Opening ceremony

The Axion and Dark Photon Experiment and its Future Perspective

• Zhihui Peng

TBA

Flavor changing interactions of Axion and Majoron

• Xiaogang He

TBA

New physics with cosmic photons

• Boqiang Ma

We show that the recent observations of cosmic photons provide the ideal platform to study new physics like Lorentz violation, axion physics, and sterile neutrinos.

Axion search in astronomical environments

• Xiaojun Bi

报告将简单综述在天体环境下探测轴子的观测效应，并较为具体介绍轴子对高能伽马射线能谱的修正，轴子暗物质在中子星、白矮星等致密天体附近的转化信号以及在黑洞喷发的jet中轴子可能导致的辐射圆极化的产生等过程，以及当前观测利用这些过程对于轴子耦合系数的限制。

Searching for exotic spin-dependent interactions by diamond quantum sensors

• Xing Rong

Searching for physics beyond the standard model is crucial for understanding several fundamental conundrums in physics and astrophysics. Several hypothetical particles can mediate exotic spin-dependent interactions between ordinary fermions, which enable laboratory searches via the detection of the interactions. We present a platform based on diamond quantum sensors for investigating exotic spin-dependent interactions at micrometer scales. I will discuss one rencent result which is to conduct experimental searches for exotic spin-dependent interactions with an ensemble-NV-diamond magnetometer. Our work shows that NV ensembles are highly capable of probing exotic spin-spin interactions beyond the Standard Model.

Muon g-2, Long-Range Muon Spin Force, and Neutrino Oscillations

• Xiaoping Wang

Recent studies have proposed using a geocentric muon spin force to account for the (g−2)μ anomaly, with the long-range force mediator being a light axion-like particle. The mediator exhibits a CP-violating scalar coupling to nucleons and a normal derivative coupling to muons. Due to the weak symmetry, this axion inevitably couples to neutrinos, providing potential impact on neutrino oscillations. By utilizing neutrino data from BOREXINO, IceCube DeepCore, Super-Kamiokande, and SNO, we have identified that atmospheric neutrino data can impose stringent constraints on the long-range muon spin force model and the (g−2)μ parameter space. Additionally, solar neutrino data places a strong limit on the model but provides a weaker constraint on the (g−2)μ parameter space due to a sign mismatch. With optimized data analysis techniques and the potential from future experiments, such as JUNO, Hyper-Kamiokande, SNO+, and IceCube PINGU, there exists a promising opportunity to achieve even greater sensitivities. Indeed, neutrino oscillations offer a robust and distinctive cross-check for the model, offering stringent constraints on the (g−2)μ parameter space.

New Ways to Search Axion Dark Matter

• Qiaoli Yang

Axions and Axion-Like Particles are highly anticipated elementary particles. Researches have shown that they may also be an important component of dark matter. However, traditional paticle detection schemes are insensitive to this type of extremely weak interacting wave-like particles, thus innovative detection schemes may be an important factor in achieving breakthroughs. In this talk, we will discuss some innovative axion detection schemes.

Search for exotic spin-dependent interactions with spin sensors

• Xinhua Peng
• Min Jiang

TBA

The Consistent Chiral Lagrangian for Axions and Hadron Physics

• Jia Liu

TBA

Constraints on Axionlike Particles from gamma ray observations

• Lei Feng (Purple Mountain Observatory, Chinese Academy of Sciences)

Axion-like particles (ALPs) can oscillate into photons and vice versa in the magnetic fields, which may generate detectable effects on γ-ray spectra. We search for such oscillation effects in the spectra of supernova remnants caused by the photon-ALP conversion, using the Fermi Large Area Telescope and HESS gamma-ray data and constraints the parameter space of ALP.

Black hole superradiance

• Hong Zhang

Ultralight scalars and vectors are popular dark matter candidates.They could extract energy and angular momentum from a Kerr black hole (BH) if the wave length is comparable to the size of BH horizon, forming a sizeable condensate around the host BH. In this talk, I will introduce the evolution of the BH-condensate system and its gravitational wave emission. The effect of accretion will also be discussed.

High-Quality Axions in a Class of Chiral U(1) Gauge Theories

• Jin-Wei Wang (UESTC)

We show that there are many candidates for the quintessence and/or the QCD axions in a class of chiral $U(1)$ gauge theories. Their qualities are high enough to serve as the dark energy and/or to solve the strong CP problem. Interestingly, the high quality of axion is guaranteed by the gauged $U(1)$ and $Z_{2N}$ symmetries and hence free from the non-perturbative quantum gravity corrections. Furthermore, our mechanism can be easily applied to the Fuzzy dark matter axion scenarios.

Possible Dark Matter Signals from White Dwarfs

• Jia-Shu Niu (Shanxi University)

In our galaxy, the white dwarfs (WDs) will inevitably capture the dark matter (DM) particles streaming through them, if there exist interactions between DM particles and nuclei/electrons. At the same time, these DM particles can also be evaporated by the nuclei/electrons in a WD if they have proper mass and the WD is not too cold. The evaporation of DM particles will lead to a faster cooling evolution than that predicted by the stellar evolution theory. In this work, we ascribe the faster cooling evolution of three observed WDs to the capture and evaporation of DM particles, and get the possible regions of DM particle’s mass and DM-electron cross section. The results are beyond the detection capabilities of current direct detection experiments and shouldbe cross checked by more novel scenarios in the future.

Velocity Acoustic Oscillations on Cosmic Dawn 21 cm Power Spectrum as a Probe of Axion Dark Matter

• Xin Zhang (NAOC)

We investigate the feasibility of using the velocity acoustic oscillations (VAO) features on the Cosmic Dawn 21 cm power spectrum to probe small-scale density fluctuations. In the standard cold dark matter (CDM) model, Population III stars(The first generation stars) form in minihalos and affect the 21 cm signal through Ly-alpha and X-ray radiation. Such a process is modulated by the relative motion between dark matter and baryons, generating the VAO wiggles on the 21 cm power spectrum. In the axion dark matter models for which the number of minihalos is reduced, the VAO wiggles are weaker or even fully invisible. We investigate the wiggle features in the CDM with different astrophysical models and in different dark matter models. We find that (1) in the CDM model the relative streaming velocities can generate the VAO wiggles for broad ranges of there important parameters: the star formation efficiency, X-ray production efficiency, and the intensity of Lyman–Werner (LW) radiation, though for different parameters the wiggles would appear at different redshifts and have different amplitudes. (2) For the axion model with different mass, the amplitude of the VAO wiggles are also different. In the mixed model, the VAO signal is sensitive to the axion fraction. Therefore, the VAO signal can be an effective indicator for small-scale density fluctuations and a useful probe of the nature of dark matter. The Square Kilometre Array-low with ~2000 hr observation time has the ability to detect the VAO signal and constrain dark matter models.

基于相干外差检测的宽带引力波激光干涉探测

• 郑昊

TBA

Recent progress of Dark SHINE R&D

• Kang Liu (TDLI, SJTU)

Dark SHINE is a fixed-target light dark matter search experiment initiative 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 2026. Dark SHINE aims to search for the new mediator, Dark Photon, bridging the Dark sector and the ordinary matter. In this work and presentation, we present the idea of this new project and 1st prospective study in search for Dark Photon decaying into light dark matter. It also provides the opportunity to incorporate broader scope of BSM search ideas such as ALP, utilizing the fixed-target experiment of this type.

Phase Transition and Gravitational Wave in Strongly Coupled Dark Matter

• Zhiwei Wang

We go beyond the state-of-the-art by combining first principal lattice results and effective field theory approaches as Polyakov Loop model to explore the non-perturbative dark deconfinement-confinement phase transition and the generation of gravitational-waves in a dark Yang-Mills theory. We further include fermions with different representations in the dark sector. Employing the Polyakov-Nambu-Jona-Lasinio (PNJL) model, we discover that the relevant gravitational wave signatures are highly dependent on the various representations. We also find a remarkable interplay between the deconfinement-confinement and chiral phase transitions. In both scenarios, the future Big Bang Observer and DECIGO experiment have a higher chance to detect the gravitational wave signals. Most recently, via Quark-Meson model, we find the phase transition and thus gravitational wave signals will be significantly enhanced when the system is near conformal. In addition, we find that this effective field theory approach can be implemented to study the glueball dark matter production mechanism and for the first time provide a solid prediction of glueball dark matter abundance. Our prediction is an order of magnitude smaller than the existing glueball abundance results in the literature.

Massive modes on brane

• Yuxiao Liu

It is known that zero modes of gravity and matter fields in a five-dimensional brane model can be localized on the brane with an infinite extra dimension. In this talk, we mainly discuss two types of massive Kaluza-Klein modes in thick brane models, resonant Kaluza-Klein modes quasilocalized on the brane and quasinormal modes. We also discuss the relation between them.

Chiral study of the axion and light-flavor meson interactions

• Zhi-Hui Guo (Hebei Normal University)

I will talk our recent works on the axion production processes involving light-flavor mesons within chiral perturbation theory.

Updated meson, tauon and Z boson limits on invisible particles: without infrared divergences

• Yongchao Zhang

Some (light) particles $\phi$ can couple to the neutrinos and charged leptons in the standard model (SM), and thus be relevant to neutrino self-interactions, heavy neutrinos, and dark (matter) particles etc. Such particles will induce exotic decays of some SM particles, such as pion and kaon mesons, tauon, and the Z boson. The precision measurements of these SM particle can be used to set limits on the new (light) particles. We examine the limits on the decays $\pi,\, K \to \ell + \nu + \phi$, $\tau \to \pi + \nu + \phi$ and $Z \to \nu + \bar{\nu} + \phi$ from the corresponding SM decay channels. In particular, we include the 1-loop corrections to remove the infrared divergences involved in these channels. This might have implications for some ongoing and future experiments such as NA64.

Axion echo or sub-GeV dark matter

• Lei Wu

TBA

Gauged Global Strings

• Wei Xue (University of Florida)

I will present the string solutions and cosmological implications of the gauge U(1)Z × global U(1)PQ model. With two hierarchical symmetry-breaking scales, the model exhibits three distinct string solutions: a conventional global string, a global string with a heavy core, and a gauge string as a bound state of the two global strings. This model reveals rich phenomenological implications in cosmology. When incorporating this model with the QCD axion framework, the heavy-core global strings emit more axion particles due to their large tension. This radiation significantly enhances the QCD axion dark matter abundance, thereby opening up the QCD axion mass window. Furthermore, in contrast to conventional gauge strings, the gauge strings in this model exhibit a distinctive behavior, radiating axions.

A Tidal Probe to Dark Axionic Solitons

• Yu Gao (IHEP, CAS)

A population of wide-separation binary star systems can be susceptible to small-scale gravitational perturbations, including those from dark matter. Bosonic stars are spatially extended objects that can not be treated as point particles. We give a fully analytic calculation for the tidal perturbation from randomly distributed diffuse objects, and derive a form factor that fully take account of the size effect of solitons. We then discuss their evaporation effects on isolated, a.k.a. `halo-like' wide binary systems in our Galaxy, and identify high-probability `halo-like' candidates from GAIA with separations larger than 0.1 pc. Survival of the farest-separated candidates will provide a novel gravitational probe to dark matter in the form of solitons. In the case of axion-like solitons, the observational sensitivity is shown to extend into the axion mass range of m_a ~ 10^-15 - 10^-17 eV.

Radio fields sensing based on Rydberg atoms

• Linjie Zhang (Institute of laser spectroscopy, Shanxi university State Key Laboratory of Quantum Optics and Quantum Optics Devices)

Rydberg-atom-based electric fields sensing is a surge of hot issue because of the potential performance of ultra-high sensitivity, wide-bandwidth and intrinsic traceability. In this topic, the progress of quantum sensing of radio fields is introduced in turn, including Rydberg-atom-based electric meter, atomic superheterodyne receiver based on microwave-dressed Rydberg atoms. The Rydberg-atom-based atomic superheterodyne receiver, conceptualized as a novel RF electric field sensor, has significantly enhanced sensitivity, potentially surpassing the classical noise limit. The Rydberg-atom superheterodyne allows SI-traceable measurements, reaching uncertainty levels of 10−8 V cm−1. Moreover, the enhancing sensitivity using Mach-Zehnder interferometer are introduced. By the measuring the full atomic complex susceptibility, 12 dB SNR enhancement of microwave electric field sensing were achieved on the optimum frequency detuning of probe laser. The superheterodyne technology also enables the phase and frequency detection of microwave electric fields. Using L-shape beam array, Rydberg-atom phased array detection was demonstrated. To sensing Doppler frequency shift, sub-mHz frequency precision was reached. And this technique has been extended to the measurement of MHz electric fields, yielding enhanced sensitivity—an improvement by one order of magnitude compared to prior studies.

Polarized dark photon search at TASEH experiment

• Jinmian Li

Angular correlation by spin-2 ultralight dark matter and deformed Hellings-Downs curve

• Yun-Long Zhang (NAOC(National Astronomical Observatories, CAS))

The pulsar timings are sensitive to both the nanohertz gravitational-wave background and the oscillation of ultralight dark matter. The Hellings-Downs angular correlation curve provides a criterion to search for stochastic gravitational-wave backgrounds at nanohertz via pulsar timing arrays. We study the angular correlation of the timing residuals induced by the spin-2 ultralight dark matter, which is different from the usual Hellings-Downs correlation. At a typical frequency, we show that the spin-2 ultralight dark matter can give rise to the deformation of the Hellings-Downs correlation curve induced by the stochastic gravitational wave background.[2402.03984]

Development of generic no-scale inflation

• Lina Wu (Xi’an Technological University)

We develop generalized no-scale supergravity models of inflation, and then study the corresponding cosmological predictions as well as the formation of primordial black holes (PBHs) and scalar-induced gravitational waves (SIGWs). With a new parameter $a$, the generalized no-scale supergravity provides the continuous connections among the generic no-scale supergravity from string theory compactifications. The resulting prediction of the CMB, spectrum index $n_s$, and tensor-to-scalar ratio $r$ can be highly consistent with the latest Planck/BICEP/Keck Array observations. Notably, the models with $a\neq 1$ give a smaller ratio $r\leq 10^{-3}$, which is flexible even under the anticipated tighter observational constraints at the future experiments. Additionally, these models have the potential to generate a broad-band stochastic gravitational wave background, and thus explain the NANOGrav 15yr signal. Furthermore, they predict the formation of PBHs with various mass scales, which could account for a significant portion of dark matter relic density in the Universe.

Probing electroweak phase transition and cosmology in the early universe at colliders

• Wenxing Zhang

The Standard Model extended with a complex or real singlet scalar can admit a strong first order electroweak phase transition as needed for electroweak baryogenesis. The real singlet component that mixes with the Standard Model Higgs boson leads to the possibility of di-Higgs and di-boson final states in pp collisions. The complex component can provide a dark matter (DM) candidate that leads to the possibility of a b¯b+MET final state, which is a brand new search channel at the LHC. Focusing on these channels, I will discuss the prospective reach at the LHC for a heavy singlet-like scalar in regions of (c)xSM parameter space compatible with a SFOEWPT (and DM phenomenology).

Hunting Galactic Axion Dark Matter with Gravitationally Lensed Fast Radio Bursts

• Ran Gao (Beijing Normal University)

Ultralight axion or axionlike particles are one of the most promising candidates for dark matter because they are a well-motivated solution for the theoretical strong $CP$ problem and observational issues on small scales, i.e. the core-cusp problem and the satellite problem. A tiny coupling of axions and photons induces birefringence. We propose the differential birefringence measurements of multiple images of gravitationally lensed fast radio burst (FRB) systems as probes of the Galactic axion dark matter (ADM) background. In addition to general advantages of lensing systems, i.e. alleviating systematics and intrinsic astrophysical dependencies, precise measurements of lensing time delay and polarization angle in gravitationally lensed FRB systems make them a more robust and powerful probe. We show that, with a single lensed FRB system (which may be detected in large numbers in the SKA era), the axion-photon coupling under the ADM background could be constrained to be $g_{a\gamma} < 7.3 \times 10^{-11}~ \mathrm{GeV^{-1}}$ for an axion mass $m_a\sim10^{-20}~\mathrm{eV}$. This will be of great significance in achieving synergistic searches of the Galactic ADM with other astrophysical probes and laboratorial experiments.

Axion Star Detection with Gravitational Waves

• Huaike Guo (University of Chinese Academy of Sciences)

I will discuss the detection of axion stars with gravitational waves, emitted from binary systems of extreme mas ratios. This kind of system is the ideal system for detecting very light subsolar axion stars, together with all other species of boson stars.

Dark Photon Dark Matter Radio Signal from the Milky Way Electron Density

• Ariel Arza (Nanjing Normal Univerisity)

In this talk I consider Thomson-like processes between dark matter dark photons and free electrons in the Milky Way. The result is a radio signal background that can be detectable with current or future radio telescope arrays. In particular, I compute sensitivity prospects for the Atacama Large Millimeter Array (ALMA) radio telescope and for the future Square Kilometer Array (SKA), concluding that unconstrained parameter space in a wide range of dark photon masses can be probed.

Black Hole Superradiance and Gravitational Wave Beats

• Yinda Guo (Shandong University)

Ultralight bosons can extract energy and angular momentum from a Kerr black hole (BH) due to superradiant instability, resulting in the formation of a BH-condensate system. We carefully investigate the evolution of this system numerically with multiple superradiant modes. We find the BH still evolves along the Regge trajectory of the $n = 0$ modes even with the presence of the $n > 0$ modes. On the other hand, the BH-condensate system emits monochromatic gravitational waves (GWs) with a unique beat signature, which could be directly observed by GW detectors.

一维强磁场中轴子电磁响应的相干放大探测

• 高利

TBA

Introduction for the Axion 2025 Conference

• Yongchao Zhang

Intertwining Axion and gravitational waves, generations and detection.

• Sichun Sun (Beijing Institute of Technology)

Firstly, we discuss how the beyond the Standard Model hypothetical particle, the axion, can produce gravitational waves through several different mechanisms either in the astrophysical setting or the early universe. Then we present our recent new detection proposals for axions/gravitational waves using cryogenic quantum transport technology. The electric signal is enhanced by the high-quality factor of a resonant LC circuit and then amplified and detected by the cryogenic measurement technique. We demonstrate that this setup has promising sensitivity for axions with mass from kHz to GHz, and a similar device can also be used for high-frequency gravitational wave detection with the same frequency range.

BNV nucleon decay in ALP EFT

• Tong Li (Nankai University)

I will present our recent study on the baryon-number-violating nucleon decay to axion-like particle in the framework of ALP EFTs.

Dark Photon Dark Matter in QEMD and detection

• Rui-jia Zhang (Nankai University)

In this work, we construct the dark photon-photon interactions in the framework of QEMD and obtain new dark photon-photon kinetic mixings. The consequent field equations and the new Maxwell’s equations are derived. We also investigate the detection strategies of dark photon as light dark matter as well as the generic kinetic mixings in haloscope experiments.

SKA radio probes on axion-like particles and MeV scale dark matter

• Kenji Kadota

We discuss the sensitivity of the SKA radio telescope to sub-GeV dark matter and axion-like particles. Specifically, we explore how these light dark matter candidates affect large-scale structure formation and generate 21 cm radio signals detectable by the forthcoming SKA radio telescope. Additionally, we demonstrate that MeV-scale dark matter can be probed through radio emissions from the magnetospheres of white dwarfs. The complementary nature of these future radio signal bounds with current experimental bounds from other experiments will also be discussed.

Primordial Black Holes and Gravitational Waves from Axion

• Shuailiang Ge

I present a new mechanism of primordial black hole (PBH) formation from QCD axion in the context of the Peccei-Quinn symmetry breaking during inflation. The axion string-wall network re-enters horizon sufficiently late, so the closed domain walls that naturally arise in the network are sufficiently large to collapse into PBHs. Besides, free axions from the collapse of open walls bounded by strings account for dark matter. Intriguingly, our PBHs can naturally explain the gravitational microlensing events observed by the OGLE collaboration. In addition, the collapse of string-wall network will release gravitational waves (GWs), which is drastically different from that in the scaling regime. For certain parameter space of axion-like particles, such GW spectra could possibly account for the reported nHz stochastic GW background and can be tested by various GW interferometry experiments.

New ALP Constraints from Multi-messenger Studies of GW170817

• Bhupal Dev (Washington University in St. Louis)

Extreme astrophysical environments like neutron star mergers provide a new window of opportunity in our quest for physics beyond the Standard Model. I will discuss new constraints on axion-like particles coupling to photons using the multi-messenger observations of the neutron star merger event GW170817. We argue that with more accurate data on spectral and temporal profiles of the electromagnetic signals from future mergers, these constraints can be significantly improved.

Berry phase in axion physics and corresponding applications

• Jun-Chen Wang

Closing Ceremony

• Tianjun Li