10 research outputs found
The specificity of searches for , and coming from extra dimensions
We discuss the specificity of searches for hypothetical ,
and bosons at hadron colliders in single top
quark and production and Drell-Yan processes assuming these
particles to be the Kaluza-Klein excitations of the gauge bosons of the
Standard Model. In this case any process mediated by is also mediated by
the whole KK tower of its excitations, whereas to the processes mediated by
and there is not only a contribution from their KK towers, but also
from that of the graviton. The contributions of the towers above ,
and and above the first excitation of the
graviton are included with the help of effective four-fermion Lagrangians. We
compute the cross-sections of these processes taking into account the
contributions of the Standard Model gauge bosons, of their first KK modes and
of the corresponding KK towers and discuss the impact of the interference
between them. For pp-collisions at the LHC with the center of mass energy 14
TeV we found specific changes of the distribution tails due to the interference
effects. Such a modification of distribution tails is characteristic for the
processes mediated by particles coming from extra dimensions and should always
be taken into account when looking for them.Comment: 14 pages, 12 figures, LaTeX. References added, figures added, text
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A non-standard matter distribution in the RS1 model and the coupling constant of the radion
In the zero mode approximation we solve exactly the equations of motion for
linearized gravity in the Randall-Sundrum model with a non-standard
distribution of matter in the neighbourhood of the negative tension brane. It
is shown that the form of this distribution can strongly affect the coupling of
the radion to matter. We believe that such a situation can arise in models with
a realistic mechanisms of matter localization.Comment: 12 pages, LaTe
Effective Lagrangians for physical degrees of freedom in the Randall-Sundrum model
We derive the second variation Lagrangian of the Randall-Sundrum model with
two branes, study its gauge invariance and diagonalize it in the unitary gauge.
We also show that the effective four-dimensional theory looks different on
different branes and calculate the observable mass spectra and the couplings of
the physical degrees of freedom of 5-dimensional gravity to matter.Comment: 22 pages, LaTeX, typos correcte
Braneworlds in six dimensions: new models with bulk scalars
Six dimensional bulk spacetimes with 3-- and 4--branes are constructed using
certain non--conventional bulk scalars as sources. In particular, we
investigate the consequences of having the phantom (negative kinetic energy)
and the Brans--Dicke scalar in the bulk while obtaining such solutions. We find
geometries with 4--branes with a compact on--brane dimension (hybrid
compactification) which may be assumed to be small in order to realize a
3--brane world. On the other hand, we also construct, with similar sources,
bulk spacetimes where a 3--brane is located at a conical singularity.
Furthermore, we investigate the issue of localization of matter fields (scalar,
fermion, graviton, vector) on these 3-- and 4--branes and conclude with
comments on our six dimensional models.Comment: 24 pages, 1 figure, Replaced to match version published in Class.
Quant. Gra
Linearized gravity on the Randall-Sundrum two-brane background with curvature terms in the action for the branes
We study gravitational perturbations in the Randall-Sundrum two-brane
background with scalar-curvature terms in the action for the branes, allowing
for positive as well as negative bulk gravitational constant. In the zero-mode
approximation, we derive the linearized gravitational equations, which have the
same form as in the original Randall-Sundrum model but with different
expressions for the effective physical constants. We develop a generic method
for finding tachyonic modes in the theory, which, in the model under
consideration, may exist only if the bulk gravitational constant is negative.
In this case, if both brane gravitational constants are nonzero, the theory
contains one or two tachyonic mass eigenvalues in the gravitational sector. If
one of the brane gravitational constants is set to zero, then either a single
tachyonic mass eigenvalue is present or tachyonic modes are totally absent
depending on the relation between the nonzero brane gravitational constant and
brane separation. In the case of negative bulk gravitational constant, the
massive gravitational modes have ghost-like character, while the massless
gravitational mode is not a ghost in the case where tachyons are absent.Comment: 23 pages, revtex, published versio
Gravity in a stabilized brane world model in five-dimensional Brans-Dicke theory
Linearized equations of motion for gravitational and scalar fields are found
and solved in a stabilized brane world model in five-dimensional Brans-Dicke
theory. The physical degrees of freedom are isolated, the mass spectrum of
Kaluza-Klein excitations is found and the coupling constants of these
excitations to matter on the negative tension brane are calculated.Comment: 12 pages, LaTe
Searches for W' and Z' in models with large extra dimensions
Characteristic features of processes mediated by gauge bosons are discussed
in the framework of theories with large extra dimensions. It is shown that if
gauge bosons propagate in the bulk, then there arises a destructive
interference not only between W and W' (or Z and Z'), but also between W' and
Z' and the Kaluza-Klein towers of higher excitations of W and Z bosons
respectively. Specific calculations are made and plotted for the LHC with the
center of mass energy 14 TeV.Comment: 7 pages, 4 figures, added reference, corrected misprints. Talk given
at 16th International Seminar on High Energy Physics "QUARKS-2010", Kolomna,
Russia, 6-12 June, 2010. To appear in Theor. Math. Phy