17 research outputs found
Pseudo-axions in Little Higgs models
Little Higgs models have an enlarged global symmetry which makes the Higgs
boson a pseudo-Goldstone boson. This symmetry typically contains spontaneously
broken U(1) subgroups which provide light electroweak-singlet pseudoscalars.
Unless such particles are absorbed as the longitudinal component of
states, they appear as pseudoscalars in the physical spectrum at the
electroweak scale. We outline their significant impact on Little Higgs
phenomenology and analyze a few possible signatures at the LHC and other future
colliders in detail. In particular, their presence significantly affects the
physics of the new heavy quark states predicted in Little Higgs models, and
inclusive production at LHC may yield impressive diphoton resonances.Comment: 28 pages, 9 figs., accepted to PRD; footnote added, typos correcte
Simplified Models for LHC New Physics Searches
This document proposes a collection of simplified models relevant to the
design of new-physics searches at the LHC and the characterization of their
results. Both ATLAS and CMS have already presented some results in terms of
simplified models, and we encourage them to continue and expand this effort,
which supplements both signature-based results and benchmark model
interpretations. A simplified model is defined by an effective Lagrangian
describing the interactions of a small number of new particles. Simplified
models can equally well be described by a small number of masses and
cross-sections. These parameters are directly related to collider physics
observables, making simplified models a particularly effective framework for
evaluating searches and a useful starting point for characterizing positive
signals of new physics. This document serves as an official summary of the
results from the "Topologies for Early LHC Searches" workshop, held at SLAC in
September of 2010, the purpose of which was to develop a set of representative
models that can be used to cover all relevant phase space in experimental
searches. Particular emphasis is placed on searches relevant for the first
~50-500 pb-1 of data and those motivated by supersymmetric models. This note
largely summarizes material posted at http://lhcnewphysics.org/, which includes
simplified model definitions, Monte Carlo material, and supporting contacts
within the theory community. We also comment on future developments that may be
useful as more data is gathered and analyzed by the experiments.Comment: 40 pages, 2 figures. This document is the official summary of results
from "Topologies for Early LHC Searches" workshop (SLAC, September 2010).
Supplementary material can be found at http://lhcnewphysics.or
CP Studies and Non-Standard Higgs Physics
There are many possibilities for new physics beyond the Standard Model that
feature non-standard Higgs sectors. These may introduce new sources of CP
violation, and there may be mixing between multiple Higgs bosons or other new
scalar bosons. Alternatively, the Higgs may be a composite state, or there may
even be no Higgs at all. These non-standard Higgs scenarios have important
implications for collider physics as well as for cosmology, and understanding
their phenomenology is essential for a full comprehension of electroweak
symmetry breaking. This report discusses the most relevant theories which go
beyond the Standard Model and its minimal, CP-conserving supersymmetric
extension: two-Higgs-doublet models and minimal supersymmetric models with CP
violation, supersymmetric models with an extra singlet, models with extra gauge
groups or Higgs triplets, Little Higgs models, models in extra dimensions, and
models with technicolour or other new strong dynamics. For each of these
scenarios, this report presents an introduction to the phenomenology, followed
by contributions on more detailed theoretical aspects and studies of possible
experimental signatures at the LHC and other colliders.Comment: Report of the CPNSH workshop, May 2004 - Dec 2005, 542 pages. The
complete report as well as its individual chapters are also available from
http://kraml.home.cern.ch/kraml/cpnsh/report.htm
Distinguishing Little-Higgs Product and Simple Group Models at the LHC and ILC.
We propose a means to discriminate between the two basic variants of Little
Higgs models, the Product Group and Simple Group models, at the next generation
of colliders. It relies on a special coupling of light pseudoscalar particles
present in Little Higgs models, the pseudo-axions, to the Z and the Higgs
boson, which is present only in Simple Group models. We discuss the collider
phenomenology of the pseudo-axion in the presence of such a coupling at the
LHC, where resonant production and decay of either the Higgs or the
pseudo-axion induced by that coupling can be observed for much of parameter
space. The full allowed range of parameters, including regions where the
observability is limited at the LHC, is covered by a future ILC, where double
scalar production would be a golden channel to look for.Comment: 17p, submitted to PR
Publisher’s Note: Distinguishing little-Higgs product and simple group models at the CERN LHC and ILC [Phys. Rev. DPRVDAQ0556-2821 74
Supersymmetry simulations with off-shell effects for CERN LHC and ILC
At the LHC and at an ILC, serious studies of new physics benefit from a proper simulation of signals and backgrounds. Using supersymmetric sbottom pair production as an example, we show how multi-particle final states are necessary to properly describe off-shell effects induced by QCD, photon radiation, or by intermediate on-shell states. To ensure the correctness of our findings we compare in detail the implementation of the supersymmetric Lagrangian in MadGraph, Sherpa and Whizard. As a future reference we give the numerical results for several hundred cross sections for the production of supersymmetric particles, checked with all three codes
Supersymmetry simulations with off-shell effects for LHC and ILC
At the LHC and at an ILC, serious studies of new physics benefit from a proper simulation of signals and backgrounds. Using supersymmetric sbottom pair production as an example, we show how multiparticle final states are necessary to properly describe off-shell effects induced by QCD, photon radiation, or by intermediate on-shell states. To ensure the correctness of our findings we compare in detail the implementation of the supersymmetric Lagrangian in madgraph, sherpa and whizard. As a future reference we give the numerical results for several hundred cross sections for the production of supersymmetric particles, checked with all three codes
Supersymmetry Simulations with Off-Shell Effects for LHC and ILC
At the LHC and at an ILC, serious studies of new physics benefit from a proper simulation of signals and backgrounds. Using supersymmetric sbottom pair production as an example, we show how multi-particle final states are necessary to properly describe off-shell effects induced by QCD, photon radiation, or by intermediate on-shell states. To ensure the correctness of our findings we compare in detail the implementation of the supersymmetric Lagrangian in MadGraph, Sherpa and Whizard. As a future reference we give the numerical results for several hundred cross sections for the production of supersymmetric particles, checked with all three codes