137 research outputs found

### Constraints on models with universal extra dimensions from dilepton searches at the LHC

Models with universal extra dimensions predict that each Standard Model
particle is accompanied by a tower of Kaluza-Klein resonances. Canonical
searches for the production and cascade decays of first Kaluza-Klein modes
through missing transverse momentum signatures suffer in general from low
detection efficiencies because of the rather compressed Kaluza-Klein particle
mass spectrum. Here, instead we analyze signatures from the production of
second Kaluza-Klein states which can decay into Standard Model particles and
thus do not result in any missing transverse momentum. Such signatures provide
a strong sensitivity, and are of particular interest as they would allow for a
clear distinction between extra dimension models and other models of new
physics like supersymmetry. We constrain the production of second Kaluza-Klein
particles from recent LHC searches for dilepton resonances, and place limits on
the compactification scale to be larger than 715GeV, and on the masses of the
second Kaluza-Klein particles to be larger than 1.4TeV.Comment: 11 pages, 4 figures, analysis updated (inclusion of data from
CMS-PAS-EXO-12-061), MUED bound improved to R^{-1} > 715 GeV, version
published in JHE

### A composite scalar hint from di-boson resonances?

We study the light scalar resonance sector of a composite Higgs model UV
embedding based on the coset $SU(4)/Sp(4)$. Beyond the Higgs multiplet, the
pseudo Nambu-Goldstone sector of this model contains Standard Model singlets
which couple to the Standard Model gauge bosons through Wess-Zumino-Witten
anomaly terms. They can thus be produced in gluon fusion and decay into either
gluons or pairs of electroweak gauge bosons $WW$, $ZZ$, $Z\gamma$, or
$\gamma\gamma$. In this letter we show that one of the pseudo Nambu-Goldstone
boson states has appropriate couplings in order to explain a di-boson excess in
the $WW$ channel whilst not being excluded by LHC run I bounds on the di-jet,
$Z\gamma$ and $\gamma\gamma$ decay channels. A di-boson resonance production
cross section of $\sim$ 10 fb at LHC run I is not a prediction of the model,
but can be obtained if the confining gauge group is of high rank.Comment: 5 pages, 3 figures, 2 table

### Pseudo-Goldstones from Supersymmetric Wilson Lines on 5D Orbifolds

We consider a U(1) gauge theory on the five dimensional orbifold
$\mathcal{M}_4\times S^1/Z_2$, where $A_5$ has even $Z_2$ parity. This leads to
a light pseudoscalar degree of freedom $W(x)$ in the effective 4D theory below
the compactification scale arising from a gauge-invariant brane-to-brane Wilson
line. As noted by Arkani-Hamed et al in the non-supersymmetric $S^1$ case the
5D bulk gauge-invariance of the underlying theory together with the non-local
nature of the Wilson line field leads to the protection of the 4D theory of
$W(x)$ from possible large global-symmetry violating quantum gravitational
effects. We study the $S^1/Z_2$ theory in detail, in particular developing the
supersymmetric generalization of this construction, involving a pseudoscalar
Goldstone field (the `axion') and its scalar and fermion superpartners
(`saxion' and `axino'). The global nature of $W(x)$ implies the absence of
independent Kaluza-Klein excitations of its component fields. The
non-derivative interactions of the (supersymmetric) Wilson line in the
effective 4D theory arising from U(1) charged 5D fields $\Phi$ propagating
between the boundary branes are studied. We show that, similar to the
non-supersymmetric $S^1$ case, these interactions are suppressed by $\exp(-\pi
R m_{\Phi})$ where $\pi R$ is the size of the extra dimension.Comment: LaTex, 16 page

### 126 GeV Higgs in Next-to-Minimal Universal Extra Dimensions

Discovery of a Higgs boson and precise measurements of its properties open a
new window to test physics beyond the standard model. Models with Universal
Extra Dimensions are not exception. Kaluza-Klein excitations of the standard
model particles contribute to the production and decay of the Higgs boson. In
particular, the parameters associated with third generation quarks are
constrained by Higgs data, which are relatively insensitive to other searches
often involving light quarks and leptons. We investigate implications of the
126 GeV Higgs in Next-to-Minimal Universal Extra Dimensions, and show that
boundary terms and bulk masses allow a lower compactification scale as compared
to in Minimal Universal Extra Dimensions.Comment: 12 pages, 4 figure

### Constraints on split-UED from Electroweak Precision Tests

We present strongly improved electroweak precision constraints on the
split-UED model. We find that the dominating effect arises from contributions
to the muon decay rate by the exchange of even-numbered W-boson Kaluza-Klein
modes at tree-level, which so far have not been discussed in the context of UED
models. The constraints on the split-UED parameter space are translated into
bounds on the mass difference of the first Kaluza-Klein mode of fermions and
the lightest Kaluza-Klein mode, which will be tested is the LHC.Comment: 4 pages, 2 figure

### Warped Axions

We study a number of realizations of axions existing in a multi-`throat'
generalization of the warped throat geometry of a Randall-Sundrum slice of
$AdS_5$. As argued by previous authors, the problem of generating a suitable,
phenomenologically allowed Peccei-Quinn scale is simply and elegantly solved by
the warping. In compactifications with two or more throats it is possible to
simultaneously solve the Standard Model hierarchy problem by the
Randall-Sundrum mechanism while implementing interesting warped axion models.
The constructions discussed are related to holographic duals of previously
studied models of composite axions arising from strongly coupled
four-dimensional dynamics.Comment: 14 pages, 1 figure, references adde

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