arXiv subjects

Yandong Liu

Publications and source records attributed to Yandong Liu.

At least 37 records · Page 2Linked to original sources

arXiv2021

Yaw-Guided Imitation Learning for Autonomous Driving in Urban Environments

Existing imitation learning methods suffer from low efficiency and generalization ability when facing the road option problem in an urban environment. In this paper, we propose a yaw-guided imitation learning method to improve the road option performance in an end-to-end autonomous driving paradigm in terms of the efficiency of exploiting training samples and adaptability to changing environments. Specifically, the yaw information is provided by the trajectory of the navigation map. Our end-to-end architecture, Yaw-guided Imitation Learning with ResNet34 Attention (YILRatt), integrates the ResNet34 backbone and attention mechanism to obtain an accurate perception. It does not need high precision maps and realizes fully end-to-end autonomous driving given the yaw information provided by a consumer-level GPS receiver. By analyzing the attention heat maps, we can reveal some causal relationship between decision-making and scene perception, where, in particular, failure cases are caused by erroneous perception. We collect expert experience in the Carla 0.9.11 simulator and improve the benchmark CoRL2017 and NoCrash. Experimental results show that YILRatt has a 26.27% higher success rate than the SOTA CILRS. The code, dataset, benchmark and experimental results can be found at https://github.com/Yandong024/Yaw-guided-IL.git

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arXiv2021

Probing Top-philic New Physics via Four-Top-Quark Production

We explore constraints on various new physics resonances from four top-quark production based on current experimental data. Both light and heavy resonances are studied in the work. A comparison of full width effect and narrow width approximation is also made.

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arXiv2021

Probing Magnetic Moment Operators in $H γ$ Production and $H \to τ^+ τ^- γ$ Rare Decay

The magnetic moment ($a_γ$) and weak magnetic moment ($a_W$) of charged leptons and quarks are sensitive to quantum effects of new physics heavy resonances. In effective field theory $a_γ$ and $a_W$ are induced by two independent operators, therefore, one has to measure both the $a_γ$ and $a_W$ to shed lights on new physics. The $a_W$'s of the SM fermions are measured at the LEP. In this work, we analyze the contributions from magnetic and weak magnetic moment operators in the processes of $pp\to H γ$ and $gg\to H \to τ^+ τ^- γ$ at the High-Luminosity Large Hadron Collider. We demonstrate that the two processes could cover most of the parameter space that cannot be probed at the LEP.

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arXiv2021

New Physics and Two Boosted W-jets plus Missing Energy

We show that the signature of two boosted $W$-jets plus large missing energy is very promising to probe heavy charged resonances ($X^\pm$) through the process of $pp\to X^+X^-\to W^+W^- X^0 X^0$ where $X^0$ denotes dark matter candidate. The hadronic decay mode of the $W$ boson is considered to maximize the number of signal events. When the mass split between $X^\pm$ and $X^0$ is large, one has to utilize the jet-substructure technique to analyze the boosted $W$-jet. For illustration we consider the process of chargino pair production at the LHC, i.e., $pp\to χ_1^+χ^-_1 \to W^+W^-χ_1^0χ_1^0$, and demonstrate that the proposed signature is able to cover more parameter space of $m_{χ_1^\pm}$ and $m_{χ_1^0}$ than the conventional signature of multiple leptons plus missing energy. More importantly, the signature of our interests is not sensitive to the spin of heavy resonances.

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arXiv2021

The Role of the Hercules Autonomous Vehicle During the COVID-19 Pandemic: An Autonomous Logistic Vehicle for Contactless Goods Transportation

Since early 2020, the coronavirus disease 2019 (COVID-19) has spread rapidly across the world. As at the date of writing this article, the disease has been globally reported in 223 countries and regions, infected over 108 million people and caused over 2.4 million deaths (https://covid19.who.int/, accessed on Feb. 17, 2021). Avoiding person-to-person transmission is an effective approach to control and prevent the pandemic. However, many daily activities, such as transporting goods in our daily life, inevitably involve person-to-person contact. Using an autonomous logistic vehicle to achieve contact-less goods transportation could alleviate this issue. For example, it can reduce the risk of virus transmission between the driver and customers. Moreover, many countries have imposed tough lockdown measures to reduce the virus transmission (e.g., retail, catering) during the pandemic, which causes inconveniences for human daily life. Autonomous vehicle can deliver the goods bought by humans, so that humans can get the goods without going out. These demands motivate us to develop an autonomous vehicle, named as Hercules, for contact-less goods transportation during the COVID-19 pandemic. The vehicle is evaluated through real-world delivering tasks under various traffic conditions.

cs.RO↗

arXiv2019

CP violation in the top-assisted electroweak baryogenesis

The origin of the baryon asymmetry of the universe (BAU) is a longstanding problem in the high energy physics. The electroweak baryogenesis mechanism, which generates the BAU during the first order electroweak phase transition, provides a testable solution to this problem. In this paper we revisit the top-assisted electroweak baryogenesis model, which extends the standard model (SM) with only one scalar singlet. Constraints on the new CP-violating coupling as well as the mixing between the SM Higgs and the new scalar singlet are derived by considering the latest result of ACME and oblique observables. Furthermore, we derive constraints on these two parameters arising from the data of Higgs measurement at the LHC as well as the four top-quark production at the LHC.

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arXiv2019

What can We Learn from Triple Top-Quark Production?

Different from other multiple top-quark productions, triple top-quark production requires the presence of both flavor violating neutral interaction and flavor conserving neutral interaction. We describe the interaction of triple top-quarks and up-quark in terms of two dimension-6 operators; one can be induced by a new heavy vector resonance, the other by a scalar resonance. Combining same-sign top-quark pair production and four top-quark production, we explore the potential of the 13 TeV LHC on searching for the triple top-quark production.

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arXiv2019

Limiting Top-Higgs Interaction and Higgs-Boson Width from Multi-Top Productions

We demonstrate that the multi-top productions efficiently probe the CP-property of top-Higgs interaction and the Higgs-boson width at the LHC. The four top-quark production alone can exclude a purely CP-odd top-quark Yukawa coupling at the 13~TeV LHC with an integrated luminosity of $430~{\rm fb}^{-1}$, regardless the size of the Yukawa coupling. Combining the single Higgs-boson production, the $t\bar{t}H$ associated production and the four top-quark production, we show that the CP-phase of the top-quark Yukawa coupling and the Higgs-boson width can be stringently bounded at the LHC with integrated luminosities of $300~{\rm fb}^{-1}$ and $3000~{\rm fb}^{-1}$.

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arXiv2018

Probing the Higgs boson-gluon coupling via the jet energy profile at $e^+e^-$ colliders

The effective coupling of the Higgs boson to a gluon pair is one of the most important parameters to test the Standard Model and search for the new physics beyond. In this paper, we propose several new observables based on the jet energy profile to extract the effective coupling. The statistical uncertainties of the effective coupling extracted by using new observables are derived and estimated based on the simulation at the future $e^+e^-$ collider for $250$ GeV center-of-mass energy and 5 ab$^{-1}$ integrated luminosity. We found that the statistical uncertainties of effective coupling via the optimized observable can reach about $1.6\%$ in the channels of a $Z$ boson decaying to lepton pairs and is reduced by $52\%$ compared to the relevant uncertainties in the conventional approach. These new observables potentially can be helpful for the measurement of effective coupling at future $e^+e^-$ colliders.

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arXiv2017

Double Parton Scattering of Weak Gauge Boson Productions at the 13 TeV and 100 TeV Proton-Proton Colliders

We study double parton scattering (DPS) processes involving electroweak gauge bosons at the 13 TeV and 100 TeV proton-proton colliders. Specifically, we focus on three DPS channels: $W$-boson plus two jets ($W\otimes jj$), $Z$-boson plus two jets ($Z\otimes jj$), and same-sign $W$ pair production ($W^\pm\otimes W^\pm$). We demonstrate that the $Z\otimes jj$ process, which has not been paid too much attentions, is the best channel for measuring effective cross section $σ_{\rm eff}$. The accuracy of $σ_{\rm eff}$ measurement in the three DPS channels, especially the $W^\pm\otimes W^\pm$ production, is significantly improved at the 100 TeV colliders. We advocate that combined analysis of the three DPS channels could test the universality of effective cross section $σ_{\rm eff}$.

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arXiv2017

Measuring Trilinear Higgs Coupling in $WHH$ and $ZHH$ Productions at the HL-LHC

Determination of trilinear Higgs coupling ($λ_{HHH}=κλ_{HHH}^{\rm SM}$) through Higgs pair productions is a major motivation for the LHC high luminosity phase. We perform a detailed collider simulation to explore the potential of measuring $λ_{HHH}$ in the $VHH$ ($V=W,Z$) production at the HL-LHC. We find that the trilinear Higgs coupling in the SM ($λ_{HHH}^{\rm SM}$) could be measured at the level of $1.3σ$. Combining with the gluon fusion, vector boson fusion and $t\bar{t}HH$ channels, $λ_{HHH}^{\rm SM}$ is expected to be measured at the level of $3.13σ$. If no evidence of Higgs pair productions were observed, the $VHH$ production, together with the gluon fusion channel, would impose a bound of $0.5\leq κ\leq 2.2$ at the 95\% confidence level.

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arXiv2016

LHC searches for heavy neutral Higgs bosons with a top jet substructure analysis

We study the LHC searches for the heavy $CP$-odd Higgs boson $A$ and $CP$-even Higgs boson $H$ in the context of general two-Higgs-doublet model. Specifically, we consider the decay mode of $A/H\to t \bar t $ through the $b \bar b$ or $t \bar t $ associated production channels. In the so-called "alignment limit" of the two-Higgs-doublet model, this decay mode can be the most dominant one. By employing the HEPTopTagger and the multi-variable-analysis method, we present the search sensitivities for both $CP$-odd Higgs boson $A$ and $CP$-even Higgs boson $H$ via these channels at the high-luminosity LHC runs.

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arXiv2016

The Diphoton Excess, Low Energy Theorem and the 331 Model

We interpret the diphoton anomaly as a heavy scalar $H_3$ in the so-called 331 model. The scalar is responsible for breaking the $SU(3)_C\otimes SU(3)_L\otimes U(1)_X$ gauge symmetry down to the standard model electroweak gauge group. It mainly couples to the standard model gluons and photons through quantum loops involving heavy quarks and leptons. Those quarks and leptons, in together with the SM quarks and leptons, form the fundamental representation of the 331 model. We use low energy theorem to calculate effective coupling of $H_3gg$, $H_3γγ$, $H_3ZZ$, $H_3WW$ and $H_3Zγ$. The analytical results can be applied to new physics models satisfying the low energy theorem. We show that the heavy quark and lepton contribution cannot produce enough diphoton pairs. It is crucial to include the contribution of charged scalars to explain the diphoton excess. The extra neutral $Z^\prime$ boson could also explain the 2 TeV diboson excess observed at the LHC Run-I.

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arXiv2016

Semantic Scan: Detecting Subtle, Spatially Localized Events in Text Streams

Early detection and precise characterization of emerging topics in text streams can be highly useful in applications such as timely and targeted public health interventions and discovering evolving regional business trends. Many methods have been proposed for detecting emerging events in text streams using topic modeling. However, these methods have numerous shortcomings that make them unsuitable for rapid detection of locally emerging events on massive text streams. In this paper, we describe Semantic Scan (SS) that has been developed specifically to overcome these shortcomings in detecting new spatially compact events in text streams. Semantic Scan integrates novel contrastive topic modeling with online document assignment and principled likelihood ratio-based spatial scanning to identify emerging events with unexpected patterns of keywords hidden in text streams. This enables more timely and accurate detection and characterization of anomalous, spatially localized emerging events. Semantic Scan does not require manual intervention or labeled training data, and is robust to noise in real-world text data since it identifies anomalous text patterns that occur in a cluster of new documents rather than an anomaly in a single new document. We compare Semantic Scan to alternative state-of-the-art methods such as Topics over Time, Online LDA, and Labeled LDA on two real-world tasks: (i) a disease surveillance task monitoring free-text Emergency Department chief complaints in Allegheny County, and (ii) an emerging business trend detection task based on Yelp reviews. On both tasks, we find that Semantic Scan provides significantly better event detection and characterization accuracy than competing approaches, while providing up to an order of magnitude speedup.

cs.IR↗

arXiv2016

Probing Higgs Width and Top Quark Yukawa Coupling from $t\bar{t}H$ and $t\bar{t}t\bar{t}$ Productions

We demonstrate that four top-quark production is a powerful tool to constrain the top Yukawa coupling. The constraint is robust in the sense that it does not rely on the Higgs boson decay. Taking into account the projection of the $t\bar{t}H$ production by the ATLAS collaobration, we obtain a bound on Higgs boson width, $Γ_H\leq 3.1~Γ_H^{\rm SM}$, at the 14 TeV LHC with an integrated luminosity of $300~{\rm fb}^{-1}$. Increasing the luminosity to $500~{\rm fb}^{-1}$ yields $Γ_H\leq 2.1~Γ_H^{\rm SM}$.

hep-ph↗

arXiv2015

Testing LHT at the LHC Run-II

We study the Littlest Higgs model with T-parity (LHT) in the process of $pp \to W_H^+W_H^- \to W^+W^- A_H A_H$ at the 14 TeV LHC. With the $W$-jet tagging technique, we demonstrate that the bulk of the model parameter space can be probed at the level of more than $5σ$ in the signature of two fat $W$-jets plus large missing energy. Furthermore, we propose a novel strategy of measuring the principle parameter $f$ that is crucial to testify the LHT model and to fix mass spectrum, including dark matter particle. Our proposal can be easily incorporated into current experimental program of diboson searches at the LHC Run-II.

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arXiv2015

A Boost Test of Anomalous Diphoton Resonance at the LHC

The recently observed diphoton resonance around 750~GeV at the LHC Run-2 could be interpreted as a weak singlet scalar. The scalar might also decay into a pair of $Z$-boson and photon. The $Z$-boson is highly boosted and appears as a fat jet in the detector. We use the jet substructure method to explore the possibility of discovering the singlet scalar in the process of $pp\to S\to Zγ$ in the future LHC experiment.

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arXiv2015

Light Doubly Charged Higgs Boson via the $WW^*$ Channel at LHC

The doubly charged Higgs bosons $H^{\pm\pm}$ searches at the Large Hadron Collider (LHC) have been studied extensively and strong bound is available for $H^{\pm\pm}$ dominantly decaying into a pair of same-sign di-leptons. In this paper we point out that there is a large cavity in the light $H^{\pm\pm}$ mass region left unexcluded. In particular, $H^{\pm\pm}$ can dominantly decay into $WW$ or $WW^*$ (For instance, in the type-II seesaw mechanism the triplet acquires a vacuum expectation value around 1 GeV.), and then it is found that $H^{\pm\pm}$ with mass even below $2m_W$ remains untouched by the current collider searches. Searching for such a $H^{\pm\pm}$ at the LHC is the topic of this paper. We perform detailed signal and background simulation, especially including the non-prompt $t\bar{t}$ background which is the dominant one nevertheless ignored before. We show that such $H^{\pm\pm}$ should be observable at the 14 TeV LHC with 10-30 fb$^{-1}$ integrated luminosity.

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