421 research outputs found
Dark matter clues in the muon anomalous magnetic moment
We study the possibility to explain the non-baryonic dark matter abundance
and improve the present fits on the muon anomalous magnetic moment through the
same new physics. The only viable way to solve simultaneously both problems
which is known to date is by using supersymmetric theories. However in this
work we show that massive brane fluctuations (branons) in large
extra-dimensions models can provide a more economical alternative to
supersymmetry. This is so because the low-energy branon physics depends
effectively on only three parameters. Next collider experiments, such as LHC or
ILC, will be sensitive to branon phenomenology in the natural parameter region
where the theory is able to account for the two effects.Comment: 4 pages, 3 figures, REVTeX
Applicability constraints of the Equivalence Theorem
In this work we study the applicability of the Equivalence Theorem, either
for unitary models or within an effective lagrangian approach. There are two
types of limitations: the existence of a validity energy window and the use of
the lowest order in the electroweak constants. For the first kind, we consider
some methods, based on dispersion theory or the large limit, that allow us
to extend the applicability. For the second, we have obtained numerical
estimates of the effect of neglecting higher orders in the perturbative
expansion.Comment: Final version to appear in Phys. Rev. D. Power counting and energy
range estimates have been refined, improved referencing. 4 postscript
figures, uses revtex. FT-UCM 1/9
Branon radiative corrections to collider physics and precision observables
In the context of brane-world scenarios, we study the effects produced by the
exchange of virtual massive branons. A one-loop calculation is performed which
generates higher-dimensional operators involving SM fields suppressed by powers
of the brane tension scale. We discuss constraints on this scenario from
colliders such as HERA, LEP and Tevatron and prospects for future detections at
LHC or ILC. The most interesting phenomenology comes from new four-particles
vertices induced by branon radiative corrections, mainly from four fermion
interactions. The presence of flexible branes modifies also the muon anomalous
magnetic moment and the electroweak precision observables.Comment: 23 pages, 4 figures, LaTe
LHC sensitivity to the resonance spectrum of a minimal strongly interacting electroweak symmetry breaking sector
We present a unified analysis of the two main production processes of vector
boson pairs at the LHC, VV-fusion and qqbar annihilation, in a minimal strongly
interacting electroweak symmetry breaking sector. Using a unitarized
electroweak chiral Lagrangian formalism and modeling the final V_L V_L strong
rescattering effects by a form factor, we describe qqbar annihilation processes
in terms of the two chiral parameters that govern elastic V_L V_L scattering.
Depending on the values of these two chiral parameters, the unitarized
amplitudes may present resonant enhancements in different angular
momentum-isospin channels. Scanning this two parameter space, we generate the
general resonance spectrum of a minimal strongly interacting electroweak
symmetry breaking sector and determine the regions that can be probed at the
LHC.Comment: Final version to appear in Phys. Rev. D, including a more detailed
exposition and a few more references. Conclusions and results unchanged. 14
pages, 5 figure
A global fit of and elastic scattering in ChPT with dispersion relations
We apply the one-loop results of the ChPT suplemented
with the inverse amplitude method to fit the available experimental data on
and scattering. With esentially only three parameters we
describe accurately data corresponding to six different channels, namely
and . In addition we
reproduce the first resonances of the and channel with the
right mass corresponding to the and the particles.Comment: 19 pages, 5 figures available on request, FT/UCM/10/9
Some model-independent phenomenological consequences of flexible brane worlds
In this work we will review the main properties of brane-world models with
low tension. Starting from very general principles, it is possible to obtain an
effective action for the relevant degrees of freedom at low energies (branons).
Using the cross sections for high-energy processes involving branons, we set
bounds on the different parameters appearing in these models. We also show that
branons provide a WIMP candidate for dark matter in a natural way. We consider
cosmological constraints on its thermal and non-thermal relic abundances. We
derive direct detection limits and compare those limits with the preferred
parameter region in the case in which the EGRET excess in the diffuse galactic
gamma rays is due to dark matter annihilation. Finally we will discuss the
constraints coming from the precision tests of the Standard Model and the muon
anomalous magnetic moment.Comment: 10 pages, 6 figures. Contribution to the Proceedings of the Second
International Conference on Quantum Theories and Renormalization Group in
Gravity and Cosmology, IRGAC 2006, Barcelona, 11-15 July, 200
- âŠ