Reexamination of the Constraint on Topcolor-Assisted Technicolor Models from R_b

Abstract

Recent study on the charged top-pion correction to R_b shows that it is negative and large, so that the precision experimental value of R_b gives rise to a severe constraint on the topcolor-assisted technicolor models such that the top-pion mass should be of the order of 1 TeV. In this paper, we restudy this constraint by further taking account the extended technicolor gauge boson correction which is positive. With this positive contribution to R_b, the constraint on the topcolor-assisted technicolor models from R_b changes significantly. The top-pion mass is allowed to be in the region of a few hundred GeV depending on the models.

6-page RevTex file using epsfig.sty for the insertion of the three figures. Discussion on the oblique correction parameter T is added. Version for publication in Phys. Rev. D

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• The branching ratio $R_b$ in the littlest Higgs model
• Chromomagnetic Dipole Moment of the Top Quark Revisited
• Top-quark FCNC Productions at LHC in Topcolor-assisted Technicolor Model
• Pseudoscalar Higgs Bosons at the LHC: Production and Decays into Electroweak Gauge Bosons Revisited
• Probing Topcolor-Assisted Technicolor from Like-sign Top Pair Production at LHC
• $A_{FB}^b$ and $R_b$ at LEP and New Right-Handed Gauge Bosons
• The rare top decay $t\to cg$ in topcolor assisted technicolor models
• Studying top quark decay into the polarized W-boson in the TC2 model
• Unparticle Physics and A_{FB}^b on the Z pole
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• Production of the top-pions at the THERA collider based $\gamma p$ collisions
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• Detecting the neutral top-pion at future muon colliders
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• Rare decays $B_s\to l^{+}{l}^{-}$ and $B\to K{l}^{+}{l}^{-}$ in \the topcolor-assisted technicolor model
• Topcolor assisted technicolor models and muon anomalous magnetic moment
• Top quark decay t -> cb\bar{b} in topcolor-assisted technicolor models
• Neutral top-pion and the rare top decays $t\to c{l}_i{l}_j$
• Signatures of the neutral top-pion in $e\gamma$ collisions
• The scalars from the topcolor scenario and the spin correlations of the top pair production at the LHC
• PGB pair production at LHC and ILC as a probe of the topcolor-assisted technicolor models
• Photoproduction of the charged top-pions at the LHeC
• Single top production associated with a neutral scalar at LHC in topcolor-assisted technicolor
• R_b Constraints on Littlest Higgs Model with T-parity
• Distinguishing technicolor models via tt-bar productions at polarized photon colliders
• Lepton flavor violating signals of the neutral top-pion in future lepton colliders
• $B_s\to \varphi l^{+}{l}^{-}$ decays in the topcolor-assisted technicolor model
• The charged top-pion production associated with the bottom quark pair as a probe of the topcolor-assisted technicolor model at the LHC
• Charged Higgs Pair Production at the LHC as a Probe of the Top-Seesaw Assisted Technicolor Models