Cosmo‑Astro‑Particle Symposium (CAP 2025) & The 19th TeV Workshop

Firstly, we briefly discuss how the hypothetical beyond-the-Standard-Model particle, the axion, can produce gravitational waves through several mechanisms. Then we present some of our recent proposals for detecting axions/gravitational waves, including cryogenic quantum transport technology, traditional spin systems, and specially engineered artificial magnetoelectric materials. We demonstrate...

Ref. ATLAS-CONF-2025-012
This note presents a combination of searches for Higgs boson pair (HH) production performed by the ATLAS and CMS Collaborations using proton-proton collision data sets recorded at $\sqrt{s}$ = 13 TeV at the LHC Run 2, corresponding to integrated luminosities ranging between 126 and 140 fb$^{-1}$. The upper limit at the 95% confidence level on the total HH production...

Axion-like particles (ALPs) are well-motivated extensions of the standard model (SM) that appear in various new physics scenarios. Searching for long-lived ALPs is a promising direction in collider experiments. This report discusses the potential of the HL-LHC to probe long-lived ALPs via their displaced vertex signatures within the photophobic ALP scenario.

We develop a general framework for the computation of light-portal dark matter direct detection, incorporating a consistent treatment of finite momentum transfer. In this framework, dark matter interacts with Standard Model matter through a light mediator, which simultaneously serves as the force carrier for dark matter self-interaction, potentially with a distinct coupling strength. The...

In this work we study the prospect of detecting light CP-even and CP-odd scalars. We develop the general formalism for the scalar production and decay from mesons at LHC, given modified couplings of the scalars to the SM particles, as well as summarizing the relevant GeV-scale experiment constraints. We then analyze the complete long-lived particle of 2HDM, and reaches of light scalars in...

Recent observations from the James Webb Space Telescope have revealed an unexpectedly high abundance of massive galaxies at very high redshifts, challenging the standard $\Lambda$CDM cosmological framework. Cosmic strings, which can act as nonlinear seeds in the early Universe, provide a promising explanation for this tension. In this talk, I will present our recent work on the impact of...

In this work we consider cosmological gravitational production of Dirac sterile neutrinos as dark matter candidates during and after inflation. In the former, the Higgs field experiences large quantum fluctuations driving its average field value to the Hubble scale and above facilitating the sterile neutrino production. However, the production efficiency due to classical gravity still remains...

Effective field theory (EFT) concept provides a necessary tool for obtaining general predictions of low energy theory valid below its unitarity breaking scale (cutoff scale). Early Universe inflation and subsequent reheating could be a unique setup for testing potentially observable effects coming from the derivative expansion of the corresponding EFT around the flat space vacuum. In this...

The amount of information propagated by an intermediate heavy particle exhibits characteristic features in inelastic scatterings with n≥3 final particles. As the total energy increases, the entanglement entropy, between its decay products and other final particles, exhibits a universal sharp dip, suppressed by its small decay rate. This indicates an entanglement suppression from a low-energy...

The ATLAS and CMS experiments are unique drivers of our fundamental understanding of nature at the energy frontier. In this contribution to the update of the European Strategy for Particle Physics, we update the physics reach of these experiments at the High-Luminosity LHC (HL-LHC) in a few key areas where they will dominate the state-of-the-art for decades to come.

Axions and axion-like particles can be probed through gravitational waves indirectly, often referred to as “audible axions”. The usual concept of audible axion relies on the coupling between the axions and the gauge fields. Here we consider an axion-like mechanism with coupling to the Nieh–Yan term. This interaction leads to the direct and efficient production of gravitational waves during the...

In this Letter we explore, for the first time, the constraints on lepton flavor violating (LFV) dark matter (DM) scenarios via the astrophysical photons and positrons, including both the annihilation and decay modes, ${\tt DM(+DM)}\to e^\pm \mu^\mp, e^\pm \tau^\mp, \mu^\pm \tau^\mp$. Given the presence of LFV interactions in various DM models and the challenge of probing such interactions at...

A comprehensive study of triple Higgs boson production in the 42 decay final state is performed for the first time at a future 100 TeV hadron collider. The analysis incorporates modified Higgs self-couplings via trilinear Higgs self-coupling 3 and quartic Higgs self-coupling 4, enabling for a model-independent investigation of potential new physics effects. Higgs bosons are reconstructed...

The James Webb Space Telescope (JWST) observations have identified a class of compact galaxies at high redshifts ((4 \lesssim z \lesssim 11)), dubbed ``little red dots'' (LRDs). The supermassive black holes (SMBHs) of $10^{5\text{--}8}{\rm\,M}_{\odot}$ in LRDs favor a heavy-seed origin.
We propose a mechanism for their formation: Clusters of primordial black holes, formed through long-short...

Inspired by string theory and cosmological constant problem, it is plausible that the Universe’s vacuum structure is characterized by a landscape of metastable vacua. If the dark vacuum is metastable, bubbles of lower-energy phases can nucleate at an approximately constant rate. Because the Hubble expansion rate is monotonically non-increasing with cosmic time, such nucleation can eventually...

In cosmology, correlation functions on a late-time boundary can arise from both field redefinitions and bulk interactions, which are usually believed to generate distinct results. In this letter, we propose a counterexample showcasing that correlators from local field redefinitions can be identical to the ones from bulk interactions. In particular, we consider a two-field model in de Sitter...

Effective field theories (EFTs) provide a powerful framework to parametrise unknown aspects of possible ultraviolet (UV) physics. However, compared to traditional EFTs for scattering amplitudes in flat space, there are at least three distinct sources of subtlety in EFTs for cosmological correlators in de Sitter space, which include (1) the expansion of the spacetime background itself, (2) the...