even and odd modular weights to these sectors, respectively. The physical allowed ranges of oscillation parameters are used to identify the viable region of modulus parameter $\tau$ in its fundamental domain. With the complex modulus $\tau$ serving as the unique source of CP violation (all other parameters are real) the framework realizes successful low-scale leptogenesis through CP-violating decays of the lightest right-handed neutrino into Standard Model leptons and the Higgs boson. The requisite CP asymmetry arises from one-loop diagrams involving dark-sector states, obviating the need for degenerate mass spectra and thereby circumventing the usual resonant leptogenesis mechanism. The observation of a long-lived charged particle (${\eta }^{\pm }$) in collider experiments would offer compelling evidence for the inert scalar sector of the model and provide a crucial experimental hint on the dark-sector assisted generation of neutrino masses and leptogenesis.

   hep-phPRD(2026)·11 citations
6. 06*

   Physical implications of a double right-handed gauge symmetry

   Duong Van Loi🇻🇳 · A. E. Cárcamo Hernández🇨🇱 · N. T. Duy🇻🇳 · D. T. Binh🇻🇳 · Cao H. Nam🇻🇳

   Guided by the flipping principle, we propose a novel extension of the Standard Model based on a double right-handed $U(1)$ gauge symmetry. In this framework, all left-handed fermions are neutral, while right-handed fermions of the third generation carry charges distinct from those of the first two generations. This structure naturally explains the observed Standard Model fermion mass hierarchy: the heavy masses of the third generation are generated at tree level, while the lighter masses of the first and second generations arise radiatively at the one-loop level. For the active neutrino sector, the tiny masses are generated through a combination of tree-level and two-loop seesaw mechanisms. Crucially, this approach successfully reproduces the observed neutrino mass hierarchy, with the atmospheric mass-squared difference generated at tree level and the solar neutrino mass squared difference emerging at the two-loop level. These hierarchical patterns stem from the interplay between gauge invariance and a residual parity symmetry that survives the spontaneous breaking of the extended gauge group. The same residual symmetry stabilizes a viable scalar singlet dark matter candidate, which we show can reproduce the observed relic abundance while remaining consistent with current direct detection bounds. After addressing constraints from electroweak precision tests and flavor-changing neutral currents, we explore the discovery prospects for the new neutral bosons at existing and future colliders, including the LEP, LHC, and a future ILC.

   hep-phPRD(2026)·1 citation
7. 07*

   Distribution Functions of Radially Excited Pion using the Light-Front Quark Model

   Ashutosh Dwibedi🇮🇳 · Satyajit Puhan🇮🇳 · Sabyasachi Ghosh🇮🇳 · Harleen Dahiya🇮🇳

   We investigate the internal structure of the ground ($1S$) and the first two radially excited ($2S,3S$) states of the pion within the light-front quark model. The valence Fock sector is described using pure harmonic-oscillator eigenstates and mixed states formed as orthogonal linear combinations of these eigenfunctions. The optimal wavefunction parameters are determined through a variational procedure based on a QCD-motivated effective Hamiltonian. Using the resulting light-front wavefunctions, we study the pion distribution amplitude, parton distribution function, and electromagnetic form factor. After QCD evolution, the ground state distribution amplitude and parton distribution function are found to be in good agreement with available experimental data. At the model scale, the parton distribution functions of the $1S$ and $2S$ states show clear sensitivity to state mixing, while the distribution amplitudes and electromagnetic form factors are weakly sensitive. In contrast, for the $3S$ state, all three observables exhibit a pronounced sensitivity to mixing. The decay constants of the mixed states are also found to decrease sequentially with increasing radial excitation.

   hep-phnucl-th1 citation
8. 08*

   Complex Mass Shells for Coloured quarks and their Asymptotic Confinement

   Richard Kerner · Jerzy Lukierski

   The present paper is the continuation of our previous work (R. Kerner and J. Lukierski, Nuclear Physics B, 2021) where we introduced a Z3-symmetric covering of the Lorentz group as a natural symmetry describing the quark fields. In the current version of QCD quarks are described by coloured triplets of standard Dirac fields. In contrast, we proposed to describe the colour triplets of quarks by entangled Z_3-graded Lee-Wick type fields, one with real mass and the two remaining ones with mutually conjugate complex masses. This is obtained by attributing colour degrees of freedom to six Pauli spinors, three endowed with colours and three with anti-colours, which are united into one 12-component generalized ``coloured Dirac spinor". Thus entangled triplet of quark fields is described on-shell by a linear Schoeodinger-like system akin to the Dirac equation. The sixth-order dispersion relations lead to solutions suitably vanishing in asymptotic region, exhibiting the well established confinement property of coloured quarks' degrees of freedom. We add that in the so modified approach to QCD one should employ in the quark sector the Z3-graded extension of the Lorentz symmetries, which do not commute with hidden SU(3) colour transformations (see Kerner and Lukierski 2021, Kerner 2018}). Propagators and interaction with gluon and electromagnetic fields are discussed in the last section.

   hep-phhep-thBulg.J.Phys.(2025)·0 citations
9. 09*

   Low-energy $N\varphi$ scattering from a pole-enhanced triangle diagram

   Mao-Jun Yan🇨🇳 · Chun-Sheng An🇨🇳 · Cheng-Rong Deng🇨🇳

   We investigate low-energy $N\varphi$ scattering driven by a pole-enhanced triangle-like diagram, in which the two-Kaon-exchange contribution is promoted by the near-threshold $\Lambda (1405)$ pole in the $N\bar{K}$ subsystem. Using an unphysical Kaon mass motivated by lattice simulations, we evaluate the $N\varphi$ scattering length and find that this mechanism generates an attractive interaction with a magnitude of $-1.1$ to $-0.5\mathrm{fm}$. Spin-dependent effects are not treated explicitly and are expected to provide subleading corrections in the near-threshold region. We further analyze the low-energy behavior of the triangle-like diagram amplitude and show that the scattering length depends on the parameter $\delta$, defined as the mass difference between the $K\bar{K}$ threshold and the $\varphi$ meson, and the pole position of $\Lambda (1405)$, where the $\Lambda (1405)$ plays a crucial role to understand $N\varphi$ interaction. Furthermore, by employing physical hadron masses, our calculated scattering length is found to be consistent with current experimental data, providing a unified description across both unphysical and physical mass regimes. This type of interaction differs from that associated with van der Waals-type forces or the long-range tail of two-pion exchange, highlighting the role of three-body dynamics encoded in the pole-enhanced triangle-like diagram in shaping the near-threshold $N\varphi$ interaction.

   hep-phPLB(2026)·1 citation
10. 10*

    Probing Dark Matter annihilation in the Galactic Centre with TRIDENT

    Yingwei Wang🇨🇳 · Xinhui Chu🇨🇳 · Andrew Cheek🇨🇳 · Iwan Morton-Blake🇨🇳 · Qichao Chang🇨🇳 · Gwenael Giacinti🇨🇳 · Samy Kaci🇨🇳 · Xin Xiang🇨🇳 · Donglian Xu🇨🇳 · Fuyudi Zhang🇨🇳

    We determine the future sensitivity of the TRIDENT neutrino telescope to dark matter annihilation in the Galactic Centre. By applying the full detector design and assuming an NFW halo profile, we show that TRIDENT will probe annihilation cross-section down to $⟨\sigma v⟩\approx 5\times 10^{-27}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ for $10\mathrm{TeV}$ dark matter, falling below the thermal freeze-out benchmark. The analysis is carried out with all-flavour neutrino interactions, where we demonstrate that cascade events, primarily due to ${\nu }_{e,\tau }$, show greater sensitivity to a dark matter signal compared to the more commonly studied track events. Furthermore, we highlight the impact of a previously overlooked background, Galactic neutrinos produced from interactions between hadronic cosmic rays and interstellar gas. We find dark matter sensitivities are more strongly degraded in the high energy region above $\sim 10\mathrm{TeV}$, with a maximal weakening of approximately a factor of 2. This effect remains smaller than the uncertainty associated with the dark matter density profile but can nonetheless mimic a positive annihilation signal. We contextualise these results with a concrete particle model and show that TRIDENT will be able to probe the most interesting untested parts of parameter space.

    hep-phastro-ph.HEhep-exPRD(2026)·1 citation
11. 11*

    Quarkonium light-cone distribution amplitudes: twist structure and mass dependence

    Shuai Xu🇨🇳 · Xiao-Nan Li🇨🇳 · Jin-Zhong Han🇨🇳 · Bai-Hui Cheng🇨🇳 · Li-Li Chen🇨🇳 · Qin Chang🇨🇳

    We present a systematic study of the leading- and next-to-leading-twist light-cone distribution amplitudes (LCDAs) of ground-state pseudoscalar and vector quarkonium within the light-front quark model (LFQM). By implementing the replacement $M\to M_0$, we analyze the longitudinal and transverse structures of the LCDAs, together with their Gegenbauer moments, $\xi$-moments, and transverse momentum moments. We show that charge-conjugation symmetry enforces the exact vanishing of all odd Gegenbauer moments and odd $\xi$-moments. For pseudoscalar quarkonium, the twist-2 and twist-3 LCDAs become identical, which leads to the same Gegenbauer moments, $\xi$-moments, and transverse momentum moments. For vector quarkonium, although the twist-2 and twist-3 LCDAs differ in the case of finite quark masses, they progressively converge as the quark mass increases. In the heavy-quark limit, all quarkonium LCDAs satisfy ${\varphi }_2^A={\varphi }_3^P\simeq {\varphi }_2^{\parallel }\simeq {\varphi }_3^{\perp }$, demonstrating an emergent twist-independence of quarkonium distribution amplitudes. We further find that the LCDAs become increasingly peaked and narrower with increasing quark mass, indicating that the meson system becomes increasingly close to a nonrelativistic bound state, with a more uniform and stable distribution of internal longitudinal momentum. For all quarkonium, the peak value exhibits a simple phenomenological scaling behavior governed by the ratio $m/\beta$. The transverse momentum moments increase with the meson mass, indicating a progressively more compact bound-state structure. These results reveal a universal and systematic evolution of quarkonium LCDAs driven by the quark mass.

    hep-phJHEP(2026)·1 citation
12. 12*

    Probing the microscopic origin of prompt and non-prompt $D^0$ production through event-shape engineering in proton-proton collisions at the LHC

    Aswathy Menon Kavumpadikkal Radhakrishnan🇮🇳 · Suraj Prasad🇮🇳 · Purnima Srivastava🇮🇳 · Raghunath Sahoo🇮🇳

    Heavy-flavour hadrons are produced in the early stages of ultra-relativistic collisions at the LHC via hard partonic interactions and experience the whole system evolution. The study of prompt and non-prompt $D^0$ mesons provides an independent avenue to test the theories of quantum chromodynamics and to investigate beauty hadron production. Moreover, the production of both prompt and non-prompt $D^0$ is influenced by microscopic processes such as multi-partonic interactions (MPI) and hadronisation through fragmentation. In this study, an attempt is made to understand the production of prompt and non-prompt $D^0$ mesons in proton-proton collisions at $\sqrt{s}=13.6$ TeV using the PYTHIA8 event generator, which offers a qualitative description of charm production. The role of the transverse momentum transfer in the hardest partonic scattering (${\hat{p}}_{\mathrm{T}}$), MPI, and color reconnection is systematically explored. In addition, the charged particle production in different topological regions with respect to the leading $D^0$ meson is studied to assess the influence of the $D^0$ meson on the event topology and to examine the selection biases arising from the use of charged particle multiplicity as an event classifier.

    hep-phhep-exnucl-exnucl-th0 citations
13. 13*

    Chiral anomaly in the ${\eta }^{(\prime )}\to {\pi }^{+}{\pi }^{-}\gamma$ and ${\eta }^{(\prime )}\to {\pi }^{+}{\pi }^{-}{l}^{+}{l}^{-}$ decays

    M. K. Volkov🇷🇺 · A. A. Osipov🇷🇺 · K. Nurlan🇷🇺 · A. A. Pivovarov🇷🇺

    We report the presence of a flavor-violating correction to the $VAAA$-type anomaly, ${\delta }^{(\prime )}$, induced by the surface terms of the anomalous quark triangle diagram, previously found in the $\eta ,{\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}\gamma$ decay amplitudes, and investigate its impact on the corresponding semileptonic decay modes of $\eta$ and ${\eta }^{\prime }$. The magnitude of ${\delta }^{(\prime )}$ can be set from the experimental data on the ${\eta }^{(\prime )}\to {\pi }^{+}{\pi }^{-}\gamma$ decay width. We then estimate another low-energy constant, the slope parameter ${\alpha }^{(\prime )}$. The impact of different schemes for describing $\eta$-${\eta }^{\prime }$ mixing on the value of ${\delta }^{(\prime )}$ and ${\alpha }^{(\prime )}$ is discussed. The predictions are shown to be in complete agreement with the available experimental data.

    hep-phPRD(2026)·0 citations
14. 14*

    Light cone QCD sum rules study of the rare radiative ${\Xi }_{bb}^{\ast }\to {\Xi }_b\gamma$ decay

    T. M. Aliev🇹🇷 · A. Ozpineci🇹🇷 · Y. Sarac🇹🇷

    The rare radiative decay ${\Xi }_{bb}^{\ast }\to {\Xi }_b\gamma$ is investigated within the light cone QCD sum rules approach. This decay proceeds through the flavor changing neutral current $b\to s$ transition in the Standard Model. The hadronic matrix element of the considered decay is parameterized in terms of four tensor form factors $T_1^V(q^2)$, $T_2^V(q^2)$, $T_1^A(q^2)$ and $T_2^A(q^2)$. The sum rules for these form factors describing the ${\Xi }_{bb}^{\ast }\to {\Xi }_b\gamma$ decay are derived at $q^2=0$ point using the ${\Xi }_b$ distribution amplitudes. The results of the form factors are employed to calculate the corresponding decay width. Our finding indicates that this weak radiative decay could be within reach of future high statistics studies of doubly heavy baryons at LHCb and upcoming facilities.

    hep-phPRD(2026)·0 citations
15. 15*

    Perspectives on QCD, Topology and the Strong CP Problem

    Anthony G. Williams🇦🇺

    The strong $CP$ problem occupies a unique position in modern particle physics, connecting nonperturbative quantum chromodynamics, topology, anomalies and the global structure of gauge theories. It has motivated extensive theoretical developments, including instantons, the $\theta$ vacuum, lattice studies of topological charge, and the Peccei-Quinn mechanism and its associated axion phenomenology. At the same time, the relationship between local quantum field theory, global topology and the conventional construction of the $\theta$ vacuum continues to raise important conceptual and mathematical questions. This review presents a pedagogical overview of the strong $CP$ problem from the perspectives of its historical development, physical motivation and mathematical formulation. Beginning with the conventional formulation of the problem and the local structure of QCD, we review the roles of the axial anomaly, topological charge density, topological susceptibility, instantons, lattice gauge theory, and the Hamiltonian and Euclidean formulations of nonperturbative QCD. A recurring theme is the distinction between local structures that follow directly from relativistic quantum field theory and additional global constructions commonly employed in the conventional treatment of topological sectors and $\theta$ vacua. The review clarifies which aspects of the conventional framework are direct consequences of established local quantum field theory and which rely on additional mathematical assumptions concerning global topology. In particular, standard nonperturbative results involving local correlation functions and topological susceptibility can be formulated without requiring the full global construction of topological sectors and the $\theta$ vacuum. Alternative viewpoints and outstanding conceptual questions are also discussed.

    hep-ph4 citations
16. 16*

    Exclusive Decays of the Fully Heavy Tetraquarks into Light Mesons

    Feng Feng🇨🇳 · Ming-Ming Liu🇨🇳

    In this work, we investigate the exclusive decays of the fully heavy tetraquark states $T_{4c,b}$ into light mesons, specifically $\pi$ and $K$, using the framework of Non-Relativistic QCD (NRQCD) and collinear QCD factorization for hard exclusive processes. We estimate the decay widths to be $10^{-9}$ GeV and $10^{-14}$ GeV for the decays $T_{4c}\to {\pi }^{+}{\pi }^{-}$ and $T_{4b}\to {\pi }^{+}{\pi }^{-}$ (and similarly for $K^{+}{K}^{-}$), respectively. The branching ratio for $T_{4c}\to {\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ is on the order of $10^{-8}$, making it currently unobservable in existing experiments. The factorization of $T_{4c,b}$ into light hadrons shares similarities with the decay $J/\psi \to p\bar{p}$. However, unlike the latter process, the decay $T_{4c,b}\to {\pi }^{+}{\pi }^{-}(K^{+}{K}^{-})$ exhibits unique features that arise only in processes involving multiple incoming or outgoing particles. One such feature is the necessity of maintaining the $i\epsilon$-prescription for the denominators or propagators due to the divergences in the kinematic region of interest. Employing the sector decomposition method, along with the aid of the Cheng-Wu theorem and the {\tt QHull} program, we present a systematic approach to handle the convolutions and phase-space integrations. This method can also be extended to similar processes, such as $T_{4c,b}\to p\bar{p}$, as well as to phase-space integrations where each denominator is a linear combination of integration variables.

    hep-phPRD(2026)·5 citations
17. 17*

    Atmospheric Mass-Squared Splitting at Sub-Percent Precision as a $CPT$ Symmetry Probe

    T. V. Ngoc🇻🇳 · S. Cao🇻🇳 · P. T. Quyen🇻🇳

    In this paper, we present an improved test of $CPT$ symmetry in the neutrino sector by analyzing the atmospheric mass-squared splittings, $\Delta m_{31}^2$ and $\Delta {\overline{m}}_{31}^2$, using on-going JUNO and future DUNE and Hyper-Kamiokande experiments. Our study focuses on the discrepancy ${\delta }_{\nu \overline{\nu }}(\Delta m_{31}^2)=\Delta m_{31}^2-\Delta {\overline{m}}_{31}^2$, achieving unprecedented precision by exploiting the high statistics and reduced systematic uncertainties of these facilities. The combined analysis yields a sensitivity to $CPT$ violation at the level of $2\times 10^{-5}{\text{eV}}^2$ at $3\sigma$ confidence level, representing a $60\%$ improvement over the joint T2K-NO$\nu$A-JUNO analysis. These results highlight the crucial role of multi-experiment synergies in testing fundamental symmetries of nature.

    hep-phhep-ex0 citations
18. 18*

    The DIS dipole picture cross section in exact kinematics

    Magnus Bertilsson🇸🇪 · Tuomas Lappi🇫🇮 · Heikki Mäntysaari🇫🇮 · Xuan-Bo Tong🇫🇮

    We implement a finite energy constraint in the dipole picture of deep inelastic scattering by restricting the invariant mass of the produced partonic system by the virtual photon-target center of mass energy. We show that, for $Q^2=1$GeV${}^2$, the effect of this constraint can reach up to $\sim$35% for charm quarks and $\sim$7% for light quarks at $x=0.01$, but then rapidly decreases at smaller $x$ or larger $Q^2$.

    hep-ph3 citations
19. 19*

    Probing the spin parity structure of hidden charm pentaquarks from spectroscopy and magnetic moments

    Pallavi Gupta🇮🇳

    We investigate the spin parity JP assignments of experimentally observed hidden charm pentaquark states within a baryon meson molecular framework. The pentaquark mass spectrum is obtained using the Gursey Radicati mass formula, with parameters fixed through a global fit to 41 experimentally established hadron masses. The resulting spectrum is then used to assign JP quantum numbers to the observed pentaquark candidates. Within this framework, the nonstrange states Pc 4312, Pc4440, and Pc 4457 are identified with the JP = 1/2, 3/2, and 5/2 configurations, respectively. The recently reported Belle state Pcs4459, which carries strangeness, is interpreted as the strange member of the SU3 flavor octet with JP = 3/2. Magnetic moments are subsequently evaluated using explicitly constructed wave functions. Their systematic behavior across SU3 flavor multiplets and different spin parity assignments satisfies the expected sum-rule relations and indicates that magnetic moments can serve as a useful observable for refining the quantum-number identification of hidden charm pentaquark states in future studies.

    hep-phPRD(2026)·1 citation
20. 20*

    Gross-Pitaevskii-Poisson equations with a $\xi R{\varphi }^4$ non-minimal coupling term

    Bryan Cordero-Patino🇪🇸 · Álvaro Duenas-Vidal🇪🇨 · Jorge Segovia🇪🇸

    In scenarios where the Peccei-Quinn symmetry breaks after inflation, small-scale axion inhomogeneities may gravitationally collapse into bound structures. The evolution of these systems is typically modeled through cosmological perturbation theory applied to the Einstein-Klein-Gordon equations. In the non-relativistic regime, this framework reduces to the Gross-Pitaevskii-Poisson or Schrödinger-Poisson equations, depending on whether axion self-interactions are taken into account. In this work, a non-minimal gravitational coupling term $\xi R{\varphi }^4$ is included into the axion's relativistic action as a way to introduce a gravitationally mediated pairwise interaction. By performing a perturbative expansion and subsequently taking the non-relativistic limit, an alternative set of equations that govern the early stages of structure formation is obtained.

    hep-phgr-qchep-exhep-thUniverse(2026)·0 citations
21. 21*

    CP violating signal at DUNE in presence of nonstandard interactions and the role of second oscillation maxima

    Rajrupa Banerjee🇮🇳 · Jogesh Rout🇮🇳 · Sudhanwa Patra🇮🇳 · Poonam Mehta🇮🇳

    Neutrino oscillation among the three active neutrino flavors is well established and supported by experiments at diverse length scales and energy scales. It may be noted that five of the neutrino oscillation parameters in the three-flavor paradigm, namely the three mixing angles (${\theta }_{12}$, ${\theta }_{13}$, ${\theta }_{23}$) and the two mass-squared differences ($\Delta m_{21}^2$, $\Delta m_{31}^2$) are measured to a reasonable degree of precision. The three unknowns that are expected to be deciphered in the near future are the Dirac CP phase, $\delta$, the neutrino mass ordering, and the octant of ${\theta }_{23}$. The next generation of long baseline experiments, such as the Deep Underground Neutrino Experiment (DUNE), aims to resolve these unanswered questions. In the present work, by considering DUNE as an example, we assess the ability of long baseline experiments to extricate the intrinsic contribution from observables related to CP violation in scenarios with Standard Interaction (SI) and beyond. Additionally, we analyze the role of the second oscillation maximum in addressing the above mentioned questions. By carrying out event level and statistical analyses, we assess the potential of DUNE to probe CP violation effects both within and beyond the standard paradigm.

    hep-ph1 citation
22. 22*

    Constraints on Axion-Like Particles with the Silicon Detector at a Nuclear Reactor

    Yuanlin Gong🇨🇳 · Jun Guo🇨🇳 · Ning Liu🇨🇳 · Liangliang Su🇩🇪 · Wen-Na Yang🇨🇳

    Axion and axion-like particles (ALPs), predicted in various extensions of the Standard Model, can be abundantly produced in nuclear reactors via the Primakoff process. In this work, we explore the detection of ALPs in silicon detectors through plasmon excitations. Owing to their relativistic nature, reactor-produced ALPs can efficiently excite plasmon resonances, while the accompanying energetic photon typically escapes from the thin detector without depositing an appreciable amount of energy. Utilizing the data from the Connie and Atucha-II experiments, we set the 90\% confidence level upper limits on the ALP-photon coupling $g_{a\gamma \gamma }$ over the axion mass range $0.1-100$ keV. We further show that, for an exposure of 30 kg$\cdot$yr, the projected sensitivity of vIOLETA exceeds the current NEON limit by a factor of three in the same mass range. This improvement would expand the explored region of the QCD axion and ALP parameter space.

    hep-ph6 citations
23. 23*

    Off-axis vortex scattering of electron-positron annihilation into a photon pair

    Yi Liao🇨🇳 · Quan-Yu Wang🇨🇳 · Yuanbin Wu🇨🇳

    The off-axis triple-vortex scattering process of $e^{-}{e}^{+}\to \gamma \gamma$ is studied theoretically, in which the positron is in a plane-wave state and the electron and photons are in vortex states. We develop a theoretical formalism for the process, which allows us to study the effects of various vortex parameters and scattering angle. We adopt a Bessel-Gaussian type wave packet for the initial vortex electron for the purpose of normalization. Numerical calculations are performed for an electron and a positron with a moderate energy around $1\text{MeV}$. Our results demonstrate strong impacts of the scattering angle and the topological charges on the cross section and distributions in the energy and cone angles of the vortex photons. This could provide insight into off-axis vortex scattering and also a possible approach to distinguishing and detecting vortex electrons by off-axis vortex scattering.

    hep-ph1 citation
24. 24*

    EPOS4 Model Predictions for Global Observables in Pb-Pb Collisions at $\sqrt{s_{NN}}$ = 5.36 TeV

    Hirak Kumar Koley🇮🇳 · Subikash Choudhury🇮🇳 · Mitali Mondal🇮🇳

    The study of the Quark-Gluon Plasma (QGP), a deconfined state of nuclear matter, remains a central focus of high-energy heavy-ion collision experiments. The recent operation of the Large Hadron Collider (LHC) in Run 3 at the new center-of-mass energy of $\sqrt{s_{NN}}=5.36$ TeV necessitates theoretical predictions to characterize the energy dependence and bulk properties of the medium. In this study, we present comprehensive EPOS4 model predictions for key global observables in Pb-Pb collisions at $5.36$ TeV. We focus on the centrality dependence of the charged-particle pseudorapidity density ($d{N}_{ch}/d\eta$), integrated yields ($dN/dy$), mean transverse momentum ($⟨p_T⟩$) for light-flavor hadrons (${\pi }^{\pm },K^{\pm },p(\bar{p})$), and the charged particle nuclear modification factor ($R_{AA}$). The EPOS4 framework successfully captures the strong mass-dependent rise of $⟨p_T⟩$ with multiplicity, a definitive signature of collective radial flow. Furthermore, the predicted charged hadron $R_{AA}$ demonstrates a clear suppression, consistent with energy loss mechanisms incorporated into the model. By comparing these predictions to existing $5.02$ TeV data, we demonstrate that the EPOS4 model offers a consistent and robust description of heavy-ion dynamics, projecting minimal energy evolution for these bulk and hard-probe observables between the two energies.

    hep-phhep-exnucl-thPoS(2026)·1 citation
25. 25*

    Dynamical gluon effects in twist-3 generalized parton distributions of the proton

    Ziqi Zhang🇨🇳 · Chandan Mondal🇨🇳 · Siqi Xu🇨🇳 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸

    Within the Basis Light-Front Quantization framework, we systematically investigate the subleading-twist (twist-3) generalized parton distributions (GPDs) of the proton's valence quarks beyond the Wandzura--Wilczek (WW) approximation. The twist-3 GPDs are not independent; through the equations of motion they decompose into a non-genuine contribution and a genuine twist-3 term. The latter encodes quark--quark--gluon correlations and involves interference between the light-front Fock sectors |qqq> and |qqqg>, which are typically neglected in the WW approximation. Using light-front wave functions obtained from diagonalizing the proton light-front Hamiltonian for its |qqq> and |qqqg> Fock components, we compute these GPDs via their overlap representations. To further explore their physical implications, we also evaluate several twist-3--related quantities, including the quark orbital angular momentum, the total quark spin contribution, and the quark spin--orbit correlation. Our results provide new nonperturbative input on higher-twist dynamics particularly multi-parton interference effects relevant for future measurements at the EicC and the EIC.

    hep-phnucl-thPRD(2026)·1 citation
26. 26*

    Asymptotic Padé Predictions up to Six Loops in QCD and Eight Loops in $\lambda {\varphi }^4$

    J.A. Gracey🇬🇧 · I. Jack🇬🇧 · D.R.T. Jones🇬🇧

    We assess the accuracy of our previous Asymptotic Padé predictions of the five-loop QCD $\beta$-function and quark mass anomalous dimension in the light of subsequent exact results. We find the low-order coefficients in an expansion in powers of $N_F$ (the number of flavours) were correct to within $1\%$. Furthermore an examination of recent results in $\lambda {\varphi }^4$ theory indicates that the Asymptotic Padé methods deliver predictions which increase in accuracy with loop order. Encouraged by this, we present six-loop Asymptotic Padé predictions for the QCD $\beta$-function and quark mass anomalous dimension, and also for the eight-loop $\beta$-function in $O(N)$ $\lambda {\varphi }^4$ theory.

    hep-phhep-thPRD(2026)·0 citations
27. 27*

    Single Production of a Vector-Like Top as a Probe of Charged Higgs Bosons at a Muon-Proton Collider

    R. Benbrik🇲🇦 · M. Berrouj🇲🇦 · M. Boukidi🇵🇱 · H. Chatoui🇲🇦 · M. Ech-chaouy🇲🇦 · K. Kahime🇲🇦 · K. Salime🇲🇦

    We investigate the discovery prospects for a vector-like top partner ($T$) within the Type-II Two-Higgs-Doublet Model (2HDM-II) at future high-energy $\mu p$ colliders. The analysis focuses on the charged Higgs decay mode ${\mu }^{+}p\to {\nu }_{\mu }\bar{b}T\to {\nu }_{\mu }\bar{b}{H}^{+}b$, with the subsequent decay $H^{+}\to t\bar{b}$ yielding a final state with multiple $b$-jets and a charged lepton. A detailed detector-level simulation is carried out for benchmark configurations with charged Higgs masses around 600-650~GeV and vector-like top masses in the range $m_T\simeq 1.0$-$1.8$~TeV. For an integrated luminosity of 100~fb${}^{-1}$, discovery significances above $5\sigma$ are obtained across several benchmark points, remaining robust against systematic uncertainties up to 20\%. At higher luminosities of 234~fb${}^{-1}$, the sensitivity exceeds $10\sigma$ for the lightest benchmarks and stays above $5\sigma$ even in the presence of 30\% systematics.

    hep-phEPJC(2026)·3 citations
28. 28*

    Unitarity limits on triple gauge boson production

    O.J. P. Éboli🇧🇷 · M. C. Gonzalez-Garcia🇺🇸

    We derive the unitarity constraints on anomalous quartic gauge couplings originating from the $f{\bar{f}}^{\prime }\to V{V}^{\prime }{V}^{\prime \prime }$ channel with $V^{{(}^{\prime }){(}^{\prime \prime })}=\gamma$, $Z$, $W^{\pm }$, and $H$. We also assess the importance of these bounds on the present and future experimental searches.

    hep-phhep-exPRD(2026)·1 citation
29. 29*

    Charting the Flavour Structure of Dark Matter

    Simone Biondini🇩🇪 · Admir Greljo🇨🇭 · Xavier Ponce Díaz🇨🇭 · Alessandro Valenti🇨🇭

    What flavour structure of $t$-channel thermal dark matter remains compatible with current flavour physics and direct detection bounds? We broadly chart the space of hypotheses using the framework of flavour symmetries and their breaking patterns. We then focus on scenarios in which the fermionic dark matter and its scalar mediator are flavour singlets, falling into the class of rank-1 flavour violation. For two representative benchmarks, quarkphilic ($q_L$) and leptophilic ($e_R$), we perform a comprehensive phenomenological analysis, fitting the relic abundance and examining the interplay among flavour observables, direct detection, and collider searches. Our results quantify the allowed deviations from flavour-symmetric limits and assess the discovery prospects in future flavour and direct detection experiments.

    hep-phastro-ph.COhep-exhep-thPRD(2026)·2 citations
30. 30*

    Rare and Experimentally Challenging Supersymmetry Signatures

    Laura Jeanty🇺🇸 · Lawrence Lee🇺🇸

    Supersymmetry has long played a central role in the search for physics beyond the Standard Model at colliders, providing a comprehensive and internally consistent framework for generating well-motivated experimental signatures. For more than fifteen years of LHC operation, the CMS and ATLAS collaborations have achieved remarkable sensitivity to a wide range of supersymmetric signatures. Despite this unprecedented reach, no conclusive evidence for supersymmetry has emerged. If supersymmetry is nature's solution to outstanding questions in particle physics, it is necessarily challenging to find. In this article, we review supersymmetric signatures that are particularly rare or otherwise challenging, with a focus on searches at the Large Hadron Collider. We highlight experimental challenges relating to detector constraints and analysis difficulties, in addition to model challenges in the interpretation and optimization of searches. We also identify regions of signature space that remain comparatively unconstrained and therefore represent promising targets for future exploration.

    ↳ hep-exhep-ph4 citations
31. 31*

    AMBER -- A Strong-Interaction Facility at CERN

    Bernhard Ketzer🇩🇪 · Michela Chiosso (for the AMBER Collaboration)🇮🇹

    AMBER (NA66) is a fixed-target facility at the M2 beam line of CERN SPS, which performs worldwide unique research on the internal structure and the excitation spectrum of hadrons. The approved first phase of the experiment focuses on three main physics topics: (i) the measurement of the production cross section of antiprotons in $p-\text{He}$ and $p-p/d$ collisions over a wide energy range; (ii) the precise measurement of the electric form factor of protons at small momentum transfers using a high-energy muon beam; (iii) the determination of pion and kaon quark PDFs through Drell-Yan and charmonium production measurements with negative and positive meson beams. Phase-2 will focus on measurements with an intense kaon beam. The high-energy muon, pion and kaon beams required for these measurements are only available at CERN.

    ↳ hep-exhep-phnucl-exNucl.Phys.News(2026)·2 citations
32. 32*

    Lattice QCD determination of the $\gamma Z$ box contribution to the proton weak charge

    Zhao-long Zhang🇨🇳 · Xu Feng🇨🇳 · Mikhail Gorchtein🇩🇪 · Lu-Chang Jin🇺🇸 · Chuan Liu🇨🇳 · Chien-Yeah Seng🇺🇸

    We present the first lattice QCD determination of the $\gamma Z$ box contribution to parity-violating electron-proton scattering, ${\square }_{\gamma Z}$ , a key ingredient for the precise tests of the Standard Model via the proton weak charge. Our calculation covers the electron beam energies up to $E=155MeV$. For the axial-vector component, we achieve reduced uncertainties across the entire energy range compared with phenomenological estimates. For the vector component, the uncertainties remain slightly larger after continuum extrapolation. At $E=0$, where the vector part vanishes, we obtain ${\square }_{\gamma Z}=0.00412(9)$ , reducing the uncertainty by a factor of $2$ relative to the most precise previous determination. Incorporating this result yields an updated weak charge of $Q_W^p=0.06987(50)$ . The calculated energy dependence of ${\square }_{\gamma Z}$ further provides a first-principles input for the upcoming P2 experiment at Mainz, which will operate at the optimized beam energy of $155MeV$ to extract $Q_W^p$.

    ↳ hep-lathep-phnucl-th3 citations
33. 33*

    Axion Signal Search Using Hybrid Nuclear-Electronic Spin Systems

    Xiangjun Tan🇬🇧 · Zhanning Wang🇦🇺

    Conventional nuclear magnetic resonance searches for the galactic axion wind lose sensitivity at low frequencies due to the unfavourable scaling of inductive readout. Here, we propose a hybrid architecture where the hyperfine interaction transduces axion-driven nuclear precession into a high-bandwidth electron-spin readout channel. We demonstrate analytically that this dispersive upconversion preserves the specific sidereal and annual modulation signatures required to distinguish dark matter signals from instrumental backgrounds. When instantiated in a silicon ${}^{209}\text{Bi}$ donor platform, the hybrid sensor is projected to outperform direct nuclear detection by more than an order of magnitude over the $10^{-16}-10^{-6}\text{eV}$ wide mass range. With collective enhancement, the design reaches a $5\sigma$ sensitivity to DFSZ axion-nucleon couplings within one year, establishing hyperfine-mediated sensing as a competitive path for compact, solid-state dark matter searches.

    ↳ quant-phhep-exhep-ph1 citation
34. 34*

    Oscillatory Freeze from Inertial Holographic Dark Energy

    Swapnil Kumar Singh🇮🇳

    We study a generalized holographic dark energy model in which the infrared cutoff depends on the Hubble parameter and its first two time derivatives. The inclusion of the $\ddot{H}$ term introduces a finite relaxation timescale for the horizon degrees of freedom, which can be interpreted as an effective entropic inertia of the holographic vacuum energy. The resulting background dynamics admit late--time solutions in which the cosmic expansion gradually halts. In the underdamped regime, the Hubble parameter undergoes exponentially damped oscillations and asymptotically approaches $H\to 0$. The scale factor grows monotonically but by a finite amount, while curvature invariants decay exponentially, leading to an asymptotically Minkowski spacetime without future singularities. We confront the full nonlinear background evolution with cosmic chronometer measurements of the Hubble parameter and find good agreement with current late--time expansion data, with a reduced chi--squared ${\chi }^2/\nu \simeq 0.52$. At observable redshifts, oscillatory features are strongly suppressed and remain consistent with existing constraints.

    ↳ gr-qcastro-ph.COhep-phhep-th0 citations
35. 35*

    Heavy hadron spectrum from 2+1+1 flavor MILC lattices

    Sabiar Shaikh🇮🇳 · Protick Mohanta🇮🇳 · M. Padmanath🇮🇳 · Subhasish Basak🇮🇳

    We study the mass spectra and various mass differences of heavy hadrons containing one or more bottom quarks using MILC's $N_f=2+1+1$ HISQ gauge ensembles at three lattice spacings. For the valence quarks, we employ a combination of lattice actions: the NRQCD action is used for bottom quarks, the anisotropic Clover action for charm quarks, and the $O(a)$-improved Wilson--Clover action for strange and lighter (up/down) quarks. Heavy hadron operators with at least one bottom quark are constructed by considering all possible combinations with charm, strange, and light quarks corresponding to various quantum numbers.

    ↳ hep-lathep-phnucl-th1 citation
36. 36*

    Robust Preference for Dark Sector Interactions

    Tian-Nuo Li🇺🇸 · William Giarè🇺🇸 · Guo-Hong Du🇺🇸 · Yun-He Li🇺🇸 · Eleonora Di Valentino🇬🇧 · Jing-Fei Zhang🇺🇸 · Xin Zhang🇺🇸

    Recent DESI baryon acoustic oscillation data reveal deviations from $\Lambda$CDM cosmology, conventionally attributed to dynamical dark energy (DE). We demonstrate that these deviations are equally, if not better, explained by interactions between dark matter and dark energy (IDE), without requiring a time-varying DE equation of state. Using a unified framework, we analyze two IDE models - coupled quintessence and coupled fluid - against the latest CMB (Planck, ACT, SPT), DESI BAO, and SN (including DES-Dovekie recalibrated) data. Both IDE scenarios show robust evidence for non-vanishing interactions at the 3-5$\sigma$ level, with marginalized constraints significantly deviating from the $\Lambda$CDM limit. This preference persists even under DES-Dovekie SN recalibration, which weakens dynamical DE evidence. Crucially, for the same number of free parameters, IDE models provide fits to low- and high-redshift data that match or exceed the performance of the CPL dynamical DE parametrization. Our results establish IDE as a physically motivated alternative to dynamical DE, highlighting the necessity of future cosmological perturbation measurements (e.g., weak lensing, galaxy clustering) to distinguish between these paradigms.

    ↳ astro-ph.COgr-qchep-phhep-th76 citations
37. 37*

    Tachyonic gravitational dark matter production after inflation

    Giorgio Laverda🇵🇹 · Tomás Mendes🇵🇹 · Javier Rubio🇪🇸

    We propose a novel gravitational mechanism for the non-thermal production of dark matter driven by curvature-induced tachyonic instabilities after inflation. Departing from the commonly studied non-minimal couplings to gravity, our framework considers a real spectator scalar field coupled quadratically to spacetime curvature invariants. We show that the rapid reorganization of spacetime curvature at the end of inflation can dynamically render the dark matter field tachyonic, triggering a short-lived phase of spontaneous symmetry breaking and explosive particle production. As a concrete and theoretically controlled example, we focus on the Gauss-Bonnet topological invariant. By combining analytical estimates with $3+1$ classical lattice simulations in the spectator field approximation, we track the out-of-equilibrium evolution of the system and compute the resulting dark matter abundance. We find that this purely gravitational mechanism can robustly reproduce the observed dark matter relic density over a wide range of masses and inflationary scales, providing also a simple fitting function that enables a lattice-independent application of our results.

    ↳ astro-ph.COgr-qchep-phJCAP(2026)·4 citations
38. 38*

    Learning the relations between neutron star and nuclear matter properties with symbolic regression

    N. K. Patra🇨🇳 · Tuhin Malik🇵🇹 · Kai Zhou🇨🇳 · Constança Providência🇵🇹

    The equation of state (EOS) of dense matter in neutron stars (NSs) remains uncertain, particularly at supra-nuclear densities where complex nuclear interactions and the potential presence of exotic matter, like hyperons, come into play. The complex relationships existing between nuclear matter and neutron star properties are investigated. The focus is on their nonlinearities and interdependencies. In our analysis, we apply a machine learning algorithm known as symbolic regression, paired with principal component analysis, to datasets generated from Bayesian inference over relativistic mean-field models. A systematic Principal Component Analysis has allowed to break down the percentage contribution of each element or feature in the relationships obtained. This study examines two main models (datasets): the NL model, which includes nucleonic degrees of freedom; and the NL-hyp model, which includes hyperons in addition to nucleons. Our analysis confirms a robust correlation between the tidal deformability of a 1.4 \(M_\odot\) neutron star and $\beta$-equilibrium pressure at twice the nuclear saturation density. This correlation remains once hyperons are included. The contribution of the different nuclear matter properties at saturation to the radius and tidal deformability was calculated. It was shown that the isovector properties have the largest impact, with a contribution of about 90\%. We also studied the relationship between the proton fraction at different densities and various symmetry energy parameters defined at saturation density. For the hyperon data set, we took into account the effects of the negatively charged hyperon $\Xi$ in order to recover the relationships. Our study reveals the individual impact of various symmetry energy parameters on proton fractions at different densities.

    ↳ nucl-thastro-ph.SRgr-qchep-ph+10 citations
39. 39*

    Spacetime Quasicrystals

    Latham Boyle🇬🇧 · Sotirios Mygdalas🇨🇦

    Self-similar quasicrystals (like the famous Penrose and Ammann-Beenker tilings) are exceptional geometric structures in which long-range order, quasiperiodicity, non-crystallographic orientational symmetry, and discrete scale invariance are tightly interwoven in a beautiful way. In this paper, we show how such structures may be generalized from Euclidean space to Minkowski spacetime. We construct the first examples of such Lorentzian quasicrystals (the spacetime analogues of the Penrose or Ammann-Beenker tilings), and point out key novel features of these structures (compared to their Euclidean cousins). We end with some (speculative) ideas about how such spacetime quasicrystals might relate to reality. This includes an intriguing scenario in which our infinite $(3+1)$D universe is embedded (like one of our spacetime quasicrystal examples) in a particularly symmetric $(9+1)$D torus $T^{9,1}$ (which was previously found to yield the most symmetric toroidal compactification of the superstring). We suggest how this picture might help explain the mysterious seesaw relationship $M_{\mathrm{Pl}}{M}_{\mathrm{vac}}\approx M_{\mathrm{EW}}^2$ between the Planck, vacuum energy, and electroweak scales ($M_{\mathrm{Pl}}$, $M_{\mathrm{vac}}$, $M_{\mathrm{EW}}$).

    ↳ hep-thgr-qchep-phmath-ph+22 citations
40. 40*

    New Cold Dark Matter Crisis Revealed by Multiscale Cluster Lensing

    Priyamvada Natarajan🇺🇸 · Barry T. Chiang🇺🇸 · Isaque Dutra🇺🇸

    The properties of substructure in galaxy clusters, exquisitely probed by gravitational lensing, offer a stringent test of dark matter (DM) models. Combining strong- and weak-lensing data for massive clusters, we map their total mass -- dominated by DM -- over the dynamic range needed to confront small-scale predictions for collisionless cold DM (CDM). Using state-of-the-art lens models, we extract four key subhalo properties: the mass function, projected radial distribution, internal density profile, and tidal truncation radius. We find that the subhalo mass functions and truncation radii are consistent with CDM expectations. In contrast, the inner density profiles and radial distributions of subhalos are strongly discrepant with CDM. The incidence of galaxy-galaxy strong lensing from subhalo cores exceeds CDM predictions by nearly an order of magnitude, requiring inner density slopes as steep as $\gamma \gtrsim 2.5$ within $r\lesssim 0.01R_{200}$ consistent with core-collapsed self-interacting DM (SIDM), while the same subhalos behave as collisionless in their outskirts. Additionally, the observed radial distribution of subhalos hosting bright cluster member galaxies, explicitly modeled in the lens reconstructions, remains incompatible with CDM. Taken together, these small-scale stress tests reveal an intriguing paradox and challenge the DM microphysics of purely collisionless CDM, motivating hybrid scenarios -- such as a dual-component model with both CDM and SIDM or entirely new classes of DM theories.

    ↳ astro-ph.COastro-ph.GAhep-phApJL(2026)·8 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.