arXiv subjects

Soojin Lee

Publications and source records attributed to Soojin Lee.

27 records · Page 2Linked to original sources

arXiv2022

Status of the two-Higgs-doublet model in light of the CDF $m_W$ measurement

The most recent $W$-boson mass measurement by the CDF collaboration with a substantially reduced uncertainty indicates a significant deviation from the standard model prediction, as large as $7σ$ if taken literally. Then the Peskin-Takeuchi parameters of $S$ and $T$ shift to larger values, which has profound consequences in searching for physics beyond the SM. In the framework of two-Higgs-doublet models, we study the effect of the new $W$-boson mass measurement on the parameter space. Combined with other constraints including theoretical requirements, flavor-changing neutral currents in $B$ physics, the cutoff scale above 1 TeV, Higgs precision data, and direct collider search limits from the LEP, Tevatron, and LHC experiments, we find upper bounds on the masses of the heavy Higgs bosons: $M_{H, A, H^\pm} \lesssim 1.1$ TeV in type I, II, X, and Y for the normal Higgs scenario; $M_{H^\pm} \lesssim 450 $ GeV and $M_{A} \lesssim 420 $ GeV in type I and X for the inverted scenario where the heavier $CP$-even Higgs boson is the observed one. Another important finding is that type II and type Y in the inverted scenario are completely excluded. Such unprecedented findings imply that the upcoming LHC run can readily close out a large portion of the still-available parameter space.

hep-ph↗

arXiv2022

CDF $W$ boson mass and muon $g-2$ in type-X two-Higgs-doublet model with a Higgs-phobic light pseudoscalar

The recent measurement of the $W$ boson mass by the CDF collaboration adds an anomaly to the long-standing discrepancy in the muon anomalous magnetic moment, $Δa_μ$. Although type-X in the two-Higgs-doublet model provides an attractive solution to $Δa_μ$ through a light pseudoscalar $A$, the model confronts the exotic Higgs decays of $h\to AA$ and the lepton flavor universality data in the $τ$ and $Z$ decays. To save the model, we propose that the light pseudoscalar be Higgs-phobic. Through the random scanning over the entire parameter space, we perform a comparative study of the Higgs-phobic type-X with and without the CDF $m_W$ measurement, called the CDF and PDG cases respectively. Both cases can explain the two anomalies as well as all the other constraints but have significant differences in the finally allowed parameter space. For example, a small region with almost degenerate masses of new Higgs bosons around 100 GeV is allowed only in the PDG case. The cutoff scale of the model is also studied via the analysis of renormalization group equations, which reaches up to $10^5~{\rm GeV}$ ($10^7~{\rm GeV}$) in the CDF (PDG) case. Since the dominant decay modes are $A\to ττ$, $H \to Z A$, and $H^\pm\to W^\pm A$ in most of the viable parameter space, we propose the $4τ+VV'$ states as the golden discovery channel at the LHC.

hep-ph↗

arXiv2022

Fermiophobic light Higgs boson in the type-I two-Higgs-doublet model

The null results in the new physics searches at the LHC do not exclude an intermediate-mass new particle if it is fermiophobic. Type-I in the two-Higgs-doublet model accommodates a fermiophobic light Higgs boson $h_{\rm f}$ if $α=π/2$. The heavier $CP$-even Higgs boson explains the observed Higgs boson at a mass of 125 GeV. We first obtain the still-valid parameter space satisfying the theoretical requirements, flavor-changing neutral currents in $B$ physics, the cutoff scale above 1 TeV, Higgs precision data, and the direct collider search bounds at high energy colliders. We also study the high energy scale behavior via the analysis of the renormalization group equations. An important result is that the fermiophobic type-I can maintain the stability of the scalar potential all the way up to the Planck scale if $m_{h_{\rm f}}$ is larger than half the observed Higgs boson mass. Since the parameter space is severely curtailed, especially for the high cutoff scale, the signal rates in the multi-photon states of new Higgs bosons at the LHC are well predicted. We suggest the processes of $4γ+VV'$ ($V^{(\prime)}=Z, W^\pm$) as the golden discovery channels for the model since they enjoy an almost background-free environment and substantial selection efficiencies for four photons.

hep-ph↗

arXiv2022

Comprehensive study of the light charged Higgs boson in the type-I two-Higgs-doublet model

In the type-I two-Higgs-doublet model, existing theoretical and experimental constraints still permit the light charged Higgs boson with a mass below the top quark mass. We present a complete roadmap for the light charged Higgs boson at the LHC through the comprehensive phenomenology study, focusing on the normal scenario where the lighter \textit{CP}-even Higgs boson is the observed Higgs boson. In type-I, it is challenging to simultaneously accommodate the light mass of the charged Higgs boson and the constraints from theory, electroweak precision data, Higgs data, $b\to s γ$, and direct search bounds. Consequently, the parameter space is extremely curtailed, which predicts somewhat definite phenomenological signatures. We find that the mass of the pseudoscalar Higgs boson, $M_A$, is the most crucial factor in the phenomenology of the charged Higgs boson. If $M_A$ is light, the charged Higgs boson decays mainly into $A W^\pm$. When $M_A$ is above the $A W^\pm$ threshold, the dominant decay mode is into $ τ^\pm ν$. Over the whole viable parameter space, we study all the possible production and decay modes of charged Higgs bosons at the LHC, and suggest three efficient channels: (i) $pp \to H^+ H^-\to [τν] [τν]$; (ii) $pp \to HA/HH/AA \to H^\pm W^\mp H^\pm W^\mp \to [τν] [τν] W W$; (iii) $pp \to H^+ H^-\to [b \bar b W ] [b \bar b W ] $. Based on the sophisticated signal-background analyses including detector simulation, we showed that the significance of the first final state is large, that of the second one is marginal around three, but the third one suffers from huge $t\bar t$ related backgrounds.

hep-ph↗

arXiv2021

Type-X two Higgs doublet model in light of the muon $\mathbf{g-2}$: confronting Higgs and collider data

The recent Fermilab measurement of the muon anomalous magnetic moment yields $4.2 σ$ deviations from the SM prediction when combined with the BNL E821 experiment results. In the Type-X two Higgs doublet model, we study the consequence of imposing the observed muon $g-2$, along with the constraints from theoretical stabilities, electroweak oblique parameters, Higgs precision data, and direct searches. For a comprehensive study, we scan the whole parameter space in two scenarios, the normal scenario where $h_{\rm SM} = h$ and the inverted scenario where $h_{\rm SM}=H$, where $h$ ($H$) is the light (heavy) CP-even Higgs boson. We found that large $\tanβ$ (above 100) and light pseudoscalar mass $M_A$ are required to explain the muon $g-2$ anomaly. This breaks the theoretical stability unless the scalar masses satisfy $M_A^2 \simeq M_{H^\pm}^2 \simeq m_{12}^2 \tanβ\approx M_{H/h}^2$. The direct search bounds at the LEP and LHC exclude the light $A$ window with $M_A \lesssim 62.5~$GeV. We also show that the observed electron anomalous magnetic moment is consistent with the model prediction, but the lepton flavor universality data in the $τ$ and $Z$ decays are not. For a separate exploration of the model, we propose the golden mode $pp \to A h/AH \to 4 τ$ at the HL-LHC.

hep-ph↗

arXiv2021

Studies of nonresonant Higgs pair production at electron-proton colliders

The measurement of the Higgs quartic coupling modifier between a Higgs boson pair and a vector boson pair, $κ_{2V}$, is expected to be achieved from vector-boson fusion (VBF) production of a Higgs boson pair. However, this process involves another unmeasured parameter, the trilinear Higgs self-coupling modifier $κ_{λ}$. A sensitivity analysis should target both parameters. Since the LHC cannot avoid the gluon fusion pollution, which becomes severe for non-SM $κ_{λ}$, an electron-proton collider is more appropriate for the comprehensive measurement. In this regard, we study the VBF production of a Higgs boson pair in the $b\bar{b}b\bar{b}$ final state at the LHeC and FCC-he. Performing detailed analysis using the simulated dataset, we devise the search strategy specialized at the LHeC and FCC-he and give a prediction for the sensitivity to both $κ_{2V}$ and $κ_{λ}$. We find that the two electron-proton colliders have high potential: the LHeC has similar exclusion prospects as the HL-LHC; the FCC-he is extremely efficient, excluding the parameter space outside $κ_{2V} \in [0.8, 1.2]$ and $κ_{λ}\in [1, 2.5]$ at 95% C.L. for the total luminosity of $10$ ab$^{-1}$ and 10% uncertainty on the background yields.

hep-ph↗

arXiv2020

Epileptic Seizure Prediction: A Semi-Dilated Convolutional Neural Network Architecture

Accurate prediction of epileptic seizures has remained elusive, despite the many advances in machine learning and time-series classification. In this work, we develop a convolutional network module that exploits Electroencephalogram (EEG) scalograms to distinguish between the pre-seizure and normal brain activities. Since these scalograms have rectangular image shapes with many more temporal bins than spectral bins, the presented module uses "semi-dilated convolutions" to create a proportional non-square receptive field. The proposed semi-dilated convolutions support exponential expansion of the receptive field over the long dimension (image width, i.e. time) while maintaining high resolution over the short dimension (image height, i.e., frequency). The proposed architecture comprises a set of co-operative semi-dilated convolutional blocks, each block has a stack of parallel semi-dilated convolutional modules with different dilation rates. Results show that our proposed solution outperforms the state-of-the-art methods, achieving seizure prediction sensitivity scores of 88.45% and 89.52% for the American Epilepsy Society and Melbourne University EEG datasets, respectively.

eess.IV↗

arXiv2020

Phenomenology of the Inert Doublet Model with a global U(1) symmetry

The inert doublet model is a minimal dark matter model with strong theoretical motivations, where the stability of dark matter is usually achieved by imposing a $Z_2$ parity. We promote the $Z_2$ parity into a global $U(1)$ symmetry and study its phenomenological implications. There are two characteristic features of the model: both the CP-even and CP-odd neutral inert scalars, $h_1$ and $h_2$, become DM candidates; the number of model parameters is one less than that with $Z_2$ parity. We first analyze the constraints from LEP experiments, electroweak precision tests, theoretical stability, Higgs precision data, dark matter relic density, and direct detection experiments. It is found that if the model is required to explain at least 10% of the observed relic density, the theory is extremely limited such that the dark matter mass is about $70\;{\rm GeV}$ and the charged Higgs boson is not very heavy. Focusing on this narrow parameter space, we calculate the production cross sections of almost all the possible mono-$X$ and mono-$XX'$ processes at the LHC. The mono-$Wγ$ process is shown to have high discovery potential with the help of the decay of the intermediate-mass charged Higgs boson into $W^\pm h_{1,2}$. A search strategy is designed to increase the potential discovery of the model for the mono-$Wγ$ signal at both the HL-LHC and the FCC-hh. The optimal cut on $E_T^{\rm miss}/\sqrt{H_T}$ is suggested to maximize the signal significance, being about $0.76$ at the HL-LHC and about $7.5$ at the FCC-hh.

hep-ph↗

arXiv2009

A New Efficient Key Management Protocol for Wireless Sensor and Actor Networks

Research on sensor networks has become much more active and is currently being applied to many different fields. However since sensor networks are limited to only collecting and reporting information regarding a certain event, and requires human intervention with that given information, it is often difficult to react to an event or situation immediately and proactively. To overcome this kind of limitation, Wireless Sensor and Actor Networks (WSANs) with immediate-response actor nodes have been proposed which adds greater mobility and activity to the existing sensor networks. Although WSANs share many common grounds with sensor networks, it is difficult to apply existing security technologies due to the fact that WSANs contain actor nodes that are resource-independent and mobile. Therefore, this research seeks to demonstrate ways to provide security, integrity, and authentication services for WSANs secure operation, by separating networks into hierarchical structure by each node's abilities and provides different encryption key based secure protocols for each level of hierarchy, Pairwise key, node key, and region key for sensor levels, and public key for actor

cs.CR↗