89 research outputs found
Signature of Randall-Sundrum Quantum Gravity model in scattering in the TeV range
We examine the implications of the Randall-Sundrum gravity models on
scattering in the TeV range.Comment: 7 pages, 4 figure
Neutrino lensing and modification of Newtonian gravity at large distances
The nature of the modification to neutrino lensing from galaxies, as caused
by possible modifications to Newtonian gravity at large distances, is studied.Comment: 6 pages, 1 figur
Black Hole Production at LHC: String Balls and Black Holes from pp and Lead-lead Collisions
If the fundamental planck scale is near a TeV, then parton collisions with
high enough center-of-mass energy should produce black holes. The production
rate for such black holes at LHC has been extensively studied for the case of a
proton-proton collision. In this paper, we extend this analysis to a lead-lead
collision at LHC. We find that the cross section for small black holes which
may in principle be produced in such a collision is either enhanced or
suppressed, depending upon the black hole mass. For example, for black holes
with a mass around 3 TeV we find that the differential black hole production
cross section, d\sigma/dM, in a typical lead-lead collision is up to 90 times
larger than that for black holes produced in a typical proton-proton collision.
We also discuss the cross-sections for `string ball' production in these
collisions. For string balls of mass about 1 (2) TeV, we find that the
differential production cross section in a typical lead-lead collision may be
enhanced by a factor up to 3300 (850) times that of a proton-proton collision
at LHC.Comment: Added some discussion, final version to appear in Phys. Rev. D (rapid
communications
Kaluza-Klein Structure Associated With Fat Brane
It is known that the imposition of orbifold boundary conditions on background
scalar field can give rise to a non-trivial vacuum expectation value (VEV)
along extra dimensions, which in turn generates fat branes and associated
unconventional Kaluza-Klein (KK) towers of fermions. We study the structure of
these KK towers in the limit of one large extra dimension and show that
normalizable (bound) states of massless and massive fermions can exist at both
orbifold fixed points. Closer look however indicates that orbifold boundary
conditions act to suppress at least half of bound KK modes, while periodic
boundary conditions tend to drive the high-lying modes to the conventional
structure. By investigating the scattering of fermions on branes, we
analytically compute masses and wavefunctions of KK spectra in the presence of
these boundary conditions up to one-loop level. Implication of KK-number
non-conservation couplings on the Coulomb potential is also examined.Comment: RevTex4, 29 pages, 7 ps figures, new references adde
Possible Z-width probe of a "brane-world" scenario for neutrino masses
The possibility that the accurately known value of the Z width might furnish
information about the coupling of two neutrinos to the Majoron (Nambu-Goldstone
boson of spontaneous lepton number violation) is proposed and investigated in
detail. Both the "ordinary" case and the case in which one adopts a "brane"
world picture with the Majoron free to travel in extra dimensions are studied.
Bounds on the dimensionless coupling constants are obtained, allowing for any
number of extra dimensions and any intrinsic mass scale. These bounds may be
applied to a variety of different Majoron models. If a technically natural
see-saw model is adopted, the predicted coupling constants are far below these
upper bounds. In addition, for this natural model, the effect of extra
dimensions is to decrease the predicted partial Z width, the increase due to
many Kaluza-Klein excitations being compensated by the decrease of their common
coupling constant.Comment: RevTeX, 12 pages, 3 figure
Modeling phase behavior for quantifying micro-pervaporation experiments
We present a theoretical model for the evolution of mixture concentrations in
a micro-pervaporation device, similar to those recently presented
experimentally. The described device makes use of the pervaporation of water
through a thin PDMS membrane to build up a solute concentration profile inside
a long microfluidic channel. We simplify the evolution of this profile in
binary mixtures to a one-dimensional model which comprises two
concentration-dependent coefficients. The model then provides a link between
directly accessible experimental observations, such as the widths of dense
phases or their growth velocity, and the underlying chemical potentials and
phenomenological coefficients. It shall thus be useful for quantifying the
thermodynamic and dynamic properties of dilute and dense binary mixtures.Comment: to be published in EPJ-
Hierarchical Neutrino Mass Matrices, CP violation and Leptogenesis
In this work we study examples of hierarchical neutrino mass matrices
inspired by family symmetries, compatible with experiments on neutrino
oscillations, and for which there is a connection among the low energy CP
violation phase associated to neutrino oscillations, the phases appearing in
the amplitude of neutrinoless double beta decay, and the phases relevant for
leptogenesis. In particular, we determine the predictions from a texture based
on an underlying SU(3) family symmetry together with a GUT symmetry, and a
strong hierarchy for the masses of the heavy right handed Majorana masses. We
also give some examples of inverted hierarchies of neutrino masses, which may
be motivated in the context of U(1) family symmetries.Comment: 34 pages. Replaced with published version -typos, corrections and
references adde
Field localization in warped gauge theories
We present four-dimensional gauge theories that describe physics on
five-dimensional curved (warped) backgrounds, which includes bulk fields with
various spins (vectors, spinors, and scalars). Field theory on the AdS
geometry is examined as a simple example of our formulation. Various properties
of bulk fields on this background, e.g., the mass spectrum and field
localization behavior, can be achieved within a fully four-dimensional
framework. Moreover, that gives a localization mechanism for massless vector
fields. We also consider supersymmetric cases, and show in particular that the
conditions on bulk masses imposed by supersymmetry on warped backgrounds are
derived from a four-dimensional supersymmetric theory on the flat background.
As a phenomenological application, models are shown to generate hierarchical
Yukawa couplings. Finally, we discuss possible underlying mechanisms which
dynamically realize the required couplings to generate curved geometries.Comment: 24 pages, 12 figures; more explanation of nonuniversal gauge
couplings added, typos corrected, references update
Vacuum Stability Higgs Mass Bound Revisited with Implications for Extra Dimension Theories
We take the standard model to be an effective theory including higher
dimensional operators suppressed by scale and re-examine the higgs
mass bounds from the requirements of vacuum stability. Our results show that
the effects of the higher dimensional operators on the higgs mass limits are
significant. As an implication of our results, we study the vacuum stability
higgs mass bounds in theories with extra dimensions.Comment: Latex, 14 pages, 1 figure. Added references. To appear in Phys. Rev.
Neutrinoless Double Beta Decay from Singlet Neutrinos in Extra Dimensions
We study the model-building conditions under which a sizeable
-decay signal to the recently reported level of~0.4 eV is due
to Kaluza--Klein singlet neutrinos in theories with large extra dimensions. Our
analysis is based on 5-dimensional singlet-neutrino models compactified on an
orbifold, where the Standard--Model fields are localized on a
3-brane. We show that a successful interpretation of a positive signal within
the above minimal 5-dimensional framework would require a non-vanishing shift
of the 3-brane from the orbifold fixed points by an amount smaller than the
typical scale (100 MeV) characterizing the Fermi nuclear momentum. The
resulting 5-dimensional models predict a sizeable effective Majorana-neutrino
mass that could be several orders of magnitude larger than the light neutrino
masses. Most interestingly, the brane-shifted models with only one bulk sterile
neutrino also predict novel trigonometric textures leading to mass scenarios
with hierarchical active neutrinos and large - and
- mixings that can fully explain the current atmospheric and
solar neutrino data.Comment: 33 pages, LaTeX, minor rewordings, references adde
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