Tue·Apr 21, 2026Tuesday·April 21, 2026

1. 01*

   Investigating the Neutrino Mass Ordering Problem via Ternary Plots

   Alexander Migala · Kate Scholberg🇺🇸

   We explore what may be deduced about the neutrino mass ordering problem from the observation of core-collapse supernova burst neutrinos in modern terrestrial detectors. We employ ternary plots in a novel way to visualize the time evolution of the flavor composition of various supernova neutrino flux models from the SNEWPY software package. Through our analysis of several models using a simplified unfolding process, we have explored potential robust discriminants between the normal and inverted mass orderings. We find that the normal and inverted mass orderings tend to occupy different regions in ternary space across different models.

   hep-phastro-ph.HEhep-ex0 citations
2. 02*

   Probing Flavor-Violating Higgs Decays in the Type-III Two-Higgs-Doublet Model at the LHC and HL-LHC

   M. L. Fernández-Pérez🇲🇽 · S. Rosado-Navarro🇻🇪 · A. Rosado🇲🇽

   We present a comparative collider study of three flavor-violating Higgs signatures in the Type-III Two-Higgs-Doublet Model (\ddHmIII) at \(\sqrt{s}=14\)~TeV: \(pp \to H \to t\bar{c} \ (\bar{t}c)\), \(pp \to H^\pm \to c\bar{b} \ (\bar{c}b)\), and \(pp \to H^\pm \to t\bar{b} \ (\bar{t}b)\). Using a common cut-based analysis and realistic detector simulation, we identify a clear phenomenological hierarchy. The neutral mode and the heavy charged mode emerge as the most robust signatures, containing parameter regions that already exceed the \(5\sigma\) benchmark at an integrated luminosity of \(300~\text{fb}^{-1}\). In contrast, the light charged channel \(H^{\pm}\to c\bar{b}\) is considerably more sensitive to the event-selection strategy because of large QCD backgrounds, although one competitive benchmark survives. Our results single out the neutral and heavy charged flavor-violating channels as the most promising targets for discovery-oriented searches and for constraining the \ddHmIII\ parameter space at the LHC and HL-LHC. All quoted significances are purely statistical and do not include systematic uncertainties.

   hep-ph0 citations
3. 03*

   Four-loop QCD mixing of current-current operators

   Joachim Brod🇺🇸 · Emmanuel Stamou🇩🇪 · Tom Steudtner🇩🇪

   We calculate the anomalous dimension of the $|\Delta S|=1$ current-current operators of the weak effective Lagrangian at next-to-next-to-next-to-leading order (NNNLO) in QCD. This constitutes the first step towards a full four-loop calculation of the QCD correction to ${ϵ}_K$, the measure for indirect CP violation in the neutral kaon system. We present fully analytic results, together with the expressions necessary to transform our results to a basis with an arbitrary different definition of evanescent operators. As an application, we calculate the corresponding results in the ``standard'' operator basis used in $B$ physics.

   hep-phEPJC(2026)·2 citations
4. 04*

   Cavity-mode couplings in axion dark matter searches

   Byeong Rok Ko🇰🇷

   Axion dark matter searches use a microwave cavity for the resonant conversion of axions into photons to enhance experimental sensitivity, with the cavity generally configured as a two-port system for both signal pickup and cavity characterization measurements. In this study, we investigated cavity-mode couplings in such a two-port system and examined their impact on axion dark matter search experiments, which typically use one strongly coupled port and one weakly coupled port. We found that, in such a two-port cavity system, the measured coupling strength of one port depends on that of the other; hence, the coupling coefficients appearing in the relation for the unloaded quality factor of the cavity mode can vary substantially with the measured coupling strengths. Meanwhile, the scanning rate, the figure-of-merit for axion dark matter searches, cancels the systematic contribution from the strongly coupled port; hence, the remaining systematic uncertainty arises only from the weakly coupled port and may be negligible, depending on its coupling strength. Nevertheless, we recommend measuring the coupling strength of the weakly coupled port to eliminate this systematic uncertainty and thereby recover any experimental sensitivity that may have been lost, for example by approximately 10\% when the coupling strength of the weakly coupled port is 0.05.

   hep-phhep-ex0 citations
5. 05*

   Proposed mixing between $2P$ and $1F$ wave charmonia

   Peng-Yu Sun🇨🇳 · Tian-Le Gao🇨🇳 · Zi-Long Man🇨🇳 · Xiang Liu🇨🇳

   We investigate $2P$-$1F$ mixing in charmonium, focusing on the close-in-mass ${\chi }_{c2}(2P)$ and ${\chi }_{c2}(1F)$ states. The conventional tensor force yields negligible mixing, motivating the inclusion of coupled-channel effects. Our unquenched calculation reveals sizable mixing angles of $7.5^{\circ }$ and $15.4^{\circ }$. We predict the corresponding two-photon and two-gluon decay widths as key observables for experimental verification. Additionally, we discuss the production of these two $2P$-$1F$ mixed states of charmonium via $\gamma \gamma$ fusion. Current data are insufficient to determine the mixing, highlighting the need for precise future measurements to resolve this aspect of charmonium spectroscopy.

   hep-phPRD(2026)·0 citations
6. 06*

   Deciphering the universal scaling of particle transverse momentum spectra in heavy-ion collisions

   Xi-Yao Guo🇨🇳 · Hua Zheng🇨🇳 · Wenchao Zhang🇨🇳 · Li-Lin Zhu🇨🇳 · Xing-Quan Liu🇨🇳 · Zhi-Guang Tan🇨🇳 · Dai-Mei Zhou🇨🇳 · Ben-Hao Sa🇨🇳

   We systematically investigate the scaling properties of the transverse momentum spectra for pions, kaons, and protons in Au+Au collisions at $\sqrt{s_{NN}}$ = 7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV, as well as in U+U collisions at $\sqrt{s_{NN}}$ = 193 GeV, across different centrality classes, using experimental data from the collaborations at the Relativistic Heavy Ion Collider (RHIC). Universal scaling emerges when the particle transverse momentum spectra are scaled by global physical quantities, i.e., the average total particle multiplicity and mean transverse momentum, confirming recent scaling findings from the data at the Large Hadron Collider (LHC) by the ExTrEMe collaboration. The scaling behavior breaks down in the high $p_T$ region and in peripheral collisions. We provide a natural explanation for these observations by invoking the Cooper-Frye formula, which is used for hadronization in hydrodynamics. Furthermore, we demonstrate the equivalence between the scaling found by the ExTrEMe collaboration and the Hwa-Yang scaling which was proposed two decades ago.

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

   Probes for CP Violation in B Decays at the FCC: A Theorist's Perspective

   Robert Fleischer🇳🇱

   CP violation offers powerful probes to explore the quark-flavour sector, where decays of B mesons have been key players since decades. I discuss a variety of probes ranging from non-leptonic to rare B decays, offering exciting opportunities at the FCC in the era after the HL-LHC and Belle II.

   hep-phhep-ex0 citations
8. 08*

   Hydrodynamics of Filtered Dark Matter: A Two-Component Approach

   Juntaro Wada🇯🇵

   We study the hydrodynamics of the Filtered Dark Matter (Filtered DM) scenario during a first-order phase transition (FOPT). In this scenario, the bubble wall is highly reflective of the dark matter (DM) fluid but transparent to radiation, making the hydrodynamic problem fundamentally different from that of the electroweak FOPT. Motivated by this property, we formulate the hydrodynamics of this system as a two-component fluid composed of DM and radiation, and find that the solutions can be classified into detonation-like and deflagration-like branches in the ballistic regime and in the local thermal equilibrium (LTE) regime. In the ballistic regime, the energy--momentum of DM that cannot enter the wall appears as a reflected mode, while in the LTE regime, it relaxes into the energy--momentum of radiation. We find that this difference in the fate of the DM fluid that cannot enter the interior of the wall leads to different hydrodynamic behaviors in the DM and radiation fluids independently and, in particular, results in different existence conditions for solutions in the deflagration-like branch. Based on these results, we further revisit the impact of hydrodynamic effects on the relic abundance of Filtered DM and demonstrate the change in the abundance induced by hydrodynamic effects. In addition, we also discuss the non-conservation of the entropy current from the viewpoint of the two-fluid system, and briefly comment on the similarity between the Filtered DM system and information-thermodynamic systems.

   hep-phastro-ph.COhep-th0 citations
9. 09*

   Boost-invariant perfect Fermi-Dirac spin hydrodynamics

   Zbigniew Drogosz🇵🇱 · Natalia Łygan🇵🇱

   We analyze the effect of using the Fermi-Dirac statistics, rather than its Boltzmann approximation, in numerical simulations of perfect spin hydrodynamics of particles with spin 1/2. The system considered is boost invariant, transversely homogeneous, with corrections to the baryon current and the energy-momentum tensor that are second order in the spin polarization tensor $\omega$, and the spin tensor considered is first order in $\omega$. The study shows the feasibility of this approach, as the special functions defined by integrals that appear in the coefficients in the Fermi-Dirac case can be conveniently parametrized. For sets of initial conditions used in previous works, the differences in parameter evolution between the two underlying particle statistics are about one order of magnitude smaller than corrections coming from spin feedback. We also discuss when and why the numerical solutions of the equations of perfect spin hydrodynamics break down for very large values of spin polarization in one of the geometric configurations considered.

   hep-phnucl-thActa Phys.Polon.B(2026)·1 citation
10. 10*

    Entropy and mean multiplicity from dipole models in the high energy limit

    Krzysztof Kutak🇵🇱 · Sándor Lökös🇵🇱

    The 1D Mueller dipole model, its high energy limit, and its generalization were investigated. To address the ambiguity stemming from different definitions of the pseudorapidity ranges in experimental measurements, we propose the entropy as the function of the logarithm of the average multiplicity, $S(\ln ⟨n⟩$, as a universal observable. From the solutions of the models, we calculate both the entropy and the average charged particle multiplicity and compare to data measured in proton-proton collisions. We obtained these quantities directly from the measured charged particle multiplicity distributions and determine the model parameters via fits. We find that the generalized dipole model provides a significantly better description of the data than the 1D Mueller model.

    hep-ph1 citation
11. 11*

    Testing $\alpha$-attractor P-model of inflation by Cosmic Microwave Background radiation

    Michał Marciniak🇵🇱 · Marek Olechowski🇵🇱 · Stefan Pokorski🇵🇱

    In a recently proposed approach to testing models of inflation by Cosmic Microwave Background (CMB) radiation the reheating temperature is directly expressed in terms of the CMB observables. Its model independent bounds translate in a given model into narrow ranges of those observables. In that approach we analyse the polynomial class of the $\alpha$-attractor inflaton potential models (P-models), in a broad range of polynomials and with the inflaton decays and fragmentation in the reheating period taken into account. The predictions for the CMB observables, the scalar spectral index $n_s$ and tensor-to-scalar ratio $r$, are compared with the Planck and Planck combined with ACT data. Both can be accommodated by that class of the $\alpha$ attractor models. The sensitivity of the results of that comparison to the reheating temperature and to the upper bound on the ratio $r$ is clearly demonstrated.

    hep-phastro-ph.COActa Phys.Polon.B(2026)·1 citation
12. 12*

    A Unified Bogoliubov Approach to Primordial Gravitational Waves: From Inflation to Reheating

    Yubing Wang🇩🇪 · Quan-feng Wu🇨🇳 · Xun-Jie Xu🇨🇳

    We present an effective numerical method that can be used to straightforwardly calculate the full spectrum of primordial gravitational waves produced during inflation and reheating. Our method is based on the Bogoliubov approach with several key improvements to overcome its shortcomings such as numerical errors at high frequencies and issues with tachyonic modes. We also present a few useful analytical examples from which one can gain crucial insights into the numerical errors. The improved method allows us to demonstrate that anharmonicity of inflaton oscillations can leave interesting fingerprints on the high-frequency part of the GW spectrum. Our numerical code is publicly available on GitHub https://github.com/xunjiexu/Unified-Bogoliubov.git.

    hep-phastro-ph.COgr-qc5 citations
13. 13*

    Shedding New Light on the $B\to \pi K$ Puzzle

    Eleftheria Malami🇩🇪

    The $B\to \pi K$ system provides a rich laboratory for testing the Standard Model and studying CP violation. A particularly important channel is $B_d^0\to {\pi }^0{K}_{\mathrm{S}}$, the only mode exhibiting both direct and mixing-induced CP violation. Recent Belle II measurements of the CP asymmetries in this decay provide valuable new input. An updated analysis incorporating these new data provides new insight on the long-standing $B\to \pi K$ puzzle. Looking ahead to the high-precision era of flavour physics, the $B\to \pi K$ system can be further exploited to potentially reveal new sources of CP violation.

    hep-phhep-ex0 citations
14. 14*

    "Neutrinoless double beta decay" is the correct name for neutrinoless double beta decay

    James M. Cline🇨🇦

    Recently arxiv:2604.12897 urged that the terminology "neutrinoless double beta decay" should be changed to "Majorana double beta decay" to properly give credit to Majorana, and to focus on the positive aspects of the phenomenon -- supposed creation of matter in the laboratory -- rather than the negative: absence of something, embarrassment over false claims of detection, and a "sociology of suspicion." I argue that the current terminology is more accurate and descriptive, and that the claimed reasons for its adoption are lacking in credibility.

    hep-phphysics.hist-ph0 citations
15. 15*

    Sequential Y(nS) suppression in high-multiplicity pp collisions: the experimental case for an early, globally correlated medium

    Renato Campanini🇮🇹

    The multiplicity-dependent suppression of ${\rm Y}(n\mathrm{S})$ states measured by CMS in $pp$ at $\sqrt{s}=7$TeV \cite{CMS2020}, and of $\psi (2S)/J/\psi$ measured by LHCb at $\sqrt{s}=13$TeV \cite{LHCb2024}, is subjected to four multi-differential tests: \emph{cone isolation}, \emph{azimuthal sectors}, \emph{transverse sphericity}, and \emph{prompt vs. non-prompt}. Cone and sphericity close a \emph{scissors constraint}: the local reading of the Comover Interaction Model is in tension with the cone data, its global reading with the sphericity data. The non-prompt flatness forces the mechanism to act at early proper times. None of the considered hadronic or string-based frameworks -- CIM local or global, PYTHIA 8 MPI \cite{Sjostrand2015}, rope hadronisation \cite{Bierlich2015}, CGC \cite{Ma2015}, Trainor TCM \cite{Trainor2008} -- naturally satisfies the four constraints simultaneously in its published form. The surviving class is an early, globally correlated medium consistent with partonic degrees of freedom, co-occurring with the ALICE strangeness enhancement \cite{ALICE_SE}, the long-range ridge \cite{CMS_ridge}, and below the threshold of the partonic baryon-meson $v_2$ \cite{ALICE_v2}, in a density window compatible with the Campanini \& Ferri equation of state \cite{Campanini2011}.

    hep-phhep-ex0 citations
16. 16*

    New physics in the $ZZh$ vertex: One-loop contributions from a radiative seesaw model

    Héctor Novales-Sánchez🇲🇽 · Humberto Vázquez-Castro🇲🇽 · Mónica Salinas🇲🇽

    Precision Higgs physics offers a sensitive window into physics beyond the Standard Model. In parallel, neutrino-oscillation experiments have established the existence of nonzero neutrino masses, thus implying the presence of new physics. Motivated by these facts, we investigate the one-loop contributions of light and heavy Majorana neutrinos to the $ZZh$ vertex within a variant of the type-I seesaw mechanism in which light-neutrino masses vanish at tree level and are then generated radiatively. We analyze the $CP$-conserving and $CP$-violating anomalous couplings which characterize the $ZZh$ vertex and study their phenomenological implications in two relevant kinematic scenarios at future lepton colliders: Higgsstrahlung production and Higgs production via neutral-current vector-boson fusion. We find that $CP$-conserving effects can reach magnitudes of order $10^{-3}$, potentially within projected future experimental sensitivities, whereas $CP$-violating contributions are strongly suppressed, lying well beyond such projections.

    hep-phhep-th0 citations
17. 17*

    Searching for dark photons in $J/\psi$ decays

    Xiao Liang🇨🇳 · Chun-Yuan Li🇨🇳 · Bin-Peng Shang🇨🇳 · Zong-Guo Si🇨🇳 · Hong-Xin Wang🇨🇳 · Xing-Hua Yang🇨🇳 · Dai-Xing Zhang🇨🇳

    A dark photon is an Abelian gauge boson from a new $U(1{)}_D$ gauge symmetry, coupled to the Standard Model via kinetic mixing, with $ϵ$ inducing an effective coupling to the electromagnetic current and $g_{\chi }$ to a stable dark matter particle $\chi$. We study $J/\psi$ two-body and four-body decays via a light-mass dark photon ($m_U<3.0$ GeV) in the framework of non-relativistic QCD (NRQCD), considering both visible and invisible decays of the dark photon into SM fermions or dark sector particles. We investigate the detection sensitivity to the dark photon mass $m_U$ and kinetic mixing parameter $ϵ$ at both the BESIII and STCF experiments.

    hep-phCPC(2026)·0 citations
18. 18*

    Polarization, Maximal Concurrence, and Pure States in High-Energy Collisions

    Yu-Xuan Liu🇨🇳 · Wei Qi🇺🇸 · Luo-Ting He🇨🇳 · Bo-Wen Xiao🇨🇳

    We establish a quantitative relation between local spin polarization and quantum entanglement in two-qubit systems by mathematically proving a closed-form upper bound on the concurrence at fixed local polarization magnitudes. The bound shows how the maximal concurrence is jointly constrained by the two local polarizations. We further demonstrate that this bound is saturated by pure states in certain cases with identical polarizations. As a concrete physical application, we consider the parity-violating process $e^{+}{e}^{-}\to Z^0\to q\bar{q}$, which generates final-state spin polarization. We show that the maximal concurrence is attained in specific kinematic regions and is significantly reduced relative to the unpolarized case. These results establish a general, process-independent framework connecting local polarization, maximal entanglement, and pure states.

    hep-phhep-exnucl-thquant-ph8 citations
19. 19*

    Soft mode dynamics associated with QCD critical point and color superconductivity -- pseudogap, anomalous dilepton production and electric conductivity

    Masakiyo Kitazawa🇯🇵 · Teiji Kunihiro🇯🇵

    We give a systematic account of the soft mode dynamics of QCD critical point and the two-flavor color-superconductivity based on the 2-flavor Nambu--Jona-Lasinio model, and investigate their effects on electromagnetic observables in relativistic heavy-ion collisions (HIC). We first demonstrate that the collective excitations coupled to the fluctuations of the respective order parameters are the soft modes associated with the phase transitions, in the sense that they acquire a prominent spectral strength in the low-energy and low-momentum region near the phase transitions, and the peak energy goes down, i.e., gets softened, and eventually vanishes at the critical point. It is shown that the diquark soft mode of the 2SC gives rise to the pseudogap, i.e., a depression in the density of states of the quark spectra around the Fermi surface above but in the vicinity of the critical temperature. Then, exploiting the ideas that were developed in condensed matter physics for describing the `para-conductivity' in the normal phase of metal superconductors, we show that the soft modes cause an anomalous enhancement of electric conductivity and the dilepton production rate, and discuss their relevance to HIC.

    hep-phnucl-thSymmetry(2026)·0 citations
20. 20*

    Three-body decay $\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ with Omnès-type final-state interactions

    Seung-il Nam🇰🇷 · Jung Keun Ahn🇰🇷

    We investigate the decay $\varphi \to {\pi }^{+}{\pi }^{-}{\pi }^0$ in an effective-Lagrangian framework that keeps the dominant $\rho \pi$ mechanism, the direct three-pion term, and a real constant background contribution explicitly separated at the amplitude level. The resonant contribution is described with the Gounaris-Sakurai propagator, the neutral channel includes ${\rho }^0$-$\omega$ mixing, and the leading elastic $I=1$, $P$-wave $\pi \pi$ final-state interaction is incorporated through the complex, $s$-dependent Omnès function ${\Omega }_1(s+i0)$. The Omnès factor is applied channel by channel to the three two-pion subsystems, while the direct amplitude is dressed by the averaged factor ${\Omega }_{\mathrm{dir}}=({\Omega }_0+{\Omega }_{+}+{\Omega }_{-})/3$. To avoid double-counting the elastic rescattering already contained in the physical $\rho \to \pi \pi$ coupling, we introduce $g_{\rho \pi \pi }^{\mathrm{bare}}=g_{\rho \pi \pi }^{\mathrm{phys}}/|{\Omega }_1(m_{\rho }^2)|$ in the Omnès-dressed $\rho$-exchange amplitude. With the final parameter set used in this work, we obtain ${\Gamma }_{\mathrm{th}}=0.6915\mathrm{MeV}$, slightly above the empirical estimate ${\Gamma }_{\exp }\approx 0.660\pm 0.020\mathrm{MeV}$, while the direct integrated weight is reproduced at the KLOE scale, $I_{\mathrm{dir}}=8.393\times 10^{-3}$. The corresponding resonant weight is $I_{\rho \pi }=0.9619$. The resulting Dalitz distribution retains the expected $\rho \pi$-dominated three-band structure and shows the localized neutral-channel deformation induced by ${\rho }^0$-$\omega$ mixing. Remaining discrepancies in the $x$ and especially the $y$ projections indicate the limitations of the present minimal single-channel Omnès implementation and motivate a next-stage analysis based on a full dispersive crossed-channel treatment and a direct fit to the efficiency-corrected KLOE Dalitz-bin data.

    hep-phPRD(2026)·0 citations
21. 21*

    Compositeness of near-threshold eigenstates with Coulomb plus short-range interactions

    Tomona Kinugawa🇯🇵 · Tetsuo Hyodo🇯🇵

    We investigate the internal structure of near-threshold $s$-wave eigenstates in a two-body system with Coulomb plus short-range interactions. Using a nonrelativistic effective field theory, we derive the expression for the compositeness in terms of the energy derivative of the self-energy, which is applicable to the present system with the non-separable Coulomb interaction. For near-threshold states, the compositeness can be written solely in terms of the Coulomb scattering length, the Coulomb effective range, and the Bohr radius, providing the weak-binding relation in the presence of the Coulomb interaction. We numerically study the pole trajectories and the compositeness and find that the Coulomb interaction qualitatively modifies the threshold behavior of the poles and the internal structure of the eigenstates. We show that when the Coulomb interaction is relatively strong, the enhancement of the compositeness near the threshold is absent, in contrast to purely short-range interactions. On the other hand, for a weak Coulomb interaction, a remnant of short-range universality survives, and near-threshold bound states tend to be composite dominant. Furthermore, even resonances are dominated by the composite component in the presence of the Coulomb interaction, owing to their continuous connection to the bound-state regime. We apply the formalism to realistic systems with near-threshold eigenstates, including exotic hadrons and nuclei.

    hep-phnucl-th1 citation
22. 22*

    Probing Cosmic-Ray-Boosted and Supernova-Sourced Sub-GeV Dark Matter with Paleo-Detectors

    Xiaoyong Chu🇨🇳 · Yue-Lin Sming Tsai🇨🇳 · Mei-Wen Yang🇨🇳

    Astrophysical dark matter particles with masses well below GeV-scale can be difficult to detect using conventional nuclear recoil experiments due to their low velocities in our Milky Way halo. Elastic scattering with high-energy cosmic rays or thermal production inside core-collapse supernovae can accelerate sub-GeV DM to (semi-)relativistic velocities, producing nuclear recoil energies above the keV threshold that paleo-detectors can record over geological timescales. Using olivine as the target with 100g$\cdot$Gyr exposure, we compute track length distributions from such (semi-)relativistic dark matter fluxes, incorporating all major backgrounds (neutrinos, uranium-chain neutrons, thorium recoils) with a statistical analysis on an Asimov dataset. We derive 95 C.L. projected sensitivity of paleo-detectors to the DM-nucleon cross section for dark matter masses between a few MeV and hundreds of MeV. Our results show that paleo-detectors are able to probe large parameter regions that are not covered by current and near-future experiments designed to detect dark matter and neutrinos. In particular, paleo-detectors offer a unique ability to record the dark matter flux from Galactic supernova events over geological times. Such cumulative exposure enables sensitivity gains of a few orders of magnitude compared to conventional experiments.

    hep-phastro-ph.HE2 citations
23. 23*

    Large CP violation in ${\Lambda }_b\to \Lambda D$ decays and extraction of the Cabibbo-Kobayashi-Maskawa angle $\gamma$

    Zhou Rui🇨🇳 · Zhi-Tian Zou🇨🇳 · Ya Li🇨🇳 · Ying Li🇨🇳

    Motivated by the first observation of CP violation in $b$-baryon decays, the search for baryonic decays exhibiting large CP violation will be a primary focus in the coming years. We propose that significant CP-violating effects exist in the decay ${\Lambda }_b\to \Lambda D$, where $D$ denotes a CP eigenstate of the $D^0-{\bar{D}}^0$ system. The predicted CP asymmetries for both the CP-even and CP-odd modes can reach magnitudes as large as $50\%$, making these decays promising targets for measurement at the LHCb experiment. Additionally, we predict for the first time several nonzero CP-violating observables associated with angular distribution parameters, providing valuable complementary information in the search for CP violation in baryon decays. Furthermore, we propose a novel strategy to extract the CKM angle $\gamma$ by combining data on angular distribution parameters and decay rates from the relevant channels. We emphasize that ${\Lambda }_b\to \Lambda D$ decays are among the most promising candidates for determining $\gamma$ in the baryon sector. Our findings may offer new insights for future theoretical and experimental investigations.

    hep-phhep-exPRD(2026)·3 citations
24. 24*

    Jet Quenching in the Smallest Hadronic Collision Systems

    Coleridge Faraday🇿🇦 · Ben Bert🇿🇦 · Jack Brand🇿🇦 · Werner Vogelsang🇩🇪 · W. A. Horowitz🇿🇦

    We present perturbative quantum chromodynamics (pQCD) predictions for high-momentum particle yield modification in very light ion collisions - ${}^{10}\mathrm{B}+{}^{10}\mathrm{B}$, ${}^6\mathrm{Li}+{}^6\mathrm{Li}$, ${}^4\mathrm{He}+{}^4\mathrm{He}$, and ${}^3\mathrm{He}+{}^3\mathrm{He}$ - with and without medium-induced energy loss. We find non-trivial suppression in symmetric systems from ${}^{208}\mathrm{Pb}+{}^{208}\mathrm{Pb}$ to ${}^3\mathrm{He}+{}^3\mathrm{He}$ and in asymmetric $A+B$ systems, with the suppression scaling approximately as $R_{AB}\simeq (\sqrt{AB}{)}^{1/3}$. Further, we find that ${}^3\mathrm{He}$ and ${}^6\mathrm{Li}$ offer particularly clean environments for observing final-state partonic energy loss from quark-gluon plasma (QGP) formation in extremely small systems. Finally, we show that energy loss models generically predict $v_2\{\mathrm{SP}\}\approx 0$ in small systems, indicating that the large measured $v_2>0$ in $p+{}^{208}\mathrm{Pb}$ is not due to energy loss.

    hep-phnucl-th0 citations
25. 25*

    Precision calculations for electroweak multi-boson processes

    S. Dittmaier🇩🇪

    We review the salient features of next-to-leading-order QCD and electroweak corrections to the scattering of two and the production of three weak gauge bosons at the Large Hadron Collider. Results for the tower of $O({\alpha }_s^m{\alpha }^n)$ corrections are shown for the exemplary processes of like-sign WW scattering and triple-W production, emphasizing the large impact of purely electroweak corrections which generically grow to $\sim -16\%$ and $\sim -7\%$ for these process types, respectively, even for integrated cross sections. Moreover, we discuss the possibility to reproduce the results of full off-shell calculations by the "vector-boson scattering approximation", "leading-pole approximations", and the "effective vector-boson approximation".

    hep-ph0 citations
26. 26*

    A Type-I Seesaw Framework with Non-Holomorphic Modular Symmetry

    Cheshta🇮🇳 · Priya🇮🇳 · Suneel Dutt🇮🇳 · B. C. Chauhan🇮🇳

    We study neutrino mass generation within the framework of non-holomorphic modular symmetry proposed by Qu and Ding. In this formalism, neutrino masses are generated via the Type-I seesaw mechanism, where the Yukawa couplings depend on non-holomorphic modular forms. The viability of the model is examined through a ${\chi }^2$ analysis using current neutrino oscillation data. The ${\chi }_{min}^2$ value is found to be $7.06$ for normal hierarchy(NH). All neutrino oscillation parameters are consistent within their $1\sigma$ allowed ranges, except the atmospheric mixing angle ${\sin }^2{\theta }_{23}$, which is predicted to lie in the second octant. The Dirac CP-violating phase(${\delta }_{CP}$) is constrained to the first and fourth quadrants, indicating relatively weak CP violation. These predictions can be tested in future long-baseline neutrino oscillation experiments. The sum of neutrino masses is compatible with the stringent bound proposed by the DESI experiment. However, the inverted hierarchy(IH) is not viable in this model, as the predicted value of ${\chi }_{min}^2$ exceeds 100, and the mixing angles ${\sin }^2{\theta }_{12}$ and ${\sin }^2{\theta }_{23}$ lie outside the $3\sigma$ allowed ranges.

    hep-phEPJC(2026)·2 citations
27. 27*

    Sexaquarks and $H$ dibaryons in the $uuddss$ system: a comparison within a constituent quark model

    M.C. Gordillo🇪🇸

    We study the $uuddss$ multiquark within a constituent quark model framework, solving the corresponding nonrelativistic Schrodinger equation by means of a diffusion Monte Carlo (DMC) method. The total wavefunction is written as the product of a radial component and an exact spin-color-flavor state, restricted to isospin $I$=0. For this isospin, all allowed flavor wave functions are included. We explore two distinct constructions of the six-quark system. In the first one, corresponding to a sexaquark, all six quarks are treated as indistinguishable and the wave function is fully antisymmetric with respect to the exchange of any two quarks. In the second one, corresponding to the $H$ dibaryon, the system is partitioned into two sets of three quarks, effectively mimicking a baryon-baryon-like configuration including hidden color terms in which antisymmetry is imposed only within each three-quark cluster. Only when the system is forced into a baryon-baryon-like configuration, and for certain values of the spin, color and flavor quantum numbers, do we obtain states with masses close to, but above, the two-baryon threshold. Those states are characterized by two loosely bound three-quark clusters separated from one another by a distance of $\sim$ 2.5 fm. The remaining structures are compact objects irrespectively of their internal wavefunction.

    hep-ph2 citations
28. 28*

    Analysis of the $D_0^{\ast }(2300)$ resonance from lattice QCD under chiral symmetry

    Jing Luo🇨🇦 · Bing Wu🇨🇳 · Pan-Pan Shi🇪🇸 · Meng-Lin Du🇨🇳

    We reanalyze the lattice spectra for $I=1/2$ $D\pi$ scattering in the $A_1^{+}$ irreducible representation from [Phys. Rev. D 111, 014503 (2025)] to investigate the impact of chiral and SU(3) flavor symmetries in $S$-wave $D\pi$ scattering and the $D_0^{\ast }(2300)$ resonance. By fitting the phase shifts obtained via Lüscher's formula with both traditional and chirally modified effective-range expansion and $K$-matrix parameterizations, we find that the chiral factor shifts the extracted pole mass closer to the threshold (especially for resonances) and substantially reduces the resonance width. These findings are confirmed by unitarized chiral perturbation theory through a direct fit to the lattice spectra with both the single-channel and the $D\pi$-$D\eta$-$D_s\bar{K}$ coupled-channel schemes. Once the coupled channels are incorporated, the two-pole structure of the $D_0^{\ast }(2300)$ emerges. The trajectories of the two poles are investigated by varying the pion mass.

    hep-phhep-latPRD(2026)·3 citations
29. 29*

    Generalized parton distributions of valence, sea, and gluon components of the proton

    Yiping Liu🇨🇳 · Siqi Xu🇨🇳 · Chandan Mondal🇨🇳 · Xingbo Zhao🇨🇳 · James P. Vary🇺🇸

    We compute the generalized parton distributions (GPDs) of valence quarks, sea quarks, and gluons in the proton using light-front wave functions obtained within the basis light-front quantization (BLFQ) framework, providing a realistic description of the nucleon at a low resolution scale. The wave functions are derived from a light-front QCD Hamiltonian without an explicit confining potential and include the three-quark, three-quark-gluon, and three-quark-quark-antiquark Fock sectors. For the first time within BLFQ, we evaluate quark GPDs at nonzero skewness in both the DGLAP and ERBL regions, while gluon GPDs are computed in the DGLAP region. The resulting GPDs exhibit qualitative features similar to, but smaller than the GUMP1.0 global extraction of GPDs based on experimental and lattice QCD data at next-to-leading order accuracy. We further compute the associated Compton form factors and obtain results consistent with the global analysis.

    hep-ph1 citation
30. 30*

    Two-body charmed anti-charmed baryonic $B$ decays

    Chun-Khiang Chua🇹🇼

    We study the rates of two-body charmed anti-charmed baryonic $\overline{B}\to {\mathbf{B}}_c{\overline{\mathbf{B}}}_c$ decays using the topological amplitude approach. All amplitudes of $\overline{B}\to {\mathbf{B}}_c({\bar{3}}_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}(3_{\mathbf{f}})$, ${\mathbf{B}}_c(6_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}(3_{\mathbf{f}})$, ${\mathbf{B}}_c({\bar{3}}_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}({\bar{6}}_{\mathbf{f}})$ and ${\mathbf{B}}_c(6_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}({\bar{6}}_{\mathbf{f}})$ decays are decomposed topologically. SU(3) breaking effects on these amplitudes, depending on the position of the $s$-quark line, are modeled. Using existing data as inputs, we obtained the following results. (i) In the low-lying $\overline{B}\to {\mathbf{B}}_c({\bar{3}}_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}(3_{\mathbf{f}})$ decays, we find that the exchange diagram is sizable. Furthermore, there is a large cancellation between internal $W$-tree and exchange $W$-tree amplitudes. The SU(3) breaking is sizable, 35% SU(3) breaking effects are needed, and they work differently in different amplitudes. The rates of $\overline{B}\to {\mathbf{B}}_c({\bar{3}}_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}(3_{\mathbf{f}})$ decays with some excited ${\mathbf{B}}_c({\bar{3}}_{\mathbf{f}})$ are also studied. (ii) The $\overline{B}\to {\mathbf{B}}_c(6_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}(3_{\mathbf{f}})$ decays, with low-lying ${\overline{\mathbf{B}}}_c(3_{\mathbf{f}})$ and low-lying and some excited ${\mathbf{B}}_c(6_{\mathbf{f}})$ baryons are studied with some predictions on rates obtained. (iii) The $\overline{B}\to {\mathbf{B}}_c({\bar{3}}_{\mathbf{f}}){\overline{\mathbf{B}}}_{\mathbf{c}}({\bar{6}}_{\mathbf{f}})$ decays with low-lying charmed anti-charmed baryons are studied with some predictions on rates obtained. (iv) Uncertainties in most predicted rates are large, reflecting our current poor understanding of the related SU(3) breaking effects. Measuring these rates can provide very useful information about these effects.

    hep-phhep-exPRD(2026)·2 citations
31. 31*

    Looking for Lights from the Darkness: Signals from MeV-scale Solar Axion-like Particles

    Yu-Cheng Qiu🇨🇳 · Yongchao Zhang🇨🇳

    The axion-like particles $a$ can be produced in the Sun via the process of $p+D\to {}^3\mathrm{He}+a$, with mass up to 5.5 MeV. The photons in the subsequent decay $a\to \gamma \gamma$ can deviate significantly from the Sun, or even from roughly the opposite direction of the Sun. The nontrivial angular and spectral distributions of such photons enable us new methods to detect the {\it lights from the darkness}. In this letter, we consider both the space detection and terrestrial experiments at the South Pole. As a result of the two-body decay and the geometric effects, there exists a critical height for the terrestrial experiments, below which there is no photon for some regions of the parameter space. With the sensitivities of $10^{-16}$ ($10^{-17}$) erg cm${}^{-2}$ s${}^{-1}$ for the MeV-scale photons in future space and terrestrial experiments, the coupling $g_{a\gamma }$ of $a$ to photons can be probed up to $3\times 10^{-12}$ ($1\times 10^{-12}$) GeV${}^{-1}$, well surpassing the current supernova limits.

    hep-phastro-ph.HE2 citations
32. 32*

    New Physics in inclusive $\bar{B}\to X_c\ell \bar{\nu }$ decays

    Alexandre Carvunis🇩🇪 · Gael Finauri🇮🇹 · Paolo Gambino🇮🇹 · Martin Jung🇮🇹 · Sandro Mächler🇮🇹

    We present the first global phenomenological fit of inclusive $\bar{B}\to X_c\ell \bar{\nu }$ observables to all available experimental data allowing for generic dimension-six New Physics interactions in the Weak Effective Theory. The fit includes both New Physics Wilson coefficients and non-perturbative QCD parameters. New Physics contributions are calculated including power corrections up to $\mathcal{O}({\Lambda }_{\mathrm{QCD}}^3/m_b^3)$ and perturbative QCD corrections up to $\mathcal{O}({\alpha }_s)$. We find no significant preference for New Physics and obtain bounds on the size of the relevant Wilson Coefficients competitive with those coming from exclusive modes.

    hep-ph0 citations
33. 33*

    Three loop QCD corrections to electroweak radiative parameters

    Tanmoy Pati🇮🇳 · Narayan Rana🇮🇳 · Alessandro Vicini🇮🇹

    We reevaluate the vacuum polarization functions for electroweak gauge bosons at three loops in QCD, employing state-of-the-art perturbative techniques. We apply these results to determine the $\mathcal{O}(\alpha {\alpha }_s^2)$ corrections to the electroweak radiative parameters $\Delta \rho$, $\Delta r$ and $\Delta \kappa$. We improve the accuracy of the calculation at this perturbative order, compared to the existing literature, and present some phenomenological implications of these results. We find a shift in the prediction of the $W$ boson mass, significant in view of the FCC precision targets. We improve the prediction of the $\overline{\mathrm{MS}}$ electric charge at $q^2=m_Z^2$ with the inclusion of these $\mathcal{O}(\alpha {\alpha }_s^2)$ corrections.

    hep-phhep-th0 citations
34. 34*

    Inflation from a Weyl-flat null origin

    Malaika Arshad🇵🇰 · Jehanzad Zafar🇨🇳 · Ahdab Althukair🇸🇦 · Bilal Ahmad🇨🇳

    We show that a Weyl-flat null origin of inflation need not be in tension with present observations. For canonical single-field inflation, any background with $ϵ(N)\to {ϵ}_{\infty }\in (0,1)$ as $N\to \infty$ is asymptotically power-law, inherits the same Weyl-flat null past boundary, and reconstructs an exponential tail in field space. This identifies the origin as an asymptotic universality class rather than a rigid exact solution. We study a minimal deformation, $ϵ(N)={ϵ}_{\infty }+(1-{ϵ}_{\infty }){\left(\frac{N_0}{N+N_0}\right)}^p$ with $p>1$, which preserves the asymptotic geometry, yields a smooth exit, and produces realistic finite-$N$ phenomenology. Solving the scalar and tensor mode equations directly in e-fold time, we find a viable corridor with $n_s$ in the Planck-preferred range and $r\sim 10^{-3}-10^{-2}$, including reheating-compatible benchmarks. The result is a calculable single-field framework in which a Penrose-compatible Weyl-flat inflationary origin survives as a realistic and testable possibility.

    hep-phastro-ph.COgr-qc0 citations
35. 35*

    The influence of the inverse Compton effect on the transverse momentum spectra of particles produced in pp collisions at \sqrt{s}=14 TeV

    M. Alizada🇦🇿 · M. Suleymanov🇦🇿

    The influence of the QED-analog of the inverse Compton effect on the transverse momentum spectra of particles produced in proton-proton collisions at energies of \sqrt{s}=14 TeV has been investigated. The analysis is based on the quark-gluon scattering process g + q --> g + q, which is the QCD analogue of Compton scattering of a photon on an electron and can lead to energy redistribution between partons, analogous to the mechanism of the inverse Compton effect. Data obtained numerically using the PYTHIA event generator (version 8.316) were used. A total of 5*10^5 proton-proton collisions at \sqrt{s}=14 TeV were analyzed. Events were classified based on the relative energies of the initial quark and gluon, which allowed us to distinguish Compton scattering (DCE) events from inverse Compton scattering (ICE) events. Particle transverse momentum spectra were obtained in the region: p_{T} < 10 GeV/c. The results showed that including inverse Compton scattering events in the analysis leads to a moderate increase in particle yield. The ratio of the spectra for ICE and DCE events remains approximately constant and is about 1.1 within statistical errors. No significant broadening of the transverse momentum spectra is observed. These results show that proton-proton collisions can serve as a reliable baseline for studies of energy redistribution mechanisms in a dense QCD medium, such as quark-gluon plasma.

    hep-phhep-ex1 citation
36. 36*

    Hunting Sterile Neutrino Dark Matter in the MeV Gap

    Shivam Gola🇮🇳 · Akash Kumar Saha🇮🇳 · Manibrata Sen🇮🇳

    We investigate the sensitivities of upcoming MeV gamma-ray telescopes to sterile neutrino dark matter in the mass range $(0.2-100)\mathrm{MeV}$. Sterile neutrinos in this regime can produce observable photon signals through radiative two-body decays and three-body decays with final-state radiation. We perform a Fisher forecasting analysis incorporating realistic astrophysical background modeling and detector response to derive projected constraints on the sterile neutrino decay rate. We find that future MeV instruments can improve existing limits by several orders of magnitude across a wide region of parameter space. Our results highlight the discovery potential of next-generation MeV telescopes in probing sterile neutrino dark matter.

    hep-phastro-ph.HE1 citation
37. 37*

    Extremely high-energy bremsstrahlung in matter

    Peter Arnold🇺🇸 · Joshua Bautista🇺🇸 · Omar Elgedawy🇨🇳 · Shahin Iqbal🇵🇰

    The theory of bremsstrahlung $e\to e\gamma$ by extremely high energy electrons passing through ordinary matter has been qualitatively incomplete. We revisit the suppression of bremsstrahlung by the Landau-Pomeranchuk-Migdal (LPM) effect, here accounting for quantum disruption of that effect from pair production. Our analysis covers the full range of ultra-relativistic electron and photon energies (subject to a few simplifying approximations).

    hep-ph2 citations
38. 38*

    Flavomons in Matter Gradients: Ray Tracing and Amplitude Evolution

    Damiano F. G. Fiorillo🇮🇹 · Georg G. Raffelt🇩🇪

    Flavor instabilities develop in neutrino plasmas through the emission of flavomons, the quanta of flavor waves. Matter gradients can sweep flavomons across the unstable wave-number range, halting their amplification. This effect is parametrically small for fast modes, where it was first identified, but we show that it strongly alters neutrino-mass-induced instabilities below the supernova shock, while leaving those outside largely unaffected. The role of these instabilities can therefore be established only through a global treatment beyond local dispersion relations. Using the WKB approximation, we derive the covariant evolution equation for the flavomon amplitude along geometrical-optics rays, enabling a global treatment of instability growth and seeding.

    hep-phastro-ph.COastro-ph.HE7 citations
39. 39*

    A new approach to long-lived particle detection at hadron colliders: the $\text{DELIGHT-SHIELD}$ concept

    Biplob Bhattacherjee🇮🇳 · Arnav Chauhan🇮🇳 · Swagata Mukherjee🇮🇳 · Rhitaja Sengupta🇩🇪 · Anand Sharma🇮🇳

    We propose a fundamental shift in the search for beyond the Standard Model long-lived particles (LLPs) at high-luminosity hadron colliders by prioritizing physical background suppression over traditional inner tracking. We introduce $\text{DELIGHT-SHIELD}$, a dedicated detector design for a 100 TeV Future Circular Collider at a dedicated interaction point for LLP searches. By replacing the inner parts of the detector with a multi-layered composite shield, followed by tracking volumes, we estimate a suppression of Standard Model hadronic and electromagnetic backgrounds by up to seven orders of magnitude analytically. Full Geant4 simulations validate the effectiveness of this design. Although the achieved suppression is somewhat lower than the analytical estimate, primarily due to secondary particle production within the shield, the residual background remains at a level that is manageable for LLP analyses. It can be further mitigated by applying energy thresholds, as well as vertexing and timing cuts in the downstream detector. Benchmarking against dark scalar model, we show that this shielding based detector concept achieves sensitivity to branching ratios as low as $\mathcal{O}(10^{-9})$ for $h\to \varphi \varphi$ process under zero background condition $-$ outperforming general-purpose detector baselines. This strategy not only expands the discovery reach for neutral LLPs but also provides a rigorous experimental handle to distinguish new physics from Standard Model punch-through backgrounds. We further discuss a phased implementation at the High-Luminosity LHC as a critical testbed for this novel detection concept.

    hep-phhep-ex0 citations
40. 40*

    Complex Quaternionic Formulations of Dirac, Electrodynamic, and Electroweak Fields and Interactions

    James Henry Atwater🇺🇸 · David Lambert🇺🇸 · Yuri Rostovtsev🇺🇸

    A simple translation between a standard representation of ${\mathfrak{sl}}_2\mathbb{C}$ and the complex-quaternions ($\mathbb{H}{\otimes }_{\mathbb{R}}\mathbb{C}$) is established and exploited to construct a novel hyper-complex description of the Dirac theory, electrodynamics, and ultimately the electroweak sector of the standard model. We find that coupling the constructed Dirac spinors to electromagnetism yields the correct magnetic moment for charged spin-1/2 particles. Extending electrodynamics to electroweak theory necessitates an algebraic distinction between the structures of the leptonic and Higgs fields not present in the standard model. The conditions of spontaneous symmetry breaking are explored using an alternative representation of weak isospin and hypercharge equivalent to an irreducible representation of $\mathfrak{su}(2)\oplus \mathfrak{u}(1)$ on ${\mathbb{C}}^4$. This alternative representation disagrees with the standard model on the overall signs of weak neutral currents.

    ↳ quant-phhep-phhep-th1 citation
41. 41*

    Dark ages bounds on nonaccreting massive compact halo objects

    Vivekanand Mohapatra🇮🇳 · Alekha C. Nayak🇮🇳

    We derive a complementary cosmological upper bound on the fraction of dark matter residing inside non-accreting massive compact halo objects (MACHOs) using the cosmic dawn and dark ages global 21-cm signal $(T_{21})$. MACHOs of mass $M\gtrsim 10^3{M}_{\odot }$ moving through the baryonic fluid during post-recombination transfer kinetic energy to the intergalactic medium via dynamical friction, thereby raising the gas temperature and distorting the 21-cm signal predicted in the $\Lambda$CDM framework. We consider both a monochromatic distribution of MACHOs and two extended mass distributions: log-normal and critical collapse. Imposing the conditions that the deviation in the global 21-cm signal $\Delta T_{21}$ does not exceed $50\mathrm{mK}$ at $z\sim 17$ or $15\mathrm{mK}$ at $z\sim 89$, and that no emission signal appears at $z\gtrsim 300$, we derive upper bounds on the MACHO fraction $f_M$ across the mass range $10^3\lesssim M_c/M_{\odot }\lesssim 10^7$. The dark ages and $z\gtrsim 300$ criterion yield constraints that are both tighter and free from astrophysical uncertainties associated with star formation, particularly $f_M=0.03$ for $M_c=10^7{M}_{\odot }$, providing a complementary cosmological window. The extended mass distributions yield bounds that are less stringent than those of their monochromatic counterparts.

    ↳ astro-ph.COastro-ph.GAhep-ph0 citations
42. 42*

    Suppressed Magnetogenesis from Ultralight Dark Matter due to Finite Conductivity

    Ramkishor Sharma🇮🇳 · Samarth Majumdar🇮🇳 · Divya Sachdeva🇮🇳

    Recently, a mechanism for generating astrophysically relevant magnetic fields via ultralight pseudoscalar dark matter, through the coupling term $g_{\varphi \gamma }\varphi F_{\mu \nu }{\tilde{F}}^{\mu \nu }$ in the Lagrangian density, was proposed in Brandenberger et al (2026) (see Ref. 1). In this scenario, the electromagnetic fields are amplified through the phenomena of parametric resonance due to the oscillatory behaviour of the pseudoscalar field. However, the analysis presented in that work does not account for the effects of a conducting medium. In this paper, we incorporate the finite conductivity of the plasma into the dynamics of the pseudoscalar and electromagnetic fields. We show that, due to the large conductivity relative to the Hubble parameter, the amplification of the electromagnetic fields due to parametric resonance is significantly suppressed. Consequently, we find that, for observationally viable values of the coupling between the electromagnetic field and the ultralight pseudoscalar field, it is not possible to generate magnetic fields of sufficient strength to explain their presence in cosmic voids.

    ↳ astro-ph.COhep-ph5 citations
43. 43*

    Isospin Decomposition of Vector and Axial Two-Body Currents via Polarized Electron--Deuteron and Electron--${}^3$He Scattering at the Electron-Ion Collider

    Guang Yang🇺🇸 · Praveen Kumar🇺🇸

    Two-particle two-hole (2p2h) excitations driven by meson-exchange currents (MEC) are among the leading nuclear uncertainties in long-baseline neutrino oscillation experiments. Three models currently implemented in neutrino event generators disagree by 20--40% on the $\omega$-integrated 2p2h cross section in the dip region on carbon (differential disagreements can reach factors of 2--3), and the axial two-body current has no direct experimental constraint beyond tritium $\beta$-decay at $Q^2=0$. We propose a measurement program at the Electron-Ion Collider (EIC) using polarized electron scattering on deuteron and ${}^3$He. Electromagnetic (EM) scattering (${\gamma }^{\ast }$ exchange) measures the vector MEC. Charged-current (CC) scattering ($W^{-}$ exchange) on the same targets measures the vector$+$axial MEC. Subtracting the two provides the first direct sensitivity to the axial two-body current, including the $V$--$A$ interference, as a function of momentum transfer. Using ${}^3$He (2~$pn$ $+$ 1~$pp$ pair) extends the decomposition to $pp$ pairs. Polarized beams and targets give access to six EM response functions on deuteron, four of which have not been previously measured. The tensor analyzing power provides a sign-flip test for $\Delta$-excitation MEC. We present projected sensitivities at $50f{b}^{-1}$ on deuteron ($\sim$5 years at $10^{33}$~cm${}^{-2}$s${}^{-1}$). The EM program can deliver $\sim 5\times 10^4$ events per $Q^2$ bin constraining the MEC transverse response to $\sim$2% per bin, the beam--target double-spin asymmetry reaches $6$--$13\sigma$ per bin, and the vector MEC $V_{pn}$ is measured to $\sim$6% per bin. The CC channel is statistics-limited, with $\sim$6--38 events per $Q^2$ bin at $50f{b}^{-1}$, requiring a luminosity upgrade beyond the current EIC baseline.

    ↳ nucl-exhep-ph0 citations
44. 44*

    Crystallography, Lorentz violation, and the Standard-Model Extension

    Marco Schreck🇧🇷 · Rogeres A. da Silva Magalhães

    The motivation behind the present work is to adopt methodology from field theory and high-energy physics to crystallography. In particular, we establish a relationship between the electromagnetic sector of the Standard-Model Extension (SME) for Lorentz invariance violation and optical media. At an effective level, electromagnetic properties associated with different crystal structures are demonstrated to be parametrized in the SME. Crystallographic and magnetic point groups provide the mathematical tools to show this correspondence. Birefringent and magnetoelectric media merit a dedicated study. Intriguing effects, which have not been described systematically in the modern literature, are rediscovered for the latter and expressed in SME language. With the setting developed at our disposal, materials with specific symmetries such as birefringent or multiferroic crystals serve as condensed-matter analogs for SME effects. It enables us to propose materials with unusual optical properties, which have not been thoroughly looked at in recent times.

    ↳ cond-mat.mes-hallcond-mat.mtrl-scihep-phhep-th1 citation
45. 45*

    Rotation-induced Relaxation of Supernova Constraints on Axionlike Particles

    Tsurugi Takata🇯🇵 · Kanji Mori🇯🇵 · Ko Nakamura🇯🇵 · Kei Kotake🇯🇵

    We study how rotation modifies the constraints on MeV-scale axion-like particles (ALPs) coupled to photons derived from SN 1987A. We constrain the ALP parameter space based on both the energy-loss argument and the gamma-ray limits, and examine how these constraints are affected by stellar rotation. Adopting initial angular velocities of ${\Omega }_0=0.0and1.0rad{s}^{-1}$ in the iron core, we carry out two-dimensional core-collapse supernova simulations for three progenitor models - a $14+9M_{\odot }$ binary and $13M_{\odot }$ and $18M_{\odot }$ single stars with solar metallicity - and estimate ALP emission rates through post-processing. We find that rotation suppresses ALP emission by reducing the core temperature via centrifugal support. Rotation also reduces the neutrino luminosity, but the suppression of ALP emission is more effective, leading to relaxed constraints within a simplified criterion based on the energy-loss argument. This relaxation is particularly pronounced in the rotating $18M_{\odot }$ model, where a substantial decrease in the central temperature occurs at $t_{pb}=0.8-1s$. In this simplified criterion, such rapid temporal variations in temperature indicate that the resulting constraints depend sensitively on both the evaluation time and the underlying supernova model. For a gamma-ray limit from the SN 1987A observation, rotation has a negligible impact on the constraint. This is because the ALP-induced gamma-ray fluence observed at Earth is proportional to the fourth power of the ALP-photon coupling constant, making the constraint relatively insensitive to the rotational suppression of ALP emission.

    ↳ astro-ph.HEhep-phPRD(2026)·1 citation
46. 46*

    In-depth analysis of the clustering of dark matter particles around primordial black holes. Part III: CMB constraints

    Julien Lavalle🇫🇷 · Vivian Poulin🇫🇷 · Pierre Salati🇫🇷

    In a mixed dark matter scenario in which primordial black holes (PBHs) would co-exist with thermally produced self-annihilating particles, one expects the former to be surrounded by extremely dense halos made of the latter, built up during radiation domination. Here, as a continuation of previous work, we derive observational limits on such a scenario from a full statistical analysis of cosmic microwave background (CMB) data. We quantify how a tiny fraction $\text{fbh}$ of PBHs could restrict the parameter space available to thermal particle dark matter, limiting the $s$-wave annihilation cross section to values $\lesssim 10^{-30}\mathrm{c}{\mathrm{m}}^3/s(\text{mchi}/100\mathrm{GeV})(\text{fbh}/10^{-6}{)}^{-3}$ if PBHs are typically heavier than $\sim 10^{-10}\text{Msun}$, which can also be turned into constraints on PBHs in this mass range. In contrast, asteroid mass or lighter PBHs could live in perfect peace with these particles. Finally, we shortly discuss the implications of the recent tentative interpretation of Subaru-HSC microlensing events as PBHs.

    ↳ astro-ph.COhep-phJCAP(2026)·3 citations
47. 47*

    Remarks on MAMI's recent determination of $B_{\Lambda }({}_{\Lambda }^3\mathrm{H})$

    Avraham Gal🇮🇱

    A recent report on ${}^7\mathrm{Li}(e,e^{\prime }{K}^{+})$ electroproduction runs by the A1 collaboration at the Mainz Microtron (MAMI) assigns a sharp pion-momentum line at $p_{{\pi }^{-}}\approx 113.8\pm 0.1$ MeV/c to ${}_{\Lambda }^3\mathrm{H}\to {\pi }^{-}+{}^3\mathrm{He}$ weak decay, resulting in exceptionally large ${}_{\Lambda }^3\mathrm{H}$ binding-energy $B_{\Lambda }({}_{\Lambda }^3\mathrm{H})=0.523\pm 0.013\pm 0.075$ MeV. Here I discuss an alternative interpretation of the observed sharp line in terms of ${}_{\Lambda }^7{\mathrm{He}}_{g.s.}\to {\pi }^{-}+{}^7\mathrm{Li}(E_{\mathrm{x}}=478$ keV) weak decay and its implications for $B_{\Lambda }({}_{\Lambda }^7\mathrm{He})$.

    ↳ nucl-thhep-phnucl-ex2 citations
48. 48*

    Classical and quantum evolution of inflationary fluctuations

    Guillermo Ballesteros🇪🇸 · Jesús Gambín Egea🇪🇸 · Alejandro Pérez Rodríguez🇺🇸

    We compare the correlation functions of inflationary perturbations computed either with quantum or classical dynamics. Even if they are enforced to agree at a specific time during inflation, classical and quantum correlations will differ at the end of inflation, provided that interactions are relevant. The difference between the results of the classical and quantum computations is exponentially sensitive to the number of e-folds elapsed from the time of agreement. We illustrate this finding with the tree-level bispectrum of the primordial curvature fluctuation and the one-loop power spectrum of tensor modes. We also show that classical evolution from a finite time does not imply the appearance of poles in the scalar bispectrum.

    ↳ hep-thastro-ph.COgr-qchep-ph4 citations
49. 49*

    Classically Forbidden Signatures of Quantum Coherence in the Mesoscopic Lipkin-Meshkov-Glick Model

    Stavros Mouslopoulos

    We derive strict quantitative conditions under which a collective quantum system of N~370 spins exhibits classically forbidden temporal correlations in a spinor Bose-Einstein condensate (BEC). The Lipkin-Meshkov-Glick (LMG) model near its Z_2-breaking quantum critical point supports a mesoscopic superposition a|P> + b|R> of two macroscopic ordered phases (|P>: m_z ~ +m_*; |R>: m_z ~ -m_*) at the Goldilocks crossover N ~ N_c, where the tunnel splitting equals k_B T and macroscopic susceptibility chi ~ N coexists with finite quantum coherence. We establish two quantum-discriminating predictions. P4 (Landau-Zener crossover, proposed discriminator): quantum tunnelling drives P_error -> 0 exponentially with quench time, while the classically non-ergodic system remains kinetically frozen at P_error -> 1 - a parametrically large, computable separation that rests on a specific kinetic foil. P5 (Leggett--Garg inequality violation, strictly model-independent): K_3 > 1 is forbidden by macrorealism for all classical models satisfying non-invasive measurability. A five-level Lindblad simulation yields K_3 ~ 1.32 and dephasing threshold gamma_phi < 0.289 s^{-1} at the BEC target (gamma_phi = 0.05 s^{-1}, N = 370, Gamma/J = 0.95) - a margin of 8.8x above the optimal measurement interval, well within current experimental reach. The threshold has a precise physical origin in the emergent collective Z_2 symmetry: exact parity eliminates the dominant dephasing cross-term and renders the LGI correlator immune to T_1 population mixing without requiring ground-state preparation (2.35x improvement over the naive mean-field estimate); constructive dynamical phase alignment of higher odd-parity states at the benchmark parameters contributes a further 2.47x. All results are reproducible from the provided self-tested Python code.

    ↳ quant-phhep-phhep-th1 citation
50. 50*

    It's all in your head -- fine-tuning arguments do not require aleatoric uncertainty

    Andrew Fowlie🇨🇳

    Prompted by misconceptions in the recent literature, we review the justifications for naturalness arguments and Occam's razor found in Bayesian statistics. We discuss the automatic Occam's razor that emerges in Bayesian formalism, bringing together points of view from diverse fields, including statistics, social sciences, physics and machine learning. In pedagogical calculations, we demonstrate that this automatic razor disfavors unnatural models in which predictions must be fine-tuned to agree with observation.

    ↳ physics.hist-phhep-phphysics.data-anSynthese(2026)·0 citations
51. 51*

    Tree Amplitudes with Charged Matter in Pure Gauge Theory

    Jacob L. Bourjaily🇺🇸 · Michael Plesser🇺🇸 · Philip Velie🇺🇸

    We describe the implementation and usage of `fermionic_amplitudes.m', a Mathematica package for the computation of tree amplitudes involving arbitrary numbers of gauge bosons and arbitrarily-charged massless fermions of (possibly) distinct flavours in pure (non-supersymmetric) gauge theory. These are given in terms of a basis of partial amplitudes involving distinct-flavoured fermions dressed by specific colour tensors. Distinct-flavour partial amplitudes are expressed as linear combinations of those involving only a single flavour, which may be evaluated as component amplitudes of (maximally) supersymmetric Yang-Mills theory. All relevant colour tensors can be realized as explicit, numeric arrays given any choice of charge generators (for any gauge theory -- including $u_1$); from these, all colour contractions relevant to cross sections may be readily computed. The complete package and a notebook demonstrating its primary usage and functionality are included in this work's submission's ancillary files on the arXiv.

    ↳ hep-thhep-ph0 citations
52. 52*

    The KM3NeT event: a primordial high energy neutrino?

    Nicolas Grimbaum Yamamoto🇧🇪 · Thomas Hambye🇧🇪

    High energy neutrinos can be injected in the early Universe from the decay or annihilation of long lived primordial relics. We analyse the possibility that the ultrahigh energy neutrino event recently observed by the KM3NeT neutrino telescope could have such an origin. This possibility has the advantage of leading to a sharp spectral feature in a way that the neutrino flux can be small at all energies except at the KM3NeT event energy. Thus, along this scenario the tension with null results from other experiments is reduced with respect to the usual power law case analysed by the KM3NeT and IceCube experiments. At such energies and for an emission around the recombination time, interactions of these neutrinos with background neutrinos prove to be relevant and must be determined from the development of a dedicated code. These interactions, as well as final state radiation processes, modify the spectrum. Interestingly, it turns out that the scenario can also leave an imprint in the CMB that could be probed in the near future. Interestingly too, this scenario does not predict an associated $\gamma$-ray flux beyond observation. All in all we do find that the high energy neutrino could be a primordial high energy neutrino, provided it has been produced around the recombination time or later.

    ↳ astro-ph.HEastro-ph.COhep-ph3 citations

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