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Technical reference for the benchmarks

Glossary

b-tagging discriminant

A value assigned to a jet that is correlated with the probability that the jet originated from a bottom quark. See b-tagging.

NanoAOD branch: Jet_btag

ΔR

Equal to sqrt(Δη2 + Δφ2). The most common metric used for distance between four-momenta in hadron colliders.

η

Pseudorapidity, a unitless geometric coordinate used in hadron colliders.

NanoAOD branches: <object type>_eta

Event

A single bunch crossing. Each entry in a NanoAOD TTree corresponds to one event. See Event (particle physics).

Flavor

A species of elementary particle, including its antiparticle. For example, electrons and positrons are of the same flavor, but muons are another flavor. See Flavour.

Four-momentum

A four-vector with units of momentum. See Four-momentum. Four-momentum in events is often specified by pT, η, φ, and mass, but addition of four-momenta is only straightforward in the Cartesian coordinates E, px, py, and pz. A nice summary of the relationships between these can found here.

NanoAOD branches: pT (in GeV): <object type>_pt, η: <object type>_eta, φ (in radians): <object type>_phi, Mass (in GeV): <object type>_mass

GeV

Gigaelectronvolt, a unit of energy. Also used as shorthand for GeV/c (a unit of momentum) and GeV/c2 (a unit of mass). See Electronvolt. In NanoAOD files, all energies, momenta, and masses are in GeV.

Invariant mass

Equal to sqrt(E2 - p2), where E and p are the energy and momentum, respectively, of a given four-momentum. See Invariant mass.

Jet

A cone of particles emitted by a collision. A jet is represeneted by a four-momentum, which is a sum over the constituent particles. See Jet (particle physics).

NanoAOD branches: Jet_<property>

Light lepton

An electron, positron, or muon. See Lepton. "Light" means less massive than a tau lepton. Neutrinos are also light leptons, but they are generally not detectable in collider experiments. Leptons are represented by their four-momentum and their charge.

NanoAOD branches: Electrons and positrons: Electron_<property>, Muons: Muon_<property> (Positrons are considered to be electrons with a positive charge.)

Missing transverse momentum

The negative vector sum of the transverse momenta of all objects in an event. The magnitude of this vector is written as ETmiss, also called missing ET (MET). See Missing energy.

NanoAOD branches: Magnitude (in GeV): MET_pt, φ (in radians): MET_phi

NanoAOD

A ROOT-based file format used by the CMS experiment. It consists of a TTree named Events with TBranches corresponding to the properties of the events.

φ

Azimuthal angle, a spherical coordinate.

NanoAOD branches (in radians): <object type>_phi

ROOT

A data analysis software framework for high energy physics (HEP). Most HEP data is stored in ROOT files, a format produced by the ROOT framework.

Transverse mass

The transverse mass of a system of missing transverse momentum and a lepton is equal to sqrt(2 * pTlepton * ETmiss * (1 - cos(Δφ))).

Transverse momentum

The projection of the momentum onto the xy-plane. The magnitude is written as pT.

NanoAOD branches: Magnitude (in GeV): <object type>_pt, φ (in radians): <object type>_phi

Trijet

A group of three jets. The four-momentum of a trijet is the sum of the three jet four-momenta.