62 research outputs found
Z' Physics and Supersymmetry
We review the status of heavy neutral gauge bosons, Z', with emphasis on
constraints that arise in supersymmetric models, especially those motivated
from superstring compactifications. We first summarize the current
phenomenological constraints and the prospects for Z' detection and diagnostics
at the LHC and NLC. After elaborating on the status and (lack of) predictive
power for general models with an additional Z', we concentrate on motivations
and successes for Z' physics in supersymmetric theories in general and in a
class of superstring models in particular. We review phenomenologically viable
scenarios with the Z' mass in the electroweak or in the intermediate scale
region.Comment: 30 pages. To appear in Perspectives in Supersymmetry, World
Scientific, ed. G. L. Kan
HERA prospects on Compositeness and New Vector Bosons
The absence of deviations from the Standard Model for the differential cross
section at HERA is used to set limits on electron quark
compositeness scale and on new vector bosons, especially the hadrophilic one
recently introduced as a possible explanation for LEP/SLC and CDF anomalies.Comment: Latex file, 7 pages and 1 ps fig, few comments on others experiments
are added, results are unchanged. To appear in Phys. Let.
TeV physics and the Planck scale
Supersymmetry is one of the best motivated possibilities for new physics at
the TeV scale. However, both concrete string constructions and phenomenological
considerations suggest the possibility that the physics at the TeV scale could
be more complicated than the Minimal Supersymmetric Standard Model (MSSM),
e.g., due to extended gauge symmetries, new vector-like supermultiplets with
non-standard SU(2)xU(1) assignments, and extended Higgs sectors. We briefly
comment on some of these possibilities, and discuss in more detail the class of
extensions of the MSSM involving an additional standard model singlet field.
The latter provides a solution to the problem, and allows significant
modifications of the MSSM in the Higgs and neutralino sectors, with important
consequences for collider physics, cold dark matter, and electroweak
baryogenesis.Comment: 17 pages, 5 figures. To appear in New Journal of Physic
CP Violation in Supersymmetric U(1)' Models
The supersymmetric CP problem is studied within superstring-motivated
extensions of the MSSM with an additional U(1)' gauge symmetry broken at the
TeV scale. This class of models offers an attractive solution to the mu problem
of the MSSM, in which U(1)' gauge invariance forbids the bare mu term, but an
effective mu parameter is generated by the vacuum expectation value of a
Standard Model singlet S which has superpotential coupling of the form SH_uH_d
to the electroweak Higgs doublets. The effective mu parameter is thus
dynamically determined as a function of the soft supersymmetry breaking
parameters, and can be complex if the soft parameters have nontrivial
CP-violating phases. We examine the phenomenological constraints on the
reparameterization invariant phase combinations within this framework, and find
that the supersymmetric CP problem can be greatly alleviated in models in which
the phase of the SU(2) gaugino mass parameter is aligned with the soft
trilinear scalar mass parameter associated with the SH_uH_d coupling. We also
study how the phases filter into the Higgs sector, and find that while the
Higgs sector conserves CP at the renormalizable level to all orders of
perturbation theory, CP violation can enter at the nonrenormalizable level at
one-loop order. In the majority of the parameter space, the lightest Higgs
boson remains essentially CP even but the heavier Higgs bosons can exhibit
large CP-violating mixings, similar to the CP-violating MSSM with large mu
parameter.Comment: 29 pp, 3 figs, 2 table
Modular Cosmology
An exploratory study of the cosmology of moduli in string theory. Moduli are
argued to be natural inflaton fields and lead to a robust inflationary
cosmology in which inflation takes place at the top of domain walls. The
amplitude of microwave background fluctuations constrains the dynamics
responsible for inflation to take place at a higher scale than supersymmetry
breaking. Models explaining this difference in scales and also preventing the
dilaton from running to infinity are proposed. The problem of dilaton
domination of the energy density of the universe is not resolved.Comment: harvmac, 37 pages, 3 figures as a separate uuencoded tar fil
Time Variation of the Fine Structure Constant Driven by Quintessence
There are indications from the study of quasar absorption spectra that the
fine structure constant may have been measurably smaller for redshifts
Analyses of other data (Sm fission rate for the Oklo natural
reactor, variation of Re -decay rate in meteorite studies,
atomic clock measurements) which probe variations of in the more
recent past imply much smaller deviations from its present value. In this work
we tie the variation of to the evolution of the quintessence field
proposed by Albrecht and Skordis, and show that agreement with all these data,
as well as consistency with WMAP observations, can be achieved for a range of
parameters. Some definite predictions follow for upcoming space missions
searching for violations of the equivalence principle.Comment: Final version, to be published in Phys Rev
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