489 research outputs found
Kaluza-Klein states at the LHC in models with localized fermions
We give a brief review of some aspects of physics with TeV size
extra-dimensions. We focus on a minimal model with matter localized at the
boundaries for the study of the production of Kaluza-Klein excitations of gauge
bosons. We briefly discuss different ways to depart from this simple analysis.Comment: 6 pages, 2 figure
Improved analysis of the bounds from the electroweak precision tests on the 4-site model
We present a new complete analysis of the electroweak precision observables
within the recently proposed 4-site Higgsless model, which is based on the
SU(2)_L x SU(2)_1 x SU(2)_2 x U(1)_Y gauge symmetry and predicts six extra
gauge bosons, W_{1,2} and Z_{1,2}. Within the epsilon_i (i=1,2,3,b)
parametrization, we compute for the first time the EWPT bounds via a complete
numerical algorithm going beyond commonly used approximations. Both
epsilon_{1,3} impose strong constraints. Hence, it is mandatory to consider
them jointly when extracting EWPT bounds and to fully take in to account the
correlations among the electroweak precison measurements. The phenomenological
consequence is that the extra gauge bosons must be heavier than 250 GeV. Their
couplings to SM fermions, even if bounded, might be of the same order of
magnitude than the SM ones. In contrast to other Higgsless models, the 4-site
model is not fermiophobic. The new gauge bosons could thus be discovered in the
favoured Drell-Yan channel already during the present run of the LHC
experiment.Comment: Latex file, 35 pages, 10 figures, corrected typos, published versio
PHASE - An event generator for six fermion physics at the LHC
PHASE is a Monte Carlo event generator, under construction, for all Standard
Model processes with six fermions in the final state at the LHC. It employs the
full set of tree level Feynman diagrams, taking into account fermion masses for
b quarks. The program can generate unweighted events for any subset of all six
fermion final states in a single run, by making use of dedicated pre-samples.
An interface to hadronization is provided.Comment: 4 pages, Latex, 1 figure. Talk given by E. Accomando at the IX
International Workshop on Advanced Computing and Analysis Techniques in
Physics Research (ACAT03), KEK, Tsukuba, December 1-5, 200
Trilepton Signal of Grand Unified Models at the Tevatron
At the Tevatron, the most promising channel to detect supersymmetry is three
leptons plus missing energy, where the leptons are 's and/or 's. This
final state appears from the production of chargino and second lighetst
neutralino. However in grand unified models with universal scalar masses at the
grand unified scale, this final state mostly consists of 's which are
hard to detect. We show that for some regions of non universality in the scalar
masses at the GUT scale based on unifying groups like SU(5) or SO(10), the
final state mostly consists of 3+ and +.
The first mode has very high detection efficiency and the second one is
expected to have high detection efficency as well. We also show that these
models can have enough events in these modes to be detected in RUN II.Comment: 7 pages, latex, 6 figure
Novel SM-like Higgs decay into displaced heavy neutrino pairs in U(1)' models
We examine the observability of heavy neutrino (nu_h) signatures of a U(1)'
enlarged Standard Model (SM) encompassing three heavy Majorana neutrinos
alongside the known light neutrino states at the the Large Hadron Collider
(LHC). We show that heavy neutrinos can be rather long-lived particles
producing distinctive displaced vertices that can be accessed in the CERN LHC
detectors. We concentrate here on the gluon fusion production mechanism gg ->
H_{1,2} -> nu_h nu_h, where H_1 is the discovered SM-like Higgs and H_2 is a
heavier state, yielding displaced leptons following nu_h decays into weak gauge
bosons. Using data collected by the end of the LHC Run 2, these signatures
would prove to be accessible with negligibly small background.Comment: 30 pages, journal versio
Charged di-boson production at the LHC in a 4-site model with a composite Higgs boson
We investigate the scope of the LHC in probing the parameter space of a
4-site model supplemented by one composite Higgs state, assuming all past,
current and future energy and luminosity stages of the CERN machine. We
concentrate on the yield of charged di-boson production giving two
opposite-charge different-flavour leptons and missing (transverse) energy,
i.e., events induced via the subprocess
+ , which enables the production in the intermediate step of all
additional neutral and charged gauge bosons belonging to the spectrum of this
model, some of which in resonant topologies. We find this channel accessible
over the background at all LHC configurations after a dedicated cut-based
analysis. We finally compare the yield of the di-boson mode to that of
Drell-Yan processes and establish that they have complementary strengths, one
covering regions of parameter space precluded to the others and vice versa.Comment: 36 pages, 13 figures, 13 table
- …