Fri·Feb 14, 2025Friday·February 14, 2025

1. 01*

   Revisiting Gauge Ambiguities for DUNE Precision

   Joshua Isaacson🇺🇸

   The de Forest prescription for handling off-shell initial states in the impulse approximation for lepton-nucleus scattering breaks gauge invariance. We discuss existing methods to address this problem and handle the form factor scale ambiguity. We demonstrate that the irreducible differences between the prescriptions are significant compared to the precision expected of next-generation accelerator neutrino experiments. A novel approach directly using the off-shell currents is proposed as a systematically improvable alternative.

   hep-phhep-exnucl-th1 citation
2. 02*

   Dark Energy from Time Crystals

   Laura Mersini-Houghton🇺🇸

   In this work, we analyze a scalar field model which gives rise to stable bound states in field space characterized by nonzero motion that breaks the underlying time translation symmetry of its Hamiltonian, known as time crystals. We demonstrate that an ideal fluid made up of these time crystals behaves as phantom dark energy characterized by an equation of state $w\le -1$, speed of sound squared $c_s^2>0$, and nonnegative energy density $\rho \ge 0$.

   hep-phgr-qchep-thMathematics(2025)·4 citations
3. 03*

   Probing Gluon Shadowing in Heavy Nuclei through Bayesian Reweighting of J/$\psi$ Photoproduction in Ultra-Peripheral Collisions

   Pengzhong Lu🇨🇳 · Zebo Tang🇨🇳 · Xin Wu🇨🇳 · Wangmei Zha🇨🇳

   The gluon distribution in nuclei plays a pivotal role in understanding quantum chromodynamics (QCD) under extreme nuclear environments, yet remains poorly constrained compared to quark distributions. Coherent \jpsi photoproduction in ultra-peripheral heavy-ion collisions ($\gamma +A\to \mathrm{J}/\psi +A$) provides a unique solution to this challenge, serving as a sensitive probe of nuclear gluon densities. In this study, we perform Bayesian reweighting on the EPPS21 and nCTEQ15 sets of nuclear parton distribution functions (nPDF) by incorporating coherent \jpsi photoproduction measurements from both RHIC and LHC. The Bayesian-reweighted gluon modification factors ${\mathrm{R}}_{\mathrm{g}}^{\mathrm{A}}(x,Q^2=2.4{\mathrm{GeV}}^2)$ reveal pronounced nuclear shadowing in the Pb nuclei, with ${\mathrm{R}}_{\mathrm{g}}^{\mathrm{Pb}}\approx 0.60$ at $x=10^{-4}$, while simultaneously achieving a great reduction of the uncertainties in the density of the gluon across the critical Bjorken-$x$ range $10^{-5}<x<10^{-3}$ compared to initial predictions of the nPDF. This work establishes coherent \jpsi photoproduction as a precision tool for gluon nPDF extraction, overcoming traditional deep-inelastic scattering limitations through perturbative QCD-calibrated probes. The constrained nPDFs demonstrate improved consistency with the experimental data across collider energies, particularly in the shadowing-dominated regime.

   hep-phhep-ex1 citation
4. 04*

   Precision tools for the simulation of double-Higgs production via vector-boson fusion

   Barbara Jäger🇩🇪 · Alexander Karlberg🇨🇭 · Simon Reinhardt🇩🇪

   We present two precision tools for the simulation of Higgs-pair production via vector-boson fusion in the kappa framework for the parameterization of non-standard Higgs couplings. A new implementation of the process is developed in the framework of the POWHEG BOX program that can be used to provide predictions at the next-to-leading order (NLO) of QCD matched to parton showers (PS). In addition, the existing proVBFHH program for the computation of next-to-next-to-leading order (NNLO) QCD and next-to-next-to-next-to-leading order QCD corrections is extended to account for values of the Higgs couplings different from the expectation of the Standard Model. We systematically compare and analyse predictions obtained with the two programs and find that the NLO+PS predictions provide a good approximation of the NNLO results for observables of the tagging jets and Higgs bosons. The results turn out to be very sensitive to the values of the modified Higgs couplings. Finally we study the non-factorizable NNLO QCD corrections to the process in the presence of anomalous couplings. We find that the size of the non-factorizable corrections is very sensitive to the anomalous couplings.

   hep-phhep-exJHEP(2025)·12 citations
5. 05*

   Double Higgs Production in Vector Boson Fusion at NLO QCD in HEFT

   Jens Braun🇩🇪 · Pia Bredt🇩🇪 · Gudrun Heinrich🇩🇪 · Marius Höfer🇩🇪

   We present the next-to-leading order QCD corrections to Higgs boson pair production in vector boson fusion, including the leading operators in the framework of Higgs Effective Field Theory (HEFT). The corresponding calculation is based on an automated interface between the Monte Carlo event generator Whizard and the one-loop amplitude generator GoSam. The QCD corrections also include non-factorising diagrams and diagrams of Higgs-Strahlung type, thus going beyond the structure function approach. We find that some constellations of anomalous couplings, while being well within the current experimental constraints, can have a significant impact on the shape of typical observables for this process.

   hep-phJHEP(2025)·18 citations
6. 06*

   Rare $W\to B_c+\gamma$ decay up to the NNLO and NLL accuracy in QCD

   Xin-Qiang Li🇨🇳 · Ya-Dong Yang🇨🇳 · Yu-Dong Zhang🇨🇳 · Dong-Hui Zheng

   We perform a detailed theoretical study of the rare radiative decay of the $W$ boson into a $B_c$ meson and an on-shell photon. The decay amplitude is described by two independent form factors, which are calculated up to the next-to-next-to-leading order (NNLO) in QCD within the nonrelativistic QCD (NRQCD) factorization formalism. Since the two typical energy scales, the $W$-boson mass $m_W$ and the $B_c$-meson mass $m_{B_c}$, involved in the process are widely separated, large logarithms of $m_W^2/m_{B_c}^2$ present in the NRQCD short-distance coefficients are also resummed to all orders in ${\alpha }_s$ up to the next-to-leading logarithmic (NLL) accuracy, by employing the light-cone factorization approach. Taking into account all these corrections, we then perform a phenomenological exploration of this rare decay. It is found that, relative to the leading-order result, the decay width of the process is reduced by the next-to-leading-order and NNLO corrections, with a net effect of $\sim 19\%$ and of $\sim 31\%$, respectively. Furthermore, the NLL resummation can considerably alter the fixed-order NRQCD predictions, especially for the $\mathcal{O}({\alpha }_s)$ correction. We also find that the radiative corrections increase the renormalization scale dependence of the branching fraction, which is however significantly reduced by the NLL resummation. The dependence of the branching fraction on the heavy-quark masses $m_{b,c}$ is also investigated, which shows a monotonic decrease (increase) with $m_c$ ($m_b$).

   hep-phJHEP(2025)·0 citations
7. 07*

   Spectral diversity in collisional neutrino-flavor conversion: flavor equipartition or swap

   Masamichi Zaizen🇯🇵

   Quantum kinetics of neutrinos are known to potentially change the classical neutrino radiation field in high-energy astrophysical sources such as core-collapse supernovae and binary neutron-star mergers. However, the mixing phenomena still have open issues in the nonlinear dynamics and the asymptotic states, particularly for recently discovered collision-induced flavor conversion. In this paper, we investigate linear and nonlinear dynamics of collisional neutrino-flavor conversion (CFC) with multi-energy neutrino gases through numerical simulations, demonstrating that the asymptotic states dramatically change depending on unstable modes dominating the system. In one unstable mode, high-energy neutrinos reach a flavor equipartition, but low-energy neutrinos return back to almost their initial states. In contrast, in the other one, rather low-energy neutrinos achieve a full flavor swap, but high-energy neutrinos undergo less flavor conversion. We clarify the distinct spectral behaviors in two different ways based on stability analysis and flavor pendulum. Our result suggests that CFC with flavor swap can become crucial at deeper radii with low electron fraction and requires more detailed theoretical modeling of neutrino quantum kinetics.

   hep-phastro-ph.HEPRD(2025)·16 citations
8. 08*

   Emergent large flavor mixing from canonical and inverse seesaws?

   Zhi-zhong Xing🇨🇳

   While the canonical seesaw mechanism provides a most natural qualitative interpretation of tiny masses for the three active neutrinos, it offers no explanation for their large flavor mixing effects. The latter can be regarded as an emergent consequence of this mechanism, in which case we are left with an intriguing cross seesaw framework in the mass basis of all the six Majorana neutrinos. To lower the mass scales of heavy neutrinos, one is motivated to invoke the inverse seesaw mechanism but has to pay the price for a fine-tuned cancellation between its two sets of new degrees of freedom, in which case the largeness of active flavor mixing is an emergent phenomenon as well. A comparison between the approximate seesaw relations in the flavor basis and those exact ones in the mass basis is also made.

   hep-phhep-exhep-thNPB(2025)·2 citations
9. 09*

   Power corrections to the production of a color-singlet final state in hadron collisions in the N-jettiness slicing scheme at NLO QCD

   Prem Agarwal🇩🇪 · Kirill Melnikov🇩🇪 · Ivan Pedron🇩🇪 · Philip Pfohl🇩🇪

   We compute next-to-leading power corrections in the zero-jettiness variable for the production of colorless final states at hadron colliders at next-to-leading order in QCD. To assess if the process-independence of leading power contributions can be extended, we attempt to construct generic expansions of phase spaces and matrix elements squared through next-to-leading power in the zero-jettiness. We highlight challenges associated with the collinear limit, where universality no longer holds at the subleading power, making the result process-dependent. We show that quantities that need to be calculated in the collinear limit can be obtained using Berends-Giele currents, enabling computation of power corrections to high-multiplicity final states. As a concrete example, we apply our method to compute power corrections in the zero-jettiness for lepton pair as well as multi-photon production in $q\bar{q}$ collisions.

   hep-phJHEP(2025)·4 citations
10. 10*

    Non-renormalizable grand unification utilizing the leptoquark mechanism of neutrino mass

    Çağlar Doğan🇹🇷

    We analyze a non-supersymmetric, non-renormalizable grand unified theory whose particle content is that of the Georgi-Glashow model augmented only by scalars from the \textbf{10} and \textbf{35} representations. A prediction of our model is a color sextet, weak isodoublet whose mass lies at 1 TeV (10 TeV) and that does not couple to Standard Model fermions at tree level. The leptoquark mechanism through which Majorana neutrinos radiatively acquire their masses relates the neutrino mass matrix to that of the down-type quarks. A consequence of this relation and perturbativity of coupling constants is the upper bound of $2.5\times 10^{15}$ GeV on the masses of the scalar leptoquarks $S_1^{\ast }$ and ${\tilde{R}}_2$. Electroweak mixing of these leptoquarks induces a B-L violating decay of the proton which indirectly contrains the mass of ${\tilde{R}}_2$ to be greater than $2.1\times 10^9$ GeV. We find the grand unification scale to exceed $1.4\times 10^{16}$ GeV in all scenarios considered.

    hep-phPTEP(2025)·1 citation
11. 11*

    Investigation of full heavy $QQQ{Q}^{\prime }\bar{Q}$ pentaquark candidates

    K. Azizi🇮🇷 · Y. Sarac🇹🇷 · H. Sundu🇹🇷

    Recent breakthroughs in research and experimentation have led to the identification of numerous exotic states in particle physics. Each new discovery not only sparks excitement for future findings but also fuels interest in uncovering additional unknown states. Motivated by this perspective and the recent identification of both standard and exotic hadrons with an increasing number of heavy quarks, this study conducts a spectroscopic analysis of possible pentaquark candidates with spin-parity ${\frac{1}{2}}^{-}$, and quark content of $cccb\bar{c}$ and $bbbc\bar{b}$. The masses of these states are calculated by considering the relevant Lorentz structures, including $\text{slashed}p$ and $\text{mathbbm}1$, yielding the following results, respectively: for the $P_{(4cb)}$ state, $m_{P_{(4cb)}}=11388.30\pm 107.79$~MeV and $m_{P_{(4cb)}}=11368.30\pm 112.68$~MeV, and for the $P_{(4bc)}$ state, $m_{P_{(4bc)}}=20998.30\pm 121.52$~MeV and $m_{P_{(4bc)}}=20990.50\pm 125.87$~MeV. Additionally, the current coupling constants of these states to the vacuum, which are essential for analyzing their potential decay modes, are also provided in this study.

    hep-phhep-exhep-latEPJC(2025)·4 citations
12. 12*

    Communicating Likelihoods with Normalising Flows

    Jack Y. Araz🇺🇸 · Anja Beck🇺🇸 · Méril Reboud🇫🇷 · Michael Spannowsky🇬🇧 · Danny van Dyk🇬🇧

    We present a machine-learning-based workflow to model an unbinned likelihood from its samples. A key advancement over existing approaches is the validation of the learned likelihood using rigorous statistical tests of the joint distribution, such as the Kolmogorov-Smirnov test of the joint distribution. Our method enables the reliable communication of experimental and phenomenological likelihoods for subsequent analyses. We demonstrate its effectiveness through three case studies in high-energy physics. To support broader adoption, we provide an open-source reference implementation, nabu.

    hep-phcs.LGhep-exphysics.data-anEPJC(2026)·2 citations
13. 13*

    Neutrino Masses and Phenomenology in Nnaturalness

    Manuel Ettengruber🇫🇷

    In this paper, it is shown that $N$naturalness scenarios share the intrinsic mechanism to suppress neutrino masses with other infrared neutrino mass models. In such models like extra-dimensional theories or many species theories, the large number of mixing partners is responsible for the neutrino mass suppression. It is shown how neutrino mass matrices arise in $N$naturalness models and the resulting neutrino mixing is analyzed. The first result is that a totally democratic coupling among the different sectors like in the original models is already ruled out by the fact that neutrinos are not massless. In the case where the sector couplings deviate from the intersector ones a tower of additional neutrino mass eigenstates appears whose difference between the squared masses, $\Delta m_{ij}^2$, is determined fully by the theory. The resulting phenomenology of such a tower is investigated and the unique signals in neutrino oscillation experiments, neutrino mass measurements, and neutrinoless double beta decay experiments are discussed. This opens the door for terrestrial tests of $N$naturalness whose phenomenology was so far focused on Cosmology.

    hep-phhep-exhep-thPRD(2025)·6 citations
14. 14*

    Explainable AI-assisted Optimization for Feynman Integral Reduction

    Zhuo-Yang Song🇨🇳 · Tong-Zhi Yang🇨🇭 · Qing-Hong Cao🇨🇳 · Ming-xing Luo🇨🇳 · Hua Xing Zhu🇨🇳

    We present a novel approach to optimizing the reduction of Feynman integrals using integration-by-parts identities. By developing a priority function through the FunSearch algorithm, which combines large language models and genetic algorithms, we achieve significant improvements in memory usage and computational efficiency compared to traditional methods. Our approach demonstrates substantial reductions in the required seeding integrals, making previously intractable integrals more manageable. Tested on a variety of Feynman integrals, including one-loop and multi-loop cases with planar and non-planar configurations, our method demonstrates remarkable scalability and adaptability. For reductions of certain Feynman integrals with many dots and numerators, we observed an improvement by a factor of 3058 compared to traditional methods. This work provides a powerful and interpretable framework for optimizing IBP reductions, paving the way for more efficient and practical calculations in high-energy physics.

    hep-phhep-thJHEP(2026)·31 citations
15. 15*

    Ultra-high-energy event KM3-230213A constraints on Lorentz Invariance Violation in neutrino sector

    Petr Satunin🇷🇺

    We discuss the constraints on superluminal neutrino Lorentz Invariance Violation (LIV) parameters from the observation of the ultra-high-energy event KM3-230213A by KM3NeT collaboration in cases of linear $n=1$ and quadratic $n=2$ LIV scenarios. Assuming extragalactic origin of the event, we obtain the constraints on LIV mass scale ${\Lambda }_{n=1}=1.1\times 10^{30}\text{mbox}GeV$ and ${\Lambda }_{n=2}=1.1\times 10^{19}\text{mbox}GeV$ from the absence of neutrino splitting.

    hep-phastro-ph.HEEPJC(2025)·21 citations
16. 16*

    Cosmological phase transitions from the functional measure

    Bruno Berganholi🇧🇷 · Gláuber C. Dorsch🇧🇷 · Iberê Kuntz🇧🇷 · Beatriz M. D. Sena🇧🇷 · Giovanna F. do Valle🇧🇷

    We investigate how competitive gravitational wave detectors can be to current and near-future colliders in probing a model where the new physics is completely encapsulated in a modified scalar sector. For this, we study a model where an additional logarithmic term arises in the scalar potential due to a non-trivial path integral measure, which is constructed using effective field theory. This new term alters the dynamics of cosmological phase transitions and could lead to potentially detectable gravitational waves from the early Universe. Our results confirm the expectation that the intensity of such spectrum is highly correlated to the scalar field's self-coupling, and that gravitational wave experiments could therefore be used to probe these couplings with an accuracy competitive with the projected sensitivity of near-future colliders.

    hep-phhep-thJHEP(2025)·4 citations
17. 17*

    $B\to K+$invisible, dark matter, and $CP$ violation in hyperon decays

    Xiao-Gang He🇨🇳 · Xiao-Dong Ma🇨🇳 · Jusak Tandean🇨🇳 · German Valencia🇦🇺

    Recently the Belle II Collaboration has reported a measurement of the $B^{+}\to K^{+}\nu \bar{\nu }$ rate that is higher than the standard-model expectation. Since the emitted neutrinos are unobserved, the excess could be due to the $B^{+}$ decaying into a $K^{+}$ and a dark-matter pair. We entertain this possibility in a two-Higgs-doublet model supplemented with a real singlet scalar boson acting as the dark matter. This model also accommodates strangeness-changing interactions providing new sources of $CP$ violation which can affect hyperon and kaon nonleptonic transitions. We find that the resulting $CP$ violation in the hyperon sector can be significant, reaching the current empirical bounds, after taking into account constraints from kaon mixing and decay and from dark-matter relic-density data and direct searches including the Migdal effect. We demonstrate that the hyperon and kaon processes are complementary probes of this new-physics scenario. Its prediction for sizable hyperon $CP$ violation is potentially testable in ongoing experiments, such as BESIII, Belle II, and LHCb, and in next-generation ones like PANDA and at the Super Tau Charm Facility.

    hep-phhep-exJHEP(2025)·18 citations
18. 18*

    Modified Homotopic approach for diffractive production

    Carlos Contreras🇨🇱 · José Garrido🇨🇱 · Eugene Levin🇮🇱 · Rodrigo Meneses🇨🇱

    We review the recent developments of the use of the homotopy method for solving the non-linear evolution equation for the diffractive production in deep inelastic scattering. We introduce part of the non-linear corrections in the linear term. This simplified non-linear evolution equation is solved analytically taking into account the initial and boundary conditions for the process. It turns out that these corrections are rather small and can be estimated in the regular iterative procedure.

    hep-phnucl-thActa Phys.Polon.Supp.(2025)·0 citations
19. 19*

    From ADONE's multi-hadron production to the $J/\Psi$ discovery

    Mario Greco (Department of Mathematics and Physics and INFN, University of Roma Tre, Rome, Italy)🇮🇹

    The physics at Frascati in the years 60's - 70's is reviewed together with the $J/\Psi$ discovery.

    hep-phHiHEP(2025)·0 citations
20. 20*

    Wigner multiplets in QFT: dark sector and CPT-violating scenarios

    Cheng-Yang Lee🇨🇳 · Ruifeng Leng🇨🇳 · Siyi Zhou🇨🇳

    The classification of elementary particles based on unitary irreducible representations of the Poincare group has been a cornerstone of modern Quantum Field Theory (QFT). While the Standard Model (SM) does not inherently include Dark Matter (DM), any fundamental DM candidate should still conform to this classification or its extensions. Beyond the standard representations, Wigner introduced a class of nontrivial states characterized by an additional discrete degree of freedom, known as the Wigner degeneracy. We systematically investigate the QFT of such Wigner degenerate multiplets, particularly focusing on the massive spin-1/2 case. We construct a theoretical framework where the two-fold Wigner spinor fields, ${\psi }_{\pm \frac{1}{2}}(x)$, form a doublet representation. We analyze their transformation properties under discrete symmetries (C, P, and T), revealing novel mixing effects due to Wigner degeneracy and an emergent accidental U(2) global symmetry. Furthermore, we explore their Yukawa and gauge interactions, demonstrating that such interactions generally break the CPT symmetry. However, we derive conditions for the CPT conservation and discuss potential phenomenological consequences beyond the SM. These results provide new insights into the possible role of Wigner-degenerate states in fundamental physics, particularly in the dark sector.

    hep-phhep-thJHEP(2025)·1 citation
21. 21*

    Custodial Naturalness

    Thede de Boer🇩🇪 · Manfred Lindner🇩🇪 · Andreas Trautner🇩🇪

    Custodial Naturalness is a new symmetry-based idea to explain the large separation between the electroweak (EW) scale and ultraviolet completions of the Standard Model (SM). Classical scale invariance is combined with an enhanced scalar-sector custodial symmetry and both are spontaneously broken by dimensional transmutation at a new intermediate scale. The SM-like Higgs boson is an elementary pseudo-Nambu-Goldstone-Boson (pNGB) of the extended custodial symmetry, which naturally explains the suppression of the EW scale without a little hierarchy problem. We explain details of the general mechanism, its minimal realization and simplest extensions which populate Higgs-, gauge-, and neutrino portals and introduce candidates for particle Dark Matter (DM). We show the stability of the mechanism under inclusion of new sources of explicit custodial symmetry violation, as well as under variations of boundary conditions at the high scale. Custodial Naturalness is experimentally testable - including a specific correlation between the Higgs and top quark masses, as well as by the prediction of a new heavy $Z^{\prime }$ gauge boson and a new dilaton-like scalar which are well-motivated targets for future colliders and Higgs factories. The cosmological evolution features a strongly supercooled phase transition implying that consequences of Custodial Naturalness may also be tested by gravitational wave observatories.

    hep-phhep-exJHEP(2025)·6 citations
22. 22*

    Internal color contributions to flux tube entanglement entropy

    Rocco Amorosso🇺🇸 · Sergey Syritsyn🇺🇸 · Raju Venugopalan🇺🇸

    In recent work arXiv:2410.00112, we introduced and computed entanglement entropy of the color flux tube (FTE${}^2$) between a heavy quark-antiquark pair in (2+1)D Yang-Mills theory. Our numerical results suggest that FTE${}^2$ can be partitioned into a component corresponding to transverse vibrations of the flux tube and an internal color entropy. Further, motivated by analytical (1+1)D calculations, and SU(2) (2+1)D Yang-Mills numerical results, we argued that the internal entropy takes the form $⟨F⟩\log (N_c)$, with $⟨F⟩$ the number of times, on average, that the flux tube crossed a boundary between region $V$ and its complement. We extend here our FTE${}^2$ study to consider different geometries of region $V$, varying the number of boundary crossings, and number of colors. Our preliminary results support the conjectured form of the internal entropy, albeit with noteworthy subtleties relating to the partial/full intersections of the flux tube with the region $V$.

    ↳ hep-lathep-phhep-thnucl-thPoS(2025)·4 citations
23. 23*

    CP violation studies at Super Tau-Charm Facility

    Hai-Yang Cheng🇹🇼 · Zhi-Hui Guo🇨🇳 · Xiao-Gang He🇨🇳 · Yingrui Hou🇨🇳 · Xian-Wei Kang🇨🇳 · Andrzej Kupsc🇸🇪 · Ying-Ying Li🇨🇳 · Liang Liu🇨🇳 · Xiao-Rui Lyu🇨🇳 · Jian-Ping Ma🇨🇳 · Stephen Lars Olsen🇰🇷 · Haiping Peng🇨🇳 and 7 other authors

    Charge-parity ($CP$) violation in the tau-charm energy region is a promising area for sensitive tests of Standard Model (SM) predictions and searches for new, beyond the SM physics. A future Tau-Charm Facility that operates at center-of-mass energies between 2.0 and 7.0 GeV, with a peak luminosity of $0.5\times 10^{35}$~cm${}^{-2}$s${}^{-1}$, would provide huge numbers of hadrons and tau ($\tau$) leptons that are produced in low-background environments and with well understood kinematic properties. In this report, prospects for unique studies of $CP$ violation in the decay of charmed hadrons, and in the production and decay of hyperons and $\tau$ leptons at a next-generation tau-charm facility are discussed. In addition, opportunities for improved tests of $CPT$ invariance test in $K^0-{\bar{K}}^0$ mixing are presented.

    ↳ hep-exhep-ph12 citations
24. 24*

    Searching for axion dark matter gegenschein of the Vela supernova remnant with FAST

    Wenxiu Yang🇯🇵 · Yitian Sun🇨🇦 · Yougang Wang🇯🇵 · Katelin Schutz🇨🇦 · Yichao Li🇺🇸 · Calvin Leung🇺🇸 · Wenkai Hu🇿🇦 · Shuanghao Shu🇨🇳 · Kiyoshi Masui🇺🇸 · Xuelei Chen🇯🇵

    Axions are one of the leading dark matter candidates. If we are embedded in a Milky Way dark matter halo comprised of axions, their stimulated decay would enable us to observe a counterimage (``axion gegenschein") with a frequency equal to half the axion mass in the opposite direction of a bright radio source. This spectral line emission will be broadened to $\Delta \nu /\nu \sim {\sigma }_d/c\sim 10^{-3}$ due to the velocity dispersion of dark matter, ${\sigma }_d$. In this pilot study, we perform the first search for the expected axion gegenschein image of Vela supernova remnant (SNR) with 26.4 hours of effective ON-OFF data from the Five-hundred-meter Aperture Spherical radio Telescope (FAST) L-band (1.0 - 1.5~GHz) 19-beam receiver. Our null detection limits the axion-photon coupling strength to be $g_{a\gamma \gamma }\lesssim 2\times 10^{-10}{\mathrm{GeV}}^{-1}$ in the mass ranges of $8.7\mu \mathrm{eV}\le m_a\le 9.44\mu \mathrm{eV}$ and $10.85\mu \mathrm{eV}\le m_a\le 12.01\mu \mathrm{eV}$. These results provide a stronger constraint on $g_{a\gamma \gamma }$ in this axion mass range than the current limits obtained by the direct search of axion decay signal from galaxy clusters which uses FAST observations, but is a factor of $\sim 3$ times weaker than the current CAST limit.Based on our observation strategy, data processing methods, and results, the expected sensitivity will reach $\sim 10^{-11}{\mathrm{GeV}}^{-1}$ with $\sim 2000$ hours of observation in the future.

    ↳ astro-ph.COhep-phApJ(2025)·4 citations
25. 25*

    First Look at Quartic-in-Spin Binary Dynamics at Third Post-Minkowskian Order

    Dogan Akpinar🇬🇧 · Fernando Febres Cordero🇺🇸 · Manfred Kraus🇲🇽 · Alexander Smirnov🇷🇺 · Mao Zeng🇬🇧

    We compute the conservative and radiation-reaction contributions to classical observables in the gravitational scattering between a spinning and a spinless black hole to the fourth order in spin and third order in the gravitational constant. The conservative results are obtained from two-loop amplitudes for the scattering process of a massive scalar with a massive spin-$s$ field $(s=0,1,2)$ minimally coupled to gravity, employing the recently introduced spin interpolation method to resolve all spin-Casimir terms. The two-loop amplitude exhibits a spin-shift symmetry in both probe limits, which we conjecture to be a sign of yet unknown integrability of Kerr orbits through the quartic order in spin and to all orders in the gravitational constant. We obtain the radial action from the finite part of the amplitude and use it to compute classical observables, including the impulse and spin kick. This is done using the recently introduced covariant Dirac brackets, which allow for the computation of classical scattering observables for general (non-aligned) spin configurations. Finally, employing the radiation-reaction amplitude proposed by Alessio and Di Vecchia, together with the Dirac brackets, we obtain radiation-reaction contributions to observables at all orders in spin and beyond the aligned-spin limit. We find agreement with known results up to the quadratic order in spin for both conservative and radiation-reaction contributions. Our results advance the state of the art in the understanding of spinning binary dynamics in general relativity and demonstrate the power and simplicity of the Dirac bracket formalism for relating scattering amplitudes to classical observables.

    ↳ hep-thgr-qchep-phPRL(2025)·38 citations
26. 26*

    Numerical evidence for a CP broken deconfined phase at $\theta =\pi$ in 4D SU(2) Yang-Mills theory through simulations at imaginary $\theta$

    Mitsuaki Hirasawa🇮🇹 · Masazumi Honda🇯🇵 · Akira Matsumoto🇯🇵 · Jun Nishimura🇯🇵 · Atis Yosprakob🇯🇵

    We investigate the possibility of the spontaneous breaking of CP symmetry in 4D SU(2) Yang-Mills at $\theta =\pi$, which has recently attracted much attention in the context of the higher-form symmetry and the 't Hooft anomaly matching condition. Here we provide a numerical evidence that the CP symmetry is indeed spontaneously broken at low temperature and it gets restored above the deconfining temperature at $\theta =\pi$, which is consistent with the anomaly matching condition and yet differs from the situation predicted in the large-$N$ limit. We avoid the severe sign problem by performing simulations at imaginary $\theta$. We obtain the critical temperature of the CP restoration and that of deconfinement at $\theta =\pi$ by analytic continuation, which leads to the above conclusion.

    ↳ hep-lathep-phhep-thPoS(2025)·0 citations
27. 27*

    Non-Perturbative Hamiltonian and Higher Loop Corrections in USR Inflation

    Hassan Firouzjahi🇮🇷 · Bahar Nikbakht🇮🇷

    Calculating the action and the interaction Hamiltonian at higher orders in cosmological perturbation theory is a cumbersome task. We employ the formalism of EFT of inflation in the decoupling limit for single-field ultra slow-roll (USR) inflation and obtain a non-perturbative Hamiltonian in terms of the Goldstone field $\pi$. To complete the dictionary, a non-linear relation between the curvature perturbations and $\pi$ is presented. Using these results, we compute higher-order loop corrections in USR models with a sharp transition to the attractor phase, relevant for PBHs formation. It is shown that in the idealized picture in which the transition from the USR phase to SR phase is instantaneous and sharp, the loop corrections on long CMB scales increase rapidly with the number of loops $L$ and the setup may go out of perturbative control.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2026)·9 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.