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FERMILAB-CONF-10-083-E-PPD
Searches for Heavy Vector Bosons at CDF
Michael Goldt
for the CDF Collaboration
tNew Mexco Center for Particle Physics
University of New Mexico
Abstract. The existence of additional vector bosons are theoretically well motivated, arising natu-
rally in many extensions of the Standard Model. Experimentally, such particles typically have clean
signatures and therefore should be observed in hadron colliders if they are produced. We review
recent searches for heavy vector bosons with CDF at the Tevatron and provide limits on their pro-
duction.
Keywords: Z',W', gauge boson, CDF, Tevatron
PACS: 12.60.Cn
One of the most compelling arguments for physics beyond the SM is that there is some
high-energy unification of the forces of nature. Additional vector bosons (Z',W') arise
naturally in extensions of the standard model (SM) with gauge unification, such as E6
and SO(10) models, as well as in other extensions of the SM, for example models with
extra dimensions or little Higgs models. (See reference [1] for a theoretical review of
Z' models.) If there is left-right symmetry at some high energy scale, then this provides
a natural mechanism for light neutrino masses and predicts a (right-handed) W'. (See
reference [2] for a theoretical review of W' models.) Experimentally, the production
of heavy vector bosons may result in high-mass lepton pair or lepton-neutrino events
which provide striking signatures. They may also appear in channels with higher SM
backgrounds such as di-jet events, di-boson events and single top events.
Lepton pair production: CDF has searched for high-mass di-lepton pairs (ee, pt)
in large luminosity samples (2.5 fb1 and 2.3 fb1 respectively). [3, 4] While the
background is dominanted by Drell-Yan, in these large data sets backgrounds from QCD
(di-jets, W+jets) and other SM process (di-tau, top, di-boson) contribute significantly to
the high-mass tail. In the di-electron channel there is a 2.5 sigma fluctuation around 240
GeV with width consistent with the experimental resolution. Otherwise, the agreement
between the data and the SM expectation is spectacular.
The di-electron excess could be evidence for new physics, for example as an indica-
tion of new strong dynamics in the model by Cata et al. [5] This theory predicts a narrow
spin-1 boson instead of the SM Higgs. However, this theory also has lepton universality,
and there is no evidence for a corresponding signal in the di-muon channel. The data
has been used to excluded a portion of the paramter space for this model, the ratio of
effective couplings versus new boson mass.
The di-electron mass spectrum can be used to set limits on various Z's (see Figure 1).
The theoretical cross sections are given for SM couplings and couplings to Z's from the
string-inspired gauge group E6. In general, constraints in particular models are weaker
CP1200, ]7'" International Conference on Supersymmetry and the Unification of Fundamental Interactions,
edited by P. Nath, G. Alverson, and B. Nelson
2009 American Institute of Physics 978-0-7354-0737-4/09/$25.00
734
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Synchrotron-based high-pressure research in materials science, article, Date Unknown; (https://digital.library.unt.edu/ark:/67531/metadc927019/m1/1/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.