Jin Min Yang

Probing top quark decay into a light top squark in the supersymmetric standard model at the upgraded Fermilab Tevatron

We investigate the possibility of observing the exotic decay mode of the top quark into the lightest top squark ({tilde t}{sub 1}) and neutralino ({tilde {chi}}{sub 1}{sup 0}) in the minimal supersymmetric standard model with R parity at the upgraded Fermilab Tevatron. First we examine the bounds for the branching fraction B(t{r_arrow}{tilde t}{sub 1}{tilde {chi}}{sub 1}{sup 0}) from the available experimental data, and then consider all possible backgrounds and investigate the possibility of observing this final state at the Tevatron. We find that this final state is unobservable at run 1. However, run 2 can either discover it, or establish strong limits ({approximately}1{percent}) on the branching fraction of this decay. {copyright} {ital 1998} {ital The American Physical Society}

The b quark mass effect in the QCD correction to charged Higgs boson decay of the top quark

Abstract Keeping the mass of the bottom quark, we calculate the O(α s ) QCD correction to the process t → H + b. The results differ significantly from that of neglecting the b quark mass. The corrections imply a larger reduction of partial width relative to the tree-level result.

Supersymmetric electroweak corrections to single top quark production at the Fermilab Tevatron

We calculate the O({alpha}{sub ew}M{sub t}{sup 2}/M{sub W}{sup 2}) supersymmetric (SUSY) electroweak corrections to single top quark production via q{bar q}{sup {prime}}{r_arrow}t{bar b} at the Fermilab Tevatron in the minimal supersymmetric model. The supersymmetric electroweak corrections to the cross section are at most a few percent for tan{beta} {gt} 1, but can exceed 10{percent} for tan{beta} {lt} 1. The combined effects of SUSY electroweak corrections and the Yukawa corrections can exceed 10{percent} for favorable parameter values, which might be observable at a high-luminosity Tevatron. {copyright} {ital 1997} {ital The American Physical Society}

Strong supersymmetric quantum effects on top quark production at the Fermilab Tevatron

The supersymmetric QCD corrections to top quark pair production by q¯ q annihilation in p¯ p collisions are calculated in the minimal supersymmetric model. We consider effects of the mixing of the scalar top quarks on the corrections to the total

Supersymmetric QCD corrections to single top quark production at the Fermilab Tevatron

We evaluate the supersymmetric QCD corrections to single top quark production via q{bar q}{sup {prime}}{r_arrow}t{bar b} at the Fermilab Tevatron in the minimal supersymmetric model. We find that within the allowed range of squark and gluino masses the supersymmetric QCD corrections can enhance the cross section by a few percent. The combined effects of SUSY QCD, SUSY EW, and the Yukawa couplings can exceed 10{percent} for the smallest allowed tan{beta}({approx_equal}0.25) but are only a few percent for tan{beta}{gt}1. {copyright} {ital 1997} {ital The American Physical Society}

One-loop QCD corrections to top quark decay into a neutralino and light stop squark.

We calculate the one-loop QCD corrections to {ital t}{r_arrow}{ital {tilde t}}{sub 1}{tilde {chi}}{sup 0}{sub {ital j}} using the dimensional reduction scheme, including QCD and supersymmetric QCD corrections. The analytic expressions for the corrections to the decay width are given, which can easily be extended to {ital t}{r_arrow}{tilde {chi}}{sup +}{sub {ital j}}{ital {tilde b}}{sub {ital i}}. The numerical results show that the correction amounts to more than a 10{percent} reduction in the partial width relative to the tree level result. We also compare the corrections in the no-mixing top squark case with those in the mixing top squark case. {copyright} {ital 1996 The American Physical Society.}

Supersymmetric electroweak parity nonconservation in top quark pair production at the Fermilab Tevatron

Abstract We evaluate the supersymmetric (SUSY) electroweak corrections to the effect of parity nonconservation in q q → t t production at the Fermilab Tevatron predicted by the Minimal Supersymmetric Model (MSSM). We find that the parity nonconserving asymmetry from the SUSY electroweak and SUSY Yukawa loop corrections predicted by the minimal supergravity (mSUGRA) model and the MSSM models with scenarios motivated by current data is about one percent. It will be challenging to observe such a small asymmetry at the Tevatron with 10 fb−1 of luminosity. It could however be observable if both the top- and bottom-squarks are light and tan β is smaller than 1, though theses parameters are not favored by mSUGRA.

PHASE-STRUCTURE OF LATTICE-Z (2) GAUGE-HIGGS THEORY BY VARIATIONAL CUMULANT EXPANSION

Abstract We use the variational cumulant expansion method to study the four-dimensional lattice Z(2) gauge theory coupled to a radially varied scalar field which is assumed to take discrete values. Its phase structure is given in different cases. The comparison with the results from other approaches is also presented.

An analytical study of lattice gauge theory at finite temperature

Abstract We extended the variational cumulant expansion for lattice gauge theories to finite temperature. The phase diagram of the Z(2) gauge model is given in four dimensions. The asymmetric Z(2) model at finite temperature is also treated.