1,690 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

### B Decays in an Asymmetric Left-Right Model

Motivated by recently observed disagreements with the SM predictions in $B$
decays, we study $b \to d, s$ transitions in an asymmetric class of $SU(2)_L
\times SU(2)_R \times U(1)_{B-L}$ models, with a simple one-parameter structure
of the right handed mixing matrix for the quarks, which obeys the constraints
from kaon physics. We use experimental constraints on the branching ratios of
$b \to s \gamma$, $b \to c e {\bar \nu}_e$, and $B_{d,s}^0 -\bar{B}^0_{d,s}$
mixing to restrict the parameters of the model: $\displaystyle {g_R}/{g_L},
M_{W_2}, M_{H^\pm}, \tan \beta$ as well as the elements of the right-handed
quark mixing matrix $V^R_{CKM}$. We present a comparison with the more commonly
used (manifest) left-right symmetric model. Our analysis exposes the parameters
most sensitive to $b$ transitions and reveals a large parameter space where
left- and right-handed quarks mix differently, opening the possibility of
observing marked differences in behaviour between the standard model and the
left-right model.Comment: 32 pages and 8 figure

### Constraints on the mass and mixing of Z' bosons

We tested several models in which the Standard Model (SM) gauge group is
extended by an additional U(1) gauge symmetry, against available electroweak
precision data to impose limits on the mass of the neutral Z' boson, M_Z',
predicted in all such models, and on the Z-Z' mixing angle, theta_ZZ', at 95%
C.L. We found lower limits on M_Z' of order 1 TeV in most cases, while
theta_ZZ' was found to be constrained to very small values.Comment: Format fixed, 5 pages, 2 figures, Talk given at the 17th
International Conference on Supersymmetry and the Unification of Fundamental
Interactions (SUSY09), Boston, MA, USA, 5-10 June 2009, to be published in
the conference proceedings (AIP

### Blowing-Up the Four-Dimensional Z_3 Orientifold

We study the blowing-up of the four-dimensional Z_3 orientifold of
Angelantonj, Bianchi, Pradisi, Sagnotti and Stanev (ABPSS) by giving nonzero
vacuum expectation values (VEV's) to the twisted sector moduli blowing-up
modes. The blowing-up procedure induces a Fayet-Iliopoulos (FI) term for the
``anomalous'' U(1), whose magnitude depends linearly on the VEV's of the
blowing-up modes. To preserve the N=1 supersymmetry, non-Abelian matter fields
are forced to acquire nonzero VEV's, thus breaking (some of) the non-Abelian
gauge structure and decoupling some of the matter fields. We determine the form
of the FI term, construct explicit examples of (non-Abelian) D and F flat
directions, and determine the surviving gauge groups of the restabilized vacua.
We also determine the mass spectra, for which the restabilization reduces the
number of families.Comment: 19 pages, Late

### Z' Searches: From Tevatron to LHC

The CDF collaboration has set lower limits on the masses of the Z' bosons
occurring in a range of E_6 GUT based models. We revisit their analysis and
extend it to certain other E_6 scenarios as well as to some general classes of
models satisfying the anomaly cancellation conditions, which are not included
in the CDF analysis. We also suggest a Bayesian statistical method for finding
exclusion limits on the Z' mass, which allows one to explore a wide range of
the U(1)' gauge coupling parameter. This method also takes into account the
effects of interference between the Z' and the SM gauge bosons.Comment: 5 pages. Talk given at the XXIInd Rencontres de Blois, Loire, France,
16-20 July 201

### Physics Implications of Precision Electroweak Experiments

A brief review is given of precision electroweak physics, and its implications for establishing the standard model and constraining the possibilities for new physics at the TeV scale and beyond

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