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Z' near the Z-pole
We present a fit to precision electroweak data in the standard model extended
by an additional vector boson, Z', with suppressed couplings to the electron
compared to the Z boson, with couplings to the b-quark, and with mass close to
the mass of the Z boson. This scenario provides an excellent fit to
forward-backward asymmetry of the b-quark measured on the Z-pole and \pm 2 GeV
off the Z-pole, and to lepton asymmetry, A_e, obtained from the measurement of
left-right asymmetry for hadronic final states, and thus it removes the tension
in the determination of the weak mixing angle from these two measurements. 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. We explore in detail
properties of the Z' needed to explain the data and present a model for Z' with
required couplings. The model preserves standard model Yukawa couplings, it is
anomaly free and can be embedded into grand unified theories. It allows a
choice of parameters that does not generate any flavor violating couplings of
the Z' to standard model fermions. Out of standard model couplings, it only
negligibly modifies the left-handed bottom quark coupling to the Z boson and
the 3rd column of the CKM matrix. Modifications of standard model couplings in
the charged lepton sector are also negligible. It predicts an additional down
type quark, D, with mass in a few hundred GeV range, and an extra lepton
doublet, L, possibly much heavier than the D quark. We discuss signatures of
the Z' at the Large Hadron Collider and calculate the Z'b production cross
section which is the dominant production mechanism for the Z'.Comment: 26 pages, 18 figures, minor modifications, one fig. added, results
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Z-Pencils
The matrix pencil (A,B) = {tB-A | t \in C} is considered under the
assumptions that A is entrywise nonnegative and B-A is a nonsingular M-matrix.
As t varies in [0,1], the Z-matrices tB-A are partitioned into the sets L_s
introduced by Fiedler and Markham. As no combinatorial structure of B is
assumed here, this partition generalizes some of their work where B=I. Based on
the union of the directed graphs of A and B, the combinatorial structure of
nonnegative eigenvectors associated with the largest eigenvalue of (A,B) in
[0,1) is considered.Comment: 8 pages, LaTe
Z' Physics
The limits on extra neutral gauge bosons, which could be reached at LEP2, are
reviewed. Exclusion and discovery limits are discussed for f\bar f and WW
production.Comment: 20 pages Latex, 7 figures included by epsfig, Contribution to the
Proceedings the workshop "Physics at LEP2", Geneva, 199
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