38 research outputs found
More Jets in more LHC searches
Multi jet observables are a powerful tool to new physics as well as a boost to standard
analysis strategies. We show their use in a reasonably model independent dark matter
search and a jet veto Higgs analysis. We find however that, these observables are
plagued by huge theoretical uncertainties connected to unphysical scale parameters.
In the democratic limit we compute analytically the all order resummed jet spectrum
at leading log. It obeys so called staircase scaling. With the help of state of the art
Monte Carlo tools we study the jet spectrum features in great detail. In addition we
also study so called Poisson scaling. This allows us to develop a data driven strategy
to fix the standard model multi jet backgrounds
Jets plus Missing Energy with an Autofocus
Jets plus missing transverse energy is one of the main search channels for
new physics at the LHC. A major limitation lies in our understanding of QCD
backgrounds. Using jet merging we can describe the number of jets in typical
background channels in terms of a staircase scaling, including theory
uncertainties. The scaling parameter depends on the particles in the final
state and on cuts applied. Measuring the staircase scaling will allow us to
also predict the effective mass for Standard Model backgrounds. Based on both
observables we propose an analysis strategy avoiding model specific cuts which
returns information about the color charge and the mass scale of the underlying
new physics.Comment: 15 pages, 9 figures, 3 table
Establishing jet scaling patterns with a photon
Staircase and Poisson scaling are two typical patterns we observe for the exclusive number of jets at high energy hadron colliders. We examine these scaling properties for photon plus jets production at the LHC and find that this channel is well suited to study these features. We illustrate and discuss when to expect each of the two patterns, how to induce a transition through kinematic cuts, and how photons are related to heavy gauge bosons. Measurements of photon+jets production is therefore providing valuable information on exclusive jet scaling, which is going to help to eventually understand the theoretical origin of exclusive jet scaling properties in more detail
From Jet Counting to Jet Vetoes
The properties of multi-jet events impact many LHC analysis. The exclusive
number of jets at hadron colliders can be described in terms of two simple
patterns: staircase scaling and Poisson scaling. In photon plus jets production
we can interpolate between the two patterns using simple kinematic cuts. The
associated theoretical errors are well under control. Understanding such
exclusive jet multiplicities significantly impacts Higgs searches and searches
for supersymmetry at the LHC.Comment: 4 pages, 4 figures, to appear in the proceedings of XX International
Workshop on Deep-Inelastic Scattering and Related Subjects, 26th-30th March
2012, University of Bon
Stress-testing the VBF approximation in multijet final states
We consider electro-weak Higgs plus three jets production at NLO QCD beyond
strict VBF acceptance cuts. We investigate, for the first time, how accurate
the VBF approximation is in these regions and within perturbative
uncertainties, by a detailed comparison of full and approximate calculations.
We find that a rapidity gap between the tagging jets guarantees a good
approximation, while an invariant mass cut alone is not sufficient, which needs
to be confronted with experimental choices. We also find that a significant
part of the QCD corrections can be attributed to Higgs-Strahlungs-type
topologies.Comment: 6 pages, 5 figures, add VBSCAN report numbe
Herwig 7.1 Release Note
A new release of the Monte Carlo event generator Herwig (version 7.1) is now
available. This version introduces a number of improvements, notably: multi-jet
merging with the dipole shower at LO and NLO QCD; a new model for soft
interactions and diffraction; improvements to mass effects and top decays in
the dipole shower, as well as a new tune of the hadronisation parameters.Comment: 7 pages, 7 figures. Herwig is available from
https://herwig.hepforge.org