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 $e$'s and/or $\mu$'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 $\tau$'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$l$+${\rlap/E}_T$ and $\tau ll$+${\rlap/E}_T$. 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 $q\bar q\to e^+\nu_e \mu^-\bar\nu_\mu$ + ${\rm{c.c.}}$, 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