JetMaker

Purpose

To cover the functionality of smearing the Cluster formed by ClusterMaker and to complete the Jet construction by adding non-isolated muons.
The existence of a class responsible for jet construction allows the implementation of a range of Jet Finders, according to future new users requirements.

Jet Definition

Jets are Clusters which have not been associated with isolated particles (electrons or photons) and which then pass some pre-defined kinematic criteria.
In order to form Jets, JetMaker smears the cluster four-momentum, adds non-isolated muons which falls in a predefined R-cone around the Jet and tag the Jet with a flavour.
The JetCandidate is kept and labelled as a reconstructed Jet if its energy is greater than a given threshold and its eta passes the eta fiducial cut.
Options for low and high luminosity allow to tune the smearer algorithm, adding to the smearing function a pile-up effect for high luminosity.

JetMaker Overview

The default jet finder algorithm builds jets from cells not in the clusters, clusters and non-isolated muons.
Then it performs the following operations:

Obtains all clusters from the Transient Event Store (TES)
Obtains all non-isolated muons from TES.
Examines all Clusters, and retains only those not associated with isolated electrons and isolated photons.
Creates a JetCandidates by smearing the four-momentum of the Cluster. A JetSmearer object encapsulates the parametrization of this operation.
Finds the nearest non-isolated muon to the Jet direction: if it is within a cone of radius R = 0.4 (the actual value is the same for the barrel and the forward region, but different data can be implemented), it is added to the Jet.
This muon is then removed from the vector of muons available to further jet construction for that event.
A JetCandidate is made, which is checked for passing kinematic cuts on E_t and eta, E_t > 10 and eta < 5.0;
The HepMC structure is scanned for a tau-meson or a heavy quark which could tag the Jet.
If none of these tags are found, the jet is labelled as u-quark.
The tagged Jet is then ouput to the TES.

JetMaker uses the helper class TesIO to perform input/output operations from the TES.

User Requirements Satisfied

The design fulfills requirements of Sec 3.1.5 of the ARD.

JetMaker Detail

jobOptions Properties

jobOptions properties are steering parameters which can be set by the user in the jobOptions file.
They are declared in the constructor and initialised to Default Values.
The options for this algorithm are:

MinimumPT - Acceptance cut
MaximumEta - Acceptance cut
DoSmearing - Flag to choose whether to smear or not
Luminosity - LHC luminosity(high/low)
RconeB - Barrel Region RCone size
RconeF - Forward region RCone size
bPtMin - B-jet minimum pT
bMaxDeltaR - Maximum distance between jet and b-quark
cPtMin - C-jet minimum pT
cMaxDeltaR - Maximum distance between jet and c-quark
tauPtMin - Tau-jet minimum pT
tauMaxDeltaR - Maximum distance between jet and tau
etaTagMax - Maximum eta of tagging quark
BarrelForwardEta - Eta value of Barrel/Forward Region Boundary
tauJetPtRatio - Ratio of jet/tau momentum
RandSeed - Random number generator seed for smearing
InputLocation - Location on TES of input Clusters
OutputLocation - Location on TES of output Jets
MuonLocation - Location on TES of input Muons
McTruthLocation - Location on TES of MCTruth particles

Initialisation

The initialise method is called once at the beginning of the job.

create a new instance of the JetSmearer object, characterized by the private data which parametrize the smearing process;

return a SatusCode type variable, which indicates the success or failure of the inizialize operation.

JetMaker initialisation sequence diagram

Execute Sequence

access HepMC events record in the event store to extract Clusters and Muons
smear Cluster and create a reconstructed Jet {create };

adds Muon
tag the Jet
check if all kinematical requirements are satisfied
add the Jet to the collection and register Jet which has been successfully created to the TES

JetMaker execution sequence diagram

Class Diagram

The various classes discussed above are shown in the class diagram.
JetMaker class diagram