arXiv subjects

Guo Lei

Publications and source records attributed to Guo Lei.

At least 37 records · Page 2Linked to original sources

arXiv2014

NNLO QCD corrections to Higgs pair production via vector boson fusion at hadron colliders

The measurement of the Higgs pair production via vector boson fusion can be used to test the trilinear Higgs self-coupling and the $VVHH$ $(V=Z,W)$ quartic gauge interactions. In this paper we present the calculations of the next-to-next-to-leading-order QCD corrections to the SM Higgs boson pair production via vector boson fusion at hadron colliders with the center-of-mass energy of $14$, $33$, and $100 {\rm TeV}$ by using the structure function approach, and study the residual uncertainties from the factorization/renormalization scale, parton distribution functions and $α_s$ on the total cross section. We also provide the distributions of transverse momenta, rapidities, invariant mass and azimuthal angle separations of final Higgs bosons. We observe a considerable quantitative reduction in the scale uncertainty due to the next-to-next-to-leading-order QCD corrections, and find that the total cross section is sensitive to the trilinear Higgs self-coupling.

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arXiv2014

Next-to-next-to-leading order QCD corrections to light Higgs pair production via vector boson fusion in type-II two-Higgs-doublet model

We present the precision predictions on the pair production of light, $CP$-even Higgs in weak vector boson fusion (VBF) up to the QCD next-to-next-to-leading-order (NNLO) at hadron colliders within the $CP$-conserving type-II two-Higgs-doublet model (2HDM(II)) by adopting the structure function approach. We investigate the model parameter dependence, residual uncertainties from the factorization/renormalization scale, PDFs and $α_s$ on the integrated cross section at the QCD NNLO, and find that the NNLO QCD corrections can reduce the scale uncertainty significantly. By analyzing the kinematic distributions of final Higgs bosons, we can extract the $CP$-even Higgs resonance via $H^0 \to h^0 h^0$ channel as a means of probing the extension of the Standard Model (SM) Higgs sector.

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arXiv2014

Diphoton plus $Z$ production at the ILC at ${\cal O}(α^4)$

Precision measurement for the production of a $Z$-boson in association with two photons is important for investigating the Higgs boson and exploring new physics at the International Linear Collider. It could be used to study the $ZZγγ$ anomalous quartic gauge coupling. In this work we report on our calculation of the full ${\cal O} (α^4)$ contributions to the $e^+e^- \to Z γγ$ process in the standard model, and we analyze the electroweak (EW) quantum effects on the total cross section. We investigate the dependence of the $Zγγ$ production rate on the event selection scheme and provide distributions for some important kinematic observables. We find that the next-to-leading order (NLO) EW corrections can enhance the total cross section quantitatively from $2.32\%$ to $9.61\%$ when the colliding energy goes up from $250 GeV$ to $1 TeV$, and the NLO EW corrections show obviously a non trivial phase space dependence. We conclude that in studying the signal process $e^+e^- \to ZH \to Z γγ$, the background process $e^+e^- \to Z γγ$ can be suppressed significantly if we take appropriate kinematic cuts on the final products.

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arXiv2014

Precise predictions for $A_H q_-$ associated production in the littlest Higgs model with $T$ parity at the LHC

In the framework of the littlest Higgs model with $T$ parity, we present complete calculations for the $A_H q_-$ $(q_-=u_-, \bar{u}_-,d_-, \bar{d}_-,c_-, \bar{c}_-,s_-, \bar{s}_-)$ associated production up to the QCD next-to-leading order (NLO) at the CERN Large Hadron Collider with subsequent pure weak decay of $T$-odd mirror quark. We apply the PROSPINO scheme to avoid the double counting problem and to keep the convergence of the perturbative QCD description. The theoretical correlations between the integrated cross section and the factorization and renormalization scale, the global symmetry-breaking scale and the Yukawa coupling parameter are studied separately. We also provide the kinematic distributions of the final decay products. Our numerical results show that the NLO QCD correction reduces the scale uncertainty and enhances the leading-order integrated cross section remarkably, with the $K$ factor varying in the range of $1.41 \sim 1.68$ ($1.58 \sim 1.89$) as the increment of the global symmetry-breaking scale $f$ from $500~{\rm GeV}$ to $1.5~{\rm TeV}$ ($1.1~{\rm TeV}$) at the $\sqrt{s} = 14~{\rm TeV}$ ($8~{\rm TeV}$) LHC. We find that it is possible to select the signal events of the $A_Hq_-$ production from its background by putting proper cuts on the final leading jet and missing energy.

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arXiv2013

Next-to-leading order QCD corrections to $HW^{\pm}γ$ production at the LHC

The Higgs boson production associated with a $W$-boson and a photon at the Large Hadron Collider (LHC) can be used to probe the coupling between Higgs boson and vector gauge bosons and discover a signature of new physics. We present the precision predictions up to the QCD next-to-leading-order (NLO) in the standard model for this process involving the subsequential weak decays of the final Higgs and $W$-boson. The dependence of the leading order (LO) and the QCD NLO corrected integrated cross sections on the factorization/renormalization energy scale is studied. We provide the LO and QCD NLO corrected distributions of the transverse momenta and rapidities of final products. We find that the LO cross section is significantly enhanced by the QCD NLO correction, and the $K$-factor value is obviously related to the physical observables and the phase space regions.

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arXiv2013

$J/ψ$ production associated with a $W$-boson at the $7 TeV$ LHC

We calculate the complete next-to-leading order (NLO) QCD corrections to the $J/ψ+W$ associated production within the factorization formalism of nonrelativistic QCD at the $7 TeV$ LHC. We provide the numerical results for the leading-order (LO), NLO QCD corrected differential cross sections of the $J/ψ$ transverse momentum by adopting the event selection criteria requested by the ATLAS experiment. We find that the differential cross section at the LO is significantly enhanced by the NLO QCD corrections.

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arXiv2013

Single (anti-)top quark production in association with a lightest neutralino at LHeC

In this paper we examine thoroughly the single (anti-)top quark production associated with a lightest neutralino at the possible CERN Large Hadron Electron Collider (LHeC). We calculate the full next-to-leading order (NLO) QCD corrections to the process including all the nonresonant diagrams and do not assume the production and decay factorization for the possible resonant top squarks in the R-parity violating minimal supersymmetric standard model with 19 unrelated parameters. We investigate numerically the effects of the relevant supersymmetry (SUSY) parameters on the cross section, and present the transverse momentum distributions of final (anti-)top quark at both the leading-order (LO) and the QCD NLO. We find that the NLO QCD corrections enhance the LO cross sections in most chosen parameter space, and the NLO QCD impacts on the transverse momentum distributions of the final (anti-)top quark might be resolvable in some cases. We conclude that even with recently known experimental constraints the on SUSY parameters, the production rate could still achieve notable value in the admissible parameter space.

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arXiv2013

$WWγ/Z$ production in the Randall-Sundrum model at LHC and CLIC

We study the $W^+W^-γ(Z)$ productions at both the CERN Large Hadron Collider (LHC) and the Compact Linear Collider (CLIC) in the framework of the Randall-Sundrum (RS) model. The impacts of the virtual RS Kaluza-Klein (KK) graviton on these processes are studied and compared with the standard model (SM) background. We present the integrated and differential cross sections in both the RS model and the SM. The results show that the relative RS discrepancies at the CLIC differ from those at the LHC, particularly in the transverse momentum and rapidity distributions. We also find that the RS signature performance, as a result of the resonance character of the RS KK-graviton spectrum, is distinctively unlike that in the large extra dimensions model. We conclude that the CLIC with unprecedented precision and high center-of-mass energy has a potential advantage over the LHC in exploring the effects of the RS KK graviton on the $W^+W^-γ(Z)$ production processes.

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arXiv2013

Precise QCD predictions on $W_HZ_H$ production in the littlest Higgs Model with $T$ parity at the LHC

We investigate the effects of the littlest Higgs model with $T$ parity up to the QCD next-to-leading order (NLO) on the $W_H^{\pm} Z_H$ productions at the CERN Large Hadron Collider (LHC), and discuss the kinematic distributions of final decay products and the theoretical dependence of the cross section on the factorization/renormalization scale. We find the QCD NLO corrections reduce the scale uncertainty of the leading order cross section in case of $μ_F=μ_R$. By adopting the PROSPINO subtraction scheme (scheme (II)) in analysing the QCD NLO contributions, we can obtain the numerical results which keep the convergence of the perturbative QCD description. Our results by adopting scheme (II) at the $14 {\rm TeV}$ ($8 {\rm TeV}$) LHC show that the $K$-factor for the $W_H^+ Z_H$ production varies in the range of $1.01 \sim 1.10$ ($1.00 \sim 1.08$), while the $K$-factor for the $W_H^- Z_H$ production varies in the range of $1.11 \sim 1.13$ ($1.11 \sim 1.12$), when the global symmetry breaking scale $f$ goes from $400 {\rm GeV}$ to $1.5 {\rm TeV}$ ($1 {\rm TeV}$).

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arXiv2013

Probe R-parity violating stop resonance at the LHeC

We investigate the possibility of detecting single sqaurk production at the proposed LHeC collider, in the framework of R-parity violating supersymmetry. Taking advantage of the enhancement of the direct resonance production of squark and the distinctive kinematics distributions of $\tilde{q}\rightarrow l q$ two body decay final states, the LHeC provides excellent opportunities of probing R-violating $\hat{L}\hat{Q}\hat{D}$ interactions at unprecedented level compared to all the knowledge derived from indirect low energy nucleon measurements. If no apparent deviation from SM predictions on high invariant mass of muon and b-quark final states at the LHeC with 1$fb^{-1}$ data, the sensitivities on $\hat{L}\hat{Q}\hat{D}$ coupling constant $λ^{'}_{131} \times λ^{'}_{233}$ can be improved by nearly four orders, at energy scale about 100 GeV.

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arXiv2012

Triple $Z^0$-boson production in large extra dimensions model at ILC

We investigate the effects induced by the interactions of the Kaluza-Klein (KK) graviton with the standard model (SM) particles on the triple $Z^0$-boson production process at the ILC in the framework of the large extra dimension (LED) model. We present the dependence of the integrated cross sections on the electron-positron colliding energy $\sqrt{s}$, and various kinematic distributions of final $Z^0$ bosons and their subsequential decay products in both the SM and the LED model. We also provide the relationship between the integrated cross section and the fundamental scale $M_S$ by taking the number of the extra dimensions ($d$) as 3, 4, 5, and 6, respectively. The numerical results show that the LED effect can induce a observable relative discrepancy for the integrated cross section ($δ_{LED}$), which can reach the value of $13.11% (9.27%)$ when $M_S = 3.5 (3.8) TeV$ and the colliding energy $\sqrt{s} = 1 TeV$. We find the relative discrepancy of LED effect can even reach few dozen percent in the high transverse momentum area or the central rapidity region of the final $Z^0$-bosons and muons.

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arXiv2012

QCD corrections to $J/ψ$ plus $Z^0$-boson production at the LHC

The $J/ψ+Z^0$ associated production at the LHC is an important process in investigating the color-octet mechanism of non-relativistic QCD in describing the processes involving heavy quarkonium. We calculate the next-to-leading order (NLO) QCD corrections to the $J/ψ+Z^0$ associated production at the LHC within the factorization formalism of nonrelativistic QCD, and provide the theoretical predictions for the distribution of the $J/ψ$ transverse momentum. Our results show that the differential cross section at the leading-order is significantly enhanced by the NLO QCD corrections. We conclude that the LHC has the potential to verify the color-octet mechanism by measuring the $J/ψ+Z^0$ production events.

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arXiv2012

$WWZ/γ$ production in large extra dimensions model at LHC and ILC

We investigate the effect induced by the Kaluza-Klein (KK) graviton in the $W^+W^-γ/Z$ production in the framework of the large extra dimensions (LED) model at both the CERN Large Hadron Collider (LHC) and the International Linear Collider (ILC). The integrated cross sections and various kinematic distributions in the LED model are presented and compared with those in the standard model. The results show that the contributions from KK-graviton exchange remarkably affect the observables of the triple gauge boson ($W^+W^-γ/Z$) production processes at both the ILC and the LHC, particularly either in the high transverse momentum region or in the central rapidity region. We also find that the relative LED discrepancy for the $W^+W^-γ/Z$ production at the LHC is generally larger than that at the ILC due to the additional LED contribution via $gg$ fusion subprocess and the KK-graviton exchanging resonant effect induced by the continuous large colliding energy in $pp$ collision. We conclude that the $W^{+}W^{-}γ$ and $W^{+}W^{-}Z$ productions at the LHC could have the distinct advantage over at the ILC from the aspect of effectively exploring the LED signal in measuring $W^+W^-γ/Z$ production.

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arXiv2012

$W_H$-pair Production in the Littlest Higgs Model with T parity in next-to-leading order QCD at LHC

In the framework of the littlest Higgs model with $T$ parity, we study the $W_H$-pair production at the CERN Large Hadron Collider up to the QCD next-to-leading order (NLO). The kinematic distributions of final decay products and the theoretical dependence of the cross section on the factorization/renormalization scale are analyzed. We adopt the PROSPINO scheme in the QCD NLO calculations to avoid double counting and keep the convergence of the perturbative QCD description. Our numerical results show that the QCD NLO corrections significantly reduce the scale uncertainty, and enhance the leading order integrated cross section with a $K$-factor in the range of $1.10-1.22$ ($1.09-1.17$) with the symmetry breaking scale $f$ varying from $400 GeV$ ($400 GeV$) to $1.5 TeV$ ($1.0 TeV$) at the $14 TeV$ $(8 TeV)$ LHC. We find that it is possible to select the signal events of the $W_H$-pair production from the $pp\to W^+ W^- \to e^+ μ^-ν_{e}\barν_μ+X$ background with high ratio of signature over background by taking proper lower limits on transverse momenta, invariant mass of the final charged leptons and the missing transverse momentum.

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arXiv2012

QCD correction to gluino decay to $t\bar{t}\tildeχ^0_1$ in the MSSM

We calculate the complete next-to-leading order QCD corrections to the three-body decay of gluino into top-pair associated with a lightest neutralino in the minimal supersymmetric standard model. We obtain that the LO and NLO QCD corrected decay widths of $\tilde{g} \to t \bar{t} \tildeχ_1^0$ at the ${\rm SPS 6}$ benchmark point are $0.1490 GeV$ and 0.1069 GeV respectively, and the relative correction is -28.2%. We investigate the dependence of the QCD correction to $\tilde{g} \to t \bar{t} \tildeχ_1^0$ on $\tanβ$ and the masses of gluino, scalar top quarks and the lightest neutralino around the ${\rm SPS6}$ benchmark point, separately. We find that the NLO QCD corrections suppress the LO decay width, and the absolute relative correction can exceed 30% in some parameter space. Therefore, the QCD corrections to the three-body decay $\tilde{g} \to t\bar{t}\tildeχ^0_1$ should be taken into account for the precise experimental measurement at future colliders. Moreover, we study the distributions of the top-pair invariant mass ($M_{t\bar t}$) and the missing energy ($E^{miss}$), and find that the line shapes of the LO distributions of $M_{t\bar t}$ and $E^{miss}$ are not obviously distorted by the NLO QCD corrections.

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arXiv2012

Associated $Z^0H^0$ production with leptonic decays at LHC in next-to-leading order QCD

In this work we investigate the effects of the littlest Higgs model (LHM) up to the QCD next-to-leading order (NLO) on the $Z^0H^0$ associated production at the CERN Large Hadron Collider (LHC). We study the dependences of the leading order and NLO QCD corrected integrated cross sections for this process on the factorization/renormalization scale and the LHM parameters. We also provide the distributions of the transverse momenta of final decay products $μ^-$ and $τ^-$. Our results show that the heavy neutral gauge bosons $Z_H$ and $A_H$ could induce significant discrepancies from the standard model predictions. It is found that when the LHM parameters are taken as $c=0.5$, $c^{\prime}=0.22$, $f=4 TeV$ and $μ=(M_H+M_Z)/2$, the effects at the $\sqrt{s}=14 TeV$ LHC from the heavy neutral gauge boson are about 12.83% and 10.37% to the leading order and NLO QCD corrected integrated cross sections, respectively. We also conclude that the NLO QCD corrections at the $\sqrt{s}=14 TeV$ LHC can obviously reduce the scale uncertainty of the integrated cross section, and significantly enhance the differential cross sections of $p_T^{μ^-}$ and $p_T^{τ^-}$. It demonstrates that the precision measurement of the $Z^0H^0$ associated production process at the LHC could provide the clue of the LHM physics.

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arXiv2012

Next-to-leading order QCD predictions for $Z^0 H^0 + {\rm jet}$ production at LHC

We calculate the complete next-to-leading order (NLO) QCD corrections to the $Z^0H^0$ production in association with a jet at the LHC. We study the impacts of the NLO QCD radiative corrections to the integrated and differential cross sections and the dependence of the cross section on the factorization/renormalization scale. We present the transverse momentum distributions of the final $Z^0$-, Higgs-boson and leading-jet. We find that the NLO QCD corrections significantly modify the physical observables, and obviously reduce the scale uncertainty of the LO cross section. The QCD K-factors can be 1.183 and 1.180 at the $\sqrt{s}=14 TeV$ and $\sqrt{s}=7 TeV$ LHC respectively, when we adopt the inclusive event selection scheme with $p_{T,j}^{cut}=50 GeV$, $m_H=120 GeV$ and $μ=μ_r=μ_f=μ_0 \equiv 1/2(m_Z+m_H)$. Furthermore, we make the comparison between the two scale choices, $μ=μ_0$ and $μ=μ_1=1/2(E_{T}^{Z}+E_{T}^{H}+ \sum_{j}E_{T}^{jet})$, and find the scale choice $μ=μ_1$ seems to be more appropriate than the fixed scale $μ=μ_0$.

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arXiv2012

Single slepton production associated with a top quark at LHC in NLO QCD

Single slepton production in association with a top quark at the CERN Large Hadron Collider (LHC) is one of the important processes in probing the R-parity violation couplings. We calculate the QCD next-to-leading order (NLO) corrections to the $pp \to t\slep^{-}(\bar{t}\slep^{+})+X$ process at the LHC and discuss the impacts of the QCD corrections on kinematic distributions. We investigate the dependence of the leading order (LO) and the NLO QCD corrected integrated cross section on the factorization/renormalization energy scale, slepton, stop-quark and gluino masses. We find that the uncertainty of the LO cross section due to the energy scale is obviously improved by the NLO QCD corrections, and the exclusive jet event selection scheme keeps the convergence of the perturbative series better than the inclusive scheme. The results show that the polarization asymmetry of the top-quark will be reduced by the NLO QCD corrections, and the QCD corrections generally increase with the increment of the $\tilde{t}_1$ or $\tilde{g}$ mass value.

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