Related papers: Shifting $R_b$ with $A^b_{FB}$
In light of the discovery of a Higgs-like particle at the LHC, we revisit the status of the precision electroweak data, focusing on two discrepant observables: 1) the long-standing 2.4 sigma deviation in the forward-backward asymmetry of…
The W-boson mass measurement recently reported by the CDF II experiment exhibits a significant deviation from both the Standard Model prediction and previous measurements. There is also a long-standing deviation between the Standard Model…
The couplings of the fermions to the Z boson are of great importance in establishing the validity of the Standard Model and in looking for physics beyond it. The couplings of the b-quark to the Z boson have been the subject of much…
Motivated by the $3.2\sigma(1.4\sigma)$ deviations between the recent experimental value for $A_{FB}^{b}(R_{b})$ and the standard model(SM) prediction, we examine the effect of new physics(NP) on the $Zb \bar{b}$ couplings $g_L^b$ and…
It is argued that the recent Belle data, consistent with no activity in the spectrum of the $B^* \bar B + B \bar B^*$ pairs at the mass of the $Z_b(10650)$ resonance, imply that the part of the interaction between heavy mesons that depends…
We observe that quantities like (f_{B_s}/f_B) / (f_{D_s} /f_D) are predicted to be unity both by heavy quark and by light quark flavor symmetries. Hence, the deviation from the symmetry prediction must be simultaneously small in both…
The Standard Model (SM) prediction for the \PZ-boson pole $b$-quark forward-backward (FB) asymmetry is: $(A_{FB}^{0,b})_{th} = 0.1030 \pm 0.0002$. The LEP electron-positron collider measured instead $A_{FB}^{0,b} = 0.0992 \pm 0.0016$, value…
The mixing of the known quarks with new heavy singlets can modify significantly some observables with respect to the Standard Model predictions. We analyse the range of deviations permitted by the constraints from precision electroweak data…
The top quark forward-backward asymmetry A_{FB}^t measured at the Tevatron is above the Standard Model prediction by more than 2-sigma deviation, which might be a harbinger for new physics. In this work we examine the contribution to…
We explore the "Beautiful Mirrors" model, which aims to explain the measured value of $A^b_{FB}$, discrepant at the $2.9\sigma$ level. This scenario introduces vector-like quarks which mix with the bottom, subtly affecting its coupling to…
An analysis of the Forward-Backward Asymmetry (FBA) in the decay $B^\pm \to K^\pm K^\mp K^\pm$ is carried out based on the LHCb data. It is found that the large FBA observed for the invariant mass of the $K^+ K^-$ pair around 1.5 GeV can be…
We find that the tree-level predictions of the forward-backward production asymmetries on the Z resonance for b and c quarks, A_FB, in an SO(5) x U(1) gauge-Higgs unification model are markedly close to the central values of the Particle…
Measurements of b and c quark asymmetries using data collected at LEP 1 are described. The relative merits of each of the individual techniques used is emphasised as is the most profitable way of combining them. Effects of radiative…
The forward-backward asymmetry ${\cal A}_{\rm FB}$ in $B\to K^*\ell^+\ell^-$ decay is a sensitive probe of New Physics. Previous studies have focused on the sensitivity in the position of the zero. However, the short distance effective…
We consider the physics of an extra $U(1)$ gauge boson $Z'$, which can mix with $Z$ through intermediate fermion loops. The loop contribution due to the heavy top quark significantly affects the low-energy observables, and for $m_{Z'}>m_Z$,…
We analyze various models for the top quark forward-backward asymmetry ($A^t_{FB}$) at the Tevatron, using the latest CDF measurements on different $A^t_{FB}$s and the total cross section. The axigluon model in Ref. \cite{paul} has…
The measured value of A_b, the Z \bar bb asymmetry parameter, disagrees with the Standard Model at 99% confidence level. If genuine the discrepancy could indicate new interactions unique to third generation quarks, implying enhanced Z…
The recent Tevatron measurement of the forward-backward asymmetry of the top quark shows an intriguing discrepancy with Standard Model expectations, particularly at large $\ttbar$ invariant masses. Measurements of this quantity are subtle…
We introduce and define operatively in a model independent way a new ``heavy" b-vertexparameter, $\eta_b$, that can be derived from the measurement of a special polarization asymmetry for production of b-quarks on Z resonance. We show that…
Combining precision measurements and the Higgs boson search limit, the electroweak data has evolved to a point where new physics is favored whether the 3.2 sigma A_{FB}^b anomaly is genuine or not. Such new physics could greatly alter the…