arXiv subjects

Ma Wen-Gan

Publications and source records attributed to Ma Wen-Gan.

At least 55 records · Page 3Linked to original sources

arXiv2012

Associated production of $Υ(1S)W$ at LHC in next-to-leading order QCD

We investigate the complete next-to-leading order (NLO) QCD corrections to $Υ(1S) +W$ production at the LHC, and predict theoretically the distribution of the $Υ(1S)$ transverse momentum. We analyse the contributions from different components up to the QCD NLO in the \ppUW process. Our results show that the \ppUW process has a large production rate and could be potentially detected at the LHC. We see that the differential cross section for the $Υ(1S)$ direct-production at the LO is significantly enhanced by the QCD corrections, and the $b\bar{b} [ ^3S_1^{(8)} ]$ contribution component dominates in the whole plotted $p_T^{Υ(1S)}$ region. We have also calculated the $Υ(1S)$ meson indirect-productions via feed-down decays of $Υ(2S)$, $Υ(3S)$, $χ_{b1}(1P)$, $χ_{b2}(1P)$, $χ_{b1}(2P)$, and $χ_{b2}(2P)$ mesons. We find that the $Υ(1S)$ indirect-productions can give important contributions to the distribution of $p_T^{Υ(1S)}$ for the \ppUW process at the NLO. We conclude that the studying the $Υ(1S)+W$ production at the LHC could provide an interesting opportunity in testing the nonrelativistic QCD factorization formalism.

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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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arXiv2012

Revisiting the large extra dimension effects on $W$-pair production at the LHC in NLO QCD

In the framework of the large extra dimensions (LED) model, we investigate the effects induced by the Kaluza-Klein (KK) gravitons up to the QCD next-to-leading order (NLO) on the $W$-pair production followed by a subsequential $W$-decay at the CERN LHC. We depict the regions in the $\mathcal{L}-M_{S}$ parameter space where the LED effect can and cannot be observed from the analyses of the $pp \to W^+W^- + X$ and $pp \to W^+W^- \to W^{\pm}l^{\mp}\stackrel{(-)}ν + X$ processes. We find that the ability of probing the LED effects can be improved by taking the cutoffs for the invariant mass of $W$-pair and the transverse momentum of the final lepton. Our results demonstrate that the NLO QCD corrections to observables are significant, and do not show any improvement for the renormalization/factorization scale uncertainty on the QCD NLO corrected cross section, because the LO result underestimates the scale dependence.

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arXiv2012

QCD corrections to the $γγb\bar b$ production at the ILC

The $e^+e^- \to γγb\bar b$ is an irreducible background process in measuring the $H^0 \to γγ$ decay width, if Higgs boson is produced in association with a $Z^0$-boson which subsequently decays via $Z^0 \to b\bar b$ at the ILC. In this paper we study the impact of the ${\cal O}(α_s)$ QCD corrections to the observables of the $e^+e^- \to γγb\bar b$ process in the standard model. We investigate the dependence of the leading-order and ${\cal O}(α_s)$ QCD corrected cross sections on colliding energy and the additional jet veto schemes. We also present the results of the LO and ${\cal O}(α_s)$ QCD corrected distributions of the transverse momenta of final particles, and the invariant masses of $b\bar b$- and $γγ$-pair.

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arXiv2011

$W_H/Z_H$ production associated with a T-odd (anti)quark at the LHC in NLO QCD

In the framework of the littlest Higgs model with T parity, we study the $W_H/Z_H$ production in association with a T-odd (anti)quark of the first two generations at the CERN Large Hadron Collider up to the QCD next-to-leading order. The kinematic distributions of final decay products and the theoretical dependence of the cross section on the factorization/renormalization scale are discussed. We apply three schemes in considering the QCD NLO contributions and find that the QCD NLO corrections by adopting the (II) and (III) subtraction schemes can keep the convergence of the perturbative QCD description and reduce the scale uncertainty of the leading order cross section. By using these two subtraction schemes, the QCD NLO corrections to the $W_H(Z_H) q_-$ production process enhance the leading order cross section with a K-factor in the range of $1.00 \sim 1.43$.

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arXiv2011

Next-to-leading order QCD corrections to $t\bar tγ$ production at the 7 TeV LHC

We present the theoretical predictions including the complete next-to-leading order (NLO) QCD corrections to the top-quark pair production in association with a photon at the LHC with center-of-mass system energy of $7 {\rm TeV}$. The uncertainties of the leading order (LO) and NLO QCD corrected cross sections due to the renormalization/factorization scale, and the distributions of the transverse momenta of final top-quark and photon are studied. Moreover, we provide the numerical results of the LO, NLO QCD corrected cross sections and the corresponding $K$-factors with different photon transverse momentum cuts. We also discuss the impact of QCD corrections to the \ppttga in case of there existing the exotic top-quark with an electric charge of $-4e/3$ at the $7 {\rm TeV}$ LHC.

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arXiv2011

QCD NLO predictions to $W$-pair production in association with a massive (anti)bottom-jet at the LHC

The $W$-pair production in association with a massive (anti)bottom jet is not only an important background to a number of interesting processes, such as the single top production associated with a W boson, but also a potential background to new physics searches. We present the calculations of the total and differential cross sections for the $W^+W^-+ b(\bar{b})$ jet productions at the LHC up to the QCD next-to-leading order (NLO). Our results by adopting the QCD NLO contribution collection scheme-I show that the K factors can be 1.66 and 1.21 with the inclusive and exclusive two-jet event selection schemes respectively, when we set $m_H=120 GeV$, $μ=m_W+m_b/2$ and take the constraints of $p_{T,b(\bar{b})}>25 GeV$, $|y_{b(\bar{b})}|<2.5$ for $b(\bar{b})$ jet. We find that the stabilization of the theoretical prediction for the integrated cross section for the $pp \to W^+W^-b(\bar b)+X$ up to the QCD NLO requires a veto on a second isolated hard jet and the inclusion of the QCD NLO contribution from the $W^+W^-b\bar{b}(bb, \bar{b}\bar{b})$ production with the final two $b(\bar{b})$ quarks being merged as one jet.

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arXiv2011

The light MSSM neutral Higgs boson production associated with an electron and a jet at the LHeC

We study the light CP-even neutral Higgs boson production in association with an electron and a jet at the possible CERN large hadron-electron collider within the minimal supersymmetric standard model. We investigate the possible supersymmetric effects on this process and compare our standard model numerical results with those in previous work. We present the leading-order and QCD next-to-leading-order corrected total cross sections and the distributions of the transverse momenta of the final electron, the light neutral Higgs boson, and jet in the minimal supersymmetric standard model. Our results show that the scale dependence of the leading-order cross section is obviously reduced by the QCD next-to-leading-order corrections. The K factor of the QCD correction to the total cross section at the large hadron-electron collider varies from 0.893 to 1.048 when the factorization/renormalization scale $μ$ goes up from $0.2 m_Z$ to $3.8 m_Z$ in our chosen parameter space.

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arXiv2010

QCD corrections to $J/ψ$ production in association with a $W$-boson at the LHC

We calculate the next-to-leading order (NLO) QCD corrections to the $J/ψ+W$ production at the LHC, and provide the theoretical distribution of the $J/ψ$ transverse momentum. Our results show that the differential cross section $\frac{dσ}{dp_T^{J/ψ}}$ at the LO is significantly enhanced by the NLO QCD corrections. We believe that the comparison between the theoretical predictions for the $J/ψ+W$ production and the experimental data at the LHC can provide a verification for the colour-octet mechanism of non-relativistic QCD in the description of the processes involving heavy quarkonium.

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arXiv2010

Supersymmetric QCD and CP-violation effects in $t \bar t Z^0$ production at the LHC

We investigate the NLO QCD and the CP-violation effects in $t\bar{t}Z^0$ production at the Large Hadron Collider(LHC) in the minimal supersymmetric standard model(MSSM). Our calculation shows that the total NLO QCD correction in the framework of the CP-conserving MSSM significantly improves the scale uncertainty at the leading order, and the contribution from the pure supersymmetric QCD (pSQCD) correction can exceed $-8\%$ with the restrictions of $90~GeV < p_T^t < 120~GeV$ and $120~GeV < p_T^Z < 150~GeV$, where $p_T^t$ and $p_T^Z$ are the transverse momenta of the top-quark and $Z^0$ gauge boson, respectively. Our numerical results demonstrate that the pure SUSY QCD correction generally suppresses the total SM-like QCD correction in the CP-conserving MSSM, and tends to be a constant when either $\tilde{t}_1$ or $\tilde{g}$ is heavy enough. We find also that the CP-odd asymmetry ${\cal A}_Φ$ can reach $2.17 \times 10^{-3}$, if the CP-phase angle really exists in the coupling of gluino-stop-top.

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arXiv2010

Seesaw Type I and III at the LHeC

We study the potential of testing the seesaw type I and III models at the LHeC, an e-p collision mode at the CERN collider. The e-p collision mode provides an excellent place to study lepton number violating process e^- p \to N j + X \to l^+ W^- j + X with W^- into hadron jets. Here N is a heavy Majorana neutrino and j is a hard hadron jet. With the electron energy E_e = 140 GeV and proton energy E_p = 7 TeV, we find that the cross section for the heavy neutrino N production can be as large as a few fb for the mass scale as high as 1 TeV, higher than what can be achieved by the p-p collision mode of LHC with the same related heavy neutrino couplings.

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