108 research outputs found
Legal architecture and design for Gulf Cooperation Council economic integration
The Cooperation Council for the Arab States of the Gulf (GCC) is generally regarded as a success story for economic integration in Arab countries. The idea of regional integration gained ground when the GCC Charter was signed. The Charter envisioned a closer economic relationship between member states. Although economic integration among GCC member states is an ambitious step in the right direction, there are gaps and challenges ahead. The best way to address the gaps and challenges that exist in formulating integration processes in the GCC is to start with a clear set of rules and put the necessary mechanisms in place. Integration attempts must also exhibit a high level of commitment in order to deflect dynamics of disintegration that have all too often frustrated meaningful integration in Arab countries. At present the rules of GCC regarding governance structure, dispute resolution mechanism, relationship with the WTO, and accession of new members are not detailed. If the GCC can address these issues, it could become an economic powerhouse within Arab countries and even Asia
Finding Z' bosons coupled preferentially to the third family at CERN LEP and the Fermilab Tevatron
Z' bosons that couple preferentially to the third generation fermions can
arise in models with extended weak (SU(2)xSU(2)) or hypercharge (U(1)xU(1))
gauge groups. We show that existing limits on quark-lepton compositeness set by
the LEP and Tevatron experiments translate into lower bounds of order a few
hundred GeV on the masses of these Z' bosons. Resonances of this mass can be
directly produced at the Tevatron. Accordingly, we explore in detail the limits
that can be set at Run II using the process p pbar -> Z' -> tau tau -> e mu. We
also comment on the possibility of using hadronically-decaying taus to improve
the limits.Comment: LaTeX2e, 24 pages (including title page), 13 figures; version 2:
corrected typographical errors and bad figure placement; version 3: added
references and updated introduction; version 4: changes to compensate for old
latex version on arXiv server; version 5: additional references, and embedded
fonts in eps files for PRD; version 6: corrected some minor typos to address
PRD referee's comment
The structure of electroweak corrections due to extended gauge symmetries
This paper studies models with extended electroweak gauge sectors of the form
SU(2) x SU(2) x U(1) x [SU(2) or U(1)]. We establish the general behavior of
corrections to precision electroweak observables in this class of theories and
connect our results to previous work on specific models whose electroweak
sectors are special cases of our extended group.Comment: 18 pages, 2 figures; added a referenc
Probing anomalous top quark interactions at the Fermilab Tevatron Collider
We study the effects of dimension-six operators contributing to the vertex in top quark pair production at the Tevatron collider. We derive both
the limits from Run 1 data and the potential bounds from future runs (Run 2 and
3). Although the current constraints are not very strong, the future runs are
quite effective in probing these operators. We investigate the possibility of
disentangling different operators with the invariant mass
distribution and the top quark polarization asymmetry. We also study the
effects of a different set of operators contributing to single top production
via the coupling. We derive the current and potential future bounds
on these anomalous operators and find that the upgraded Tevatron can improve
the existing constraints from for one of the operators.Comment: 20 pages, 2 figures, REVTEX, some clarifying remarks adde
New Supersymmetric Contributions to
We calculate the electroweak-like one-loop supersymmetric contributions to
the rare and flavor-violating decay of the top quark into a charm quark and a
gauge boson: , with . We consider loops of both charginos
and down-like squarks (where we identify and correct an error in the
literature) and neutralinos and up-like squarks (which have not been calculated
before). We also account for left-right and generational squark mixing. Our
numerical results indicate that supersymmetric contributions to can be
upto 5 orders of magnitude larger than their Standard Model counterparts.
However, they still fall short of the sensitivity expected at the
next-generation top-quark factories.Comment: 13 pages, LaTex, 1 figure included. Final version to appear in
Physical Review D. Chargino contribution dealt with in greater detail. Minor
revisions in tex
Beautiful Mirrors and Precision Electroweak Data
The Standard Model (SM) with a light Higgs boson provides a very good
description of the precision electroweak observable data coming from the LEP,
SLD and Tevatron experiments. Most of the observables, with the notable
exception of the forward-backward asymmetry of the bottom quark, point towards
a Higgs mass far below its current experimental bound. The disagreement, within
the SM, between the values for the weak mixing angle as obtained from the
measurement of the leptonic and hadronic asymmetries at lepton colliders, may
be taken to indicate new physics contributions to the precision electroweak
observables. In this article we investigate the possibility that the inclusion
of additional bottom-like quarks could help resolve this discrepancy. Two
inequivalent assignments for these new quarks are analysed. The resultant fits
to the electroweak data show a significant improvement when compared to that
obtained in the SM. While in one of the examples analyzed, the exotic quarks
are predicted to be light, with masses below 300 GeV, and the Higgs tends to be
heavy, in the second one the Higgs is predicted to be light, with a mass below
250 GeV, while the quarks tend to be heavy, with masses of about 800 GeV. The
collider signatures associated with the new exotic quarks, as well as the
question of unification of couplings within these models and a possible
cosmological implication of the new physical degrees of freedom at the weak
scale are also discussed.Comment: 21 pages, 4 embedded postscript figures, LaTeX. Two minor corrections
performe
Implications of texture 4 zero lepton mass matrices for U_{e3}
Lepton mass matrices similar to texture 4 zero quark mass matrices, known to
be quite successful in explaining the CKM phenomenology, have been considered
for finding the mixing matrix element U_{e3} (\equiv s_{13}) respecting the
CHOOZ constraint, with s_{12} and \Delta m_{12}^2 constrained by SNP and s_{23}
and \Delta m_{23}^2 constrained by ANP. Taking charged lepton mass matrix M_l
to be diagonal, we find that the ranges of s_{13} corresponding to different
SNP solutions very well include the corresponding values of s_{13} found by
Akhmedov et al. by considering neutrino mass matrix M_{\nu} with no texture
zeros. Considering M_l and M_{\nu} both to be real and non-diagonal, s_{13}
ranges for the four SNP solutions come out to be: \sim 0-0.19 (LMA),
0.038-0.093 (SMA), 0.042-0.095 (LOW), 0.038-0.096 (VO) which remain of the same
order when M_l and M_{\nu} are considered to be complex and non-diagonal.Comment: 13 pages, LaTe
Single Top Quark Production via FCNC Couplings at Hadron Colliders
We calculate single top-quark production at hadron colliders via the
chromo-magnetic flavor-changing neutral current couplings and . We find that the strength for the anomalous ()
coupling may be probed to () at the Tevatron with of data and
() at the LHC with of data. The two couplings may be
distinguished by a comparision of the single top signal with the direct top and
top decay signals for these couplings.Comment: 18 pages, 6 figures, 3 table
Flavor changing scalar couplings and production at hadron colliders
We calculate the contributions of the flavor changing scalar ()
couplings arised from topcolor-assisted technicolor () models at
tree-level to the and production at the Tevatron and
experiments. We find that the production cross sections are very small at the
Tevatron with , which is smaller than 5 fb in most of the
parameter space of models. However, the virtual effects of the
couplings on the production can be easily detected at the
with via the final state
().Comment: 10 pages,5 figure
On the phenomenology of a Z' coupling only to third-family fermions
The phenomenology of an additional U(1) neutral gauge boson Z' coupled to the
third family of fermions is discussed. One might expect such a particle to
contribute to processes where taus, b and t quarks are produced. Precision data
from LEP1 put severe constraints on the mixing and heavy-boson mass. We find
that the effects of such a particle could not be observed at hadronic
colliders, be it at the Tevatron or the LHC, because of the QCD background. At
LEP2 and future e^+e^- linear colliders, one could instead hope to observe such
effects, in particular for b\bar b final states.Comment: 36 pages, LaTeX, including 12 figure
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