arXiv subjects

Honglei Li

Publications and source records attributed to Honglei Li.

At least 19 recordsLinked to original sources

arXiv2026

New Avenues of Heavy Neutral Lepton at Muon Collider

With initial state radiation, the multi-TeV muon collider can be regarded as an electroweak boson collider. The dominant production mode of the certain process becomes the vector boson fusion channel, because the corresponding cross section typically increases logarithmically at high energies. This also holds true for new physics beyond the standard model. Within the $U(1)$ gauged extension of seesaw models, the heavy neutral lepton has additional interactions with the new gauge boson $Z'$ and heavy Higgs $H$. In this paper, we investigate the production of heavy neutral lepton $N$ via the new vector boson fusion processes $Z'Z'\to H\to NN$ with and $Z'Z'\to NN$ without heavy Higgs at the multi-TeV muon collider. Different from the canonical vector boson fusion processes $WW/ZZ\to H\to NN$, the new process $Z'Z'\to H\to NN$ is not suppressed by the small mixing angle $\alpha$ between the Higgs bosons. Meanwhile, the pair production process $Z'Z'\to NN$ is also viable even for heavy Higgs $m_H> \sqrt{s}$. Therefore, these new avenues provide alternative pathways to probe the intrinsic feature of the heavy neutral lepton. We then perform a detailed analysis of the lepton number violation signals via the new vector boson fusion with heavy Higgs $\mu^+\mu^-\to \mu^+\mu^- H \to \mu^+\mu^- NN$ and without heavy Higgs $\mu^+\mu^-\to \mu^+\mu^- NN$, followed by $N\to \mu^\pm jj$, where the two jets from $W$ boson decay are treated as one fat-jet $J$.

hep-ph↗

arXiv2026

Novel Signatures of Heavy Neutral Lepton at Muon Collider

The Higgs-strahlung process $\ell^+\ell^-\to Z h$ is one of the most important production channels of the standard model Higgs boson $h$ at the lepton colliders. The cross section reaches the maximum value slightly above the threshold $\sqrt{s}\sim m_Z+m_h$, and decreases as $\sim 1/s$ at high energies. In the gauged extension models, the new gauge boson $Z'$ and heavy Higgs boson $H$ exist after the symmetry breaking. The heavy Higgs-strahlung process $\ell^+\ell^-\to Z' H$ would also reach the maximum cross section around the threshold $\sqrt{s}\sim m_{Z'}+m_H$. Therefore, the future high energy lepton colliders, such as the TeV scale muon collider, are promising to probe this new process. If heavy neutral lepton $N$ is introduced to generate the tiny neutrino masses via seesaw mechanism, novel signatures could arise from $\mu^+\mu^-\to Z' H \to NN +NN \to 4 \mu^\pm +4J$ and $\mu^+\mu^-\to Z' H \to \mu^+\mu^- +NN \to 3 \mu^\pm+ \mu^\mp +2J$, where the fat-jets $J$ come from the hadronic decay of $W$ bosons. In this paper, we investigate the same-sign tetralepton signature $4\mu^\pm+4J$ and the same-sign trilepton signature $3\mu^\pm +\mu^\mp + 2J$ at the 3 TeV and 10 TeV muon collider.

hep-ph↗

arXiv2026

Study the property of $W^{\prime}$ at future $e^-p$ collider

As a strong candidate for new physics beyond the Standard Model, the exotic charged gauge boson $W^{\prime}$ has attracted extensive research interest. In this work we investigate the interactions of the $W^{\prime}$ boson at the electron-proton colliders. The process $e^- u \to \nu_e d$ and $e^- u \to e^\pm jjj$ with $t$-channel $W^{\prime}$ exchange are studied. The polarization of the initial-state electrons has a significant impact on the cross section of the studied process, while the angular distribution of the final-state leptons serves as an important observable for the interactions of the $W^{\prime}$ boson. In some specific regions of the parameter space, the detectable mass range for the $W^{\prime}$ boson can reach around 10 TeV, and the coupling strength can achieve a precision of approximately 1\% relative to the interaction strength of the Standard Model. Especially, $e^- u \to e^+ jjj$ process is forbidden within the Standard Model, which would constitute important evidence in the search for the Left-Right Symmetric Model.

hep-ph↗

arXiv2025

Collider Probes of Four-Lepton Final States in Maximally Flavor-Violating $U(1)_{L_{\mu}-L_{\tau}}$ Model

We investigate the collider signatures of the maximally flavor-violating $U(1)_{L_\mu-L_\tau}$ model, where a new gauge boson $Z^\prime$ and scalar triplets induce lepton flavor-changing interactions in the $\mu$-$\tau$ sector. Focusing on four-lepton final states at multi-TeV lepton colliders, we conduct a detailed analysis of cross sections, asymmetries, and polarization effects. We show that the signal cross section is highly sensitive to $m_{Z^\prime}$ and the effective parameters $\tilde{g}/m_{Z^\prime}$, while remaining largely insensitive to the triplet Yukawa couplings within the phenomenologically allowed region. The forward-backward asymmetry exhibits a characteristic monotonic dependence on $m_{Z^\prime}$, and beam polarization can significantly suppress Standard Model backgrounds while enhancing new physics contributions. We find that over the phenomenologically allowed parameter space, the predicted observables remain highly sensitive to the underlying model parameters. These results demonstrate that multi-lepton final states are powerful probes of the $U(1)_{L\mu - L_\tau}$ framework and offer valuable guidance for future searches at muon and electron-positron colliders.

hep-ph↗

arXiv2025

Reviving $Z^\prime$ Portal Dark Matter with Conversion Mechanism

In many new physics models with extended gauge symmetry, the new gauge boson $Z'$ could mediate the interactions between the dark matter and standard model particles. For the conventional $Z^\prime$ portal dark matter, the collider and the direct detection constraints typically pose a significant challenge. To address this pressing issue, we present in this paper a new benchmark model based on the gauged $U(1)_{B-L}$ symmetry, which introduces a Dirac dark fermion $\tilde{\chi}_1$ and a heavier partner $\tilde{\chi}_2$ with zero and nonzero $U(1)_{B-L}$ charge, respectively. Including the mass term $\delta m \bar{\tilde{\chi}}_1\tilde{\chi}_2$ results in the dark fermions $\chi_1$ and $\chi_2$ in the mass eigenstate, where the lighter one $\chi_1$ is regarded as the dark matter candidate. Various intriguing processes for the relic density arise with the compressed mass spectrum $m_{\chi_1}\simeq m_{\chi_2}$, such as the coscattering $\chi_2f\to\chi_1f$, the conversion $\chi_2\chi_i\to\chi_1\chi_j$, and the coannihilation $\chi_1\chi_2\to f\bar{f}$ processes. Suppressed by the small mixing angle $\theta$ between the dark fermions, the small effective gauge coupling of dark matter $\chi_1$ to the gauge boson $Z'$ is one distinct feature of this model, rendering phenomenology in many aspects more promising. In this paper, we investigate the production of dark matter through new mechanisms within the frameworks of resonance and secluded scenarios. The impacts of phenomenological constraints from collider, dark matter, and cosmology are also taken into account. We report that the conversion mechanism is both favored by the resonance and secluded scenarios under current constraints.

hep-ph↗

arXiv2025

Seesaw Portal to Super Heavy Dark Matter with $Z_3$ Symmetry

Right-handed neutrinos $N$ are introduced to explain the origin of the tiny neutrino masses via the seesaw mechanism. Required by relatively large Yukawa coupling and leptogenesis, masses of right-handed neutrinos are beyond $10^{9}$ GeV. Such heavy right-handed neutrino can mediate the production of super heavy dark matter $\chi$ via the freeze-in mechanism. In the minimal $Z_2$ symmetric model, the right-hand neutrino portal interaction is $y_N \phi \bar{\chi} N$ with the dark scalar $\phi$. One drawback of the $Z_2$ symmetric model is that the mass ordering $m_N>m_\phi$ with long-lived $\phi$ is almost ruled out by Big Bang Nucleosynthesis. In this paper, we propose that by extending the dark symmetry to $Z_3$, one additional interaction $y_\chi \phi \bar{\chi}^c \chi$ is further allowed. In this way, the new decay mode $\phi\to \chi\chi$ would lead to the dark scalar $\phi$ being short-lived even with a feeble $y_\chi$, thus it is allowed by the cosmological constraints. The phenomenology of the $Z_3$ symmetric super heavy dark matter model is also studied in this paper.

hep-ph↗

arXiv2025

New Physics Search at the CEPC: a General Perspective

The Circular Electron-Positron Collider (CEPC), a proposed next-generation Higgs factory, provides new opportunities to explore physics beyond the Standard Model (SM). With its clean electron-positron collision environment and the ability to collect large samples of Higgs, W, and Z bosons, the CEPC enables precision measurements and searches for new physics. This white paper outlines the CEPC's discovery potential, including studies of exotic decays of the Higgs, Z, and top quarks, dark matter and dark sector phenomena, long-lived particles, supersymmetry, and neutrino-related signatures. Advanced detector technologies and reconstruction techniques, such as one-to-one correspondence reconstruction and jet origin identification, significantly improve sensitivity to rare and weakly interacting processes. The CEPC is particularly well suited to probe the electroweak phase transition and test models of electroweak baryogenesis and dark sector interactions. In addition, global fit analyses highlight the CEPC's complementary role in constraining a wide range of new physics scenarios. These features position the CEPC as a powerful tool for exploring the next frontier in fundamental particle physics in the post-Higgs discovery era.

hep-ex↗

arXiv2025

Lepton Number Violation Higgs Decay at Muon Collider

In this paper, we consider the scalar singlet extension of type-I seesaw, where a scalar singlet $S$ and heavy neutral lepton $N$ are further introduced. The Majorana mass term of heavy neutral lepton is generated through the Yukawa interaction with the scalar singlet, which then induces the lepton number violation decays of SM Higgs $h$ and heavy Higgs $H$ via mixing of scalars. As a pathway to probe the origin of heavy neutral lepton mass, we investigate the lepton number violation Higgs decay signature at the TeV-scale muon collider. The dominant production channel of Higgs bosons at the TeV-scale muon collider is via vector boson fusion. So we perform a detailed analysis of the signal process $\mu^+\mu^-\to \nu_\mu \bar{\nu}_\mu h/H \to \nu_\mu \bar{\nu}_\mu NN $ followed by $ N \to \mu^\pm jj$, where the two jets from $W$ boson decay are treated as one fat-jet $J$. With an integrated luminosity of $1(10)~\text{ab}^{-1}$, the 3 (10) TeV muon collider could discover the lepton number violation SM Higgs decay $h\to \mu^\pm\mu^\pm JJ$ signature for the Higgs mixing parameter $\sin\alpha>0.05(0.009)$. Meanwhile, a large parameter space can be detected by the lepton number violation heavy Higgs decay $H\to \mu^\pm\mu^\pm JJ$ signature for $m_H\lesssim1 (3)$ TeV and $\sin\alpha\gtrsim0.03(0.005)$ at the 3 (10) TeV muon collider. Therefore, the lepton number violation SM and heavy Higgs decay signatures are both promising at the TeV scale muon collider.

hep-ph↗

arXiv2025

Prospects of $Z'$ Portal Dark Matter in $U(1)_{L_\mu-L_\tau}$

The gauged $U(1)_{L_\mu-L_\tau}$ model is well-motivated to explain the muon $g-2$ anomaly and dark matter in previous studies. However, the latest NA64$\mu$ experiment has almost excluded all the parameter space for the muon $g-2$, which indicates that the light dark matter benchmark scenarios interpreting muon $g-2$ in previous studies are also not allowed at present. In light of many recent and future experimental results, we revisit the minimal $Z'$ portal dark matter in $U(1)_{L_\mu-L_\tau}$. Focus on the phenomenology of dark matter $\chi$, we first explore the viable parameter space for the light dark matter under various tight constraints. Around the $Z'$ resonance, we find that there is still a large parameter space for $m_\chi\gtrsim10$ MeV via thermal freeze-out. On the other hand, the constraints on $Z'$ above the electroweak scale are quite loose but are less studied for dark matter. We also investigate the heavy dark matter around the TeV scale and corresponding constraints. A large part of the parameter space for dark matter is within the reach of future experiments.

hep-ph↗

arXiv2024

Flavor Physics at the CEPC: a General Perspective

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $Z$ pole, the expected production of 4 Tera $Z$ bosons will provide unique and highly precise measurements of $Z$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $Z$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $\tau$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $WW$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals.

hep-ex↗

arXiv2024

Research of Extra Charged Gauge Boson $W^{\prime}$ in Alternative Left-Right Model at Future Muon Collider

The study of extra charged gauge boson beyond the Standard Model has always been of great interest. Future muon colliders will have a significant advantage in discovering exotic particles. In this paper, by studying the $\mu^+ \mu^- \to W^{\prime +} W^{\prime -} \to e^+ e^- n_e \bar{n}_e$ process, we explore the properties of $W^\prime$ in the alternative left-right model. The cross section and angular distribution of the final electron are investigated in the scenario of different $W^\prime$ mass and right-handed coupling constant. The forward-backward asymmetry is also an important observable to reflect the properties of $W^\prime$. We provide a method to effectively suppress the background processes. With specific kinematic cuts, the significance can reach $5.17\sigma$ for 4.8 TeV $W^\prime$ at the collision energy of 10 TeV.

hep-ph↗

arXiv2024

Single Production of Doubly Charged Higgs at Muon Collider

In this paper, we study the single production of doubly charged Higgs $H^{\pm\pm}$ in the type-II seesaw at the high energy muon collider. Compared with the pair production channel $\mu^+\mu^-\to H^{++} H^{--}$, the single production channel $\mu^+\mu^-\to \mu^\mp\ell^\mp H^{\pm\pm}$ in principle could probe the mass region above the threshold $m_{H^{\pm\pm}}>\sqrt{s}/2$. The single production channel depends on the Yukawa coupling $h$, which is related to the neutrino oscillation parameters. We show that the Majorana phases $\phi_1$ and $\phi_2$ have great impact on the individual cross section of the single production. We find that the same sign dilepton signature from $H^{\pm\pm}\to \ell^\pm\ell^\pm$ could probe $m_{H^{\pm\pm}}\lesssim2.6(7.1)$ TeV at the 3 (10) TeV muon collider when the triplet VEV $v_\Delta\lesssim3$ eV.

hep-ph↗

arXiv2024

Phenomenological study of heavy neutral gauge boson in the left-right symmetric model at future muon collider

The exotic neutral gauge boson is a powerful candidate for the new physics beyond the standard model. As a promising model, the left-right symmetric model has been proposed to explain the neutrino mass, dark matter, and matter-antimatter asymmetry, etc., in which exotic gauge bosons $Z^\prime, W^{\prime \pm}$ have been put forward as well as other new right-handed particles. We investigate the $\mu^+ \mu^- \to q\bar{q} $ and $ \mu^+ \mu^- \to l^+ l^- $ processes involving the $Z^\prime$ boson as an intermediate particle. The coupling strength, decay width and mass are the key parameters on the production and decay processes of the $Z^\prime$ boson. The results indicate that the angular distributions of final particles are sensitive to the couplings of $Z^\prime$ to the other fermions. Asymmetries defined from the angular distributions are ideal quantities to demonstrate the discrepancy between the standard model process and the processes with $Z^\prime$ participated and they are also appropriate observables to discriminate the couplings of $Z^\prime$ to other particles. Compared with the current results at the Large Hadron Collider (LHC), the future muon collider has a great potential to explore the new parameter space with $Z^\prime$ boson.

hep-ph↗

arXiv2024

Common Origin of Dark Matter and Leptogenesis in $U(1)_{B-L}$

In this paper, we investigate the common parameter space of dark matter and leptogenesis in the $U(1)_{B-L}$ symmetry. This model involves a complex scalar $\phi$, sterile neutrinos $N$, and Majorana dark matter $\chi$, where only dark matter $\chi$ is charged under the $Z_2$ symmetry. Masses of $N$ and $\chi$ are generated via the Yukawa interactions to $\phi$ after breaking of the $U(1)_{B-L}$ symmetry. TeV scale sterile neutrinos $N$ are responsible for the generation of baryon asymmetry through the resonance leptogenesis mechanism. The new particles in the $U(1)_{B-L}$ have a significant impact on the dilution of $N$, thus on leptogenesis. Meanwhile, the annihilation processes of dark matter $\chi$ are almost identical to that of $N$, which indicates that both leptogenesis and dark matter are closely related to satisfying the observed results simultaneously. Under various theoretical and experimental constraints, the viable common parameter space of dark matter and leptogenesis is obtained for both global and local $U(1)_{B-L}$ symmetry.

hep-ph↗

arXiv2024

Displaced Heavy Neutral Lepton from New Higgs Doublet

Heavy neutral leptons $N$ are introduced to explain the tiny neutrino masses via the seesaw mechanism. For proper small mixing parameter $V_{\ell N}$, the heavy neutral leptons $N$ become long-lived, which leads to the displaced vertex signature at colliders. In this paper, we consider the displaced heavy neutral lepton from the neutrinophilic Higgs doublet $\Phi_\nu$ decay. The new Higgs doublet with MeV scale VEV can naturally explain the tiny neutrino masses with TeV scale $N$. Different from current experimental searches via the $W^\pm\to \ell^\pm N$ decay, the new decays as $H^\pm\to \ell^\pm N$ are not suppressed by the small mixing parameter $V_{\ell N}$. Therefore, a larger parameter space is expected to be detected at colliders. We then investigate the promising region at the 14 TeV HL-LHC and the 3 TeV CLIC. According to our simulation, the DV signature could probe $|V_{\ell N}|^2\gtrsim10^{-19}$ with $m_N<m_{H^+}$, which covers the seesaw predicted value $|V_{\ell N}|^2\sim m_\nu/m_N$. We could probe $m_{H^+}\lesssim1200$ GeV at the 14 TeV HL-LHC and $m_{H^+}\lesssim1490$ GeV at the 3 TeV CLIC.

hep-ph↗

arXiv2024

Detect2Interact: Localizing Object Key Field in Visual Question Answering (VQA) with LLMs

Localization plays a crucial role in enhancing the practicality and precision of VQA systems. By enabling fine-grained identification and interaction with specific parts of an object, it significantly improves the system's ability to provide contextually relevant and spatially accurate responses, crucial for applications in dynamic environments like robotics and augmented reality. However, traditional systems face challenges in accurately mapping objects within images to generate nuanced and spatially aware responses. In this work, we introduce "Detect2Interact", which addresses these challenges by introducing an advanced approach for fine-grained object visual key field detection. First, we use the segment anything model (SAM) to generate detailed spatial maps of objects in images. Next, we use Vision Studio to extract semantic object descriptions. Third, we employ GPT-4's common sense knowledge, bridging the gap between an object's semantics and its spatial map. As a result, Detect2Interact achieves consistent qualitative results on object key field detection across extensive test cases and outperforms the existing VQA system with object detection by providing a more reasonable and finer visual representation.

cs.CV↗

arXiv2023

Phenomenology of Heavy Neutral Gauge Boson at Muon Collider

Heavy neutral gauge boson $Z^\prime$ is proposed in many new physics models. It has rich phenomena at the future muon collider. We study the properties of $Z^\prime$ boson with the process of $μ^+ μ^- \rightarrow q \bar{q}$, $μ^+ μ^- \rightarrow l^+ l^-$, $μ^+ μ^- \rightarrow Z H$ and $μ^+ μ^- \rightarrow W^+ W^-$. The discrepancy of $Z^\prime$ coupling to different types of particles can be shown in the cross section distributions around the resonance peak of various decay modes. Angular distributions of the final quark or lepton in $μ^+ μ^- \rightarrow q \bar{q}/l^+ l^- $ process are sensitive to the parameters such as mass of $Z^\prime$ and the $Z-Z^\prime$ mixing angle. The interaction of new gauge boson coupling to the standard model gauge particles and Higgs boson are also studied through $μ^+ μ^- \rightarrow Z H \rightarrow l^+l^- b \bar{b}$ and $μ^+ μ^- \rightarrow W^+W^- \rightarrow l^+l^- ν_l \barν_l$. The cross section and the final particles' angular distributions with the contribution of $Z^\prime$ boson differ from those processes with only standard model particles. A forward-backward asymmetry defined by the angular distribution is provided to show the potential of searching for new physics at the muon collider. Especially, the beam polarization with certain value can effectively enlarge the forward-backward asymmetry.

hep-ph↗

arXiv2023

Probing Dirac Neutrino Properties with Dilepton Signature

The neutrinophilic two Higgs doublet model is one of the simplest models to explain the origin of tiny Dirac neutrino masses. This model introduces a new Higgs doublet with eV scale VEV to naturally generate the tiny neutrino masses. Depending on the same Yukawa coupling, the neutrino oscillation patterns can be probed with the dilepton signature from the decay of charged scalar $H^\pm$. For example, the normal hierarchy predicts BR$(H^+\to e^+ν)\ll$ BR$(H^+\to μ^+ν)\approx$ BR$(H^+\to τ^+ν)\simeq0.5$ when the lightest neutrino mass is below 0.01 eV, while the inverted hierarchy predicts BR$(H^+\to e^+ν)/2\simeq$ BR$(H^+\to μ^+ν)\simeq$ BR$(H^+\to τ^+ν)\simeq0.25$. By precise measurement of BR$(H^+\to \ell^+ν)$, we are hopefully to probe the lightest neutrino mass and the atmospheric mixing angle $θ_{23}$. Through the detailed simulation of the dilepton signature and corresponding backgrounds, we find that the 3 TeV CLIC could discover $M_{H^+}\lesssim1220$ GeV for NH and $M_{H^+}\lesssim1280$ GeV for IH. Meanwhile, the future 100 TeV FCC-hh collider could probe $M_{H^+}\lesssim1810$ GeV for NH and $M_{H^+}\lesssim2060$ GeV for IH.

hep-ph↗