547 research outputs found
Continuum Superpartners
In an exact conformal theory there is no particle. The excitations have
continuum spectra and are called "unparticles" by Georgi. We consider
supersymmetric extensions of the Standard Model with approximate conformal
sectors. The conformal symmetry is softly broken in the infrared which
generates a gap. However, the spectrum can still have a continuum above the gap
if there is no confinement. Using the AdS/CFT correspondence this can be
achieved with a soft wall in the warped extra dimension. When supersymmetry is
broken the superpartners of the Standard Model particles may simply be a
continuum above gap. The collider signals can be quite different from the
standard supersymmetric scenarios and the experimental searches for the
continuum superpartners can be very challenging.Comment: 15 pages, 5 figures, talk at SCGT09 Workshop, Nagoya, Japan, 8-11
Dec, 200
The AdS/CFT/Unparticle Correspondence
We examine the correspondence between the anti-de Sitter (AdS) description of
conformal field theories (CFTs) and the unparticle description of CFTs. We show
how unparticle actions are equivalent to holographic boundary actions for
fields in AdS, and how massive unparticles provide a new type of infrared
cutoff that can be simply implemented in AdS by a soft breaking of conformal
symmetry. We also show that processes involving scalar unparticles with
dimensions d_s<2 or fermion unparticles with dimensions d_f<5/2 are insensitive
to ultraviolet cutoff effects. Finally we show that gauge interactions for
unparticles can be described by bulk gauge interactions in AdS and that they
correspond to minimal gauging of the non-local effective action, and we compute
the fermion unparticle production cross-section.Comment: 26 pages, 1 figur
Top and Bottom: a Brane of Their Own
We consider extra dimensional descriptions of models where there are two
separate strongly interacting sectors contributing to electroweak symmetry
breaking (``topcolor'' type models). In the extra dimensional picture there
would be two separate (anti-de Sitter) bulks meeting on the Planck brane, with
each bulk having its own corresponding IR (TeV) brane. Sources for electroweak
symmetry breaking can then be localized on both of these IR branes, while the
different generations of fermions may be separated from each other. We describe
the modes propagating in such a setup, and consider the cases where the
electroweak symmetry breaking on either of the two IR branes come either from a
higgsless scenario (via boundary conditions) or a (top-)Higgs. We show that the
tension that exists between obtaining a large top quark mass and the correct
value of the Zb\bar{b} couplings in ordinary higgsless models can be largely
relieved in the higgsless--top-Higgs versions of the two IR brane models. This
may also be true in the purely higgsless--higgsless case, however since that
model is necessarily in the strongly coupled regime the tree-level results for
the properties of the third generation may get large corrections. A necessary
consequence of such models is the appearance of additional pseudo-Goldstone
bosons (``top-pions''), which would be strongly coupled to the third
generation.Comment: 34 pages, LaTeX, 6 figures. v2: figure 2 fixed, footnote, comments
and references adde
Catalysis by alkali and alkaline-earth metal ions in nucleophilic attack of methoxide ion on crown ethers bearing an intra-annular acetoxy group
Rates of reaction of methoxide ion with crown ethers bearing an intra-annular acetoxy group are markedly enhanced by alkali and alkaline-earth metal bromides as a result of much stronger interactions of the metal ions with transition states than with reactants.\ud
\ud
Rates of reactions of methoxide ion with crown ethers bearing an intra-annular acetoxy group markedly enhanced by alkali and alkaline-earth metal bromides as a result of much stronger interactions of the metal ion with transition state than with reactants
Dimensions of Supersymmetric Operators from AdS/CFT
We examine the AdS/CFT correspondence through a manifestly 5D supersymmetric
formalism, corresponding to a 4D N=1 supersymmetric CFT. We find that the
dimensions of scalar and fermionic component operators are simply related, and
that there is a smooth transition of scalar operator dimensions through the
value d_s = 2. By using this formalism, we also show that the formula used in
the string literature for the dimension of fermion operators is incomplete.Comment: 11 page
Composite Higgs Sketch
The coupling of a composite Higgs to the standard model fields can deviate
substantially from the standard model values. In this case perturbative
unitarity might break down before the scale of compositeness is reached, which
would suggest that additional composites should lie well below this scale. In
this paper we account for the presence of an additional spin 1 custodial
triplet of rhos. We examine the implications of requiring perturbative
unitarity up to the compositeness scale and find that one has to be close to
saturating certain unitarity sum rules involving the Higgs and the rho
couplings. Given these restrictions on the parameter space we investigate the
main phenomenological consequences of the spin 1 triplet. We find that they can
substantially enhance the Higgs di-photon rate at the LHC even with a reduced
Higgs coupling to gauge bosons. The main existing LHC bounds arise from
di-boson searches, especially in the experimentally clean channel where the
charged rhos decay to a W-boson and a Z, which then decay leptonically. We find
that a large range of interesting parameter space with 700 GeV < m(rho) < 2 TeV
is currently experimentally viable.Comment: 37 pages, 12 figures; v4: sum rule corrected, conclusions unchange
Breaking the electroweak symmetry and supersymmetry by a compact extra dimension
We revisit in some more detail a recent specific proposal for the breaking of
the electroweak symmetry and of supersymmetry by a compact extra dimension.
Possible mass terms for the Higgs and the matter hypermultiplets are considered
and their effects on the spectrum analyzed. Previous conclusions are reinforced
and put on firmer ground.Comment: 25 pages, LaTeX, 9 eps figure
Curing the Ills of Higgsless Models: the S Parameter and Unitarity
We consider various constraints on Higgsless models of electroweak symmetry
breaking based on a bulk SU(2)_L x SU(2)_R x U(1)_{B-L} gauge group in warped
space. First we show that the S parameter which is positive if fermions are
localized on the Planck brane can be lowered (or made vanishing) by changing
the localization of the light fermions. If the wave function of the light
fermions is almost flat their coupling to the gauge boson KK modes will be
close to vanishing, and therefore contributions to the S parameter will be
suppressed. At the same time the experimental bounds on such Z' and W' gauge
bosons become very weak, and their masses can be lowered to make sure that
perturbative unitarity is not violated in this theory before reaching energies
of several TeV. The biggest difficulty of these models is to incorporate a
heavy top quark mass without violating any of the experimental bounds on bottom
quark gauge couplings. In the simplest models of fermion masses a sufficiently
heavy top quark also implies an unacceptably large correction to the Zb\bar{b}
vertex and a large splitting between the KK modes of the top and bottom quarks,
yielding large loop corrections to the T-parameter. We present possible
directions for model building where perhaps these constraints could be obeyed
as well.Comment: 21 pages, LaTeX, 5 figures. References and acknowledgements adde
The Universal Real Projective Plane: LHC phenomenology at one Loop
The Real Projective Plane is the lowest dimensional orbifold which, when
combined with the usual Minkowski space-time, gives rise to a unique model in
six flat dimensions possessing an exact Kaluza Klein (KK) parity as a relic
symmetry of the broken six dimensional Lorentz group. As a consequence of this
property, any model formulated on this background will include a stable Dark
Matter candidate. Loop corrections play a crucial role because they remove mass
degeneracy in the tiers of KK modes and induce new couplings which mediate
decays. We study the full one loop structure of the corrections by means of
counter-terms localised on the two singular points. As an application, the
phenomenology of the (2,0) and (0,2) tiers is discussed at the LHC. We identify
promising signatures with single and di-lepton, top antitop and 4 tops: in the
dilepton channel, present data from CMS and ATLAS may already exclude KK masses
up to 250 GeV, while by next year they may cover the whole mass range preferred
by WMAP data.Comment: 45 pages, 3 figure
Mass-Matching in Higgsless
Modern extra-dimensional Higgsless scenarios rely on a mass-matching between
fermionic and bosonic KK resonances to evade constraints from precision
electroweak measurements. After analyzing all of the Tevatron and LEP bounds on
these so-called Cured Higgsless scenarios, we study their LHC signatures and
explore how to identify the mass-matching mechanism, the key to their
viability. We find singly and pair produced fermionic resonances show up as
clean signals with 2 or 4 leptons and 2 hard jets, while neutral and charged
bosonic resonances are visible in the dilepton and leptonic WZ channels,
respectively. A measurement of the resonance masses from these channels shows
the matching necessary to achieve . Moreover, a large single
production of KK-fermion resonances is a clear indication of compositeness of
SM quarks. Discovery reach is below 10 fb of luminosity for resonances
in the 700 GeV range.Comment: 28 pages, 18 figure
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