arXiv subjects

Han Liang

Publications and source records attributed to Han Liang.

At least 55 records · Page 3Linked to original sources

arXiv2007

Revisiting the QCD corrections to the R-parity violating processes $p\bar{p}/pp \to eμ+X$

We present the theoretical predictions up to QCD NLO for the cross section of high-mass electron-muon pair production at the Tevatron and the LHC, considering only the dominant contributions from the third-generation sneutrino. The dependence of the renormalization and factorization scales on the total cross section, and the effects on the K-factor due to the uncertainty of parton distribution function(PDF) have been carefully investigated. By considering soft-gluon resummation effects to all order in $α_s$ of leading logarithm, we present the transverse momentum distributions of the final $eμ$ pair.

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arXiv2007

QCD corrections to t\bar t b \bar b productions via photon-photon collisions at linear colliders

We calculated the complete next-to-leading order(NLO) QCD corrections to the $t\bar t b \bar b$ production process at a $γγ$ collider in the standard model(SM). The calculation of the one-loop QCD correction includes the evaluations of the hexagon and pentagon amplitudes. We studied the NLO QCD corrected total cross section, the distributions of transverse momenta of final top- and bottom-quark states, and the dependence of the cross section on renormalization scale $μ$. It shows that NLO QCD correction generally increases the LO cross section in our chosen parameter space, and the K-factor varies from 1.70 to 1.14 when colliding energy goes up from $400 GeV$ to $2 TeV$. We find that the correction distinctly changes the distributions of transverse momenta of the final top- and bottom-quark states, and the NLO QCD correction obviously improves the independence of the cross section for process $γγ\to t\bar t b\bar b$ on the renormalization scale.

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arXiv2007

Associated production of graviton with $e^+e^-$ pair via photon-photon collisions at a linear collider

We investigate the process \rreeG at the future International Linear Collider(ILC), where G_n is the Kaluza-Klein graviton in the Large Extra Dimension Model. When the fundamental energy scale is of a few ${\rm TeV}$, the cross section of this process can reach several hundred fb at a photon-photon collider with $\sqrt{s}=500 \sim 1000 GeV$, and the cross section in J=2 polarized photon collision mode is much larger than that in J=0 polarized photon collision mode. We present strategies to distinguish the graviton signal from numerous SM backgrounds, and find that the graviton signal with extra dimensions $δ=3$ can be detected when ${\rm M_S} \le 2.67(1.40) {\rm TeV}$ and $γγ$ c.m.s. energy $\sqrt{s}=1000(500) {\rm GeV}$ in unpolarized photon collision mode, while the detecting upper limit can be increased to 2.79(1.44) ${\rm TeV}$ in $+ -$ ($λ_1=1$, $λ_2=-1$) polarized photon collision mode(with photon polarization efficiency $P_γ=0.9$).

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arXiv2007

The effects of the little Higgs models on $t\bar{t} h^0$ production via $γγ$ collision at linear colliders

In the frameworks of the littlest Higgs($LH$) model and its extension with T-parity($LHT$), we studied the associated $t\bar th^0$ production process $e^+ e^- \to γγ\to t \bar t h^0$ at the future $e^+e^-$ linear colliders up to QCD next-to-leading order. We present the regions of $\sqrt{s}-f$ parameter space in which the $LH$ and $LHT$ effects can and cannot be discovered with the criteria assumed in this paper. The production rates of process $γγ\to t \bar t h^0$ in different photon polarization collision modes are also discussed. We conclude that one could observe the effects contributed by the $LH$ or $LHT$ model on the cross section for the process $e^+ e^- \to γγ\to t \bar t h^0$ in a reasonable parameter space, or might put more stringent constraints on the $LH$/$LHT$ parameters in the future experiments at linear colliders.

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arXiv2007

Flavor changing effects on single charged Higgs boson production associated with a bottom-charm pair at CERN Large Hadron Collider

We study flavor changing effects on the \ppbchT process at the Large Hadron Collider(LHC), which are inspired by the left-handed up-type squark mixings in the Minimal Supersymmetric Standard Model(MSSM). We find that the SUSY QCD radiative corrections to $bcH^\pm$ coupling can significantly enhance the cross sections at the tree-level by a factor about $1.5 \sim 5$ with our choice of parameters. We conclude that the squark mixing mechanism in the MSSM makes the \ppbchT process a new channel for discovering a charged Higgs boson and investigating flavor changing effects.

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arXiv2007

Full one-loop electroweak corrections to $h^0(H^0,A^0) H^\pm W^\mp$ associated productions at $e^+e^-$ linear colliders

We study the complete one-loop electroweak(EW) corrections to the processes of single charged Higgs boson production associated with a neutral Higgs boson$(h^0,H^0,A^0)$ and a gauge boson $W^\pm$ in the framework of the minimal supersymmetric standard model(MSSM). Numerical results at the ${\rm SPS1a'}$ benchmark point as proposed in the SPA project, are presented for demonstration. We find that for the process $e^+e^-\to h^0H^\pm W^\mp$ the EW relative correction can be either positive or negative and in the range of $-15%\sim 20%$ in our chosen parameter space. While for the processes $e^+e^-\to H^0(A^0)H^\pm W^\mp$ the corrections generally reduce the Born cross sections and the EW relative corrections are typically of order $-10%\sim -20%$.

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arXiv2006

QCD corrections to the R-parity violating processes $p\bar{p}/pp \to eμ+X$ at hadron colliders

We present the QCD corrections to the processes $p\bar{p}/pp \to eμ+X$ at the Tevatron and the CERN large hadron collider(LHC). The numerical results show that variation of K factor is in the range between $1.28(1.32)$ and $1.79(1.58)$ at the Tevatron(LHC). We find that the QCD correction part from the one-loop gluon-gluon fusion subprocess is remarkable at the LHC and should be taken into account.

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arXiv2006

The annihilation decays $B^-_c \to η^{'}(η,π^0) l^- \barν$

We investigate the simileptonic OZI-forbidden annihilation decays $B^-_c \to η^{'}(η,π^0) l^- \barν$ for $l=μ,e$ in the perturbative QCD, and carry out a precise calculation without any approximation for the one-loop contributions, which involves integrals of 4- and 5-point loop functions. Our results show that the branching ratios of decays $B^-_c \to η^{'} l^- \barν$, $B^-_c \to ηl^- \barν$ and $B^-_c \to π^0 l^- \barν$, turn out to be of orders $10^{-4}$, $10^{-5}$ and $10^{-6}$, respectively, which could be observable in the future experiments at the LHC.

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arXiv2006

Electroweak radiative corrections to the Higgs-boson production in association with $Z^0$-boson pair at $e^+ e^-$ colliders

We present the full ${\cal O}(α_{ew})$ electroweak radiative corrections to the Higgs-boson production in association with $Z^0$-boson pair at an electron-positron linear collider(LC) in the standard model. We analyze the dependence of the full one-loop corrections on the Higgs-boson mass $m_{H}$ and colliding energy $\sqrt{s}$. We find that the corrections significantly suppress the Born cross section, and the ${\cal O}(α_{ew})$ electroweak radiative corrections are generally between 1.0% and -15% in our chosen parameter space, which should be taken into consideration in the future precise experiments.

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arXiv2006

Full one-loop electroweak and NLO QCD corrections to the associated production of chargino and neutralino at hadron colliders

We study the process of the association production of chargino and neutralino including the NLO QCD and the complete one-loop electroweak corrections in the framework of the minimal supersymmetric standard model(MSSM) at the Fermilab Tevatron and the CERN Large Hadron Collider (LHC). In both the NLO QCD and one-loop electroweak calculations we apply the algorithm of the phase-space slicing(PSS) method. We find that the NLO QCD corrections generally increase the Born cross sections, while the electroweak relative corrections decrease the Born cross section in most of the chosen parameter space. The NLO QCD and electroweak relative corrections typically have the values of about 32% and -8% at the Tevatron, and about 42% and -6% at the LHC respectively. The results show that both the NLO QCD and the complete one-loop electroweak corrections to the processes $p \bar p/pp \to \widetildeχ_1^{\pm} \widetildeχ_2^0+X$ are generally significant and should be taken into consideration in precision experimental analysis.

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arXiv2006

NLO supersymmetric QCD corrections to the $t \bar b H^-$ associated production at hadron colliders

We present the next-to-leading order QCD corrected total cross sections and the distributions of the transverse momenta of the final anti-bottom-quark, top-quark and charged Higgs-boson for the processes of $p\bar p/pp \to t\bar b H^-+X$ in the minimal supersymmetric standard model(MSSM) at the Tevatron and the LHC. We find that the NLO QCD corrections significantly modify the leading-order distributions of the transverse momenta of final particles($p_T^b$, $p_T^t$ and $p_T^{H^-}$), and the total NLO QCD corrections reduce the dependence of the cross section on the renormalization and factorization scales, especially the NLO QCD corrected cross sections at the LHC are nearly independent of these scales. Our results show that the relative correction is obviously related to $m_{H^-}$ and $\tanβ$, and the total NLO QCD relative corrections can be beyond -50% at the Tevatron and approach -40% at the LHC in our chosen parameter space.

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arXiv2005

Full one-loop supersymmetric corrections to charged Higgs boson pair production in $γγ$ collisions

The complete one-loop electroweak corrections to charged Higgs boson pair production in $γγ$ collision mode at linear colliders in the minimal supersymmetric standard model (MSSM), are calculated in this paper. We discuss the dependence of the corrections to the subprocess $γγ\to H^{+}H^{-}$ on the related parameters, such as the colliding energy, charged Higgs boson mass $M_{H^{\pm}}$ and some supersymmetric parameters $\tan β$, $M_{SUSY}$ and gaugino mass parameter $M_2$. We find that the corrections generally reduce the Born cross sections and the relative one-loop corrections to both the subprocess typically in the range of -10% to -30%. We also present the numerical results at the SPS1a' point from the SPA project. We conclude that the full one-loop electroweak corrections to subprocess $γγ\to H^{+}H^{-}$ and the parent process $e^+e^- \to γγ\to H^{+}H^{-}$ are significant and therefore should be considered in precise analysis of charged Higgs boson pair productions via $γγ$ collision at future linear colliders.

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arXiv2005

Full one-loop supersymmetric electroweak corrections to $t\bar{t}h^{0}$ associated production in $e^+e^-$ annihilation

We present a precise calculation of the lightest neutral Higgs boson production associated with top quark pair at a linear collider. The full one-loop electroweak ${\cal O}(α_{ew})$ contributions to the process $e^+e^- \to t\bar t h^0$ within the minimal supersymmetric standard model (MSSM) are included. We analyze the dependence of the electroweak corrections on the MSSM parameters such as $M_{A^0}$, $\tanβ$, $M_2$, $A_{f}$, $M_{SUSY}$ and $μ$. The results show that the full one-loop electroweak radiative corrections turn out to be about -20% quantitatively and thus are important for future $e^+e^-$ linear colliders.

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arXiv2005

NLO Supersymmetric QCD Corrections to $t \bar t h^0$ Associated Production at Hadron Colliders

We calculate NLO QCD corrections to the lightest neutral Higgs boson production associated with top quark pair at hadron colliders in the minimal supersymmetric standard model(MSSM). Our calculation shows that the total QCD correction significantly reduces its dependence on the renormalization/factorization scale. The relative correction from the SUSY QCD part approaches to be a constant, if either $M_S$ or $m_{\tilde{g}}$ is heavy enough. The corrections are generally moderate(in the range of few percent to 20%) and under control in most of the SUSY parameter space. The relative correction is obviously related to $m_{\tilde{g}}$, $A_t$ and $μ$, but not very sensitive to $\tanβ$, $M_S$ at both the Tevatron and the LHC with our specified parameters.

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arXiv2005

Pair Production of Charged Higgs Bosons from Bottom-Quark Fusion

For very large values of $\tanβ$, charged Higgs boson pair production at the Large Hadron Collider (LHC) from the scattering of two bottom quarks can proceed dominantly. We investigated the cross sections of charged Higgs boson pair production via the subprocess $b\bar{b} \to H^+H^-$ at the LHC including the next-to-leading order (NLO) QCD corrections in the minimal supersymmetric standard model (MSSM). We find that the NLO QCD corrections can significantly reduce the dependence of the cross sections on the renormalization and factorization scales.

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arXiv2005

The effects of large extra dimensions on associated $t\bar{t} h^0$ production at linear colliders

In the framework of the large extra dimensions (LED) model, the effects of LED on the processes \rrtth and \eetth at future linear colliders are investigated in both polarized and unpolarized collision modes. The results show that the virtual Kaluza-Klein (KK) graviton exchange can significantly modify the standard model expectations for these processes with certain polarizations of initial states. The process \rrtth with $\sqrt{s}=3.5 TeV$ allows the effective scale $Λ_T$ to be probed up to 7.8 and 8.6 TeV in the unpolarized and $P_γ = 0.9$, J=2 polarized $γγ$ collision modes, respectively. For the \eetth process with $\sqrt{s}=3.5 TeV$, the upper limits of $Λ_T$ to be observed can be 6.7 and 7.0 TeV in the unpolarized and $P_{e^+} = 0.6$, $P_{e^-} = 0.8$, $-+$ polarized $e^+e^-$ collision modes, respectively. We find the \rrtth channel in J=2 polarized photon collision mode provides a possibility to improve the sensitivity to the graviton tower exchange.

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arXiv2005

Full one-loop QCD and electroweak corrections to sfermion pair production in $γγ$ collisions

We have calculated the full one-loop electroweak (EW) and QCD corrections to the third generation scalar-fermion pair production processes $e^+e^- \to γγ\to \tilde{f_i}\bar{\tilde{f_i}} (f=t,b,τ)$ at an electron-positron linear collider(LC) in the minimal supersymmetric standard model (MSSM). We analyze the dependence of the radiative corrections on the parameters such as the colliding energy $\sqrt{\hat s}$ and the SUSY fundamental parameters $A_f$, $\tan β$, $μ$, $M_{SUSY}$ and so forth. The numerical results show that the EW corrections to the squark-, stau-pair production processes and QCD corrections to the squark-pair production processes give substantial contributions in some parameter space. The EW relative corrections to squark-pair production processes can be comparable with QCD corrections at high energies. Therefore, these EW and QCD corrections cannot be neglected in precise measurement of sfermion pair productions via $γγ$ collision at future linear colliders.

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arXiv2004

Probing R-parity violating interactions via $p\bar{p} \to eμ+X$ channel on Tevatron

We investigated the lepton flavor violation processes $p\bar{p} \to eμ+X$ induced by R-parity violating interactions at the Tevatron hadron collider. The theoretical calculation and Monte Carlo simulation demonstrate that with a set of suitable cuts on experimental observables, one might be capable to reduce the standard model physical background to a controllable level so that the signals of R-parity violating interactions could be detected distinctively. Furthermore, clear sneutrino information could be abstracted from the purified event sample where other SUSY scalar quark 'pollution' is heavy suppressed. We conclude that with a reasonable assumption of $10fb^{-1}$ integrated luminosity, the Experiments at the Tevatron machine would have potential to discover sneutrino in the region of $m_{\tildeν}\le400GeV$ via lepton flavor violation $eμ$ production channels, or extend the mass scale constraint up to $m_{\tildeν}\ge 550 GeV$ at 95% CL.

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