所有结果

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

Li, CS; Oakes, RJ; Yang, JM; Zhou, HY分类： 物理学 >> 基本粒子与场物理学

We calculate the O(alpha(cw)M(t)(2)/M-W(2)) supersymmetric (SUSY) electroweak corrections to single top quark production via --> |

Yukawa corrections to top quark pair production in photon-photon collisions

Li, CS; Yang, JM; Zhu, YL; Zhou, HY分类： 物理学 >> 基本粒子与场物理学

The O(alpha m(t)(2)/m(w)(2)) Yukawa corrections to top quark pair production in photon-photon collisions ate calculated in the standard model (SM), the general two-Higgs-doublet model (2HDM), as well as the minimal supersymmetric model (MSSM). We found that the correction to the cross section can only reach a few percent in the SM, but can be quite significant (> 10%) in the 2HDM and MSSM for favorable parameter values, which may be observable at high energy e(+)e(-) colliders. |

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

Li, CS; Oakes, RJ; Yang, JM; Zhou, HY分类： 物理学 >> 基本粒子与场物理学

We calculate the one-loop QCD corrections to t-->(t) over tilde(1)<(chi)over tilde>(0)(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 t--><(chi)over tilde>(+)(j)(b) over tilde(i). The numerical results show that the correction amounts to more than a 10% 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. |

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

Li, CS; Oakes, RJ; Yang, JM; Zhou, HY分类： 物理学 >> 基本粒子与场物理学

We evaluate the supersymmetric QCD corrections to single top quark production via q (q) over bar'-->t (b) over bar 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% for the smallest allowed tan beta(similar or equal to 0.25) but are only a few percent for tan beta>1. |

分类： 物理学 >> 基本粒子与场物理学

We discuss single top quark production via u(i) (d) over bar(j)-->t (b) over bar at the Fermilab Tevatron in the minimal supersymmetric model with R-parity violation. We find that within the allowed range of coupling constants, the lepton-number-violating couplings can give rise to observable effects when the slepton mass lies in a specific narrow range. For the baryon number-violating couplings, the contribution to the production rate can be quite large in the presently allowed range of the coupling constants. We show that the measurement of single top quark production at the upgraded Tevatron can be used to constrain a linear combination of products of the R-parity-violating couplings. |

Dimension-six CP-violating operators of the third-family quarks and their effects at colliders

Yang, JM; Young, BL分类： 物理学 >> 基本粒子与场物理学

We list all possible dimension-six CP-violating SUc(3) x SUL(2) x U-Y(1)-invariant operators involving the third-family quarks, which can be generated by new physics at a higher energy scale. The expressions of these operators after electroweak symmetry breaking and the induced effective couplings Wt (b) over bar,Xb (b) over bar, and Xt (t) over bar (X = Z,gamma,g,H) are also presented. We evaluate sample contributions of these operators to CP-odd asymmetries of transverse polarization of the top quark in single top quark production at the upgraded Fermilab Tevatron, the same polarization effect in top-quark-top-antiquark pair production at the NLC, and the CP-odd observables of momentum correlations among the top quark decay products at the NLC. The energy and luminosity sensitivity in probing this CP-violating new physics is also studied. |

分类： 物理学 >> 基本粒子与场物理学

We evaluate the supersymmetric (SUSY) electroweak corrections to the effect of parity nonconservation in --> |

分类： 物理学 >> 基本粒子与场物理学

We list all possible dimension-six CP-conserving SUc(3)xSU(L)(2)xU(Y)(1)-invariant operators involving the third-family quarks which could be generated by new physics at a higher scale. Expressions for these operators after electroweak gauge symmetry breaking and the induced effective couplings Wt(b) over bar, Xb(b) over bar, and Xt(t) over bar (X = Z, gamma,g, H) are presented. Analytic expressions for the tree level contributions of all these operators to the observables R-b and A(FB)(b) at CERN LEP I, sigma(e(+)e(-) --> ) and A(FB)(b) at LEP II, sigma(e(+)e(-) --> --> |

Gravitino dark matter from gluino late decay in split supersymmetry

Wang, F; Wang, WY; Yang, JM分类： 物理学 >> 基本粒子与场物理学

In split-supersymmetry (split-SUSY), gluino is a metastable particle and thus can freeze out in the early universe. The late decay of such a long-life gluino into the lightest supersymmetric particle (LSP) may provide much of the cosmic dark-matter content. In this work, assuming the LSP is gravitino produced from the late decay of the metastable gluino, we examine the Wilkinson microwave anisotropy probe (WMAP) dark-matter constraints on the gluino mass. We find that to provide the full abundance of dark matter, the gluino must be heavier than about 14 TeV and thus not accessible at the CERN large hadron collider (LHC). |

分类： 物理学 >> 基本粒子与场物理学

If all the supersymmetry particles (sparticles) except a light Higgs boson are too heavy to be directly produced at the Large Hadron Collider and Tevatron, a possible way to reveal evidence for supersymmetry is through their virtual effects in other processes. We examine such supersymmetric QCD effects in bottom pair production associated with a light Higgs boson at the Large Hadron Collider and Tevatron. We find that if the relevant sparticles (gluinos and squarks) are well above the TeV scale, too heavy to be directly produced, they can still have sizable virtual effects in this process. For large tan beta, such residual effects can alter the production rate by as much as 40%, which should be observable in future measurements of this process. |