arXiv subjects

Shou-hua Zhu

Publications and source records attributed to Shou-hua Zhu.

68 records · Page 4Linked to original sources

arXiv2006

Spontaneous electro-weak symmetry breaking and cold dark matter

In the standard model, the weak gauge bosons and fermions obtain mass after spontaneous electro-weak symmetry breaking, which is realized through one fundamental scalar field, namely Higgs field. In this paper we study the simplest scalar cold dark matter model in which the scalar cold dark matter also obtains mass through interaction with the weak-doublet Higgs field, the same way as those of weak gauge bosons and fermions. Our study shows that the correct cold dark matter relic abundance within $3σ$ uncertainty ($ 0.093 < Ω_{dm} h^2 < 0.129 $) and experimentally allowed Higgs boson mass ($114.4 \le m_h \le 208$ GeV) constrain the scalar dark matter mass within $48 \le m_S \le 78$ GeV. This result is in excellent agreement with that of W. de Boer et.al. ($50 \sim 100$ GeV). Such kind of dark matter annihilation can account for the observed gamma rays excess ($10σ$) at EGRET for energies above 1 GeV in comparison with the expectations from conventional Galactic models. We also investigate other phenomenological consequences of this model. For example, the Higgs boson decays dominantly into scalar cold dark matter if its mass lies within $48 \sim 64$ GeV.

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arXiv2006

Detecting an invisible Higgs boson at Fermilab Tevatron and CERN LHC

In this paper, we study the observability of an invisible Higgs boson at Fermilab Tevatron and CERN LHC through the production channel $ q \bar{q} \to Z H \to \ell^+\ell^-+ \ptmiss $, where $\ptmiss$ is reconstructed from the $\ell^+\ell^-$ with $\ell=e$ or $μ$. A new strategy is proposed to eliminate the largest irreducible background, namely $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to ν\barν)$. This strategy utilizes the precise measurements of $ q \bar{q} \to Z(\to \ell^+\ell^-) Z(\to \ell^+\ell^-)$. For $m_H=120$ GeV and with luminosity $30 fb^{-1}$ at Tevatron, a $5σ$ observation of the invisible Higgs boson is possible. For $m_H=114 \sim 140$ GeV with only $10 fb^{-1}$ luminosity at LHC, a discovery signal over $5σ$ can be achieved.

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arXiv2006

QCD Effects in High Energy Processes

In this talk, some important QCD effects in Higgs physics, supersymmetry and top physics, as well as the factorization and resummation techniques in QCD are reviewed.

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arXiv2005

Study of V_LV_L\to t\bar{t} at the ILC Including O(alpha_s) QCD Corrections

In the event that the Higgs mass is large or that the electroweak interactions are strongly interacting at high energy, top quark couplings to longitudinal components of the weak gauge bosons could offer important clues to the underlying dynamics. It has been suggested that precision measurements of W_L W_L \to t\bar{t} and Z_L Z_L \to t\bar{t} might provide hints of new physics. In this paper we present results for O(alpha_s) QCD corrections to V_LV_L\to t\bar{t} scattering at the ILC. We find that corrections to cross sections can be as large as 30% and must be accounted for in any precision measurement of VV\to t\bar{t}.

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arXiv2005

Study of V_LV_L to t tbar at the ILC Including O(alpha_s) QCD Corrections

In the event that the Higgs mass is large or that the electroweak interactions are strongly interacting at high energy, top quark couplings to longitudinal components of the weak gauge bosons could offer important clues to the underlying dynamics. It has been suggested that precision measurements of W_L W_L to t tbar and Z_L Z_L to t tbar might provide hints of new physics. In this paper we present results of O(alpha_s) QCD corrections to V_LV_L to t tbar scattering at the ILC. We find that corrections to cross sections can be as large as 30% and must be accounted for in any precision measurement of VV to t tbar.

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arXiv2005

$W^- \to τ\bar ν_τ$ 3-sigma anomaly in new physics beyond the standard model

Among so-called three 3-sigma anomalies in high energy physics, the excess of the branching ratio $W^- \to τ\bar ν_τ$ with respect to the electrons and muons is especially interesting because (1) in the standard model (SM), $W^-\ell\bar ν_\ell$ is the pure left-handed charge-current which has been tested precisely already, at least for the first two generation fermions, and (2) the $W^\pm$ two-body leptonic decay is the cleanest one among three anomalies due to its simpler kinematics and less hadronic uncertainties. In this paper, we explore the possibilities to account for the anomaly in type II two-Higgs-doublet model (2HDM) and minimal supersymmetric model (MSSM), as well as effective lagrangian approach by introducing anomalous left- and right-handed $W^-τ\barν_τ$ couplings. Our results show that 2HDM and MSSM can hardly accommodate $W^- \to τν_τ$ anomaly, and the anomaly is only marginally consistent to the measurements of $τ\to ν_τ\ell \bar ν_\ell$ at 95% confidence level with the presence of anomalous couplings. In the allowed regions, the right-handed coupling of $W^-τν_τ$ shifts from 0 in SM to $\sim 0.12$ while the left-handed one from 1 to $\sim 1.005$.

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arXiv2004

Chargino Pair Production at Linear Collider and Split Supersymmetry

Recently N. Arkani-Hamed and S. Dimopoulos proposed a supersymmetric model \cite{Arkani-Hamed:2004fb}, dubbed "Split Supersymmetry" in Ref. \cite{Giudice:2004tc}, which can remove most of the unpleasant shortcomings of TeV Supersymmetry. In this model all scalars except one finely tuned Higgs boson are ultra heavy while the neutralino and chargino might remain light in order to achieve gauge coupling unification and accord with the dark matter density. In this paper, we investigated the impact of this new model on chargino pair production at next generation linear colliders. Our numerical results show that this process can be used to probe sneutrino mass up to 10 TeV. Therefore, precise measurements of chargino pair production at the linear colliders could distinguish Split Supersymmetry from TeV Supersymmetry.

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arXiv2003

CP violation in $B \to ΦK_S$ in a model III 2HDM

The mixing induced time dependent CP asymmetry, direct CP asymmetry, and branching ratio in $B \to ΦK_S$ in a model III 2HDM are calculated, in particular, neutral Higgs boson contributions are included. It is shown that satisfying all the relevant experimental constraints, for time dependent CP asymmetry $S_{ϕK}$ the model III can agree with the present data, $S_{ϕk}=-0.39\pm 0.41$, within the $1σ$ error, and the direct CP asymmetry which is zero in SM can be about $ -8% \sim -20%$ in the reasonable regions of parameters.

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arXiv2003

Supersymmetric QCD corrections to lightest Higgs boson associated production with top quark pair at Linear Colliders

Supersymmetric (SUSY) QCD corrections to the lightest neutral Higgs boson associated production with top quark pair are studied in the minimal supersymmetric standard model (MSSM) at Linear colliders. Our calculations show that the SUSY QCD effects generally are very moderate (say 10%) and under control, except for some rescattering effects which lead to a breakdown of perturbation theory and require a more detailed study. In the vicinity of the production threshold for the favorable model parameters under the framework of the on-shell renormalization scheme, SUSY QCD can be as large as about -50%. Such effects might be acted as the probe to determine the sign of $M_{LR}\equiv A_t-μ/\tanβ$.

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arXiv2003

Complete next-to-leading order QCD corrections to charged Higgs boson associated production with top quark at the CERN Large Hadron Collider

The complete next-to-leading order (NLO) QCD corrections to charged Higgs boson associated production with top quark through $b g \to tH^{-}$ at the CERN Large Hadron Collider are calculated in the minimal supersymmetric standard model (MSSM) and two-Higgs-doublet model in the $\bar{MS}$ scheme. The NLO QCD corrections can reduce the scale dependence of the leading order (LO) cross section. The K-factor (defined as the ratio of the NLO cross section to the LO one) does not depend on $\tanβ$ if the same quark running masses are used in the NLO and LO cross sections, and varies roughly from $\sim 1.6$ to $\sim 1.8$ when charged Higgs boson mass increases from 200 GeV to 1000 GeV.

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arXiv2002

Next-to-leading order QCD corrections to $bg \to t W^-$ at the CERN Large Hadron Collider

The next-to-leading order QCD corrections to the Standard Model process of single top production, $bg \to t W^-$, for the CERN Large Hadron Collider with $\sqrt{s}=14$ TeV have been calculated. For renormalization and factorization scales $μ=μ_0$ ($μ_0=m_t+m_W$), the NLO hadronic cross section is $\sim 37 $ pb, while $\sim 25 $ pb for tree level. The NLO QCD corrections can enhance the cross section by a factor from 1.33 to 1.66 for $\frac{μ_0}{2} < μ< 2 μ_0$.

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arXiv2002

Rare decay $B\to X_sl^+l^-$ in a CP spontaneously broken two Higgs doublet model

The Higgs boson mass spectrum and couplings of neutral Higgs bosons to fermions are worked out i n a CP spontaneously broken two Higgs doublet model in the large tan$β$ case. The differential branching ratio, forward-backward asymmetry, CP asymmetry and lepton polarization for $B\to X_s l^+ l^-$ are computed. It is shown that effects of neutral Higgs bosons are quite significant when $\tanβ$ is large. Especially, the CP violating normal polarization $P_N$ can be as large as several percents.

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arXiv2002

$O(α_s)$ Corrections to $b \bar b \to W^{\pm}H^{\mp}$ at the CERN Large Hadron Collider

The $O(α_{s})$ corrections to the cross section for $b \bar b \to W^{\pm}H^{\mp}$ at the LHC are calculated in the minimal supersymmetric standard model (MSSM) in the $\bar{MS}$ and OS (on-mass-shell) renormalization schemes. The results in two schemes are in good agreement. In the $\bar{MS}$ scheme, the QCD corrections are negative and within $ -14% \sim -20%$ for charged Higgs mass up to 1 TeV and $\tanβ>15$. For $\tanβ=2$, the magnitude of the QCD corrections can be greater than 30%.

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arXiv2002

Heavy quark polarizations of $e^+e^-\to q \bar q h$ in the general two Higgs doublet model

The polarizations of the heavy quark ($q=t$ or $b$) in the process $e^+e^- \to q \bar q h$ have been calculated in the general two Higgs doublet model. The CP violating normal polarization of the top quark can reach 8%, and $2 \sim 3%$ for the bottom quark, while it is zero in the standard model. The longitudinal and transverse polarizations of the bottom quark can be significantly different from those in SM and consequently could aslo be used as the probe of the new physics.

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