New vector boson near the<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>Z</mml:mi></mml:math>-pole and the puzzle in precision electroweak data

Abstract

We show that a ${Z}^{\ensuremath{'}}$ 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 ${R}_{b}$ measured on the $Z$-pole and $\ifmmode\pm\else\textpm\fi{}2\text{ }\text{ }\mathrm{GeV}$ off the $Z$-pole, and to ${A}_{e}$ obtained from the measurement of left-right asymmetry for hadronic final states. It also leads to a significant improvement in the total hadronic cross section on the $Z$-pole and ${R}_{b}$ measured at energies above the $Z$-pole. In addition, with a proper mass, it can explain the excess of $Zb\overline{b}$ events at LEP in the 90--105 GeV region of the $b\overline{b}$ invariant mass.