arXiv subjects

Tao Han

Publications and source records attributed to Tao Han.

At least 181 records · Page 10Linked to original sources

arXiv2020

Leptonic Scalars at the LHC

We explore the collider prospects of neutrino non-standard interaction with a Standard Model (SM) gauge-singlet leptonic scalar $ϕ$ carrying two units of lepton-number-charge. These leptonic scalars are forbidden from interacting with the SM fermions at the renormalizable level and, if one allows for higher-dimensional operators, couple predominantly to SM neutrinos. For masses at or below the electroweak scale, $ϕ$ decays exclusively into neutrinos. Its characteristic production signature at hadron collider experiments like the LHC would be via the vector boson fusion process and leads to same-sign dileptons, two forward jets in opposite hemispheres, and missing transverse energy, i.e., $pp \to \ell_α^\pm \ell_β^\pm jj + E_T^{\rm miss}$ ($α,\, β= e,\, μ, τ$). Exploiting the final states of electrons and muons, we estimate, for the first time, the sensitivity of the LHC to these lepton-number-charged scalars. We show that the LHC sensitivity is largely complementary to that of low-energy precision measurements of the decays of charged leptons, charged mesons, $W$, $Z$ and the SM Higgs boson, as well as the neutrino beam experiments like MINOS, and searches for neutrino self-interactions at IceCube and in cosmological observations. For $ϕ$ mass larger than roughly 10 GeV, our projected LHC sensitivity would surpass all existing bounds.

hep-ph↗

arXiv2020

Smart Contract-based Secure Spectrum Sharing in Multi-Operators Wireless Communication Networks

Multiple-operators (multi-OPs) spectrum sharing mechanism can effectively improve the spectrum utilization in fifth-generation (5G) wireless communication networks. The secondary users are introduced to opportunistically access the licensed spectrum of idle operators (OPs). However, the identity privacy and data security issues raise great concerns about the secure spectrum sharing among multi-OPs. To address these challenges, a consortium blockchain trust framework is proposed for the spectrum sharing in multi-OPs wireless communication networks in this paper. A real consortium blockchain is constructed among multi-OPs. The Multi-Ops Spectrum Sharing (MOSS) smart contract is designed on the constructed consortium blockchain to implement the spectrum trading among multi-OPs. Without the need of trustless spectrum broker, the MOSS smart contract enforces multi-OPs to share the spectrum truthfully and designs a punishment mechanism to punish malicious OPs. Simulation results tested on the Remix integrated development environment (IDE) indicate the feasibility of the designed MOSS smart contract. The performance analysis of the proposed consortium blockchain trust framework demonstrates that the privacy, openness and fairness of the proposed solution are better than traditional spectrum allocation solutions.

cs.NI↗

arXiv2020

EdgeSlice: Slicing Wireless Edge Computing Network with Decentralized Deep Reinforcement Learning

5G and edge computing will serve various emerging use cases that have diverse requirements of multiple resources, e.g., radio, transportation, and computing. Network slicing is a promising technology for creating virtual networks that can be customized according to the requirements of different use cases. Provisioning network slices requires end-to-end resource orchestration which is challenging. In this paper, we design a decentralized resource orchestration system named EdgeSlice for dynamic end-to-end network slicing. EdgeSlice introduces a new decentralized deep reinforcement learning (D-DRL) method to efficiently orchestrate end-to-end resources. D-DRL is composed of a performance coordinator and multiple orchestration agents. The performance coordinator manages the resource orchestration policies in all the orchestration agents to ensure the service level agreement (SLA) of network slices. The orchestration agent learns the resource demands of network slices and orchestrates the resource allocation accordingly to optimize the performance of the slices under the constrained networking and computing resources. We design radio, transport and computing manager to enable dynamic configuration of end-to-end resources at runtime. We implement EdgeSlice on a prototype of the end-to-end wireless edge computing network with OpenAirInterface LTE network, OpenDayLight SDN switches, and CUDA GPU platform. The performance of EdgeSlice is evaluated through both experiments and trace-driven simulations. The evaluation results show that EdgeSlice achieves much improvement as compared to baseline in terms of performance, scalability, compatibility.

cs.NI↗

arXiv2020

The Search for Electroweakinos

In this review, we consider a general theoretical framework for fermionic color-singlet states, including a singlet, a doublet and a triplet under the standard model SU(2)$_{\rm L}$ gauge symmetry, corresponding to the Bino, Higgsino and Wino in Supersymmetric theories, generically dubbed as "electroweakinos" for their mass eigenstates. Depending on the relations among their three mass parameters and the mixings after the electroweak symmetry breaking, this sector leads to rich phenomenology potentially accessible at the current and near-future experiments. We discuss the decay patterns of the electroweakinos and their observable signatures at colliders. We review the existing bounds on the model parameters. We summarize the current status for the comprehensive searches from the ATLAS and CMS experiments at the LHC. We comment on the prospects for future colliders. An important feature of the theory is that the lightest neutral electroweakino can be identified as a WIMP cold dark matter candidate. We take into account the existing bounds on the parameters from the dark matter direct detection experiments and discuss the complementarity for the electroweakino searches at colliders.

hep-ph↗

arXiv2020

Focus on Semantic Consistency for Cross-domain Crowd Understanding

For pixel-level crowd understanding, it is time-consuming and laborious in data collection and annotation. Some domain adaptation algorithms try to liberate it by training models with synthetic data, and the results in some recent works have proved the feasibility. However, we found that a mass of estimation errors in the background areas impede the performance of the existing methods. In this paper, we propose a domain adaptation method to eliminate it. According to the semantic consistency, a similar distribution in deep layer's features of the synthetic and real-world crowd area, we first introduce a semantic extractor to effectively distinguish crowd and background in high-level semantic information. Besides, to further enhance the adapted model, we adopt adversarial learning to align features in the semantic space. Experiments on three representative real datasets show that the proposed domain adaptation scheme achieves the state-of-the-art for cross-domain counting problems.

cs.CV↗

arXiv2019

Nonstandard neutrino interactions at COHERENT, DUNE, T2HK and LHC

We study how nonstandard neutrino interactions (NSI) may be probed by a combination of coherent elastic neutrino-nucleus scattering, neutrino oscillation and collider data, from COHERENT, DUNE, T2HK and the high-luminosity (HL) LHC. We focus on NSI induced by a new flavored gauge boson $Z'$ in a generic anomaly-free ultraviolet-complete model. For $Z'$ masses above 10 GeV, the HL-LHC has the best sensitivity regardless of the flavor structure of the model. For masses between 0.01 GeV-10 GeV, current LHCb data and future COHERENT data have the best sensitivity unless the $Z'$ couplings to the first and second generation leptons are suppressed, in which case DUNE and T2HK have the best sensitivity. For $Z'$ masses between about 5 MeV-20 MeV, DUNE and T2HK have the best sensitivity. We also show how joint analyses of COHERENT and LHC data may constrain such models.

hep-ph↗

arXiv2019

Neutrino Non-Standard Interactions: A Status Report

This report summarizes the present status of neutrino non-standard interactions (NSI). After a brief overview, several aspects of NSIs are discussed, including connection to neutrino mass models, model-building and phenomenology of large NSI with both light and heavy mediators, NSI phenomenology in both short- and long-baseline neutrino oscillation experiments, neutrino cross-sections, complementarity of NSI with other low- and high-energy experiments, fits with neutrino oscillation and scattering data, DUNE sensitivity to NSI, effective field theory of NSI, as well as the relevance of NSI to dark matter and cosmology. We also discuss the open questions and interesting future directions that can be pursued by the community at large. This report is based on talks and discussions during the Neutrino Theory Network NSI workshop held at Washington University in St. Louis from May 29-31, 2019 (https://indico.cern.ch/event/812851/)

hep-ph↗

arXiv2019

Learning-Assisted Secure End-to-End Network Slicing for Cyber-Physical Systems

There is a pressing need to interconnect physical systems such as power grid and vehicles for efficient management and safe operations. Owing to the diverse features of physical systems, there is hardly a one-size-fits-all networking solution for developing cyber-physical systems. Network slicing is a promising technology that allows network operators to create multiple virtual networks on top of a shared network infrastructure. These virtual networks can be tailored to meet the requirements of different cyber-physical systems. However, it is challenging to design secure network slicing solutions that can efficiently create end-to-end network slices for diverse cyber-physical systems. In this article, we discuss the challenges and security issues of network slicing, study learning-assisted network slicing solutions, and analyze their performance under the denial-of-service attack. We also present a design and implementation of a small-scale testbed for evaluating the network slicing solutions.

cs.NI↗

arXiv2019

Persistent Insulator: Avoidance of Metallization at Megabar Pressures in Strongly Spin-Orbit-Coupled Sr2IrO4

It is commonly anticipated that an insulating state collapses in favor of an emergent metallic state at high pressures as the unit cell shrinks and the electronic bandwidth broadens to fill the insulating energy band gap. Here we report a rare insulating state that persists up to at least 185 GPa in the antiferromagnetic iridate Sr2IrO4, which is the archetypical spin-orbit-driven Jeff = 1/2 insulator. This study shows the electrical resistance of single-crystal Sr2IrO4 initially decreases with applied pressure, reaches a minimum in the range, 32 - 38 GPa, then abruptly rises to fully recover the insulating state with further pressure increases up to 185 GPa. Our synchrotron x-ray diffraction and Raman scattering data show the onset of the rapid increase in resistance is accompanied by a structural phase transition from the native tetragonal I41/acd phase to an orthorhombic Pbca phase (with much reduced symmetry) at 40.6 GPa. The clear-cut correspondence of these two anomalies is key to understanding the stability of the insulating state at megabar pressures: Pressure-induced, severe structural distortions prevent the expected metallization, despite the 26% volume compression attained at the highest pressure accessed in this study. Moreover, the resistance of Sr2IrO4 remains stable while the applied pressure is tripled from 61 GPa to 185 GPa. These results suggest that a novel type of electronic Coulomb correlation compensates the anticipated band broadening in strongly spin-orbit-coupled materials at megabar pressures.

cond-mat.str-el↗

arXiv2019

SUSY Signals from QCD Production at the Upgraded LHC

Weak-scale supersymmetry remains to be one of the best-motivated theories of physics beyond the Standard Model. We evaluate the sensitivities of the High Luminosity (HL) and High Energy (HE) upgrades of the LHC to gluinos and stops, decaying through the simplified topologies $\tilde{g} \to q \bar{q} χ^0$, $\tilde{g} \to t \bar{t} χ^0$ and $\tilde{t} \to t \tildeχ^0$. Our HL-LHC analyses improve on existing experimental projections by optimizing the acceptance of kinematic variables. The HE-LHC studies represent the first 27 TeV analyses. We find that the HL-(HE-)LHC with 3 ab$^{-1}$ (15 ab$^{-1}$) of integrated luminosity will be sensitive to the masses of gluinos and stops at 3.2 (5.7) TeV and 1.5 (2.7) TeV, respectively, decaying to massless neutralinos.

hep-ph↗

arXiv2019

Dark Matter Blind Spots at One-Loop

We evaluate the impact of one-loop electroweak corrections to the spin-independent dark matter (DM) scattering cross-section with nucleons ($σ_{\rm SI}$), in models with a so-called blind spot for direct detection, where the leading-order prediction for the relevant DM coupling to the Higgs boson, and therefore $σ_{\rm SI}$, are vanishingly small. Adopting a simple illustrative scenario in which the DM state results from the mixing of electroweak singlet and doublet fermions, we compute the relevant higher order corrections to the scalar effective operator contributions to $σ_{\rm SI}$, stemming from both triangle and box diagrams involving the SM and dark sector fields. It is observed that in a significant region of the singlet-doublet model-space, the one-loop corrections ``unblind'' the tree-level blind spots and lead to detectable SI scattering rates at future multi-ton scale liquid Xenon experiments, with $σ_{\rm SI}$ reaching values up to a few times $10^{-47} {~\rm cm}^2$, for a weak scale DM with $\mathcal{O}(1)$ Yukawa couplings. Furthermore, we find that there always exists a new SI blind spot at the next-to-leading order, which is perturbatively shifted from the leading order one in the singlet-doublet mass parameters. For comparison, we also present the tree-level spin-dependent scattering cross-sections near the SI blind-spot region, that could lead to a larger signal. Our results can be mapped to the blind-spot scenario for bino-Higgsino DM in the MSSM, with other sfermions, the heavier Higgs boson, and the wino decoupled.

hep-ph↗

arXiv2019

Electroweak Dark Matter at Future Hadron Colliders

In a large class of scenarios, dark matter (DM) particles that belong to a multiplet of the standard model (SM) weak interactions are challenging to probe in direct detection experiments due to loop-suppressed cross-sections. Direct production at colliders is thus crucial to look for such DM candidates, and under current estimates, future runs of the 14-TeV LHC are projected to probe masses of around 300 GeV for DM belonging to an SU(2) doublet (Higgsino-like), and 900 GeV for SU(2) triplet (wino-like). We examine how far this mass reach can be extended at the proposed 27-TeV high-energy upgrade of the LHC (HE-LHC), and compare the results to the case for a 100-TeV hadron collider. Following a detector setup similar to that of the ATLAS tracking system for the Run-2 LHC upgrade, with a new Insertable B-Layer (IBL), a disappearing charged track analysis at the HE-LHC can probe Higgsino-like (wino-like) DM mass of up to 600 GeV (2.1 TeV) at the 95% C.L. The monojet and missing transverse momentum search, on the otherhand, has a weaker reach of 490 GeV (700 GeV) at 95% C.L. for the Higgsino-like (wino-like) states. The mass range accessible in the collider searches can be complementary to the indirect detection probes using gamma rays from dwarf-spheroidal galaxies.

hep-ph↗

arXiv2019

Precision Higgs Physics at CEPC

The discovery of the Higgs boson with its mass around 125 GeV by the ATLAS and CMS Collaborations marked the beginning of a new era in high energy physics. The Higgs boson will be the subject of extensive studies of the ongoing LHC program. At the same time, lepton collider based Higgs factories have been proposed as a possible next step beyond the LHC, with its main goal to precisely measure the properties of the Higgs boson and probe potential new physics associated with the Higgs boson. The Circular Electron Positron Collider~(CEPC) is one of such proposed Higgs factories. The CEPC is an $e^+e^-$ circular collider proposed by and to be hosted in China. Located in a tunnel of approximately 100~km in circumference, it will operate at a center-of-mass energy of 240~GeV as the Higgs factory. In this paper, we present the first estimates on the precision of the Higgs boson property measurements achievable at the CEPC and discuss implications of these measurements.

hep-ex↗

arXiv2019

Type-II 2HDM under the Precision Measurements at the $Z$-pole and a Higgs Factory

Future precision measurements of the Standard Model (SM) parameters at the proposed $Z$-factories and Higgs factories may have significant impacts on new physics beyond the Standard Model in the electroweak sector. We illustrate this by focusing on the Type-II two Higgs doublet model (Type-II 2HDM). The contributions from the heavy Higgs bosons at the tree-level and at the one-loop level are included in a full model parameter space. We perform a multiple variable global fit and study the extent to which the parameters of non-alignment and non-degenerate masses can be probed by the precision measurements. We find that the allowed parameter ranges are tightly constrained by the future Higgs precision measurements, especially for small and large values of $\tanβ$. Indirect limits on the masses of heavy Higgs can be obtained, which can be complementary to the direct searches of the heavy Higgs bosons at hadron colliders. We also find that the expected accuracies at the $Z$-pole and at a Higgs factory are quite complementary in constraining mass splittings of heavy Higgs bosons. The typical results are $|\cos(β-α)| < 0.008, |Δm_Φ| < 200\ {\rm GeV}$, and $\tanβ\sim 0.2 - 5$. The reaches from CEPC, FCC-ee and ILC are also compared, for both Higgs and $Z$-pole precision measurements.

hep-ph↗

arXiv2019

Implication of Higgs Precision Measurement on New Physics

Future precision measurements of the Standard Model (SM) parameters at the proposed Z-factories and Higgs factories may have significant impacts on new physics beyond the Standard Model (BSM). We illustrate this by focusing on the Type-II two Higgs doublet model. A multi-variable global fitting is performed with full one loop contributions to relevant couplings. The Higgs signal strength measurements at proposed Higgs factories can provide strong constraints on new physics and are found to be complementary to the Z-pole measurements.

hep-ph↗

arXiv2018

Charm-quark Yukawa Coupling in $h\rightarrow c\bar{c}γ$ at LHC

It is extremely challenging to probe the charm-quark Yukawa coupling at hadron colliders primarily due to the large Standard Model (SM) background (including $h\to b\bar b$) and the lack of an effective trigger for the signal $h\to c\bar c$. We examine the feasibility of probing this coupling at the LHC via a Higgs radiative decay $h\rightarrow c\bar{c}γ$. The existence of an additional photon in the final state may help for the signal identification and background suppression. Adopting a refined triggering strategy and utilizing basic machine learning, we find that a coupling limit of about 8 times the SM value may be reached with $2σ$ sensitivity after the High Luminosity LHC (HL-LHC). Our result is comparable and complementary to other projections for direct and indirect probes of $h\to c\bar c$ at the HL-LHC. Without a significant change in detector capabilities, there would be no significant improvement for this search from higher energy hadron colliders.

hep-ph↗

arXiv2018

Indirect Detection of Neutrino Portal Dark Matter

We investigate the feasibility of the indirect detection of dark matter in a simple model using the neutrino portal. The model is very economical, with right-handed neutrinos generating neutrino masses through the Type-I seesaw mechanism and simultaneously mediating interactions with dark matter. Given the small neutrino Yukawa couplings expected in a Type-I seesaw, direct detection and accelerator probes of dark matter in this scenario are challenging. However, dark matter can efficiently annihilate to right-handed neutrinos, which then decay via active-sterile mixing through the weak interactions, leading to a variety of indirect astronomical signatures. We derive the existing constraints on this scenario from Planck cosmic microwave background measurements, Fermi dwarf spheroidal galaxies and Galactic Center gamma-rays observations, and Alpha Magnetic Spectrometer - 02 antiprotons observations, and also discuss the future prospects of Fermi and the Cherenkov Telescope Array. Thermal annihilation rates are already being probed for dark matter lighter than about 50 GeV, and this can be extended to dark matter masses of 100 GeV and beyond in the future. This scenario can also provide a dark matter interpretation of the Fermi Galactic Center gamma ray excess, and we confront this interpretation with other indirect constraints. Finally we discuss some of the exciting implications of extensions of the minimal model with large neutrino Yukawa couplings and Higgs portal couplings.

hep-ph↗

arXiv2018

Higgs Pair Production at Future Hadron Colliders: From Kinematics to Dynamics

The measurement of the triple Higgs coupling is a key benchmark for the LHC and future colliders. It directly probes the Higgs potential and its fundamental properties in connection to new physics beyond the Standard Model. There exist two phase space regions with an enhanced sensitivity to the Higgs self-coupling, the Higgs pair production threshold and an intermediate top pair threshold. We show how the invariant mass distribution of the Higgs pair offers a systematic way to extract the Higgs self-coupling, focusing on the leading channel $pp\to hh+X\to b\bar b\ γγ+X$. We utilize new features of the signal events at higher energies and estimate the potential of a high-energy upgrade of the LHC and a future hadron collider with realistic simulations. We find that the high-energy upgrade of the LHC to 27 TeV would reach a 5$σ$ observation with an integrated luminosity of 2.5 ab$^{-1}$. It would have the potential to reach 15% (30%) accuracy at the 68% (95%) confidence level to determine the SM Higgs boson self-coupling. A future 100 TeV collider could improve the self-coupling measurement to better than 5% (10%) at the 68% (95%) confidence level.

hep-ph↗