AZ′with enhanced couplings to quarks: A bridge from CERN LEP 1, SLC, and CDF to LEP 2 anomalies

Abstract

In order to explain possible departures from the standard model ͑SM͒ predictions for bb and cc production at the Z peak, we propose the existence of a ZЈ vector boson with enhanced couplings to quarks. We first show that this proposal is perfectly consistent with the full set of LEP 1 and SLC results. In particular, Z-ZЈ mixing effects naturally explain the fact that ⌫ b and ⌫ c deviate from the SM in opposite directions. We then show that there is a predicted range for enhanced ZЈqq couplings which explains, for a precise and interesting range of ZЈ masses, the excess of dijet events seen at CDF. A ZЈ with such couplings and mass would produce clean observable effects in bb and in total hadronic production at LEP 2.

Status of Precision Tests of the Standard Model

“…It was pointed out in refs. [89], [90] that if the e ect was real it could be explained in terms of a new vector boson Z 0 of mass around 1 TeV coupled mainly to quarks rather than leptons. In the presence of simultaneous anomalies in R b , R c and the jet yield at large E T , i t w as attractive to present a unique explanation for all three e ects.…”

Search forZ′viaZHassociated production at the LHC

“…Constraints on Z ′ mass and coupling strength with the SM particles have been obtained through e + e − → ff process at the electron-positron collider [13][14][15]. Especially, the precision measurements at the Z pole give limit on the Z − Z ′ mixing [16].…”

Leptophobic massive vector boson at the Fermilab Tevatron and the CERN LHC

“…[7] and independently by Chiapetta et al in Ref. [8] to explain recent experimental deviations from the Standard Model, has the remarkable feature (as the experimental data demand) that the axial and vector couplings of the Z ′ , especially to u-type quarks, are quite large. It will turn out that the effective Z ′ uū coupling is of the order of the strong (QCD) coupling constant α S .…”

“…[7,8] if one only takes the CDF data into account. But the main intention of this paper is to present predictions of the Z ′ model for further measurements at the Tevatron, like dijet angular distributions, and of course at the LHC pp-collider.…”