相关论文: Electroweak Precision Data and a Heavy Z'
The Standard Model (SM) with a light Higgs boson provides a very good description of the precision electroweak observable data coming from the LEP, SLD and Tevatron experiments. Most of the observables, with the notable exception of the…
We show that a Z' with suppressed couplings to the electron compared to the Z-boson, with couplings to the b-quark, and with a mass close to the mass of the Z-boson, provides an excellent fit to forward-backward asymmetry of the b-quark and…
We discuss the possibility of breaking the electroweak symmetry in theories with extra dimensions via boundary conditions, without a physical Higgs scalar in the spectrum. In these models the unitarity violation scale can be delayed via the…
The constraints on the mixing angles of the standard fermions with new heavy particles that can appear in many extensions of the electroweak theory are reviewed. Some emphasis is put in distinguishing the effects of a mixing with new states…
The absence of a light Higgs boson causes vector boson couplings to become strong at 1 TeV. A general framework for a systematic and consistent treatment is provided by effective theories of electroweak symmetry breaking. Already in…
We consider for the first time the leading large top mass corrections, arising at higher order in electroweak interactions, to the rare decays $K\to\pi\nu\bar\nu$ and the related modes $B\to X_s\nu\bar\nu$ and $B\to l^+l^-$. Higher order…
We calculate the two-loop QCD correction to the scalar quark contributions to the electroweak gauge-boson self-energies at zero momentum-transfer in the supersymmetric extension of the Standard Model. We then derive the $O(\alpha_s)$…
This article provides the calculation of an effective vertex function between a nucleon and a $Z^\prime$ boson that couples preferentially to either the top quark or the third generation of fermions, for the purpose of calculating…
The agreement of electroweak measurements with theory places limits on the masses of the top quark and the $W$ boson. It is shown how these limits arise and what constraints various measurements (particularly a top quark mass determination)…
We review the available constraints on the low energy supersymmetry. The bulk of the electroweak data is well screened from supersymmetric loop effects, due to the structure of the theory, even with superpartners generically light, ${\cal…
We study the effects of an extra U(1)' gauge boson with flavor changing couplings with fermion mass eigenstates on certain B meson decays that are sensitive to such new physics contributions. In particular, we examine to what extent the…
A Lagrangian of electroweak interactions without Higgs is used to study the contributions of quarks and leptons to the masses of the W and the Z bosons. It is shown that the $SU(2)\times U(1)$ symmetry is broken by both fermion masses and…
Anomalous interactions involving the top quark contribute to some of the most difficult observables to directly access experimentally. They can give however a sizeable correction to very precisely measured observables at the loop level.…
The contribution to the muon anomalous magnetic moment from the fermion triangle loop diagrams connected to the muon line by a photon and a $Z$ boson is reanalyzed in the unitary gauge. With use of the anomalous axial-vector Ward identity,…
The inclusion of the unstable features of a spin-1 particle, without breaking the electromagnetic gauge invariance, can be properly accomplished by including higher order contributions as done in the so-called fermion loop scheme (for the W…
By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark. Invoking the…
We consider extending the Standard Model by including an additional Abelian gauge group broken at low energies under which the right-handed top quark is the only effectively charged Standard Model fermion. The associated gauge boson $(Z')$…
It is notorious that, contrary to all other precision electroweak data, the forward-backward asymmetry for b quarks $A_{FB}^b$ measured in Z decays at LEP1 is nearly three standard deviations away from the predicted value in the Standard…
The two-loop corrections to the electroweak gauge bosons quartic couplings growing quadratically with the Higgs boson mass are calculated in the Standard Model in the limit of large Higgs mass. The corrections to WWWW, WWZZ and ZZZZ…
The phenomenological model of an extra U(1) neutral gauge Z' boson coupled to heavy quarks is presented. In particular, we discuss the probability for a light $Z_{2}$ mass eigenstate decay into a bound state composed of heavy quarks via…