Basic Physics Objects: Glossary

CMS physics objects include: muons, electrons, taus, photons, and jets.

Missing transverse momentum is derived from physics objects (negative vector sum).

Objects are stored in separate collections in the AOD files

Objects can be accessed one-by-one via a for loop

Physics objects in CMS inherit common member functions for the 4-vector quantities of transverse momentum, polar/azimuthal angles, and mass/energy.

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.

Member functions for these algorithms are documented on public TWiki pages.

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

Member functions for these algorithms are documented on public TWiki pages.

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

Trigger paths are stored as a map with names paired to prescale values

4-vector information is stored for objects matching a specific, configurable, trigger filter

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All physics objects have multiple identification and isolation schemes.

POET implements the most common identification and isolation criteria used in analyses.

MET exists in all events, but significant differences can be seen between samples with and without real MET.

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Triggers usually impose various kinematic restrictions on objects of interest.

Final state objects produced promptly from the proton collision are typically required to have significant momentum, tight ID quality, and to be isolated (depending on the topology of the physics process.

Veto objects are typically selected using looser criteria so that the efficiency of the veto is very high.

Correlations between objects can be used either to select specifically for signal events or reject background events.