arXiv subjects

Hong-Hao Zhang

Publications and source records attributed to Hong-Hao Zhang.

At least 19 recordsLinked to original sources

arXiv2026

Leptophilic scalar dark matter in U(1)$_{L_μ-L_τ}$: Evading direct detection and prospective neutron star heating

Leptophilic dark matter (DM) is a well-motivated thermal weakly interacting massive particle framework that can evade stringent nuclear-recoil searches while remaining testable via DM-induced heating of neutron stars (NSs). In this work, we study leptophilic scalar DM in a $U(1)_{L_μ-L_τ}$ gauge extension of the Standard Model, which provides a common leptophilic portal for all scenarios considered. To reproduce the observed relic abundance while suppressing direct-detection signals, we investigate three benchmark realizations: (i) a secluded DM scenario in which the relic density is set by annihilation into $U(1)_{L_μ-L_τ}$ gauge bosons and two pseudo-Nambu-Goldstone boson (pNGB) DM models based on (ii) an $SO(4)$ symmetry and (iii) an $SO(3)$ symmetry. In the $SO(4)$ pNGB model, the DM mass arises at tree level from a soft breaking term, while the elastic scattering amplitude is suppressed by a symmetry-protected cancellation. In the $SO(3)$ pNGB model, the DM mass is generated radiatively at one loop via the $U(1)_{L_μ-L_τ}$ gauge interaction, and we show that this gauging preserves the same cancellation mechanism, maintaining compatibility with direct-detection null results. We perform a systematic parameter scan imposing relic density, direct and indirect detection, and neutrino trident constraints and identify viable sub-TeV to TeV DM candidates. Under the optimistic maximal-heating assumption that the capture rate reaches the geometric limit and that the captured DM population efficiently thermalizes and attains capture-annihilation equilibrium inside NSs, we find that the remaining parameter space can be tested by near-infrared observations of old NSs, providing sensitivity complementary to terrestrial searches in regions that are currently weakly constrained.

hep-ph↗

arXiv2026

Scale-invariant Schrödinger geometry in symmetric teleparallel gravity

We construct a locally scale-invariant formulation of Schrödinger geometry in symmetric teleparallel gravity. The unique scale transformation preserving autoparallelism, torsionlessness and the Schrödinger affine structure is first identified, from which a quadratic scale-invariant action is obtained. Using the Palatini formalism, we show that the conditions required for scale invariance are exactly those ensuring that the affine connection is dynamically reduced to the Schrödinger form. Our results establish a direct correspondence between local scale symmetry and length-preserving affine geometry, providing a new geometric framework for scale-invariant metric-affine gravity.

gr-qc↗

arXiv2026

Machine learning study on single production of a singlet vectorlike lepton at the Large Hadron Collider

Vectorlike leptons are nonchiral, colorless fermions from new physics beyond the Standard Model, appearing in many theoretical extensions. We investigate the prospect for detecting the single production of a singlet vectorlike lepton that mixes with the $τ$ lepton at the Large Hadron Collider. The corresponding final states are classified as the three- and four-lepton search channels. The machine learning algorithm XGBoost is employed to enhance signal-background discrimination. Our analysis indicates that, at $\sqrt{s} = 14~\mathrm{TeV}$ with an integrated luminosity of $3000~\mathrm{fb}^{-1}$ under the assumption of negligible systematic uncertainties, the expected $2σ$ exclusion limits in the three- and four-lepton channels can reach vectorlike lepton masses up to $500$ and $405~\mathrm{GeV}$ in the parameter region allowed by the electroweak oblique parameter constraint, respectively. These findings demonstrate that machine learning techniques can substantially improve the sensitivity of collider searches for vectorlike leptons.

hep-ph↗

arXiv2026

Warm inflation in Weyl geometric gravity

We investigate the warm inflationary scenario in the Weyl geometric gravity theory, in which the action is constructed by adding matter to the simplest conformally invariant gravitational action in Weyl geometry. The $\tilde{R}^2$ theory can be formulated equivalently as a linear theory supplemented by an additional scalar degree of freedom originating from higher-order curvature terms, with the equations of motion obtained via variational methods. We investigate the cosmological implications of the theory by considering the warm inflationary scenario of the early evolution of the Universe, in which radiation, the inflaton field, and the Weyl vector coexist. We consider the widely studied linear dissipation coefficient model along with a quartic potential, and investigate the influence of the Weyl vector term on the dynamics. We have performed numerical computations for different coupling models, and we have successfully developed a warm inflationary model in which the Universe transitions naturally from an inflationary epoch to a radiation-dominated era. The relevant cosmological observables have been calculated and compared with the latest observational constraints from the ACT data.

gr-qc↗

arXiv2025

Schrödinger-type $f(Q,T)$ gravity-nonmetricity driven cosmological evolution from inflation to the late Universe

We consider an $f(Q, T)$ gravity theory with a Schrödinger type vectorial non-metricity. In the presence of such a non-metricity, the length of vectors is preserved under autoparallel transport. We obtain the field equations assuming a vanishing total scalar curvature, implemented by a Lagrange multiplier, and investigate their cosmological implications. To do this, we derive the generalized Friedmann equations which now have terms involving the non-metricity and the Lagrange multiplier. Then, we consider two distinct cosmological applications of the model. First of all, by adopting distinct forms of these two basic variables and investigate the possibility of the existence of warm inflationary scenarios within the framework of these models. In particular, we consider the case that the non-metricity is described by a constant vector, and we show that with this assumption we recover standard general relativity. The scenario in which the Lagrange multiplier is a constant is also investigated, and we show that radiation can be created during the very early phases of expansion. The amount of radiation peaks at a certain time after which, there is a transition from an accelerating inflationary phase to a decelerating one. Moreover, we perform a detailed comparison of the predictions of the considered Schrödinger type cosmology with a set of observational data for the Hubble function, including Cosmic Chronometers, Type Ia Supernovae, and Baryon Acoustic Oscillations, using a Markov Chain Monte Carlo (MCMC) analysis, by adopting a simple linear form for the Lagrange density. The model predictions are also compared with the results of the $Λ$CDM standard paradigm. Our results indicate that the Schrödinger $f(Q,T)$ type theory can give a good description of the observational data for both the very early and the late Universe.

gr-qc↗

arXiv2025

Probing Long-Lived Photophobic Axion-Like Particles via Prompt Leptons and Mono-$γ$ at FCC-ee and CEPC

We investigate the potential to probe axion-like particles (ALPs) under the photophobic scenario at the FCC-ee and CEPC at the Z-pole, with $\sqrt{s} = 91.2$ GeV. The signal process is $$ e^+e^- \to Z \to γa,\quad a \to \ell^+ \ell^-, $$ where we consider final states with two prompt leptons and one photon, or only one photon (Mono-$γ$). We estimate the sensitivity to the ALP mass $m_a$ and associated energy scale $Λ$ for $a\toμ^+μ^-$ and $a\toτ^+τ^-$ (with leptonic decays of the $τ$) by use of a XGBoost classifier. For an integrated luminosity of 150 ab$^{-1}$ at the Z-pole, the combined leptonic channel can probe the ALP scale $Λ$ between $10$ to $700$~TeV, depending on the ALP mass. The Mono-$γ$ signal offers a complementary probe, reaching $Λ$ up to $2000$~TeV for masses below $20$~GeV.

hep-ph↗

arXiv2025

Interpreting the KM3-230213A PeV Neutrino Event via Vector Dark Matter Decay and Its Multi-Messenger Signatures

The KM3NeT Collaboration recently reported the detection of an ultra-high-energy neutrino event KM3-230213A with a reconstructed energy of $220^{+570}_{-110}$ PeV, the most energetic astrophysical neutrino ever detected. The absence of convincing electromagnetic counterparts motivates exploration of exotic origins beyond standard astrophysical processes. We present a vector dark matter model based on a new $U(1)_X$ gauge symmetry to interpret this event through superheavy dark matter decay. Our analysis demonstrates that dark matter lifetimes in the range $7.3 \times 10^{28}$ to $2.9 \times 10^{30}$ s can successfully account for the KM3-230213A event while satisfying stringent constraints from gamma-ray observations. Moreover, the spontaneous breaking of $U(1)_X$ in our model naturally predicts cosmic string formation, generating a stochastic gravitational wave background with string tension $4.5 \times 10^{-11} \lesssim Gμ\lesssim 1.2 \times 10^{-10}$, consistent with recent pulsar timing array observations. This multi-messenger consistency across neutrinos, gamma-rays, and gravitational waves validates our vector dark matter interpretation of the KM3-230213A event while providing testable predictions for upcoming multi-wavelength experiments.

hep-ph↗

arXiv2025

Leptogenesis assisted by scalar decays

We present a pragmatic approach to lower down the mass scale of right-handed neutrinos in leptogenesis by introducing a scalar decaying to right-handed neutrinos. The key point of our proposal is that the out-of-equilibrium decays of the scalar provide an additional source for right-handed neutrinos and hence the lepton asymmetry. This mechanism works well at low temperatures when the washout of the generated lepton asymmetry is suppressed. Thus, the lepton asymmetry can be effectively produced despite the washout effect is strong or not. Through a comprehensive analysis, we demonstrate that such a scalar-assisted leptogenesis can typically decrease the viable right-handed neutrino mass scale by one to three orders of magnitude.

hep-ph↗

arXiv2025

Explaining the $B_{d(s)} \rightarrow K^{(\ast)}\bar{K}^{(\ast)}$ puzzle via chiral-flip in $R$-parity violating MSSM with seesaw mechanism

We study the non-leptonic puzzle of $B_{d(s)} \rightarrow K^{(\ast)}\bar{K}^{(\ast)}$ decay in the $R$-parity violating minimal supersymmetric standard model (RPV-MSSM) extended with the inverse seesaw mechanism. In this model, the chiral flip of sneutrinos can contribute to the observables $L_{K\bar{K}}$ and $L_{K^{\ast}\bar{K}^{\ast}}$, that is benefit for explaining the relevant puzzle. We also find that this unique effect can engage in the $B_s$-$\bar{B}_s$ mixing. We utilize the scenario of complex $λ^\prime$ couplings to fulfill the recent stringent constraint of $B_s$-$\bar{B}_s$ mixing, and examine other related bounds of $B,K$-meson decays, lepton decays, neutrino data, $Z$ decays, oblique parameters, CP violations (CPV), etc. Besides, inspired by the new measurement of ${\cal B}(B^+ \rightarrow K^+ν\barν)$ by Belle II, which shows about $2.7σ$ higher than the Standard Model (SM) prediction, we also investigate the New Physics (NP) enhancement to this observable.

hep-ph↗

arXiv2025

Heavy neutrino mixing prospects at hadron colliders: a machine learning study

We apply machine learning to the searches of heavy neutrino mixing in the inverse seesaw in the framework of left-right symmetric model at the high-energy hadron colliders. The Majorana nature of heavy neutrinos can induce the processes $pp \to W_R^\pm \to \ell_α^\pm N \to \ell_α^\pm \ell_β^{\mp,\,\pm} jj$, with opposite-sign (OS) and same-sign (SS) dilepton and two jets in the final state. The distributions of the charged leptons $\ell = e ,\, μ$ and jets and their correlations are utilized as input for machine learning analysis. It is found that for both the OS and SS processes, XGBoost can efficiently distinguish signals from the standard model backgrounds. We estimate the sensitivities of heavy neutrino mass $m_N$ and their mixing in the OS and SS $ee$, $μμ$ and $eμ$ final states at $\sqrt{s} = 14$ TeV, 27 TeV and 100 TeV. It turns out that the heavy neutrinos can be probed up to 17.1 TeV and 19.5 TeV in the OS and SS channels, respectively. The sine of the mixing angle of heavy neutrinos can be probed up to the maximal value of $\sqrt2/2$ and 0.69 in the OS and SS channels, respectively.

hep-ph↗

arXiv2025

Constraining the Secluded and Catalyzed Annihilation Dark Matter with Fermi-LAT and Planck Data

We propose a dark matter (DM) model with a complex scalar charged under a hidden gauge symmetry, denoted as $U(1)_D$. The scalar field is the DM candidate while the $U(1)_D$ gauge field $A'$ plays the role of a mediator, which connects the dark sector to the standard model (SM) sector via a tiny kinetic mixing. We find that both the secluded and catalyzed annihilation scenarios can be realized in this model. The phenomenology of DM, including relic density, indirect detection (Fermi-LAT), and CMB (Planck) constraints, is discussed. We also extend our discussion to DM with other spins, including Dirac fermion and vector boson. Our analysis is carried out in two models, denoted as $U(1)_D \times U(1)_Y$ and $U(1)_D \times U(1)_{L_μ-L_τ}$, with the former corresponding to $A'$ kinetically mixing with the $U(1)_Y$ gauge field $B$ and the latter corresponding to $A'$ mixing with the $U(1)_{L_μ-L_τ}$ gauge field $Z'$. We find that, in previous studies, the indirect detection limits were overly restrictive because they only considered the simplified $2\mathrm{DM} \to 2\mathrm{SM}$ annihilation channel. In contrast, by performing a complete calculation of the gamma-ray and CMB constraints from the process $2\mathrm{DM} \to 2A' \to 4\mathrm{SM}$ in the models we consider, we observe weaker constraints in both the $U(1)_D \times U(1)_Y$ and $U(1)_D \times U(1)_{L_μ-L_τ}$ models, with the $U(1)_D \times U(1)_{L_μ-L_τ}$ model being subject to the weakest constraints overall since it involves less hadronic decay processes.

hep-ph↗

arXiv2025

General Discussions on the SU(2) Vector Boson Dark Matter Model with a Single Higgs Multiplet -- Lagrangian, Discrete Subgroups, and Scalar Classifications

The vector boson dark matter particles which stem from some broken gauge symmetries usually requires some unbroken symmetries to keep themselves stable. In the previous literature, some simplest cases have been discussed, in which the unbroken symmetry is provided by a remnant subgroup of the gauge group. It would be interesting to ask whether all the possible remnant subgroups as well as all the possible coupling forms can be enumerated. Classifying all the Higgs components into different mass degenerate representations to simplify the diagonalization processes is also necessary. Rather than the ambitious target of providing a general solution to all kinds of gauge groups configured with all forms of the Higgs multiplets, in this paper, we concentrate on the case of $\text{SU(2)}_{\text{D}}$ gauge group together with a single Higgs multiplet. We enumerate all possible discrete subgroups that can survive up to $n=21$, where $n$ is the dimension of the Higgs multiplet. We also provide the general algorithms to enumerate all possible renormalizable operators, to write down the general forms of the vacuum expectation value (VEV) configurations, and to give the detailed results of all the mass degenerate irreducible representations embedded in the Higgs multiplet.

hep-ph↗

arXiv2024

Constraining Axion-Like Particles from observations of AGN B2 2234+28A and 3C 454.3

Axion-photon oscillation effect provides a possible explanation for the presence of very-high-energy (VHE) $γ$-ray signals from distant sources. In this work, we propose a model-dependent method to select possible sources that may give sufficient constraints on the axion parameters. We investigate such effect in the spectra of active galactic nuclei (AGN) B2 2234+28A and 3C 454.3 based on data obtained from Fermi Large Area Telescope (Fermi-LAT) and MAGIC U.L. We utilize the Markov Chain Monte Carlo method to fit the axion parameters, yielding a result of $g_{aγ}=3.05^{+0.51}_{-0.31} \times 10^{-11}$ GeV$^{-1}$ for the axion-photon coupling strength and $m_{a}=5.25^{+2.35}_{-2.65} \times 10^{-8} $ eV for the axion mass. We also perform 95\% confidence level (CL) constraints to set an upper limit for $g_{aγ}$.

astro-ph.HE↗

arXiv2024

Modeling the Time Evolution of Compact Binary Systems with Machine Learning

This work introduces advanced computational techniques for modeling the time evolution of compact binary systems using machine learning. The dynamics of compact binary systems, such as black holes and neutron stars, present significant nonlinear challenges due to the strong gravitational interactions and the requirement for precise numerical simulations. Traditional methods, like the post-Newtonian approximation, often require significant computational resources and face challenges in accuracy and efficiency. Here, we employed machine learning algorithms, including deep learning models like Long Short-Term Memory (LSTM) and Temporal Convolutional Network (TCN), to predict the future evolution of these systems based on extensive simulation data. Our results demonstrate that employing both LSTM and TCN even as black-box predictors for sequence prediction can also significantly improve the prediction accuracy without PINNs as PDE solvers with prior knowledge or inductive bias. By employing LSTM and TCN, we obtained $R^2$ values of 99.74\% and 99.19\% for the evolutionary orbits of compact binaries dataset, respectively. Our models demonstrate the ability to effectively capture the dynamics of the binaries, achieving high prediction performance with significantly reduced computational overhead by a factor of 40, compared to conventional numerical methods. This study paves the way for more effective and computationally scalable approaches to the understanding of gravitational phenomena and predictive modeling in gravitational-wave astronomy.

astro-ph.CO↗

arXiv2024

Dissipated Correction Map Method with Trapezoidal Rule for the Simulations of Gravitational Waves from Spinning Compact Binary

The correction map method means extended phase-space algorithm with correction map. In our research, we have developed a correction map method, specifically the dissipated correction map method with trapezoidal rule, for numerical simulations of gravitational waves from spinning compact binary systems. This new correction map method, denoted as $CM3$, has shown remarkable performance in various simulation results, such as phase space distance, dissipated energy error, and gravitational waveform, closely resembling the high-order precision implicit Gaussian algorithm. When compared to the previously used midpoint map which denoted as $C_2$, the $CM3$ consistently exhibits a closer alignment with the highly accurate Gaussian algorithm in waveform evolution and orbital trajectory analysis. Through detailed comparisons and analyses, it is evident that $CM3$ outperforms other algorithms, including $CM2$ and $C_2$ mentioned in this paper, in terms of accuracy and precision in simulating spinning compact binary systems. The incorporation of the trapezoidal rule and the optimization with a scale factor $γ$ have significantly enhanced the performance of $CM3$, making it a promising method for future numerical simulations in astrophysics. With the groundbreaking detection of gravitational waves by the LIGO/VIRGO collaboration, interest in this research domain has soared. Our work contributes valuable insights for the application of matched filtering techniques in the analysis of gravitational wave signals, enhancing the precision and reliability of these detection.

astro-ph.IM↗

arXiv2024

Constraining Weyl type f(Q,T) gravity with Big Bang Nucleosynthesis

The Weyl type $f(Q,T)$ modified gravity theory is an extension of the $f(Q)$ and $f(Q,T)$ type theories, where $T$ is the trace of the matter energy-momentum tensor, and the scalar non-metricity $Q$ is represented in its standard Weyl form, and it is fully determined by a vector field $ω_μ$. The theory can give a good description of the observational data, and of the evolution of the late-time Universe, including a geometric explanation of the dark energy. In this work we investigate the Big Bang Nucleosynthesis (BBN) constraints on several Weyl type $f(Q,T)$ gravity models. In particular, we consider the corrections that Weyl type $f(Q,T)$ terms induce on the freeze-out temperature $\mathcal{T}_f$, as compared to the standard $Λ$CDM results. We analyze in detail three distinct cosmological models, corresponding to specific choices of the functional form of $f(Q,T)$. The first model has a simple linear additive structure in $Q$ and $T$, the second model is multiplicative in $Q$ and $T$, while the third is additive in $T$ and the exponential of $Q$. For each $f(Q,T)$ we consider first the cosmological evolution in the radiation dominated era, and then we impose the observational bound on $\left|δ\mathcal{T}_f/ \mathcal{T}_f\right|$ to obtain constraints on the model parameters from the primordial abundances of the light elements such as helium-4, deuterium and lithium-7. The abundances of helium-4 and deuterium agree with theoretical predictions, however, the lithium problem, even slightly alleviated, still persists for the considered Weyl type $f(Q,T)$ models. Generally, these models satisfy the BBN constraints, and thus they represent viable cosmologies describing the entire dynamical time scale of the evolution of the Universe.

gr-qc↗

arXiv2024

Complex scalar dark matter in a new gauged U(1) symmetry with kinetic and direct mixings

We propose a scalar dark matter model featuring a hidden gauge symmetry, denoted as U(1)_X, with two complex scalars, Phi and S. In this framework, Phi spontaneously breaks the U(1)_X gauge symmetry, while S serves as a viable dark matter candidate. Particularly, the kinetic and direct mixings between the U(1)_X and U(1)_Y gauge groups provide a portal between dark matter and the Standard Model particles. These mixings offer a plausible explanation for the W boson mass anomaly observed by the CDF Collaboration. We study the comprehensive phenomenological constraints of this model from colliders and dark matter detection experiments, including Z' searches at the LHC, the 125 GeV Higgs boson measurements, the relic density of dark matter and the indirect detection of dark matter annihilation. By randomly scanning the parameter space, we find that the regions where m_(Z') > 4750 GeV and m_(Z') < 4750 GeV for g_x close to 1 remain viable and can be tested by future experiments.

hep-ph↗

arXiv2024

Dark matter phenomenology and phase transition dynamics of the next to minimal composite Higgs model with dilaton

In this paper, we conduct a comprehensive study of the Next-to-Minimal Composite Higgs Model (NMCHM) extended with a dilaton field $χ$ (denoted as NMCHM$_χ$). A pseudo-Nambu-Goldstone boson (pNGB) $η$, resulting from the SO(6)$\to$SO(5) breaking, serves as a dark matter (DM) candidate. The inclusion of the dilaton field is helpful for evading the stringent constraints from dark matter direct detection, as it allows for an accidental cancellation between the amplitudes of DM-nucleon scattering, an outcome of the mixing between the dilaton and Higgs fields. The presence of the dilaton field also enriches the phase transition patterns in the early universe. We identify two types of phase transitions: (i) a 1-step phase transition, where the chiral symmetry and electroweak symmetry breaking (EWSB) occur simultaneously, and (ii) a 2-step phase transition, where the chiral symmetry breaking transition takes place first, followed by a second phase transition corresponding to EWSB. Since the first-order phase transitions can be strong due to supercooling in our model, we also examine the stochastic background of gravitational waves generated by these phase transitions. We find that these gravitational waves hold promise for detection in future space-based gravitational wave experiments, such as LISA, Taiji, BBO, and DECIGO.

hep-ph↗