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Yao-Bei Liu

Publications and source records attributed to Yao-Bei Liu.

At least 37 records · Page 2Linked to original sources
arXiv2017

Searches for anomalous $tqZ$ couplings from the trilepton signal of $tZ$ associated production at the 14 TeV LHC

We investigate the observability of the top anomalous $tqZ$ couplings via the trilepton signatures at the Large Hadron Collider~(LHC) with the center-of-mass energy of 14 TeV. We focus on signals of the $tZ$ associated production with the decay mode $t\to W^{+}b\to b\ell^{+}ν_{\ell}$, $Z\to \ell^{+}\ell^{-}$, and $t\bar{t}$ production with the decay mode $\bar{t}\to Z(\to \ell^{+}\ell^{-})\bar{q}$ and $t\to b\ell^{+}ν_{\ell}$, where $\ell=e, μ$ and $q$ reflects up and charm quarks. It is shown that at $3σ$ level, the FCNC top quark decay branching ratios can be probed at, respectively, about $Br(t\to uZ) \leq 1.3\times 10^{-4}$ and $Br(t\to cZ) \leq 4.2\times 10^{-4}$ with the integrated luminosity of 100 fb$^{-1}$, and probed down to $Br(t\to uZ) \leq 2.2\times 10^{-5}$ and $Br(t\to cZ) \leq 8\times 10^{-5}$ for the high-luminosity LHC with 3000 fb$^{-1}$.

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arXiv2017

Search for single production of the vector-like top partner at the 14 TeV LHC

The new heavy vector-like top partner~($T$) is one of typical features of many new physics models beyond the standard model. In this paper we study the discovery potential of the LHC for the vector-like $T$-quark both in the leptonic $T\to bW$ and $T\to t_{\rm lep}Z_{\rm lep}$ (trilepton) channels at $\sqrt{s}= 14$ TeV in the single production mode. Our analysis is based on a simplified model including a $SU(2)_L$ singlet with charge $2/3$ with only two free parameters, namely the $TWb$ coupling parameter $g^{\ast}$ and the top partner mass $m_T$. The $2σ$ exclusion limits, $3σ$ evidence and the $5σ$ discovery reach in the parameter plane of $g^{\ast}-m_T$, are, respectively, obtained for some typical integrated luminosity at the 14 TeV LHC. Finally we analyze the projected sensitivity in terms of the production cross section times branching fraction for two decay channel.

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arXiv2017

Search for single production of vector-like top partners at the Large Hadron Electron Collider

The new vector-like top partners with charge $2/3$ are a typical feature of many new physics models beyond the Standard Model (SM). We propose a search strategy for single production of top partners $T$ focusing on both the $T\to Wb$ and $T\to th$ decay channels at the Large Hadron Electron Collider (LHeC). Our analysis is based on a simplified model in which the top partner is an $SU(2)$ singlet, with couplings only to the third generation of SM quarks. We study the observability of the single $T$ through the processes $e^{+}p \to T(\to bW^{+})\barν_{e}\to b\ell^{+}+ \not E_T^{miss}$ and $e^{+}p \to T(\to th)\barν_{e}\to t(\to jj'b)h(\to b\bar{b}) \not E_T^{miss}$ at the LHeC with the proposed 140 GeV electron beam (with $80\%$ polarization) and 7 TeV proton beam. For three typical $T$-quark masses (800, 900 and 1000 GeV), the $3σ$ exclusion limits on the $TWb$ coupling are respectively presented for various values of the integrated luminosity.

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arXiv2017

Search for single production of the heavy vectorlike $T$ quark with $T\to th$ and $h\to γγ$ at the high-luminosity LHC

The vectorlike top partners $T$ are predicted in many extensions of the Standard Model (SM). In a simplified model including a single vectorlike $T$ quark with charge $2/3$, we investigate the process $pp \to Tj$ induced by the couplings between the top partner with the first and the third generation quarks at the LHC. We find that the mixing with the first generation can enhance the production cross section. We further study the observability of the single heavy top partner through the process $pp \to T(\to th)j\to t(\to b \ell ν_{\ell})h( \to γγ) j$ at the high-luminosity~(HL)-LHC~(a 14 TeV $pp$ collider with an integrated luminosity of 3 ab$^{-1}$). For three typical heavy $T$ quark masses $m_T=600,800$ and 1000 GeV, the $3σ$ exclusion limits, as well as the $5σ$ discovery reach in the parameter plane of the two variables $g^{\ast}-R_L$, are respectively obtained at the HL-LHC.

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arXiv2016

Production and decays of a light $ϕ^0$ in the LRTH model under the LHC Higgs data

In this paper we study the production and decays of a light pseudoscalar boson $ϕ^0$ with $m_{ϕ^0} \leq m_h/2$ appeared in the left-right twin Higgs (LRTH) model, and explore its phenomenological consequences when the latest LHC Higgs data are taken into account. We found that (a) the decay rate $Br(h\to ϕ^0ϕ^0)$ can be as large as $80\%$ and can suppress significantly the visible $γγ$ signal rate, but the latest LHC Higgs data put a strong constraint on it: $Br(h \to ϕ^0ϕ^0) \leq 30\%$ at $3σ$ level; (b) the $p$-value of the LRTH model is around $0.6$, smaller than that of the SM in most of the parameter space and approaches the SM value $0.8$ for a sufficiently large $f$ parameter; (c) the neutral pseudoscalar $ϕ^0$ dominantly decay into $b\bar{b}$ and the decay rate $Br(ϕ^0\to b\bar{b})$ can be larger than $80\%$ for $m_{ϕ^0}\leq 60$ GeV, and the second main decay mode is $ϕ^0\to τ^{+}τ^{-}$ with a branching ratio about $14\%$; and (d) at the future $e^-e^+$ collider with $\sqrt{s}=250$ GeV, the processes $e^{+}e^{-}\to Zh\to Z(ϕ^0ϕ^0)\to Z(4b,2b2τ)$ are promising for discovering such a light pseudoscalar $ϕ^0$.

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arXiv2016

Searches for the FCNC couplings from top-Higgs associated production signal with $h\to γγ$ at the LHC

In this paper, we study the observability of the top-Higgs flavor changing neutral current (FCNC) $tqh$ coupling through the process $pp\to qg\to t(\to \ell^{+}bν)h(\to γγ)$ at the Large Hadron Collider~(LHC), where $\ell=e, μ$. Our numerical results show that, in some parameter regions, the LHC may observe the above signals at the $5σ$ level. Otherwise, the branching ratios $Br(t\to uh)$ and $Br(t\to ch)$ can be respectively probed to $0.036\%$ and $0.13\%$ at $3σ$ level at 14 TeV LHC with the high integrated luminosity of 3000 fb$^{-1}$. On the other hand, studying the charge ratio for the lepton in top quark decay can be not only used to discriminate between signal and backgrounds, but also used to discriminate between $tuh$ and $tch$ couplings, for which anomalous single top production comes from the up initiated channel and charm initiated channel.

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arXiv2016

Searches for top-Higgs FCNC couplings via the Whj signal with $h\to γγ$ at the LHC

In this paper, we investigated the process $pp \to W^{-}hj$ induced by the top-Higgs flavor changing neutral current (FCNC) couplings at the LHC. We found that the cross section of $pp \to W^{-}hj$ mainly comes from the resonant process $pp\to W^{-}t\to W^{-}hq$ due to the anomalous $tqH$ couplings (where $q$ denotes up and charm quarks). We further studied the observability of the top-Higgs FCNC couplings through the process $pp \to W^{-}(\to \ell^{-} \barν_{\ell}) h( \to γγ) j$ and found that the branching ratios $Br(t\to qh)$ can be probed to $0.16\%$ at $3σ$ level at 14 TeV LHC with an integrated luminosity of 3000 fb$^{-1}$.

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arXiv2015

Single Higgs boson production at the ILC in the left-right twin Higgs model

In this work, we analyze three dominant single SM-like Higgs boson production processes in the left-right twin Higgs model (LRTHM): the Higgs-strahlung (HS) process $e^{+}e^{-}\rightarrow Zh$, the vector boson fusion (VBF) process $e^{+}e^{-}\to ν\barνh$ and the associate production with top pair process $e^{+}e^{-}\to t\bar{t}h$ for three possible energy stages of the International Linear Collider (ILC), and compared our results with the expected experimental accuracies for various accessible Higgs decay channels. The following observations have been obtained: (i) In the reasonable parameter space, the LRTHM can generate moderate contributions to theses processes with polarized beams; (ii) Among various Higgs boson decay channels, the $b\bar{b}$ signal strength is most sensitive to the LRTHM due to the high expected precision. For the $t\bar{t}h$ production process, the absolute value of $μ_{b\bar{b}}$ may deviate from the SM prediction by over $8.7\%$ and thus may be detectable at the future ILC with $\sqrt{s}=1$ TeV; (iii) The future ILC experiments may give strong limit on the scale parameter $f$: for the case of ILC-250 GeV, for example, the lower limit for parameter $f$ of the LRTHM is $f > 1150$ GeV at the $2σ$ level.

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arXiv2015

Constraining dark matter in the LRTH model with latest LHC, XENON100 and LUX data

In the left-right twin Higgs (LRTH) model, the neutral $\hat{S}$ is a candidate for weakly interacting massive particle (WIMP) dark matter (DM). If its mass is lighter than half of the SM-like Higgs boson $h$, the new invisible decay $h \to \hat{S}\hat{S}$ will become open. In this paper, we examine the status of a light dark matter ($\hat{S}$) under current experimental constraints including the latest LHC Higgs data, the XENON100 and LUX limit on the dark matter scattering off the nucleon. The following observations have been obtained: (i) The current ATLAS (CMS) measurements of $R_{γγ}$ can exclude the invisible Higgs branching ratio ${\rm Br}_{\rm inv}$ larger than $34\%$ ($48\%$) at $2σ$ level; (ii) the Global fits to the latest LHC and Tevatron Higgs data provide a stronger constraint: ${\rm Br}_{\rm inv}< 20\%$ ($30\%$) at $2σ$ ($3σ$) level, which could be tested in the LHC experiments; (iii) for the spin-independent scattering cross section off the nucleon, the recent XENON100 (LUX) data can exclude the invisible decay rate larger than $50\%$ $(25\%)$; and (iv) the results of direct DM searches with LUX can give strong constraint on the viable parameter space of $\{g_{h\hat{S}\hat{S}}, m_{\hat{S}}\}$ in this LRTH model.

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arXiv2014

The production and decay of the top partner $T$ in the left-right twin higgs model at the ILC and CLIC

The left-right twin Higgs model (LRTHM) predicts the existence of the top partner $T$. In this work, we make a systematic investigation for the single and pair production of this top partner $T$ through the processes: $e^{+}e^{-}\to t\ov{T} + T\bar{t}$ and $ T\ov{T}$, the neutral scalar (the SM-like Higgs boson $h$ or neutral pseudoscalar boson $ϕ^{0}$) associate productions $e^{+}e^{-}\to t\ov{T}h +T\bar{t}h$, $T\ov{T}h$, $t\ov{T}ϕ^{0}+T\bar{t}ϕ^{0}$ and $ T\ov{T}ϕ^{0}$. From the numerical evaluations for the production cross sections and relevant phenomenological analysis we find that (a) the production rates of these processes, in the reasonable parameter space, can reach the level of several or tens of fb; (b) for some cases, the peak value of the resonance production cross section can be enhanced significantly and reaches to the level of pb; (c) the subsequent decay of $T\to ϕ^{+}b \to t\bar{b}b$ may generate typical phenomenological features rather different from the signals from other new physics models beyond the standard model(SM); and (d) since the relevant SM background is generally not large, some signals of the top partner $T$ predicted by the LRTHM may be detectable in the future ILC and CLIC experiments.

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arXiv2014

Left-right twin Higgs model confronted with the latest LHC Higgs data

Motivated by the latest LHC Higgs data, we calculate the new physics contributions to the Higgs decay channels of $h\to γγ, Zγ, ττ, WW^*$ and $ ZZ^*$ in the left-right twin Higgs (LRTH) model, induced by the loops involving the heavy T-quark, the $W_H$ and $ϕ^\pm$ bosons appeared in the LRTH model. We find that (a) for a SM-like Higgs boson around 125.5 GeV, the signal rates normalized to the corresponding standard model (SM) predictions are always suppressed when new physics contributions are taken into account and approach the SM predictions for a large scalar parameter $f$; and (b) the LRTH prediction for $R_{γγ}$ agree well with the CMS measurement $R_{γγ}=0.77\pm 0.27$ at $1σ$ level, but differ with the ATLAS result. The forthcoming precision measurement of the diphoton signal at the LHC can be a sensitive probe for the LRTH model.

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arXiv2012

Associated production of the charged Higgs boson and single top quark at the LHC

The left-right twin Higgs(LRTH) model predicts the existence of the charged Higgs $ϕ^{\pm}$. In this paper, we study the production of the charged Higgs boson $ϕ^{-}$ with single top quark via the process $bg\to tϕ^{-}$ at the $CERN$ Large Hadron Collider(LHC). The numerical results show that the production cross section can reach the level of $10 pb$ in the reasonable parameter space of the LRTH model. We expect that, as long as it is not too heavy, the possible signatures of the heavy charged Higgs boson $ϕ^{-}$ might be detected via the decay mode $ϕ^{-}\to \bar{t}b$ at the LHC experiments.

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arXiv2010

Pair production of Higgs bosons associated with $Z$ boson in the left-right twin Higgs model at the ILC

The left-right twin Higgs(LRTH) model predicts the existence of three additional Higgs bosons: one neutral Higgs $ϕ^{0}$ and a pair of charged Higgs bosons $ϕ^{\pm}$. In this paper, we studied the production of a pair of charged and neutral Higgs bosons associated with standard model gauge boson $Z$ at the ILC, i.e., $e^{+}e^{-}\rightarrow Zϕ^{+}ϕ^{-}$ and $e^{+}e^{-}\rightarrow Zϕ^{0}ϕ^{0}$. We calculate the production rate and present the distributions of the various observables, such as, the distributions of the energy and the transverse momenta of final $Z$-boson and charged Higgs boson $ϕ^{-}$, the differential cross section of the invariant mass of charged Higgs bosons pair, the distribution of the angle between charged Higgs bosons pair and the production angle distributions of $Z$-boson and charged Higgs boson $ϕ^{-}$. Our numerical results show that, for the process $e^{+}e^{-}\rightarrow Zϕ^{+}ϕ^{-}$, the production rates are at the level of $10^{-1} fb$ with reasonable parameter values. For the process of $e^{+}e^{-}\rightarrow Zϕ^{0}ϕ^{0}$, we find that the production cross section are smaller than $6\times 10^{-3} fb$ in most of parameter space. However, the resonance production cross section can be significantly enhanced.

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arXiv2010

Higgs boson decays and production in the left-right twin Higgs model

The left-right twin Higgs model predicts one neutral Higgs boson $ϕ_{0}$ and it acquires mass $m_{ϕ_{0}}\sim μ_{r}$ with the $μ$ term, which can be lighter than half the SM-like Higgs boson mass in a portion of parameter space. Thus, the SM-like Higgs boson $h$ can dominantly decay into a pair of light neutral Higgs bosons especially when $m_{h}$ is below the $WW$ threshold. First, we examine the branching ratios of the SM-like Higgs boson decays and find that the new decay mode $h\rightarrow ϕ_{0}ϕ_{0}$ is dominant for the case of $m_{h}>2m_{ϕ_{0}}$. Then we study the production via gluon fusion followed by the decay into two photons or two weak gauge bosons and found that the production rate can be significantly suppressed for some part of parameter space. Finally, we comparatively study the process $γγ\rightarrow h \rightarrow b\bar{b}$ at ILC in the cases of $m_{h}>2m_{ϕ_{0}}$ and $m_{h}<2m_{ϕ_{0}}$, respectively. We find that these predictions can significantly deviated from the SM predictions, e.g., the gluon-gluon fusion channel, in the cases of $m_{h}>2m_{ϕ_{0}}$ and $m_{h}<2m_{ϕ_{0}}$, can be suppressed by about 80% and 45%, respectively. Therefor, it is possible to probe the left-right twin Higgs model via these Higgs boson production processes at the LHC experiment or in the future ILC experiment.

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arXiv2007

Pair production of charged Higgs bosons in the Left-Right Twin Higgs model at the ILC and LHC

Left-Right twin Higgs(LRTH) model predicts the existence of a pair of charged Higgs $ϕ^{\pm}$. In this paper, we study the production of the charged Higgs bosons pair $ϕ^{\pm}$ via the process $e^{+}e^{-}\to ϕ^{+}ϕ^{-}$ at the International Linear Collider(ILC). The numerical results show that the production rates are at the level of several tens fb, this process can produce the adequate distinct multi-jet final states and the SM background can be efficiently reduced. We also discuss the charged Higgs boson pair production via the process $q\bar{q}\to ϕ^{+}ϕ^{-}$ at the $CERN$ Large Hadron Collider(LHC) and estimate there production rates. We find that, as long as the charged Higgs bosons are not too heavy, they can be abundantly produced at the LHC. The possible signatures of these new particles might be detected at the ILC and LHC experiments.

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arXiv2007

Effects of little Higgs models on single top production at the $e^{-}γ$ colliders

In the framework of the littlest Higgs($LH$) model and the littlest Higgs model with T-parity($LHT$), We investigate the single top production process $e^{-}γ\to ν_{e}b\bar{t}$, and calculate the corrections of these two models to the cross section of this process. We find that in the reasonable parameter space, the correction terms for the tree-level $Wtb$ couplings coming from the $LHT$ model can generate significantly corrections to the cross section of this process, which might be detected in the future high energy linear $e^{+}e^{-}$ collider($ILC$) experiments. However, the contributions of the new gauge boson $W^{\pm}_{H}$ predicted by the $LH$ model to this process is very small.

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arXiv2007

Higgs boson pair production process $e^+e^-\to ZHH$ in the littlest Higgs model at the ILC

The physics prospect at future linear $e^{+}e^{-}$ colliders for the study of the Higgs triple self-coupling via the process of $e^{+}e^{-}\to ZHH$ is investigated. In this paper, we calculate the contribution of the new particles predicted by the littlest Higgs model to the cross sections of this process in the future high energy $e^{+}e^{-}$ collider($ILC$). The results show that, in the favorable parameter spaces preferred by the electroweak precision, the deviation of the total cross sections from its $SM$ value varies from a few percent to tens percent, which may be detected at the future $ILC$ experiments with $\sqrt{s}$=500GeV.

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