Non-Universal Correction to $Z to b {overline b}$ and Single Top Quark Production at Tevatr.pdf

a r X i v : h e p - p h / 9 6 1 1 2 4 7 v 1 6 N o v 1 9 9 6 BIHEP-TH-96-29 November 1996 Non-Universal Correction To Z → bb And Single Top Quark Production at Tevatron A. Datta a and X. Zhangb a Department of Physics and Astronomy, Iowa State University, Ames, Iowa 50011 b CCAST (World Laboratory), P.O. Box 8730, Beijing 100080, P.R. China and Inst. of High Energy Phys., Academia Sinica, P.O. Box 918(4), Beijing 100039, P.R. China Abstract New physics associated with the heavy top quark can affect top quark production and the partial decay width of Z → bb?. In this paper, we examine the correlated effects of possible new physics on Rb measured at LEP I and the single top quark production rate at Tevatron by using an effective lagrangian technique. We point out that certain operators in the effective lagrangian, constrained by the measured value of Rb, can lead to significant and potentially observable effects in single top production. 1 Introduction An important issue in high energy physics is to understand the mechanism of mass generation. In the standard model, a fundamental complex Higgs scalar is introduced to break the electroweak symmetry and generate masses. However, arguments of triviality and naturalness suggest that the symmetry breaking sector of the standard model is just an effective theory. The top quark, with a mass of the order of the weak scale, is singled out to play a key role in probing the new physics beyond the standard model[1]. If anomalous top quark couplings were to exist, their effects could show up in the top quark production rate [2], the partial decay width of Z → bb measured at LEP [1] [3], FCNC processes at low energies [4] and in top quark decays[5]. The new experimental value for Rb = 0.2178±0.0011[6] is higher than the standard model prediction of 0.2156 ± 0.0005 by 1.8σ. This still could be a possible first hint of new physics associated with the heavy top quark [7, 8]. Recently with Chris Hill, one of the authors [9](X. Zhan