We conduct a comprehensive analysis of potential annihilation processes of light dark matter (DM) in minimal Higgs portal models near the supermassive black hole [Sagittarius <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mtext> </mtext></mrow><mrow><mo>⋆</mo></mrow></msup></mrow></math> (Sgr <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mrow><mi mathvariant="normal">A</mi></mrow><mo>⋆</mo></msup></math>)] in the Galactic Center, considering interactions between DM particles mediated by either a light scalar or pseudoscalar with couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>c</mi><mi>s</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>c</mi><mi>p</mi></msub></math>. Accelerated by the supermassive black hole, DM particles can reach velocities up to half the speed of light, significantly enhancing the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>-wave annihilation cross section, allowing forbidden annihilation channels within specific mass ranges and producing unique <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray spectral signals. Utilizing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray observation from the Fermi Large Area Telescope in the direction of Sgr <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mrow><mi mathvariant="normal">A</mi></mrow><mo>⋆</mo></msup></math>, we constrain light DM parameter in the mass range of 0.3–10 GeV. Our results indicate that the couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>c</mi><mi>s</mi></msub></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>c</mi><mi>p</mi></msub></math> are constrained to the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>5</mn></mrow></msup></math>, corresponding to a DM annihilation cross section as low as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>38</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>cm</mi></mrow><mrow><mn>3</mn></mrow></msup><mo>/</mo><mi mathvariant="normal">s</mi></mrow></math>. In the future, the Very Large Gamma-Ray Space Telescope, with a larger detection area and broader detection range from 1 MeV to 1 TeV, will enhance our ability to probe sub-GeV DM and offer the opportunity to further study the forbidden annihilation scenario.

China

Chih-Ting Lu

Xiao-Yi Luo

Zi-Qing Xia

Exploring semirelativistic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>p</mi></math>-wave dark matter annihilation in minimal Higgs portal near supermassive black hole

Leptophilic axionlike particles (ALPs) exhibit rich phenomenology, focusing exclusively on interactions between an ALP and Standard Model leptons. Through integration by parts, it is shown that both the three-point interaction, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi><mover accent="true"><mo>ℓ</mo><mo stretchy="true">¯</mo></mover><mo>ℓ</mo></math>, and the four-point interaction, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi><msup><mo>ℓ</mo><mo>−</mo></msup><mi>ν</mi><msup><mi>W</mi><mo>+</mo></msup></math>, play significant roles, making the flavor portal particularly compelling. For ALPs with masses ranging from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mtext> </mtext><mtext> </mtext><mi>MeV</mi></math> to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, they can contribute to exotic hadron decays. Suppressed couplings naturally extend the ALP lifetime, presenting opportunities for detection at forward detectors. In this study, we explore ALPs with both electrophilic and muonphilic scenarios. We propose an inclusive search for various hadrons that undergo exotic decays at the LHC. In the electrophilic scenario, long-lived ALPs are searched in the Forward Search Experiment and its upgrading phase, Forward Search Experiment II. In the muonphilic scenario, where the ALP lifetime is significantly reduced due to its coupling to muons, we further investigate its detection potential at LHCb and its high-luminosity upgrade. Several benchmarks are analyzed, including electroweak-preserving, electroweak-violating, and left-right softly asymmetric models, to demonstrate possible experimental constraints.

Xu-Hui Jiang

Leptophilic axionlike particles at forward detectors

Searching for long-lived particles (LLPs) beyond the Standard Model (SM) is a promising direction in collider experiments. The Georgi-Machacek (GM) model extends the scalar sector in the SM by introducing various new scalar bosons. In this study, we focus on the parameter space that allows the light doubly charged scalar to become long-lived. This light doubly charged scalar is fermophobic and predominantly decays into a pair of on-shell or off-shell same-sign bosons. We investigate three types of signal signatures at the LHC: displaced vertices in the inner tracking detector, displaced showers in the muon system, and heavy stable charged particles. Additionally, we analyze the potential for detecting such doubly charged scalars in far detectors, including ANUBIS, MATHUSLA, FACET, FASER, CODEX-b, MoEDAL-MAPP and AL3X. By combining the LLP searches at the LHC and in far detectors, we project that the limits on the mixing angle, , (between the doublet and triplets) can cover most of the parameter space with sin ≲ 10 for the mass of doubly charged scalar starting from 50 GeV to 1050 GeV, assuming the full integrated luminosity at the LHC and HL-LHC which is complementary with the usual measurements at the LHC.

Xinyu Wang

Xinqi Wei

Yongcheng Wu

Probing long-lived doubly charged scalar in the Georgi-Machacek model at the LHC and in far detectors

The precision measurements of the muon magnetic moment and the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>W</mi></mrow></math> boson mass have sparked interest in the potential deviations from standard model (SM) predictions. While it may be premature to attribute any excesses in these precision measurements to new physics, they do offer a valuable indication of potential directions for physics beyond the SM. Additionally, the particle nature of dark matter (DM) remains a crucial enigma. Despite the absence of any definitive DM signal in direct detection and collider experiments, the Galactic Center GeV <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray excess and the AMS-02 antiproton (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mover accent="true"><mi>p</mi><mo stretchy="false">¯</mo></mover></math>) excess could potentially offer hints related to the evidence of DM. Motivated by these observations, we propose a simple DM model that addresses all these issues. This model extends the SM by incorporating singlet and doublet Dirac fermion fields, along with a doublet complex scalar field. For the viable parameter regions in this model, we find that future upgrades of the Large Hadron Collider and DM direct detection experiments can only partially probe them, while future high-energy muon colliders hold promise for exploring the unexplored parameter space.

Yi-Zhong Fan

Yao-Yu Li

Tian-Peng Tang

Vietnam

Van Que Tran

Yue-Lin Sming Tsai

Current status of inert Higgs dark matter with dark fermions

We investigate the recently reported <math><mi>t</mi><mover><mrow><mi>t</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> excess by the CMS Collaboration within the framework of conventional Two-Higgs-Doublet Models (2HDMs). Considering all four types (I, II, X, and Y), we perform a comprehensive parameter space scan using the best-fit values for a pseudoscalar boson A: <math><msub><mrow><mi>M</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>=</mo><mn>365</mn></math> GeV, <math><msub><mrow><mi>Γ</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>/</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>A</mi></mrow></msub><mo>=</mo><mn>2</mn><mtext>%</mtext></math>, and <math><mi>tan</mi><mo>⁡</mo><mi>β</mi><mo>=</mo><mn>1.28</mn></math>. Theoretical requirements and experimental constraints are systematically applied, including conditions from a bounded-below scalar potential, vacuum stability, unitarity, perturbativity, Flavor-Changing Neutral Currents (FCNCs), and direct searches at high-energy colliders. Our analysis shows that perturbativity imposes upper bounds of around 723 GeV on <math><msub><mrow><mi>M</mi></mrow><mrow><msup><mrow><mi>H</mi></mrow><mrow><mo>±</mo></mrow></msup></mrow></msub></math> and <math><msub><mrow><mi>M</mi></mrow><mrow><mi>H</mi></mrow></msub></math>. FCNC constraints exclude all viable parameter space in Types II and Y, while a small region persists in Types I and X, but this region is ultimately ruled out by recent <math><mi>t</mi><mover><mrow><mi>t</mi></mrow><mrow><mo>¯</mo></mrow></mover><mi>Z</mi></math> measurements by the ATLAS and CMS Collaborations at the LHC. We conclude that conventional 2HDMs alone cannot accommodate a pseudoscalar boson that explains the observed <math><mi>t</mi><mover><mrow><mi>t</mi></mrow><mrow><mo>¯</mo></mrow></mover></math> excess within viable parameter space. However, incorporating toponium effects in the background fit could potentially alter this conclusion.

South Korea

Taiwan

Kingman Cheung

Dongjoo Kim

Soojin Lee

Jeonghyeon Song

Can a pseudoscalar with a mass of 365 GeV in two-Higgs-doublet models explain the CMS Excess?

The dineutron as a bound chargeless nucleus of two identical nucleons has been attracting attention for many decades. In addition to the study of the formation of a bound dineutron in the outgoing channel of specific nuclear reactions, cross-section estimates have been gaining interest as research targets. We used a traditional neutron activation technique to irradiate Lu samples followed by measurements of the induced activity with HPGe spectrometer in order to detect gamma-peaks of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu reaction product when this reaction channel is not open for incident neutron energies. Based on two measurements of the instrumental gamma-ray spectra of Lu samples we reliably identified the presence of the 174 gLu isotope in the outgoing channel of the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction. Also, the cross-section for this nuclear reaction was obtained and to be equal <math altimg='si1.svg'><mrow><mn>33</mn><mo>.</mo><msubsup><mn>5</mn><mrow><mo>&#8722;</mo><mn>6.7</mn></mrow><mrow><mo>+</mo><mn>7.0</mn></mrow></msubsup></mrow></math> mb. For the first time, the dineutron as a nuclearreaction product was indirectly detected via statistically significant observation of the induced activity of 174 gLu with a corresponding cross-section estimate.

Ukraine

Ihor Kadenko

Hungary

Barna Biró

Mihály Braun

András Fenyvesi

Kateryna Okopna

Nadiia Sakhno

Loránd Zakàny

Formation of bound dineutrons in the 175Lu ( <italic>n</italic>, 2 <italic>n</italic>) 174 gLu nuclear reaction and its cross-section

This study reanalyzes the detection prospects of dark matter (DM) annihilation signals in the Galactic Center, focusing on velocity-dependent dynamics within a spike density near the supermassive black hole (Sgr A⋆). We investigate three annihilation processes — p-wave, resonance, and forbidden annihilation — under semi-relativistic velocities, leveraging gamma-ray data from Fermi and DAMPE telescopes. Our analysis integrates a fermionic DM model with an electroweak axion-like particle (ALP) portal, exploring annihilation into two or four photons. Employing a comprehensive six-dimensional integration, we precisely calculate DM-induced gamma-ray fluxes near Sgr A⋆, incorporating velocity and positional dependencies in the annihilation cross-section and photon yield spectra. Our findings highlight scenarios of resonance and forbidden annihilation, where the larger ALP-DM-DM coupling constant C  aχχ  can affect spike density, potentially yielding detectable gamma-ray line spectra within Fermi and DAMPE energy resolution. We set upper limits for C  aχχ  across these scenarios, offering insights into the detectability and spectral characteristics of DM annihilation signals from the Galactic Center.

Meiwen Yang

Zhi-Qi Guo

Zhao-Qiang Shen

Yue-Lin Tsai

Searching accretion-enhanced dark matter annihilation signals in the Galactic Centre

The Standard Model (SM) Higgs boson, the most recently discovered elementary particle, may still serve as a mediator between the SM sector and a new physics sector related to dark matter (DM). The Large Hadron Collider (LHC) has not yet fully constrained the physics associated with the Higgs boson, leaving room for such possibilities. Among the various potential mass scales of the dark sector, the sub-GeV mass range is particularly intriguing. This parameter space presents significant challenges for DM direct detection experiments that rely on nuclear recoils. Various innovative experimental methods are currently under investigation to explore this sub-GeV dark sector. The LHC, functioning as a Higgs factory, could explore this sector once the challenge of identifying DM signals is resolved. Due to the significantly lower mass of particles in the dark sector compared to the Higgs boson, these particles are expected to be highly boosted following the Higgs boson’s decay. However, detecting and identifying these highly boosted particles remains a considerable challenge at the LHC, despite their eventual decay into SM particles. We employ a well-motivated leptophobic <math> <msubsup> <mi>Z</mi> <mi>B</mi> <mo>′</mo> </msubsup> </math> $$ {Z}_B^{\prime } $$ model as a prototype to analyze the distinctive signatures from Higgs boson exotic decays into multi-photons. These signatures consist of collimated photons that fail to meet the photon isolation criteria, forming jet-like objects. Conventional analyses relying solely on the purity of energy deposits in the electromagnetic calorimeter would fail to detect these signatures, as they would be overwhelmed by background events from Quantum Chromodynamics. To effectively distinguish between such novel signal signatures and SM background events, we leverage advanced machine learning techniques, specifically the transformer encoder in a multimodal network structure. This neural network successfully separates dark sector signals from SM backgrounds, outperforming traditional event selection analyses.

Japan

A. Hammad

P. Ko

Myeonghun Park

Exploring exotic decays of the Higgs boson to multi-photons at the LHC via multimodal learning approaches

We observe that most studies of axion-like particle (ALP) production channels at the Large Hadron Collider (LHC) focus on a single type of ALP operator for each process in the effective field theory framework. In this work, we propose an alternative approach that considers two or more types of relevant ALP effective operators together in some specific ALP production channels and study their interference effects. Using the pp → tja process with a → γγ as an example, we show that this approach allows us to constrain the ALP interactions with both the W boson and the top quark, as well as their interference in a single process. For the final state with two isolated photons and a top quark decaying semi-leptonically, we predict that the future bounds on the ALP decay constant can reach around f  a  ~ 10 (20) TeV for 25 GeV &lt; M  a  &lt; 100 GeV at the LHC with 300 (3000) fb−1 luminosity.

C.J. Ouseph

Priyanka Sarmah

Exploring interference effects between two ALP effective operators at the LHC

We revisit the proton emitter $^{149}$Lu utilizing the recently developed triaxial relativistic Hartree-Bogoliubov theory in continuum (TRHBc). By incorporating the microscopic nuclear structure properties from the TRHBc theory into the WKB approximation, we successfully reproduce the measured proton-emission half-life of $^{149}$Lu within experimental uncertainties. A triaxial ground state characterized by (<math><mi>β</mi><mo>=</mo><mn>0.17</mn><mo>,</mo><mi>γ</mi><mo>=</mo><msup><mrow><mn>31</mn></mrow><mrow><mo>∘</mo></mrow></msup></math>) has been clarified for $^{149}$Lu. The inclusion of triaxiality significantly changes nuclear density distributions and potentials, which results in enhanced binding of both the nuclear system and the proton-emitting orbital. As a result, a slightly extended half-life for the proton emission of $^{149}$Lu is achieved after considering triaxial deformation degrees of freedom. The examination of the dependence of the decay width on triaxial deformation parameters highlights the significance of microscopic description of nuclear deformation beyond the proton dripline.

Qi Lu

Kai-Yuan Zhang

Shi-Sheng Zhang

Triaxial shape of the one-proton emitter Lu