Pre-Learning: CMS Physics Objects: Glossary

Physics objects are the final abstraction in the detector that can be associated to physical entities like particles.

POET is a collection of CMSSW EDAnalyzers meant to teach how to access physics objects information.

Quantities such as impact parameters and charge have common member functions.

Physics objects in CMS are reconstructed from detector signals and are never 100% certain!

Identification and isolation algorithms are important for reducing fake objects.

One can add additional informtion to the EDAnalyzer

Track access may differ, but track-related member functions are common across objects.

Physics objects in CMS are reconstructed from detector signals and are never 100% certain!

Muons typically use pre-configured identification and isolation variable member functions.

Sometime it is necessary to be able to understand the code to add new variables

Jets are spatially-grouped collections of particles that traversed the CMS detector

Particles from additional proton-proton collisions (pileup) must be removed from jets

Missing transverse energy is the negative vector sum of particle candidates

Many of the class methods discussed for other objects can be used for jets

Tagging algorithms separate heavy flavor jets from jets produced by the hadronization of light quarks and gluons

Tagging algorithms produce a disriminator value for each jet that represents the likelihood that the jet came from a b hadron

Each tagging algorithm has recommended ‘working points’ (discriminator values) based on a misidentification probability for light-flavor jets

Jet energy corrections are factorized and account for many mismeasurement effects

L1+L2+L3 should be applied to jets used for analyses, with residual corrections for data

Jet energy resolution in simulation is typically too narrow and is smeared using scale factors

Jet energy and resolution corrections are sources of systematic error and uncertainties should be evaluated

In general, the jet corrections are significant and lower the momenta of the jets with standard LHC pileup conditions.

For most jets, the JEC uncertainty dominates over the JER uncertainty.

In the endcap region of the detector, the JER uncertainty in larger and matches the JEC uncertainty.