3,862 research outputs found
Collider Phenomenology with Split-UED
We investigate the collider implications of Split Universal Extra Dimensions.
The non-vanishing fermion mass in the bulk, which is consistent with the
KK-parity, largely modifies the phenomenology of Minimal Universal Exta
Dimensions. We scrutinize the behavior of couplings and study the discovery
reach of the Tevatron and the LHC for level-2 Kaluza-Klein modes in the
dilepton channel, which would indicates the presence of the extra dimensions.
Observation of large event rates for dilepton resonances can result from a
nontrivial fermion mass profile along the extra dimensions, which, in turn, may
corroborate extra dimensional explanation for the observation of the positron
excess in cosmic rays.Comment: 23 pages, 15 figure
Extra Dimensions at the LHC
We discuss the motivation and the phenomenology of models with either flat or
warped extra dimensions. We describe the typical mass spectrum and discovery
signatures of such models at the LHC. We also review several proposed methods
for discriminating the usual low-energy supersymmetry from a model with flat
(universal) extra dimensions. (For the official website of the book, see
http://cambridge.org/us/catalogue/catalogue.asp?isbn=9780521763684 .)Comment: 33 pages, 17 figure
Constraining Bosonic Supersymmetry from Higgs results and 8 TeV ATLAS multi-jets plus missing energy data
The collider phenomenology of models with Universal Extra Dimensions (UED) is
surprisingly similar to that of supersymmetric (SUSY) scenarios. For each
level-1 bosonic (fermionic) Kaluza-Klein (KK) state, there is a fermionic
(bosonic) analog in SUSY and thus UED scenarios are often known as bosonic
supersymmetry. The minimal version of UED (mUED) gives rise to a
quasi-degenerate particle spectrum at each KK-level and thus, can not explain
the enhanced Higgs to diphoton decay rate hinted by the ATLAS collaboration of
the Large Hadron Collider (LHC) experiment. However, in the non-minimal version
of the UED (nmUED) model, the enhanced Higgs to diphoton decay rate can be
easily explained via the suitable choice of boundary localized kinetic (BLK)
terms for higher dimensional fermions and gauge bosons. BLK terms remove the
degeneracy in the KK mass spectrum and thus, pair production of level-1 quarks
and gluons at the LHC gives rise to hard jets, leptons and large missing energy
in the final state. These final states are studied in details by the ATLAS and
CMS collaborations in the context of SUSY scenarios. We find that the absence
of any significant deviation of the data from the Standard Model (SM)
prediction puts a lower bound of about 2.1 TeV on equal mass excited quarks and
gluons.Comment: 19 page
Minimal Universal Extra Dimensions in CalcHEP/CompHEP
We present an implementation of the model of minimal universal extra
dimensions (MUED) in CalcHEP/CompHEP. We include all level-1 and level-2
Kaluza-Klein (KK) particles outside the Higgs sector. The mass spectrum is
automatically calculated at one loop in terms of the two input parameters in
MUED: the radius of the extra dimension and the cut-off scale of the model. We
implement both the KK number conserving and the KK number violating
interactions of the KK particles. We also account for the proper running of the
gauge coupling constants above the electroweak scale. The implementation has
been extensively cross-checked against known analytical results in the
literature and numerical results from other programs. Our files are publicly
available and can be used to perform various automated calculations within the
MUED model.Comment: 32 pages, 4 figures, 6 tables, invited contribution for New Journal
of Physics Focus Issue on 'Extra Space Dimensions', the model file can be
downloaded from http://home.fnal.gov/~kckong/mued
Constraining compressed versions of MUED and MSSM using soft tracks at the LHC
A compressed spectrum is an anticipated hideout for many beyond standard
model scenarios. Such a spectrum naturally arises in the minimal universal
extra dimension framework and also in supersymmetric scenarios. Low
leptons and jets are characteristic features of such situations. Hence, a
monojet with has been the conventional signal at the Large Hadron
Collider (LHC). However, we stress that inclusion of -binned track
observables from such soft objects provide very efficient discrimination of new
physics signals against various SM backgrounds. We consider two benchmark
points each for minimal universal extra dimension (MUED) and minimal
supersymmetric standard model (MSSM) scenarios. We perform a detailed cut-based
and multivariate analysis (MVA) to show that the new physics parameter space
can be probed in the ongoing run of LHC at 13 TeV center-of-mass energy with an
integrated luminosity 20-50 fb. When studied in conjunction with
the dark matter relic density constraint assuming standard cosmology, we find
that compressed MUED (with ) can be already excluded from the
existing data. Also, MVA turns out to be a better technique than regular
cut-based analysis since tracks provide uncorrelated observables which would
extract more information from an event.Comment: 26 pages, 7 figures. Minor modifications in the text, references
added, accepted for publication in JHE
Universal extra dimensions after Higgs discovery
We show bounds on five- and six-dimensional universal extra dimension (UED)
models from the latest results of the Higgs searches at the LHC and from the
electroweak precision data for the S and T parameters. We consider the minimal
UED model in five dimensions and the ones in six dimensions. The highest
possible ultraviolet cutoff scale for each UED model is evaluated from the
electroweak vacuum stability by solving the renormalization group equation of
the Higgs self-coupling. This scale turns out to be lower than the conventional
one obtained from the perturbativity of the gauge coupling. The resultant 95%
C.L. lower bounds on the first Kaluza-Klein scale from the LHC results and from
the S, T analysis are 600 and 700 GeV in the minimal UED model, while those in
the six-dimensional UED models are 800-1300 GeV and 900-1500 GeV, respectively.Comment: 37 pages, 9 figures, 7 tables (v1); 38 pages, 9 figures, 7 tables,
with minor modifications, typos fixed, references added (v2); 37 pages, 10
figures, 7 tables, published version in PRD, figures modified, a figure
added, typos fixed, a reference added (v3
Physics Beyond the Standard Model and Cosmological Connections: A Summary from LCWS 06
The International Linear Collider (ILC) is likely to provide us important
insights into the sector of physics that may supersede our current paradigm
viz., the Standard Model. In anticipation of the possibility that the ILC may
come up in the middle of the next decade, several groups are vigourously
investigating its potential to explore this new sector of physics. The Linear
Collider Workshop in Bangalore (LCWS06) had several presentations of such
studies which looked at supersymmetry, extra dimensions and other exotic
possibilities which the ILC may help us discover or understand. Some papers
also looked at the understanding of cosmology that may emerge from studies at
the ILC. This paper summarises these presentations.Comment: 8 pages (including cover page) LaTeX, Summary talk presented at the
International Linear Collider Workshop in Bangalore, India in March 200
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