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Register a new userYukawa Corrections to gamma gamma --> bbar{b} in the Topcolor Assisted Technicolor Models
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We study the Yukawa corrections to the gamma gamma --> bbar{b} corss section in the topcolor assisted technicolor models at the photon-photon colliders. We find that, for the favorable parameters, the relative corrections from pseudo Goldstone bosons give out a 3.2%--5.9% decrement of the cross section from the tree level when sqrt{s}=500 GeV, the contributions from new extended technicolor gauge bosons Z* and colored gauge bosons B are negligibly small, and the relative correction arising from new color-singlet heavy gauge boson Z is less than -3.2%. Therefore, the total relative corrections are significantly larger than the corresponding corrections in the standard model, the general two Higgs doublet model and the minimal supersymmetric standard model. Since these corrections are obvious for the International Linear Colliders, the process gamma gamma --> bbar{b} is really interesting in testing the standard model and searching for the signs of technicolor.
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In this paper we calculate the technicolor correction to the production of a charged top pion in association with a W boson via bbar{b} annihilation at the CERN Large Hadron Collider in the context of the topcolor assisted technicolor model. We find that the cross section of pp rightarrow bbar{b} -> W^{pm}pi_t^{mp} at the tree level can reach a few hundred femtobarns for reasonable ranges of the parameters, roughly corresponding to the result of the process pp -> bbar{b} -> W^{pm}H^{mp} in the minimal supersymmetric standard model; the relative corrections arising from the one-loop diagrams are about a few percent to two dozen percent, and they will increase the cross section at the tree level. As a comparison, we also discuss the size of the hadron cross section via the other subprocess gg -> W^{pm}pi_t^{mp}.
We present NLO QCD results for W/Z gauge boson production with bottom quark pairs at the Tevatron including full bottom-quark mass effects. We study the impact of QCD corrections on both total cross-section and invariant mass distribution of the bottom-quark pair. Including NLO QCD corrections greatly reduces the dependence of the tree-level cross-section on the renormalization and factorization scales. We also compare our calculation to a calculation that considers massless bottom quarks and find that the bottom-quark mass effects amount to about 8-10% of the total NLO QCD cross-section and can impact the shape of the bottom-quark pair invariant mass distribution, in particular in the low invariant mass region.
We calculate the contributions to the rare decays $B to X_{s,d} u bar u$ and $B_{s,d} to l^+l^-$ from one-loop $Z^0$-penguin diagrams in the framework of Topcolor-assisted Technicolor Model. Within the parameter space, we find that: (a) the new contribution from technipions is less than 2% of the standard model prediction; (b) the top-pions can provide a factor of 10 to 30 enhancement to the ratios in question; (c) the topcolor-assisted technicolor model is consistent with the current experimental data.
In the framework of topcolor-assisted technicolor model we calculate the contributions from the pseudo Goldstone bosons and new gauge bosons to $e^+e^- to tbar{t}$. We find that, for reasonable ranges of the parameters, the pseudo Goldstone bosons afford dominate contribution, the correction arising from new gauge bosons is negligibly small, the maximum of the relative corrections is -10% with the center-of-mass energy $sqrt{s}=500$ GeV; whereas in case of $sqrt{s}=1500$ GeV, the relative corrections could be up to 16%. Thus large new physics might be observable at the experiments of next-generation linear colliders.
We comparatively analyze the flavor changing neutral current process of the $Lambda_b rightarrow Lambda ell^+ ell^-$ in the standard model as well as topcolor-assisted technicolor model using the form factors calculated via light cone QCD sum rules in full theory. In particular, we calculate the decay width, branching ratio and lepton forward-backward asymmetry related to this decay channel. We compare the results of the topcolor-assisted technicolor model with those of the standard model and debate how the results of the topcolor-assisted technicolor model depart from the standard model predictions. We also compare our results on the differential branching ratio with recent experimental data provided by CDF and LHCb Collaborations.
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