Emerging Jet Analysis
Introduction
One of the novel search strategies for new physics at the LHC are emerging jets that dominantly compose of displaced tracks and have many different vertices within the jet cone. The motivations for detailed studies of this unconventioal signature is numerous. Such new objects arise naturally in many models of dark matter with a composite dark sector where a parton shower in the dark sector is followed by displaced decays of dark pions back to SM jets. In this work, we perform a detailed study for a benchmark signal with two regular and two emerging jets. This analysis is based on reconstructing calorimeter jets with no prompt tracks from the interaction point.
Main Analysis Framework
The main analysis framework is based on xAODAnaHelpers package with set of common
EventLoop algorithms and C++ classes designed to perform basic event/ object selection, calibration, and object corrections. It can also handle output flat ntuples and different level of systematics sources.
Each step of the analysis chain is performed by a standard EL::Algorithm which employ TStore to pass information to the Algos down the chain. The final events can be stored as TTree or histograms. This package make use of minimal wrapper for CP tools to help users to properly configure the modules and connect the full chain without much effort. In addition to standard algorithms, more modules are also defined to do some specific jobs using corresponding derived classes which inherit properties from the base xAODAnaHelpers classes.
xAODAnaHelpers and EJsAnalysis codes to produce ntuples
Here you find the most important C++ codes for producing ntuples and making histograms. As an example, first inspect
confing files to run specific jobs either making Ntuples or histograms.
The ntuples are produced using the following modules:
xAH Algorithms
- Event Selection: BasicEventSelection(first algorthem in chain): Performs very basic event selection/processing — GRL, PRW, trigger selection, event cleaning, PV cut, etc.
- Object calibration: Jet calibrator: Performs jet calibration, jet uncertainties, jet cleaning (decoration). This modules saves new containers for nominal (calibrated) collection and each systematic variation to be passed down algorithm chain.
- Object selection: JetSelector, TrackSelector, TruthSelector: Selects jets, tracks, and truth particles according to user selection.
EJs Algorithms
- VrtSecInclusive DV selection: SecondaryVertexSelector
After running the ntuple producer, three versions of vertex variables are saved based on different stages of track filtering. The nominal case, with
VsiBonsai track trimming, including removal of bad-d0 associated tracks to correct φ asymmetry, is represented by branches with no extra suffix (i.e. secVtx_mass). The clean case, with removal of bad-d0 associated tracks only and no other track trimming applied, is represented by branches with the clean suffix (i.e. secVtx_mass_clean). The base case, with no track trimming of any kind, is represented by branches with the bare suffix (i.e. secVtx_mass_bare). The vertex kinematic properties are calculated with the VSI Bonsai toolkit using track parameters with respect to the displaced vertex.
- Object matching: ObjectMatcher
Thin module is employed to perform matching between different physics objects and between physics + truth objects and decorates objects accordingly for later access.
- Analysis selection: EJsxAODAnalysis
We use this module to apply actual analysis selections i.e. define signal, validation, and control regions, define Emerging Jet objects, select signal events, etc.
- Ntuple making: EJsMiniNtuple
This wrapper algorithm is used to make and output TTree(s) using
EJsHelpTreeBase class.
- Histogramming: EJsNtupleToHists
This wrapper algorithm can be used to make and output histograms from input ntuple using
EJsHistogramManager class
Hierarchy relationship between modules
Main development now within xAODAnaHelpers:
- Class Hierarchy
- Namespaces
Inspecting the definition of samples, cuts, and plots
| Model A | Model B | Model C | Model D | Model E |
| 10GeV | 4GeV | 20GeV | 40GeV | 1.6GeV |
| 20GeV | 8GeV | 40GeV | 80GeV | 3.2GeV |
| 5GeV | 2GeV | 10GeV | 20GeV | 0.8GeV |
600, 1000, 1400 GeV |
0.5, 1, 2, 20, 150, 300; 1, 2, 5, 75, 150, 300; 2, 5, 20, 75, 150 300 mm |
Testing ntuple producer
Quickly testing the cut flow on a signal sample gives:
Make some plots
The
histogram_local.sh file can be used to produce the relevant modules on top of the ntuple scripts. To get our first sets of plots, we can do
./ histogram_local.sh
A word of caution: The following commands were tested to work properly in the "bash" shell. In case you use a different shell, slight alterations might be needed.
Common flags for plotting
Introduced for MC 16 samples
sample |
ROOT color |
Model A |
kBlue-2 |
Model B |
kGreen-2 |
Model C |
kOrange-3 |
Model D |
kRed-6 |
Model E |
kCyan-6 |
QCD |
kViolet+5 |
Inclusive Signal |
kBlack |
|
Carleton Analysis Framework
To be filled.
Code explenation
References
- LHC Cross Section Working Group:
- * Production Cross Sections at √s =* 13 TeV :
- * Branching Ratios and Total Decay* Widths:
Important links
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Past Meetings:
Combined Performance Page
Cross Sections
Physics Groups
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