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The Fifth International Conference on Axion Physics and Experiment (Axion 2026)

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Description

Axion models are well motivated by their ability to solve the strong CP problem in the standard model, and provide a natural candidate for the dark matter which comprises most of the matter in the Universe. As a result, experiments are ongoing worldwide to search for axions and axion-like particles.

This conference aims to review and discuss recent progress in theoretical, phenomenological, and experimental aspects of axion models, as well as scenarios involving new sub-GeV physics such as dark photons, light dark matter, light mediators, and other related topics.

The conference topics include: axion physics and experiments, quantum sensors and their applications in axion detection, physics of dark photons, light dark matter, light mediators and other related topics in cosmology, particle physics, gravity and string phenomenology.

This conference is the fifth of the series, following Axion 2022, Axion 2023, Axion 2024 and Axion 2025.

Schedule: Arrive: 9th August(Sunday). Departure: 13th August(Thursday).
The conference will be held from the 10th (Monday) to 12th (Wednesday) of August.

Registration deadline: 18th July, 2026
Please make your reservation as soon as possible as the number of hotel rooms is limited.

Registration fee：

Category                               USD         EUR          CNY      

Faculty and postdocs:        320          280          2200   

Students:                              220          200          1800         

Conference venue：Qingdao Huanghai Hotel 青岛黄海饭店

Address: 75 Yan'an First Road, Shinan District, Qingdao, Shandong 266003, China
(Hotel Reservation Tel: +86 0532 55769999)

Contact details: 

Shoushan Bao (ssbao@sdu.edu.cn) 
Hong Zhang (hong.zhang@sdu.edu.cn) 

Secretary:   
Sen Cao (axion2026@sdu.edu.cn) Phone: +86 13810930061

 

AXION_2026_Conference_Handbook.pdf
Participants
  • Alexander Eberhart
  • Ali Muhammad
  • Andrew Fowlie
  • Bilal Ahmad
  • Bingrong Yu
  • Chao Li
  • Chen Sun
  • Chen Yuan
  • Chenhui Xie
  • Da Liu
  • Deshan Yang
  • Fangchao Liu
  • Guangshang Chen
  • GuoDong Zhang
  • Han Wang
  • Haoran Di
  • Hong Zhang
  • Hong-Yi Zhang
  • Houbing Jiang
  • Huangyu Xiao
  • Huifang Xue
  • IJEOMA PRECIOUS IWUNZE
  • Jia-Shu Niu
  • Jian Deng
  • Jianbin Jiao
  • Jiayi Liu
  • Jinbao Wang
  • Jinmian Li
  • João Paulo da Silva Melo
  • Jun Zhang
  • Junle Pei
  • Junxuan Xu
  • Kaidong Zhou
  • Kangkang Zhao
  • Ke Han
  • Keping Xie
  • Lei Yang
  • Leyun Gao
  • Lingfeng Li
  • Min Chen
  • Mirian Reetz da Silva
  • Mussawir Khan
  • Nayun Jia
  • Nick Houston
  • Pan Zheng
  • Ping He
  • Pirzada .
  • Qiaoli Yang
  • Qixuan Xu
  • Runmin Yao
  • Sen Cao
  • Shao-Feng (韶锋) Ge (葛)
  • Theo Abounnasr Martins
  • wei ji
  • Weizhi Xiong
  • Xiangjun Tan
  • Xiao-Rui Lyu
  • xu liu
  • Yajin Zhou
  • Yan-Rui Liu
  • Yandong Liu
  • Yao Huang
  • Yifan Chen
  • Yiming Yang
  • Yinda Guo
  • Youjie Lin
  • Yu Gao
  • Yu Zhang
  • Yu-Hui Zheng/KIAS
  • yuanlin gong
  • Yuesheng Dai
  • Yuichiro Nakai
  • Yun Jiang
  • Yuxuan Hao
  • Zhi-Hui Guo
  • Zhiqing Liu
  • Zhong-Zhi Xianyu
  • Zhuo-Hui Wang
  • Ziwen Yin
  • Zixin Qu
  • Zuowei Liu
  • 伟 晁
  • 守山 鲍
  • 海静 周
Contact
  • Sunday, 9 August
    • 14:00 → 20:00
      Check-in
  • Monday, 10 August
    • 08:30 → 08:50
      Opening Remark Front Area (Conference Center (2F))

      Front Area

      Conference Center (2F)
    • 08:50 → 09:50
      Plenary Session: I Front Area (Conference Center (2F))

      Front Area

      Conference Center (2F)
      Convener: Yufeng Zhou (ITP/CAS)
      • 08:50
        Probing the ultra-light dark matter with Quantum Sensors 30m
        Speaker: Prof. Jing Shu (Peking University)
        Axion2026.pdf
      • 09:20
        Paths to Solving the Strong CP Problem and the Footprints Left Behind 30m

        We explore two major approaches to the strong CP problem, the axion solution and spontaneous CP violation (SCPV). We first focus on composite axion models, which provide a compelling realization of the axion solution but face serious cosmological challenges, in particular the domain wall problem. We present a new framework based on a special embedding of gauge symmetries, where the domain wall number is reduced to unity in the ultraviolet theory, and small instanton effects induce a controlled bias term that lifts the vacuum degeneracy and allows domain walls to decay without spoiling the axion solution. We then turn to the axionless approach based on SCPV, where CP is an exact symmetry of the Lagrangian and is broken only spontaneously. In supersymmetric theories, SCPV can be realized along flat directions and stabilized by supersymmetry-breaking and non-perturbative dynamics, and the framework is compatible with viable cosmology including Affleck–Dine baryogenesis. These mechanisms provide distinct paths to resolving the strong CP problem with testable implications.

        Speaker: Yuichiro Nakai
        Axion2026.pdf
    • 09:50 → 10:20
      PHOTO & COFFEE BREAK
    • 10:20 → 12:00
      Plenary Session: II Front Area (Conference Center (2F))

      Front Area

      Conference Center (2F)
      Convener: Xiaorui Lv (University of Chinese Academy of Sciences)
      • 10:20
        Mapping the ALPs: A Naturalness Map for Axions and ALPs 25m

        The axion solution to the strong CP problem is only as robust as the Peccei-Quinn symmetry it relies on, and quantum gravity is expected to break it. We quantify the resulting axion quality problem using principled measures of fine-tuning, and show that the cost is severe. For the QCD axion to account for the observed dark matter, Planck-suppressed symmetry-breaking operators must be absent up to mass dimension $d \ge 12$; the naturalness penalty for failing to realize this protection can exceed a Bayes factor of $10^{10}$. Extending the analysis to generic axion-like particles, we map the axion mass-decay constant plane by the degree of UV protection required, and find that large portions of the sensitivity reach of laboratory experiments are already fine-tuned at the part-per-million level or worse. We argue that quality, not mass, is the central naturalness question for the axion program.

        Speaker: Andrew Fowlie (XJTLU)
        Associated arXiv paper quality_control_axions_alps.pdf
      • 10:45
        Search for light dark particles at the BESIII experiment in China 25m
        Speaker: Zhiqing Liu (Shandong University)
        Axion_Zhiqing_v2.pdf
      • 11:10
        Supernova Constraints on Lepton Flavor Violating Axions 25m

        We discuss supernova cooling limits and low-energy supernova constraints on lepton flavor violating axions.

        Speaker: Prof. Zuowei Liu
        260810-SN-LFV-axion-Qingdao-Zuowei-Liu.pdf
      • 11:35
        Axion Dark Matter from Parametric Resonance during the QCD Phase Transition 25m

        The QCD axion cosmological abundance is usually attributed to the misalignment mechanism. We will present a complementary production channel that arises during the QCD phase transition. Primordial temperature fluctuations modulate the axion mass and can trigger parametric resonance in the axion field evolution, exciting finite-momentum modes and enhancing axion production. This effect can significantly modify the predicted axion relic abundance and shift the preferred dark-matter mass range, with implications for ongoing and future axion search experiments.

        Speaker: Prof. Yang Qiaoli
        MPR.pdf
    • 12:00 → 14:00
      Lunch Zhonghua Restaurant (buffet)

      Zhonghua Restaurant (buffet)
    • 14:00 → 15:40
      Plenary Session: III Front Area (Conference Center (2F))

      Front Area

      Conference Center (2F)
      Convener: Lei Wu (Nanjing Normal University)
      • 14:00
        Same-sign dimuon probe of charged lepton flavor violation at electron–photon colliders 25m

        Observation of charged lepton flavor violation would constitute unambiguous evidence for physics beyond the Standard Model (SM). We identify a previously unexplored same-sign dimuon signature in electron--photon collisions, $\gamma e^- \to e^+\mu^-\mu^-$, mediated by an axionlike particle (ALP) with flavor-violating $e$--$\mu$ couplings. The absence of irreducible SM backgrounds and the on-shell production of the ALP render this channel intrinsically clean and highly sensitive, with only small residual backgrounds arising from detector effects. Such collisions can be realized via laser Compton backscattering at $e^+e^-$ colliders including BEPC-II with the BESIII detector, STCF, CEPC, and ILC. We find that STCF, CEPC, and ILC can probe couplings one to two orders of magnitude below existing bounds. This combination of resonant production, vanishing irreducible background, and same-sign topology would be difficult to achieve in conventional $e^+e^-$ or hadron-collider environments, establishing electron--photon collisions as a uniquely powerful probe of charged lepton flavor violation.

        Speaker: 宇 张 (合肥工业大学)
        Same sign muon pair at egamma colliders@Axion2026.pdf
      • 14:25
        Axion-Like Particles at the Electron-Ion Collider 25m

        We explore the searches for axion-like particles (ALPs) at the electron-ion collider (EIC) to be built at the Brookhaven National Laboratory. We propose search strategies with the production of diphoton in both coherent (elastic) and inelastic scatterings. We found the EIC embraces the possibility to extend the existing ALP searches.

        Speaker: Keping Xie (TDLI/SJTU)
        ALP_EIC.pdf
      • 14:50
        WIMP Meets ALP: Coherent Freeze-Out of Dark Matter 25m

        The microscopic nature of dark matter is the major open question in science. Weakly-Interacting Massive Particles (WIMPs) and Axion-Like Particles (ALPs) are the two most theoretically motivated dark matter candidates. Thousands of papers consider them separately. We point out that if both species are present in the theory, even a tiny (Planck-suppressed) interaction between them could lead to drastic modifications of their dynamics in the early universe.

        Specifically, we consider the cosmological history of a fermionic WIMP coupled to a light ALP via a quadratic coupling. Although the coupling is too feeble to thermalize the ALP, coherent forward scattering between the two sectors induces temperature-dependent mass shifts that substantially modify both WIMP freeze-out and ALP misalignment dynamics, giving rise to a novel coherent freeze-out mechanism. At high temperatures, the WIMP thermal bath spontaneously breaks the symmetry of the ALP potential, displacing the field to a new vacuum. The resulting back-reaction reduces the WIMP effective mass and significantly delays its freeze-out. Depending on the strength of the coupling, symmetry restoration occurs via either a first-order phase transition (FOPT) or a crossover. In the FOPT regime, dark matter consists solely of WIMPs, whose delayed freeze-out permits annihilation cross sections up to three orders of magnitude above the standard value, while still yielding the correct relic density. In the crossover regime, both WIMP and ALP can contribute to dark matter. Remarkably, we find an "ALP miracle": a Planck-suppressed quadratic coupling yields an ALP abundance comparable to the observed dark matter density, largely independent of its initial displacement and mass.

        Speaker: Dr Bingrong Yu (Cornell University)
        Coherent_Freeze-out.pdf
      • 15:15
        Floquet and Sideband Dynamics of Photon–Axion Mixing in Coherent Axion Backgrounds 25m

        Coherent axion dark matter provides a periodically time-dependent background for electromagnetic propagation. In the presence of an external magnetic field, the oscillating axion field acts as a temporal pump and can drive photon–axion conversion beyond the conventional static or adiabatic level-crossing picture. A unified Floquet and sideband description of this dynamics will be presented.

        Resonant photon–axion mixing can occur when the mismatch between photon and axion dispersion relations is compensated by integer harmonics of the axion oscillation frequency. This driven resonance enables efficient conversion away from the usual level-crossing regime and is missed after time averaging. It constitutes a unitary mode-conversion process, distinct from axion decay or parametric particle production, and can lead to characteristic polarization signatures relevant for astrophysical observations.

        A Floquet–Bloch sideband formulation of axion electrodynamics will be discussed. The periodic axion background generates a ladder of photon and axion sidebands. Near folded degeneracies, the system reduces to universal two-mode crossings whose stability is determined by the symplectic, or Krein, signatures of the colliding modes. This framework unifies stable avoided crossings, parametric instabilities, forward conversion, stop bands, and distributed reflection within a single language.

        Together, these results clarify how coherent axion backgrounds modify wave propagation and provide new theoretical tools for identifying observable signatures of axion dark matter.

        Speaker: Runmin Yao (HIAS, UCAS)
        Floquet and Sideband Dynamics of Photon–Axion Mixing in Coherent Axion Backgrounds.pdf
    • 15:40 → 15:55
      COFFEE BREAK
    • 15:55 → 17:35
      Plenary Session: IV Front Area (Conference Center (2F))

      Front Area

      Conference Center (2F)
      Convener: Jia-Shu Niu (Shanxi University)
      • 15:55
        Black hole superradiance of interacting multi-fields 25m

        Ultralight bosonic fields can undergo exponential amplification around rotating black holes through black hole superradiance. This process can result in black hole spin-down, continuous gravitational-wave emission, and many other observable consequences, providing a powerful probe of dark particles in the strong-gravity regime. In particular, the LVK Collaboration has placed constraints on dark scalars with masses around $10^{-12}$ eV.

        While most existing studies assume a single field, the dark sector may contain multiple particle species with nontrivial interactions. In this work, we investigate black hole superradiance in the presence of multiple interacting fields. In particular, we compute the corrections to the superradiant growth rates induced by interactions with other fields, study the nonlinear evolution of the superradiant system, and discuss the observational implications.

        We find that interactions can significantly suppress black hole superradiance and modify the superradiant evolution, even if the coupled field is not itself superradiant. We demonstrate that multi-field interactions can qualitatively alter superradiance phenomenology and should be incorporated when deriving robust constraints on the dark sector from black hole spin measurements and gravitational-wave observations.

        Speaker: Dr Jun Zhang (International Center for Theoretical Physics Asia-Pacific)
        Black Hole Superradiance of Interacting Multifield.pdf
      • 16:20
        Strong-Field Dynamics and Multimessenger Signatures of Ultralight Dark Matter 25m

        Ultralight bosons near compact objects can form gravitationally bound states, some of which grow exponentially by extracting black hole rotational energy or through relaxation from ambient waves. These states can reach field amplitudes approaching the Planck scale, leading to non-perturbative phenomena analogous to early-universe cosmology and to observational signatures far stronger than those from local dark matter detection, including electromagnetic features in black hole imaging and gravitational-wave imprints of the surrounding environment. Two examples of strong-field phenomena will be discussed. First, accreting axion clouds can enter a saturation regime in which the field approaches the decay constant, with relativistic axion emission balancing the accretion and encoding the underlying self-interactions. Second, high-energy neutrinos propagating through a dense scalar background with non-diagonal couplings can undergo parametric resonance, leading to distortions in the observed flavor ratios.

        Speaker: Yifan Chen (Tsung-Dao Lee Institute)
        Qingdaoaxion_10August26_SGP.pdf
      • 16:45
        Probing Ultralight Dark Matter with Gravitational Waves 25m

        Ultralight bosons are promising dark matter candidates that can leave observable imprints in gravitational waves. In this talk, I will discuss several complementary ways to probe ultralight scalar fields with gravitational wave observations. I will focus on black hole superradiance and the resulting stochastic gravitational wave background, including the impact of higher modes, current LIGO–Virgo constraints, and the prospects for next-generation detectors. I will also discuss how self-interactions modify these signals, and how extreme-mass-ratio inspirals in scalar-cloud environments can develop resonant features that may be detectable by future space-based detectors. These results show that gravitational waves provide a powerful multi-band probe of ultralight dark matter.

        Speaker: Dr Yuan Chen
        BHenvironment-Chen Yuan.pptx
      • 17:10
        Search for ultralight scalar dark matter with quadratic interactions 25m

        In this talk, I will discuss about my recent work on the searches for the ultralight scalar dark matter with quadratic interactions with SM fields. This will lead to the effective interactions between the ultralight dark matter and the nucleon fields phi^2 N N/f below the QCD confinement scale, which can be thought as potential barrier for the dark matter wind in the presence of ordinary matter. When the potential barrier is large enough compared with the kinetic energy of the dark matter, the dark matter flux will bounce back from the ordinary object, as a result inducing a pressure force on the object. After taking into the constraints from Supernova cooling, BBN and gravitational inverse square law test, there exists parameter spaces in our model which can be searched for by utilizing this force effect on the experiment for the test of the weak equivalence principle.

        Speaker: Da Liu (Shandong University)
        1_Ultralight Dark Matter_Qingdao169.pdf
    • 17:35 → 20:30
      Banquet & Show Ming Yuan Restaurant

      Ming Yuan Restaurant
  • Tuesday, 11 August
    • 08:30 → 10:10
      Plenary Session: V Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Yu Gao (IHEP)
      • 08:30
        Resonant enhancement of axion dark matter decay 25m

        The axion is a particularly well-motivated candidate for the dark matter comprising most of the mass of our visible Universe, leading to worldwide experimental and observational efforts toward its discovery. As is well known, resonant cavities are a primary tool in this search, where they are used to enhance the conversion rate of axions into photons in a background electromagnetic field. What is perhaps less well appreciated is that resonant cavities can also enhance the rate at which axions decay to two photons, a manifestation of the Purcell effect. We examine this possibility and show that it offers a previously unexplored method to search the axion parameter space in a way that is competitive and complementary to other approaches, with the capability to probe a well-motivated region for QCD axion dark matter. Furthermore, we establish that this method can be implemented via preexisting axion heterodyne detection schemes, enabling such experiments to perform these searches with minimal modification.

        Speaker: Nick Houston (北京工业大学)
        Axion 2026 - NHouston.pdf
      • 08:55
        Laser wakefield based axion-like particle generation and detection 25m

        The axion, a theoretically well-motivated particle, has been searched for extensively via its hypothetical interactions with ordinary matter and fields. In this talk, an axion detection approach utilizing the ultra-intense electromagnetic fields produced by laser–plasma interactions will be reported. We have developed particle-in-cell (PIC) simulation method that incorporates the axion field, the electromagnetic fields, and their interactions. By using such code we proposed a new scheme for axion generation and detection. A laser pulse firstly drives a nonlinear bubble structure inside a gas plasma and a tailor pulse propagates inside the bubble. The coupling between the laser field and the wakefield can generate axions, which then interact with both of the two fields and generate secondary electromagnetic fields. The radiated EM fields show high order frequency and spatial mode compared with the laser pulse, which gives a possible way to detect the axions. In further, to increase the detection ability, we propose a seeded photon scheme to enhance the conversion from axions to photons and it could be used in the light shinning through a wall scheme for axion detection.

        Speaker: Prof. Min Chen (Shanghai Jiao Tong University)
        Laser Wakefield Based Axion-like Particle Generation and Detection-MINCHEN-260811-FINAL.pptx
      • 09:20
        Search for axionlike particles with ferromagnetic system. 25m

        Ferromagnetic materials offer the unique advantages of an exceptionally high spin density and large remanent magnetization. When levitated, a ferromagnet can serve as an ultrasensitive magnetometer, while soft ferromagnetic materials with low remanence provide efficient magnetic shielding. In this talk, I will introduce a hybrid ferromagnetic platform that combines these complementary functionalities. The resulting system achieves ultrahigh magnetic sensitivity together with a broad detection bandwidth.

        Speaker: Prof. Wei Ji
        Search for axionlike particles with ferromagnetic system.pptx
      • 09:45
        Quantum-enhanced dark matter searches using cat states 25m

        Dark photon is one of the potential dark matter candidates with compelling cosmological origins and favorable extensions of fundamental physics beyond the Standard Model. Haloscope experiments are underway to detect the bosonic candidate by exploiting its weak couplings to the resonating electromagnetic fields in microwave cavities. Quantum metrology enables sensitive haloscope dark matter searches, particularly using nonclassical electromagnetic states, such as cat states featuring sub-Planck interference structures in phase space. Here, we present the first experimental application of four-component cat states within a high-quality superconducting microwave cavity to detect dark photons. We demonstrate an 8.1-fold enhancement in the signal photon rate and constrain the dark photon kinetic mixing angle to an unprecedented ϵ<7.32×10^(-16) near 6.44 GHz (26.6 µeV). By employing a parametric sideband drive to actively tune the cavity frequency, we achieve dark photon scan searches and background subtraction across multiple frequency bins, yielding a sensitivity at the 10^(-16) level within a 100 kHz bandwidth. Our cat-state-assisted search scheme demonstrates a substantial improvement over previous results, promising potential implications in quantum-enhanced searches for new physics.

        Speaker: Pan Zheng (Shenzhen International Quantum Academy)
        Quantum-enhanced dark matter searches using cat states.pptx
    • 10:10 → 10:25
      COFFEE BREAK
    • 10:25 → 11:40
      Plenary Session: VI Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Deshan Yang (University of Chinese Academy of Sciences)
      • 10:25
        Constraints on axions from neutrino experiments 25m

        Constraints on axions from neutrino experiments

        Speaker: Ningqiang Song (Institute of Theoretical Physics, Chinese Academy of Sciences)
        axion-Ningqiang Song.pdf
      • 10:50
        New Isocurvature Constraints and its Axionic Interpretations 25m

        Although measurements of the Cosmic Microwave Background (CMB) have shown a nearly scale-invariant primordial spectrum of adiabatic perturbations, in which the energy densities of different components (radiation, baryons, and dark matter) fluctuate proportionally, there could also exist isocurvature perturbations, in which density fluctuations of the individual components differ from the adiabatic mode. Cold dark matter isocurvature (CDI) perturbations with a variety of spectral tilts generated in pre-inflationary axion models provide one such example. In this article, we present the most updated constraints on these axion CDI perturbations using the latest CMB anisotropy measurements from Planck, the Atacama Cosmology Telescope (ACT), and the South Pole Telescope (SPT).
        We study both fixed spectral indices with values ranging from red- to blue-tilted spectra as well as the case with a free index. We find that the constraint on the spectral index gets moderately improved with the combined datasets compared to Planck alone, while the bounds on the isocurvature amplitudes for fixed spectral indices we consider do not get tighter.

        Speaker: Prof. Lingfeng Li
        New Isocurvature Constraints and its Axionic Interpretations.pdf
      • 11:15
        Axion Magnetic Resonance and the Enhanced Axion Signal 25m

        It is well-known that axions and photons can coherently convert into each other in a background magnetic field, a phenomenon commonly observed in a mixed two-level quantum system such as neutrino oscillations and nuclear spin processions. Similar to the nuclear magnetic resonance and spin flips in a qubit system, we point out that an periodic (in time or space) background magnetic field can significantly enhance the axion-photon conversion. We denote this resonance as the Axion-Magnetic Resonance (AMR).

        In this talk, I will illustrate the theoretical and experimental implications of the AMR, in particular in the context of laser-based axion searches and solar axion experiments (helioscopes). I will show its relevance for interesting some ALPs models and its capability in distinguishing different QCD axion models (KSVZ and DSFZ), independent of the axion relic abundance or cosmological history.

        Speaker: Chen Sun (HIAS-UCAS)
        talk.pdf
    • 11:40 → 14:00
      Lunch Zhonghua Restaurant (buffet)

      Zhonghua Restaurant (buffet)
    • 14:00 → 15:45
      Plenary Session: VII Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Wei Chao (BNU)
      • 14:00
        When stars dim into axions: A time-domain window on new physics 25m

        Magnetic white dwarfs may reveal axions through a simple astrophysical scenario: photons leaving the stellar surface can convert into axions while traversing the star's intense magnetic field. As the star rotates, the changing magnetic geometry can imprint a periodic, energy-dependent modulation on the observed light. Precision photometry can therefore turn rotating magnetic stars into laboratories for fundamental physics.

        Using the magnetic white dwarfs PG 1015+014 and RE J0317-853 as case studies, we show how this scenario can be tested with TESS light curves and achieve competitive sensitivity to sub-µeV axions. Intrinsic stellar variability can mimic parts of the signal, making a realistic understanding of the stellar light curves essential. More broadly, observations of multiple magnetic white dwarfs could identify axion-induced modulation through its correlations with magnetic-field geometry, wavelength, and rotation phase, opening a new time-domain window on weakly coupled particles.

        Speaker: Hong-Yi Zhang (Tsung-Dao Lee Institute, Shanghai Jiao Tong University)
        mwd-axion.pdf
      • 14:25
        Extreme-mass-ratio inspirals into axion clouds 20m
        Speaker: Qixuan Xu (Instituto Superior Técnico)
      • 14:45
        Constraining axion couplings with the Hulse-Taylor binary system 20m

        The orbital evolution of the Hulse-Taylor binary neutron star system is described with high precision by General Relativity, in which gravity is the only long-range force and gravitational waves provide the dominant energy-loss channel. We use this precision test of relativistic binary dynamics to derive new constraints on axion couplings to stable neutron-star constituents: neutrons, electrons, and muons. In the presence of exotic long-range forces and additional radiation channels, the measured orbital decay constrains the strength of quadratic axion-fermion interactions.
        Axions enjoy a perturbative shift symmetry that is broken by non-perturbative effects responsible for the axion mass. Such shift symmetry breaking can induce quadratic couplings between axions and fermions. In an ambient axion dark-matter background, these couplings mediate enhanced long-range, spin-independent forces, while also allowing binary systems to lose energy through dipole and quadrupole emission of axion waves. For light QCD axions and for models in which non-perturbative effects correct lepton masses, our bounds can be recast as limits on the axion decay constant.

        Speaker: Ziwen Yin (Tsung-Dao Lee Institute & SJTU)
        ZiwenYin_青岛.pptx
      • 15:05
        Transient Bias for CP Domain Wall Decay and Dark Matter 20m

        Spontaneous CP violation (SCPV) provides an attractive solution to the strong CP problem. However, SCPV after inflation suffers from the formation of CP domain walls, requiring the maximal temperature of the Universe to lie below the CP-breaking scale. In the present work, we then propose a dynamical mechanism that removes this cosmological constraint without introducing permanent explicit CPV. We consider a new scalar field that acquires a large field value with a nontrivial phase in the early Universe and induces a transient bias among degenerate CP vacua through a higher-dimensional interaction with a CP-breaking scalar field. This bias triggers the decay of CP domain walls after they form. As the new scalar field evolves toward the origin, the bias disappears, leaving the low-energy CP structure intact. We derive the conditions for successful domain wall decay and identify the viable parameter space. Furthermore, we point out that the coherent oscillation of the new scalar field naturally survives as dark matter, linking the resolution of the CP domain wall problem to the origin of dark matter.

        Speaker: Fangchao Liu (TDLI, SJTU)
        Transient Bias for CP Domain Wall Decay and Dark Matter.pdf
      • 15:25
        Bias with a Timer: Axion Domain Wall Decay and Dark Matter 20m

        We explore the interplay of the post-inflationary QCD axion and a light scalar field for the axion domain wall decay and dark matter (DM). The scalar field possesses a nonzero vacuum expectation value (VEV) during inflation, so that its interaction with the axion effectively serves as an explicit Peccei-Quinn (PQ) violating term. At a temperature below the PQ phase transition, the effective PQ violating interaction generates the axion potential which generally contains multiple degenerate vacua leading to the formation of the axion string-domain wall networks. The following QCD phase transition provides another contribution to the axion potential making domain walls decay before they dominate the Universe. Later, the scalar field starts to relax to the minimum of its potential with a vanishing VEV, turning off the effective PQ violating interaction so that the axion potential is aligned with the QCD vacuum. We keep track of the evolution of the axion-scalar system and discuss the production of the axion DM through the domain wall decay and the (trapped) misalignment. We find that the string-wall network in some cases can decay due to its structural instability, rather than the volume pressure, and the correct axion DM abundance is realized with the decay constant larger than that of the conventional post-inflationary QCD axion without fine tuning.

        Speaker: Sally Yuxuan Hao (TDLI, SJTI)
        axion workshop 2026.pdf
    • 15:45 → 16:00
      COFFEE BREAK
    • 16:00 → 17:40
      Plenary Session: VIII Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Mr Yandong Liu (Beijing Normal University)
      • 16:00
        Constraints on Axion-Like Particles with the Silicon Detector at a Nuclear Reactor 20m

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

        Speaker: Mr Yuanlin Gong (Nanjing Normal University)
        Yuanlin-Reactor ALP and Plasmon-Qiangdao.pptx
      • 16:20
        Semiconductor Spin-Qubit Arrays for Axion Dark Matter Search 20m

        Axions and axion-like particles are compelling dark-matter candidates whose derivative couplings to fermion spins generate an oscillatory, spin-dependent effective field, often referred to as the axion wind. This talk explores semiconductor quantum-dot spin qubits as frequency-resolved quantum sensors for axion-induced spin dynamics and, more broadly, as a platform for weak-field detection at the nanoscale. By mapping the axion–spin interaction or other weak effective-field perturbations onto controlled phase accumulation in coherent spin-qubit protocols, semiconductor devices provide a tunable architecture in which coherence time, control bandwidth, sensor filter functions, and readout fidelity can be engineered for narrowband sensing. I will discuss how spectral engineering of spin-qubit control sequences can enhance sensitivity within targeted axion-mass windows while suppressing charge noise, magnetic noise, and control-induced backgrounds. Particular emphasis will be placed on realistic noise spectra, quantum-control filter functions, weak field sensitivity limits, and the resulting coupling reach. Beyond sensitivity optimization, I will show how the motion of the terrestrial laboratory through the Galactic dark-matter halo produces characteristic sidereal and annual modulation signatures, leading to structured sideband responses that provide a robust discriminator against stationary instrumental backgrounds. Finally, I will outline prospects for hybrid electronic–nuclear spin architectures, where long-lived nuclear coherence can be combined with fast electronic-spin initialization and readout through hyperfine-mediated transduction, offering a scalable and CMOS-compatible route toward chip-integrated weak field sensing, axion searches, and broader quantum-enabled dark-matter detection.

        Speaker: Xiangjun Tan (University College London)
      • 16:40
        Detecting Axion Dark Matter by Artificial Magnetoelectric Materials 20m

        Axions are considered a key component of dark matter, characterized by very weak couplings to fermions and Chern-Simons couplings to gauge fields. We propose a novel detection mechanism based on symmetry-breaking magnetoelectric materials with a linear axionic coupling between magnetization and ferroelectric polarization. The focus is on a strain gradient $\text{Sr}_2\text{IrO}_4$ film, where the breaking of space-inversion symmetry results in an emergent polar phase and an out-of-plane magnetic moment, exhibiting a flexomagnetoelectric effect. In this material, the linear $\mathbf{P} || \mathbf{M}$ enables a direct coupling between the external axion field and the intrinsic axion-like field, which amplifies the weak electromagnetic signals induced by axions, paving the way for pioneering axion detection. In contrast to conventional detection techniques, this mechanism is expected to enhance the sensitivity of the axion-electron and axion-photon coupling, providing a novel platform for axion detection and advancing the study of dark matter through the magnetoelectric effect.

        Speaker: Mr Chenhui Xie (School of Physics, Beijing Institute of Technology, Beijing, China)
        ChenhuiXie_Axion2026.pdf
      • 17:00
        Axion Dark Matter Induced Modulation in Ferromagnetic Resonance and Spin Wave Interferometry 20m

        We propose a novel asymmetric sensitive spin wave interferometer to detect ultralight axion dark matter, which modulates spin wave properties through a weak effective magnetic field in ferromagnets. By splitting a spin wave source into two paths of different lengths and setting them to interfere destructively, the interferometer converts the axion induced phase shift into a measurable magnetization oscillation, which can radiate electromagnetic waves and also generate electrical signals via Faraday induction. The signal to noise ratios have been evaluated for three detection schemes: the linear amplifier, the single photon detector and the electrical signal detection approach, with both magnetization fluctuation noise and thermal noise taken into account. Limited by the conditions of spin wave propagation distance and the relaxation time, the accessible axion mass range is approximately 10^{−8} eV to 10^{−6} eV.

        Speaker: Jiayi Liu (Beijing Institute of Technology)
        Jiayi Liu-Axion Dark Matter Modulated Spin Wave Interferometry.pdf Jiayi Liu-Axion Dark Matter Modulated Spin Wave Interferometry.pptx
      • 17:20
        Discovering the Axiverse via Fifth Forces 20m

        If the Universe is described by string theory or other extensions of the Standard Model, several light, axion-like states are predicted to exist. However, most experiments only search for one of these states. We show that searches for fifth forces can't assume a non-relativistic potential induced by a single axion field. We discuss the strength of the non-relativistic spin-dependent and spin-independent potentials in the most general case of $N_a$ different axions and show how the shape of the potentials can be used to distinguish between different axiverse scenarios.

        Speaker: Mr Alexander Eberhart (Durham University)
        Discovering the Axiverse via Fifth Forces.pdf
    • 17:40 → 20:30
      Dinner Zhonghua Restaurant (buffet)

      Zhonghua Restaurant (buffet)
  • Wednesday, 12 August
    • 08:30 → 10:05
      Plenary Session: IX Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Yan-Rui Liu
      • 08:30
        Discussion K to pi a decay within large N_C chiral perturbation theory 25m

        The decay $K\to\pi a$ provides the most stringent particle-physics constraints on ALPs with masses below 300 MeV. Previous studies have been performed within SU(3) chiral perturbation theory, where the $\eta_0$ is integrated out. However, the explicit $\eta_0$ may play an important role, since the ALP and the $\eta_0$ belong to the same flavor-singlet sector. In this talk, we discuss the $K\to\pi a$ decay in U(3) chiral perturbation theory, focusing on the explicit $\eta_0$ contribution, the new weak operator, and the large-$N_C$ behavior of the decay amplitude.

        Speaker: 金葆 王 (河北师范大学)
        Axion-2026-wjb.pdf
      • 08:55
        A Natural Dark Matter–Dark Energy Interaction from Axion–Monopole Dynamics 25m

        We propose a natural framework for interacting dark matter and dark energy based on axion–monopole dynamics in a dark gauge sector. Dark matter is composed of dark ’t Hooft–Polyakov monopoles, while dark energy is an ultralight axion whose coupling to the dark gauge field induces an axion-dependent dyon mass through the Witten effect. This generates a direct dark matter–dark energy interaction. We show that generic models with a significant dark matter–dark energy coupling suffer from a naturalness problem: the Coleman–Weinberg potential induced by the interaction is typically much larger than the dark-energy scale. In our model, the corrections arise from a monodromy tower of dyon states, allowing them to be exponentially suppressed. In the minimal setup, the interaction strength is predicted to be $\sim 0.1\%$, below the sensitivity of current observations. We discuss scenarios in which cosmological population of higher-charge dyons can enhance the interaction to the percent level, producing an apparent phantom dark-energy equation of state.

        Speaker: Huangyu Xiao (Harvard University and Boston University)
        A Natural Dark Matter–Dark Energy Interaction from Axion–Monopole Dynamics.pptx
      • 09:20
        Search for light WIMPs with BULLKID-DM experiment using monolithic arrays of detectors 25m

        BULLKID-DM is a cryogenic experiment designed for direct detection of WIMP-like dark matter particles with a mass below 1 GeV/c$^{2}$. The detector will consist of a stack of 16 intrinsic silicon wafers, for a total mass of 800 g, that are carved in 2320 active dice with a volume of 5.4$\times$5.4$\times$5 mm$^{3}$. Each die will be instrumented with multiplexed Kinetic Inductance Detectors (KIDs), acting as a particle absorber with an individual energy threshold of 200 eV or better. The array design enables the volume fiducialization to improve background discrimination.
        To minimize the background signals from ambient radioactivities, besides using radiopure materials, a comprehensive shielding system, including a mixture of lead, copper and neutron moderator material (𝐵4𝐶) that placed both inside and outside the cryostat will be implemented. A cryogenic anti-coincidence veto system is also designed to further suppress the external gamma backgrounds. The veto system will use scintillating crystals and their light output is read out by phonon-mediated KIDs. The overall background with the veto system is expected to be close to the zero-background limit of 10$^{−2}$ counts / (keV kg day).

        This work presents the first operation of a 60 g demonstrator with 180 dice, in a surface laboratory equipped with a lead and copper radiation shield. The recorded backgrounds are in line with Geant4 simulations performed by the collaboration, paving the path to the deployment of final 800 g array. Current efforts focus on the low-radioactivity detector mounting, a cryogenic scintillating veto readout with KIDs, in situ calibration techniques, and detector upgrades such as KIDs with dedicated phonon-collecting structures and germanium substrates for multi-target capabilities.
        The demonstrator is intended to be installed at the Gran Sasso underground laboratory (LNGS) by late 2026, following successful validation, the full experiment is expected to be commissioned in 2027.

        Speaker: Kangkang ZHAO (Gran Sasso Science Institute, INFN-LNGS)
        Zhao_Axion2026_bullkid_general.pdf.pdf
      • 09:45
        New limits on muon-philic dark matter searches and other recent progresses from PKMu 20m

        The PKMu experiment uses a resistive plate chamber (RPC) muon tomography system to study cosmic-ray scattering as a probe of both secondary cosmic-ray composition and new physics. During a 63-day data-taking campaign, 1.18 million scattering events were recorded and analyzed. Template fits to the scattering-angle distribution enable precise measurements of secondary cosmic-ray components, including the electron fraction at approximately 2% precision. The same dataset is also used to search for elastic scattering between cosmic-ray muons and muon-philic dark matter. Assuming a slow dark matter component captured and thermalized within the Earth, PKMu sets a 95% confidence level upper limit of $1.61 × 10^{-17}~\mathrm{cm^2}$ on the muon–dark matter elastic scattering cross section for 1 GeV dark matter. This contribution presents these new dark matter constraints together with other recent experimental developments from PKMu.

        Speakers: Qiang Li (Peking University), Qite Li (Peking University), Chen Zhou (Peking University), Cheng-en Liu (Peking University), Leyun Gao (Peking University)
        Leyun_Gao-PKMu-20260811.pdf
    • 10:05 → 10:20
      COFFEE BREAK
    • 10:20 → 11:50
      Plenary Session: X Back Area (Conference Center (2F))

      Back Area

      Conference Center (2F)
      Convener: Hong Zhang (Shandong University -Qingdao)
      • 10:20
        Physics-Informed Neural-Network Modeling of Axion–Photon Conversion in Structured Electromagnetic Fields 20m

        The presentation concerns a physics-informed neural-network framework for solving coupled axion–Maxwell equations in inhomogeneous electromagnetic backgrounds. In particular, it considers numerical modelling of axion–photon conversion in resonant and non-uniform field configurations, with potential applications to haloscopes, helioscopes, and quantum-sensor-based axion detection.

        Speaker: Nikolai Akintsov (Nantong University)
        Akintsov_Axion_2026 (1).pptx
      • 10:40
        Deconstructing the Extra-Dimensional Axion 20m

        We present a four-dimensional deconstruction of the extra-dimensional axion arising from a $U(1)$ gauge theory in a five-dimensional orbifold, where the axion is identified with the Wilson line of the $U(1)$ gauge field and its coupling to QCD is generated by a 5D Chern-Simons (CS) term. We construct the corresponding 4D moose (quiver) gauge theory with link scalar fields, in which the axion emerges as a collective pseudo-Nambu-Goldstone boson. The axion-gluon coupling is described by a gauged Wess-Zumino-Witten term, providing the 4D counterpart of the 5D CS term. We further analyze non-perturbative effects from zero-mode and ``fractional'' instanton configurations. While the latter is exponentially suppressed in the regime corresponding to the 5D description, ensuring consistency with the higher-dimensional picture, we point out that this suppression can break down for smaller instantons whose inverse size exceeds the 5D cutoff scale, leading to a potentially significant effect. We also study axion potentials induced by bulk matter fields and boundary-localized symmetry-breaking operators, reproducing the characteristic nonlocal suppression associated with propagation in the extra dimension. Our construction provides a renormalizable 4D framework with a transparent understanding of the axion shift symmetry and its quality.

        Speaker: Junxuan Xu (TDLI)
        Deconstruction_Qingdao.pdf
      • 11:00
        S-matrix bootstrap bounds on self-interacting dark matter 20m

        Self-interacting dark matter turns the structure of galactic halos into a direct requirement on a low-energy scattering amplitude. We show that, for weakly coupled scalar dark matter, this requirement implies a much stronger mass bound on the dark matter particle than partial-wave unitarity alone. Using analyticity, crossing symmetry, locality and partial-wave unitarity, we compute the maximal allowed threshold amplitude with a dispersive primal S-matrix bootstrap, assuming only a weakly coupled EFT below a scale $\Lambda$ and allowing arbitrary UV particle content above $\Lambda$. For the benchmark self-interaction cross section $\sigma_{\rm self}=10^{-24}(M/\mathrm{GeV}),\mathrm{cm}^2$, the mass of a generic weakly coupled scalar satisfies $M<\approx 0.3,\mathrm{GeV}$ in the controlled EFT regime. If dark matter is a derivative-dominated pseudo-Nambu-Goldstone boson, the mass bound is lowered to the MeV scale or below, depending on the hierarchy $M/\Lambda$. The results presented here are based on recent joint work with Qing Chen and Shuang-Yong Zhou, arXiv:2607.13141.

        Speaker: Zhuo-Hui Wang (University of Science and Technology of China)
        S_matrix_bound_SIDM.pdf
      • 11:20
        Majoron Potential by Majorana fermion Loops 20m

        We present a diagrammatic framework for radiative Majoron potentials induced by an explicit Majorana mass $M$. Classifying one-loop diagrams by the number of fermion-number-violating ($N_{\rm FNV}$) and fermion-number-preserving ($N_{\rm FNP}$) propagators yields a heavy-mass scaling rule: pure FNV amplitudes behave as $M^{4-n}$, while mixed diagrams receive additional suppression from momentum numerators. After removing the dominant tadpole by a matching condition, the bubble diagram provides the leading Majoron mass $\propto y^2M^2$. The mixed FNV/FNP triangle supplies the complete next-to-leading $\mathcal{O}(yv/M)$ correction through a $\cos\theta$ harmonic after vacuum alignment. We analyze the one-loop Coleman-Weinberg potential for the full two-field space $V_{\rm eff}(r, \theta)$, derive the quantum-shifted vacuum and scalar Hessian, and identify the parameter conditions required for local stability. The heavy Majorana fermion decouples from irrelevant operators but leaves non-decoupling threshold corrections to relevant symmetry-breaking operators. At finite temperature, the explicit breaking spurion $M$ induces a thermal tadpole $\propto M T^2 r \cos\theta$. This term prevents the origin from ever being a stationary point, ensuring that the radial vacuum expectation value remains non-zero at all temperatures. Consequently, the system undergoes a smooth crossover rather than a true symmetry-restoring phase transition, and the pseudo-Goldstone description remains rigorously valid across all temperature regimes. The resulting effective potential is a periodic non-linear sigma model whose Wilson coefficients follow a two-parameter lattice classification.

        Speaker: Mr Mussawir Khan (State Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China)
        Mussawir_khan_IHEP.pdf
      • 11:40
        Introduction to Axion 2027 10m
        Speaker: Yun Jiang (Sun Yat-sen University)
    • 11:50 → 11:55
      Closing Remark
    • 11:55 → 14:00
      Lunch Zhonghua Restaurant (buffet)

      Zhonghua Restaurant (buffet)
    • 14:00 → 18:00
      Free
  • Thursday, 13 August
    • 08:00 → 18:00
      Check-out
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