Z′gauge bosons at the Fermilab Tevatron

Abstract

We study the discovery potential of the Tevatron for a Z ′ gauge boson. We introduce a parametrization of the Z ′ signal which provides a convenient bridge between collider searches and specific Z ′ models. The cross section for pp → Z ′ X → ℓ + ℓ − X depends primarily on the Z ′ mass and the Z ′ decay branching fraction into leptons times the average square coupling to up and down quarks. If the quark and lepton masses are generated as in the standard model, then the Z ′ bosons accessible at the Tevatron must couple to fermions proportionally to a linear combination of baryon and lepton numbers in order to avoid the limits on Z − Z ′ mixing. More generally, we present several families of U (1) extensions of the standard model that include as special cases many of the Z ′ models discussed in the literature. Typically, the CDF and D0 experiments are expected to probe Z ′ -fermion couplings down to 0.1 for Z ′ masses in the 500-800 GeV range, which in various models would substantially improve the limits set by the LEP experiments.

Search for Heavy Resonances in the Dimuon Channel with the DØ Detector

“…However, it is argued in [28] that the NLO electroweak corrections to the Z cross section are substantially smaller than the correction to the Standard Model neutral current. Moreover, the change in the width of the reconstructed mass distribution is dominated by resolution effects and the efficiency has only a small dependence on the invariant mass.…”

“…In [28], four classes of one-parameter solutions are found where the charge under the U(1) is generation-independent.…”

“…Therefore, assuming the signal acceptance is independent of c u,d , an upper limit on the SM-like Z cross-section as a function of M Z corresponds to a limit in the (c u , c d ) plane, which can then be interpreted as a limit for any generic Z model. The dependence of the signal acceptance on c u,d was investigated in [28] and found to be small. Figure 6.6 shows the 95% credibility limit on the presence of the lightest massive Randall-Sundrum graviton as a function of M G [1] , the expected limit and the RS cross section for several values of k/M Pl .…”

“…THEORY fermions that the U(1) anomalies and the anomalies of the exotic fermions under the SM group cancel). Under mild assumptions it can then be shown that far above the Z mass the cross section for Z production in pp collisions with a decay to two muons is given by [28] …”

“…For a generic Z model with an extra U (1) extension to the Standard Model gauge group (see 2.3.3 for details), the production cross-section times branching ratio can be expressed as [28] σ(pp → Z X → µ + µ − X) = π 48s c u w u (s,…”