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The Fourth International Conference on Axion Physics and Experiment (Axion 2025)

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Lakeview Xuanwu Hotel, Nanjing

Lakeview Xuanwu Hotel, Nanjing

193 Zhong Yang Road, Nanjing, Jiangsu 210009, China (Hotel Reservation Tel: +86 25 8335 8888)
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 fourth of the series, following Axion 2022, Axion 2023 and Axion 2024.

Schedule: Arrive: 27th July (Sunday). Departure: 31st July(Thursday).
The conference will be held from the 28th (Monday) to 30st (Wednesday) of July.

Registration deadline: 3rd Jun. 2025
Please make your reservation as soon as possible as the number of hotel rooms is limited.

Registration fee：2200 Yuan (CNY) for faculty and postdocs, 1800 Yuan (CNY) for students.

Workshop venue：Lakeview Xuanwu Hotel 南京玄武饭店

Address: 193 Zhong Yang Road, Nanjing, Jiangsu 210009, China
(Hotel Reservation Tel: +86 25 8335 8888)

Hotel Website: https://www.xuanwu.com.cn/index.php.html

Alternative hotel:
江苏凤凰台饭店（距离玄武饭店会场520m，步行大概8分钟）
地址：江苏省 · 南京市 · 鼓楼区 · 湖南路47号

Contact details: 

Yongchao Zhang (zhangyongchao@seu.edu.cn) Phone: 18061239328
Lina Wu (wulina@xatu.edu.cn) Phone: 18591005993

Secretary:   
Yue Lu (2238854008@qq.com) Phone: 15365073402

参会证明_certificate.pdf
Participants
  • . Pirzada
  • Andrew Cheek
  • Andrew Fowlie
  • Anna Zakharova
  • Bhupal Dev
  • Bilal Ahmad
  • Bo Wang
  • Christina Gao
  • Da Huang
  • Di Chen
  • Guanhua Gu
  • Gui-Rong Liang
  • Haidar Alfanda
  • He-Xu Zhang
  • Hong Zhang
  • Hua-Xing Chen
  • Huaike Guo
  • Imtiaz Khan
  • Jian Zhang
  • Jin-Bao Wang
  • Jingqiang Ye
  • Jinmian Li
  • Jinwei Wang
  • Junhao Zhu
  • Junhao Zhu
  • Junle Pei
  • Kaidong Zhou
  • Kevin Zhou
  • Kim Siang Khaw
  • Kiwoon Choi
  • Ligong Bian
  • Lin-Qing Gao
  • Lina Wu
  • Muhammad Ali
  • Mussawir Khan
  • Muyuan Song
  • Ngoc Khanh Vu
  • Nick Houston
  • P. S. Bhupal Dev
  • Peiwen Wu
  • Peng-Long Zhang
  • Pierluca Carenza
  • Qiaoli Yang
  • Renhui Qin
  • Sang Hui Im
  • Shaoping Li
  • Shota Nakagawa
  • Shu Li
  • Shyam Balaji
  • Sichun Sun
  • Sudhakantha Girmohanta
  • Tianjun Li
  • Tong Li
  • Wei Chao
  • Wei-Xiang Feng
  • Wenxing Zhang
  • Xiangyan An
  • Xiao He
  • Xiao He
  • Xin Zhang
  • XING RONG
  • xinxin qi
  • Yanjie Zeng
  • Yinda Guo
  • Yongcheng Wu
  • Yu Gao
  • Yu-ang Liu
  • Yu-Ming Yang
  • Yuan-Hann Chang
  • Yue Huang
  • Yue Yin
  • Yuichiro Nakai
  • Yun Jiang
  • Zheng-Wei Li
  • Zhong Zhang
  • Zihang Wang
  • Zuowei Liu
  • 典为 Dian-Wei 王 Wang
  • 国庆 魏
  • 拿云 Nayun 贾 Jia
  • 权宜 胡
  • 润琪 康
  • 琦 宋
  • 端 佘
Yongchao Zhang
  • Sunday, 27 July
    • 14:00 → 18:00
      Registration
    • 18:00 → 20:00
      Dinner 2h 锦蝶轩 (Lepapillon Restaurant)

      锦蝶轩

      Lepapillon Restaurant

      1F
  • Monday, 28 July
    • 08:15 → 08:30
      Opening ceremony 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Prof. Yongchao Zhang
    • 08:30 → 10:00
      Morning Session: I 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Yongchao Zhang
      • 08:30
        PQ-quality and scale hierarchy of extra-dimensional axions 30m

        We discuss the PQ-quality and the possible hierarchical patterns of axion scales (and couplings) for extra-dimensional axions that originate from higher-dimensional p-form gauge fields. As a concrete example, we consider a 5-dim model on Z2-orbifold involving 1-form and 3-form gauge fields, and examine how the warped geometry and fixed-point interactions affect the PQ-quality and axion scale hierarchy.

        Speaker: Prof. Kiwoon Choi
        Day1_Session1_1_choi_axion_2025.pdf
      • 09:00
        Model of the quintessence axion 30m

        We construct a model of the quintessence axion based on a gauged chiral U(1) symmetry and an additional flat fifth dimension. The required high qualities are guaranteed by the brane separation. The observed cosmological constant (i.e., the potential energy of the quintessence axion) is determined by the size of the extra dimension and the axion decay constant F_a is fixed almost at F_a ≃ 10^17 GeV, which is sufficiently large for the stability of the axion field near the hilltop of its potential. Furthermore, the movement of the axion can also easily explain the recently reported isotropic cosmic birefringence of the cosmic microwave background photon.

        Speaker: Prof. Jinwei Wang (UESTC)
        Day1_Session1_2_Wang_Jinwei_axion model.pdf
      • 09:30
        Axion from topological defects 30m

        TBA

        Speaker: Prof. Ligong Bian (Chongqing University)
        Day1_Session1_3_Bian_Ligong_Axion from topological defects_LGB.pdf
    • 10:00 → 10:30
      Photo and Coffee break 30m
    • 10:30 → 12:00
      Morning Session: II 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Yu Gao (IHEP, CAS)
      • 10:30
        Searching for Solar and Reactor Axions with XENONnT and RELICS 30m

        Searching for Solar and Reactor Axions with XENONnT and RELICS

        Axions can be produced in the Sun through processes such as inverse Compton scattering, the Primakoff effect, and the Fe57 deexcitation, and detected in noble liquid experiments via the inverse Primakoff effect and the axio-electric effect. Liquid xenon experiments, with their large exposure, low background, and low-energy thresholds, offer competitive sensitivities to axions. XENONnT, a dark matter liquid xenon experiment designed primarily for dark matter searches, has set competitive limits on axion-electron and axion-photon couplings. Additionally, axions can be produced in nuclear reactors via similar mechanisms. The RELICS experiment, currently under construction, will also employ liquid xenon to search for reactor-produced axions. In this talk, I will discuss the complementary approaches of solar and reactor axion searches, highlighting the synergies between XENONnT and RELICS in the quest for axions.

        Speaker: Jingqiang Ye (The Chinese University of Hong Kong, Shenzhen)
        axion_2025_ye.pdf
      • 11:00
        Dark photon dark matter search at the TASEH experiment 30m 玄武厅

        玄武厅

        Ball Room

        2F

        The dark photon is a well motivated candidate for the dark matter. A primary tool in this search is the cavity haloscope, which facilitates resonantly enhanced conversion to photons from dark photons. We re-examining the data taken by the Taiwan Axion Search Experiment with Haloscope (TASEH) experiment, and derive a world-leading constraint on the dark photon with mass in the 19.46 - 19.84 $\mu$eV mass range. The bound exceeds the naive `rescaling limit' by roughly one order of magnitude. In this data, we also identify a tentative signal with a local significance of 4.7 $\sigma$, previously disregarded due to an axion-specific veto, corresponding to a dark photon with mass ~ 19.5 $\mu$eV.

        Speaker: Prof. Jinmian Li
        Day1_Session2_2_DarkPhoton_TASEH_Axion2025_Jinmian Li.pdf
      • 11:30
        Gravitational Wave Birefringence in Fuzzy Dark Matter and Symmetron Cosmology 30m

        Gravitational wave (GW) birefringence is a remarkable phenomenon which provides a window to test partiy violation in gravity. In this talk, I would discuss our recent studies on the GW birefringence in the FDM and symmetron models. In particular, inspired by the complicated distributions of the Fuzzy dark matter (FDM) and the symmetron field in our Galaxy, we are led to considering the GW propagation over the light scalar profile of general spacetime dependence. We apply the well-known eikonal approximation to solve this technical problem. In the FDM case, it is shown that GWs exhibit the amplitude birefringence with the dominant contribution only depending on the GW frequency. More importantly, the birefringence factor shows a periodic time modulation with its period reflecting the FDM mass, which is the smoking gun to test this FDM-induced mechanism. In the symmetron model, we introduce a new Z_2-symmetric Chern-Simons-like coupling, which can also generate the amplitude birefringence. However, unlike the FDM case, the birefringence induced by the galactic symmetron field is suppressed due to its screening mechanism. Thus, the GW birefringence is dominantly generated by the extra-galactic symmetron distribution, which can be further used to place a reasonable constraint on this parity-violating coupling in the symmetron model.

        Speaker: Da Huang (National Astronomical Observatories, Chinese Academy of Sciences)
        GWBi0728.pdf
    • 12:00 → 14:00
      Lunch 2h 望湖璇宫 (Lakeview Revolving Restaurant)

      望湖璇宫

      Lakeview Revolving Restaurant

      20F
    • 14:00 → 15:30
      Afternoon Session: I 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Huaike Guo (University of Chinese Academy of Sciences)
      • 14:00
        Small Instantons and the Post-Inflationary QCD Axion in a Special Product GUT 30m

        We present a new framework of grand unification that is equipped with an axion solution to the strong CP problem without a domain wall problem when the Peccei–Quinn (PQ) symmetry is spontaneously broken after inflation. Our grand unified theory (GUT) is based on a symmetry breaking pattern, SU(10) × SU(5)1 → SU(5)V ⊃ SU(3)C × SU(2)L × U(1)Y, where SU(5)1 and a special embedding of SU(5)2 ⊂ SU(10) are broken to a diagonal subgroup SU(5)V. The model contains a vector-like pair of PQ-charged fermions that transform as (anti-)fundamental representations under SU(10), so that the domain wall number is one. However, after the GUT symmetry breaking, the number of vector-like pairs of PQ-charged colored fermions is larger than one, which seems to encounter the domain wall problem. This apparent inconsistency is resolved by small instanton effects on the axion potential which operate as a PQ-violating bias term and allow the decay of domain walls. We propose a domain-wall-free UV completion for an IR model where the domain wall number appears larger than one. The model gives a prediction for a dark matter axion window, which is different from that of the ordinary post-inflationary QCD axion with domain wall number one.

        Speaker: Prof. Yuichiro Nakai
        Day1_Session3_1_Axion2025-Nakai.pdf
      • 14:30
        Observation of quantum entanglement in $\Lambda \bar{\Lambda}$ pair production via electron-positron annihilation 30m

        We report the observation of quantum entanglement in $\Lambda\bar{\Lambda}$ pairs produced via electron-positron annihilation, specifically through the decay $J/\psi \to \Lambda\bar{\Lambda}$. By analyzing the angular correlations of the subsequent weak decays $\Lambda \to p\pi^-$ and $\bar{\Lambda} \to \bar{p}\pi^+$, we derive normalized observables $\mathcal{O}_i~(i=0,1,\ldots,4)$ that distinguish entangled states from separable ones. Theoretical predictions for these observables are established, with violations of separable-state bounds serving as unambiguous signatures of entanglement. Experimental measurements at $\cos\theta_\Lambda = 0$ yield $\mathcal{O}_{1\text{min}}^{\text{Observed}} = -0.7374\pm 0.0011\pm 0.0016$, significantly exceeding the classical limit of $-0.5$ with a statistical significance of 124.9$\sigma$. For $\left|\cos\theta_\Lambda\right|<0.4883$, the observed $\mathcal{O}_{1}^{\text{Observed}}$ consistently exhibits $\mathcal{O}_{1}^{\text{Observed}} < -\frac{1}{2}$ with a statistical significance of at least 5$\sigma$. Since $69.3\%$ of the decay events involving $\Lambda\to p+\pi^-$ and $\bar{\Lambda}\to \bar{p}+\pi^+$ are spacelike-separated, our results confirming the persistence of quantum entanglement in the $\Lambda\bar{\Lambda}$ system provide strong support for the non-locality of quantum mechanics. The findings are consistent with theoretical expectations under decoherence-free conditions, highlighting the potential of hyperon pairs as probes for fundamental quantum phenomena.

        Speaker: Dr Junle Pei
        Junle Pei.pdf
      • 15:00
        Probing Heavy Axion-like Particles from Massive Stars with X-rays and Gamma Rays 30m

        The hot interiors of massive stars in the later stages of their evolution provide an ideal place for the production of heavy axion-like particles (ALPs) with mass up to O(100 keV) range. We show that a fraction of these ALPs could stream out of the stellar photosphere and subsequently decay into two photons that can be potentially detected on or near the Earth. In particular, we estimate the photon flux originating from the spontaneous decay of heavy ALPs produced inside Horizontal Branch and Wolf-Rayet stars, and assess its detectability by current and future X-ray and gamma-ray telescopes.

        Speaker: Prof. P. S. Bhupal Dev
        dev_axion2025.pdf
    • 15:30 → 16:00
      Coffee break 30m
    • 16:00 → 18:30
      Afternoon Session: II 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Yun Jiang (Sun Yat-sen University)
      • 16:00
        Probe CP Structure of Axion-Like Particles at Future Lepton Collider 25m 玄武厅

        玄武厅

        Ball Room

        2F

        We study a charge-parity (CP) violating Axion-like particle (ALP) involved in both CP-even ($a F_{\mu\nu}\tilde{F}^{\mu\nu}$) and CP-odd ($a F_{\mu\nu}F^{\mu\nu}$) ALP-photon interaction at future lepton colliders. We examine the properties of the ALP and its CP structure by analyzing the $e^+e^-\to e^+e^-a\to e^+e^-\gamma\gamma$ channels. A CP-sensitive observable $\Delta\phi_{ee}$, is employed, signifying the azimuthal angular difference between the final state electrons. The constraints on the couplings of CP-violating ALPs at future lepton collider can reach $\mathcal{O}(10^{-3})$ TeV$^{-1}$, surpassing the sensitivity conducted in the electric dipole moment of electron ($e$EDM). Since the contributions originating from purely CP-even, purely CP-odd and CP-violating ALP-photon interactions exhibit distinct behaviors in the differential distribution of the observable $\Delta\phi_{ee}$, a binned likelihood analysis effectively discriminates the CP structure of the ALP. Specifically, if CP-even coupling constants are close to those of the CP-odd ALP-photon interaction under certain new symmetry assumptions, the presence of CP violation in the ALP sector can be tested upon the discovery of direct evidence for ALPs by future lepton colliders. For cases where the two coupling constants are not close to one another, an increased integral luminosity substantially enhances the sensitivity in probing CP-violating ALPs.

        Speaker: Dr Muyuan Song
        MuyuansonALPtalk.pdf
      • 16:25
        The cosmological consequences of preferred axion models 25m

        The preferred axion models are a set of minimal QCD axion models that abide by standard cosmological constraints in the post-inflationary PQ breaking scenario. It turns out that some of these models predict a period of early matter domination, driven by the additional particle content. I will discuss how this leads to a greater number of models with consistent cosmologies and alters the axion dark matter mass range. On the other hand, the decay products of the new heavy particles may contribute to the number of relativistic degrees of freedom during recombination. This allows us to make concrete predictions and distinguish against preferred axion models, even in scenarios where early matter domination doesn't occur. I will also discuss the potential for gravitational wave astronomy to probe these models.

        Speaker: Andrew Cheek (TDLI, SJTU)
        Cosmo_pref_axionMods_Cheek.pdf
      • 16:50
        Recent Dark “Matter/Photon/Higgs” search results from ATLAS 25m
        Speaker: Ngoc Khanh Vu
        DMsearches_KhanhNVU.pdf
      • 17:15
        Superradiant dark matter production from primordial black holes 25m 玄武厅

        玄武厅

        Ball Room

        2F

        Rotating primordial black holes (PBHs) in the early universe can emit particles through superradiance, a process particularly efficient when the particle's Compton wavelength is comparable to the PBH's gravitational radius. Superradiance leads to an exponential growth of particle occupation numbers in gravitationally bound states. We present an analysis of heavy bosonic dark matter (DM) production through three gravitational mechanisms: Hawking radiation, superradiant instabilities, and ultraviolet (UV) freeze-in. We consider PBHs that evaporate before Big Bang Nucleosynthesis (BBN). For both scalar and vector DM, our analysis incorporates the evolution of a second superradiant mode. We demonstrate that the growth of a second superradiant mode causes the decay of the first mode, and thus the second mode cannot further enhance the DM abundance beyond that already achieved by the first mode. Our study also reveals that while superradiance generally enhances DM production, gravitational wave (GW) emission from the superradiant cloud may significantly modify this picture. For scalar DM, GW emission reduces the parameter space where superradiance effectively augments relic abundance. For vector DM, rapid GW emission from the superradiant cloud may yield relic abundances below those achieved through Hawking radiation alone. These findings demonstrate that multiple-mode effect and GW emission play critical roles in modeling DM production from PBHs in the early universe.

        Speaker: Mr Nayun Jia (Northeastern University)
        jny_nanjing_slides.pdf
      • 17:40
        Recent Progress of DarkSHINE R&D 25m

        DarkSHINE is a fixed-target experiment initiative to search for light Dark Matter and mediators at SHINE (Shanghai high repetition rate XFEL and extreme light facility, being the 1st hard X-ray FEL in China) under construction targeting completion in 2025/2026. DarkSHINE aims to search for the new mediator, Dark Photon, bridging the Dark sector and the ordinary matter. In this contribution, we present the idea of this new project and 1st prospective study in search for Dark Photon decaying into light dark matter as well as the very recent technical R&D progresses. It also provides the opportunity to incorporate broader scope of BSM search ideas such as ALP / Anomalous Muonium / LLP / etc. and electron/photon/neutrino-nuclear interaction product measurements, utilizing the fixed-target experiment of this type. Also in the future, DarkSHINE experiment has the great potential to be upgraded into positron beam mode and search for Dark Photon via more production channels through s/t-channel annihilations. Last but not least, DarkSHINE will likely provide cross-reference experimental DATA together with future LDMX experiment, the continued NA64 experiment, etc. to become part of the global efforts for accelerator based Dark Matter searches.

        Speaker: Dr Haidar Alfanda (Tsung-Dao Lee Institute, Shanghai Jiao Tong University (CN))
        DarkSHINE_Axion_2025_0728.pdf
      • 18:05
        Probing dark matter with Central Molecular Zone ionisation 25m

        We demonstrate that the anomalous ionization rate observed in the Central Molecular Zone can be attributed to MeV dark matter annihilations into electron-positron pairs with a cuspy dark matter distribution (\gamma>1). The low annihilation cross-sections required avoid cosmological constraints and imply no detectable inverse Compton, bremsstrahlung or synchrotron emissions in radio, X and gamma rays. The possible connection to the source of the unexplained 511 keV line emission in the Galactic Center suggests that both observations could be correlated and have a common origin.

        Speaker: Shyam Balaji
        Balaji_Shyam_AXION_2025conf_SB.pdf
    • 18:45 → 20:45
      Banquet 2h 锦绣厅 (Jin Xiu Room)

      锦绣厅

      Jin Xiu Room

      2F
  • Tuesday, 29 July
    • 08:30 → 10:00
      Morning Session: III 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Yuichiro Nakai (TDLI)
      • 08:30
        Laboratory enhanced searches for decaying axion dark matter 30m 玄武厅

        玄武厅

        Ball Room

        2F

        The axion is particularly well motivated candidate for the dark matter comprising most of the mass of our visible Universe, leading to worldwide experimental and observational efforts towards its discovery. A primary technique in this search is the cavity haloscope, which is used to enhance the rate that dark matter axions convert to photons in a background electromagnetic field. As we discuss, the same haloscope technique can also be used to enhance the rate at which axions decay to two photons, as a manifestation of the Purcell effect. We explore this possibility, and show that it offers a novel method to explore the axion parameter space that is competitive and complimentary to other approaches

        Speaker: Nick Houston (北京工业大学)
        NHouston axion 2025.pdf
      • 09:00
        Are axion solutions to the CP problem fine-tuned? 30m 玄武厅

        玄武厅

        Ball Room

        2F

        TBA

        Speaker: Prof. Andrew Fowlie
        Day2_Session1_2_fowlie_axions_2025.pdf
      • 09:30
        Reconciling Neutrino Mass Bounds with Strongly Self-Interacting Dark Radiation 30m
        Speaker: Christina Gao (SUSTech)
        Day2_Session1_3_Nanjing_25_Gao.pdf
    • 10:00 → 10:30
      Coffee break 30m
    • 10:30 → 12:30
      Morning Session: IV 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Hong Zhang (Shandong University -Qingdao)
      • 10:30
        Dynamics of multi-vacuum from stochastic axion frangmentation 30m
        Speaker: Yun Jiang (Sun Yat-sen University)
        Day2_Session2_1_20250729_Multi-vacuum_v2.pdf
      • 11:00
        Search for Millicharged dark matter via Multimessenger Time-Delay Analysis of GRB GW170817A 30m 玄武厅

        玄武厅

        Ball Room

        2F

        We derive new constraints on millicharged dark matter from the multimessenger observation of GW170817. In the neutron star merger event GW170817, the first detection of a gamma-ray burst (GRB) delayed by approximately 1.7 seconds relative to the gravitational wave emission was observed. Utilizing this delay, we constrain the millicharge parameter of dark matter within the large-scale structure of the universe. For dark matter masses below 10−15 eV, the millicharge parameter is constrained to be less than 10−14, representing the most stringent limits achieved to date.

        Speaker: Dr Wenxing Zhang (Hebei University)
        Day2_Session2_2_ALP_GRB170817A.pdf
      • 11:30
        Current status of the Muon g-2 and EDM 30m

        In this talk, I will present the latest results from the Fermilab Muon g-2 experiment and the current status of the PSI muEDM experiment. I will also discuss how these muon storage experiments can be used to search for new particles, such as axions.

        Speaker: Kim Siang Khaw (SJTU)
        Day2_Session2_3_Axion2025_Khaw_20250729.pdf
      • 12:00
        Generation of Axions and Axion-Like Particles through Mass Parametric Resonance induced by Scalar Perturbations in the Early Universe 30m 玄武厅

        玄武厅

        Ball Room

        2F

        We show that scalar perturbations in the early universe could produce a significant amount of these particles primarily through mass parametric resonance effects. Notably, this mechanism does not generate additional isocurvature perturbations.

        Speaker: Prof. Qiaoli Yang (Jinan University)
        Day2_Session2_4_ALPgeneration.pdf
    • 12:30 → 14:00
      Lunch 1h 30m 望湖璇宫 (Lakeview Revolving Restaurant)

      望湖璇宫

      Lakeview Revolving Restaurant

      20F
    • 14:00 → 15:40
      Afternoon Session: III 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Wei Chao (BNU)
      • 14:00
        Distinguishing Light Scalars via CP: Dilaton and Axion at Belle II 25m

        We present a detailed phenomenological study of a light dilaton $\varphi$, arising from the spontaneous breaking of approximate scale invariance in a nearly conformal theory. Particular care is taken to account for the dilaton’s enhanced coupling to photons, originating from loops of the conformal sector, which significantly shortens its lifetime and relaxes constraints from $K \to \pi + {\rm inv.}$ searches at NA62 and cosmological constraints from the Big Bang Nucleosynthesis. New model-independent inclusive bounds from $b \to s \varphi$ transitions are obtained. Proceeding further, we consider the dilaton discovery prospect in a collider such as Belle II and outline how to distinguish it from an axion $a$ having a similar final state signature without relying on how $\varphi/a$ decays. The CP property can be used as it modifies the variation of the differential cross-section of $e^+ e^- \to e^+ e^- \varphi/a$ with the azimuthal angle between the outgoing leptons.

        Speaker: Dr Sudhakantha Girmohanta (Tsung-Dao Lee Institute)
        Girmohanta_axion2025.pdf
      • 14:25
        The Superconducting Heterodyne Approach to Axion Detection 25m

        Though most axion dark matter experiments use static background fields, the axion also induces transitions between oscillating modes of an excited cavity. This "heterodyne" detection approach benefits from the very high quality factors available in superconducting cavities, and has a parametrically enhanced signal power at low axion masses. I will review recent experimental progress on this concept, which is currently being pursued by a number of groups, with a particular focus on new results from SLAC.

        Speaker: Mr Kevin Zhou (UC Berkeley)
        Zhou_Kevin_Slides.pdf
      • 14:50
        QCD axion dark matter with Peccei-Quinn symmetry breaking by a light scalar field 25m

        QCD axion can explain the strong CP problem and dark matter (DM) simultaneously. If the Peccei-Quinn (PQ) symmetry is spontaneously broken after inflation, string-wall network would dominate the energy density in the Universe. In this talk, we consider a mixing coupling of the PQ scalar with a light scalar field which induces an extra axion potential. When the PQ scalar is mixed nonlinearly, the axion oscillation around the extra potential triggers the formation of stable domain wall. However, the system collapses due to the QCD effect as a bias, resulting in a large amount of dark matter. In addition, by estimating the misalignment production modified by the extra potential, we clarify the total abundance of axion dark matter.

        Speaker: Shota Nakagawa (Tsung-Dao Lee Institute)
        Axion_Nakagawa.pdf
      • 15:15
        Mesonic contributions to axion thermalization below the QCD crossover in the KSVZ axion model 25m

        Constraints on axions as hot dark matter (HDM) from $\Delta N_{\rm eff}$ provide an important and independent probe of axion properties. In hadronic axion models such as the KSVZ model, the axion thermalization rate below the QCD crossover temperature is typically estimated under two key assumptions: (1). thermal corrections to the reaction amplitudes are negligible at $T < M_{\rm th}/2$ with Mth the reaction threshold and (2). axion-pion interaction ($a \pi \leftrightarrow \pi\pi$) dominates unless specically suppressed.
        In this talk, we critically reexamine these assumptions by systematically calculating the relevant corrections to the axion thermalization rate in the KSVZ axion model. Our analysis emphasizes the role of nonperturbative mesonic dynamics in the relevant processes. The results also have implications for meson-driven thermalization in other axion models.

        Speaker: Jinbao Wang (东南大学)
        wjb-Axion-2025.pdf
    • 15:40 → 16:00
      Coffee break 20m
    • 16:00 → 18:45
      Afternoon Session: IV 玄武厅 (Ball Room)

      玄武厅

      Ball Room

      2F
      Convener: Tianjun Li (Institute of Theoretical Physics, Chinese Academy of Sciences)
      • 16:00
        Finite temperature effective theory for Electroweak phase transition 25m 玄武厅

        玄武厅

        Ball Room

        2F

        TBA

        Speaker: Renhui Qin (Chongqing University)
        ppt-finite temperature effective theory for electroweak phase transition.pdf
      • 16:25
        Black hole superradiance as a source of high-energy cosmic rays 25m 玄武厅

        玄武厅

        Ball Room

        2F

        Ultralight charged bosons can extract energy, angular momentum, and charge from a Kerr–Newman black hole (BH) due to superradiant instability, resulting in the formation of a BH–condensate system. In this work, we focus on a scalar field with a minicharge and numerically investigate in detail the evolution of this system. We find that even a tiny initial mass asymmetry between the positively and negatively charged components of the condensate can induce continuous charge accumulation in an initially neutral BH. BHs can accumulate charges large enough to induce the Schwinger effect, which leads to a copious production of electron–positron pairs. The particles carrying the charge opposite to that of the BH are emitted with electrical potential energies up to $\sim 10^{21}$ eV, suggesting that BH superradiance may serve as a source of high-energy cosmic rays.

        Speaker: Mr Yinda Guo (Shandong University)
      • 16:50
        Simulations of Fuzzy Dark Matter 25m 玄武厅

        玄武厅

        Ball Room

        2F

        As an alternative theory to cold dark matter (CDM), fuzzy dark matter (FDM) has recently attracted widespread attention. FDM consists of ultra-light bosons with masses around 10^{-22} eV. At typical galactic velocities, their de Broglie wavelength can reach kiloparsec (kpc) scales, thereby exhibiting unique wave-like behavior on galactic scales. This leads to complex evolutionary dynamics and observational effects, which may help address several small-scale challenges the CDM paradigm faces. Unlike other dark matter models, FDM is described by a wavefunction that follows the Schrödinger equation. In this presentation, I will introduce some of our recent work on FDM simulations, including: the construction of wavefunction initial conditions, the removal of initial velocity in FDM halo wavefunctions, self-consistent simulations of FDM and stellar systems, and tidal simulations of FDM subhalos.

        Speaker: Mr Yu-Ming Yang (IHEP)
        Fuzzy_Dark_Matter_Yang.pdf
      • 17:15
        SRF Cavity Search for Dark Photon 25m 玄武厅

        玄武厅

        Ball Room

        2F

        Superconducting radio-frequency (SRF) cavities, renowned for their exceptionally high quality factors (~10^10), have emerged as powerful tools for probing fundamental physics beyond the Standard Model. In this talk, I will introduce the first-ever scan search for dark photon dark matter using a tunable SRF cavity, achieving unprecedented sensitivity to the kinetic mixing coefficient parameter ε . By mechanically adjusting the resonant frequency of a niobium cavity in a 2 K liquid helium environment, we scanned a 1.37 MHz range centered at 1.3 GHz, setting the world’s tightest constraints on ε. Beyond terrestrial dark photon dark matter, we also demonstrate that SRF cavities can serve as sensitive detectors for galactic dark photon backgrounds, leveraging their directional sensitivity to probe potential anisotropic signals. Finally, we present a theoretical framework where an array of coupled electromagnetic detectors significantly enhances scan rates for ultralight dark matter and high-frequency gravitational waves.

        Speaker: Yanjie Zeng (ITP, CAS)
        Axion_2025_Yanjie_Zeng.pdf
      • 17:40
        Composite dark matter axion-like particles: Glueball-ALPs 25m 玄武厅

        玄武厅

        Ball Room

        2F

        I will present a composite dark matter framework based on the confinement dynamics of a dark SU(N) Yang-Mills sector. This theory gives rise to composite bound states, glueballs, that in the absence of fermions serve as dark matter candidates. I will review recent developments in understanding glueball production in the early Universe and delineate the parameter space where they can account for the entirety of dark matter. A particular focus will be placed on a novel class of states: pseudoscalar glueballs with axion-like properties, dubbed Glueball-ALPs (GALPs), bridging the phenomenology of glueballs and axion-like particles, opening new directions for modelling axion-like dark matter.

        Speaker: Dr Pierluca Carenza
        Carenza_Pierluca_Pres_ICAxion (2).pdf
      • 18:05
        Emerging axion detection in magnetoelectric materials 30m 玄武厅

        玄武厅

        Ball Room

        2F
        Speaker: Sichun Sun (Beijing Institute of Technology)
        Day2_Session4_7_Emergingaxion.pptx
      • 18:35
        Introduction of the Axion 2026 Conference 10m
        Speaker: Hong Zhang
        Day2_Session4_8_20250729_HongZhang.pptx
    • 18:45 → 20:45
      Dinner 2h 锦蝶轩 (Lepapillon Restaurant)

      锦蝶轩

      Lepapillon Restaurant

      1F
  • Wednesday, 30 July
    • 09:00 → 10:30
      Morning Session: V 聚星厅 (Ju Xing Room)

      聚星厅

      Ju Xing Room

      2F
      Convener: Prof. Yongchao Zhang
      • 09:00
        Search for Axion Dark Matter with the TASEH experiment 30m

        Haloscoope experiment, with the assumption that the Dark Matter is completely made of Axions, provides the highest Axion search sensitivity. The TASEH experiment is a Haloscope experiment with a copper coated stainless steel cavity inside a 9T magnet in a Dilution Refrigerator operating at 50 mK base temperature. An amplification chain with a self-developed Josephson Parametric Amplifier has been implemented and successfully achieved a noise level corresponding to 1.2 photon around 2.1 GHz. Data taking around this frequency is ongoing. Preliminary analysis indicates that a sensitivity of 1.5 times the benchmark KSVZ model of QCD Axion can be achieved. The contribution reports the latest progress of the TASEH experiment and the plans for the near future.

        Speaker: Prof. Yuan-Hann Chang
        Yuan_Hann_Chang_TASEH_Axion2025.pdf
      • 09:30
        The EDM inverse problem: identifying the sources of CP violation and PQ breaking with EDMs 30m
        Speaker: Sang Hui Im
        Sang_Hui_Im_EDM inverse problem_Nanjing.pdf
      • 10:00
        Laser-assisted search for axion-like particle or dark photon in strong-field QED 30m

        In this talk I propose a laser-assisted method for the search of light dark particles such as axion-like particle and dark photon. I will first introduce strong-field QED framework and laser-assisted Compton scattering. Then I will discuss the laser-induced Compton scattering to dark particles and show the prospect of detection.

        Speaker: Prof. Tong Li (Nankai University)
        Nanjing-litong1.pdf
    • 12:00 → 14:00
      Lunch 2h 锦蝶轩 (Lepapillon Restaurant)

      锦蝶轩

      Lepapillon Restaurant

      1F
    • 14:00 → 18:00
      Free discussions 4h
  • Thursday, 31 July
    • 09:00 → 13:00
      Departure
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