HEPData Observables

Observables describe the quantity that is being measured. They are used in searching and are a simplified form of the dependent variable name (yname). Thus they do not have units and a fairly broad in their scope. The table below shows the most commonly used observable names together with a list of independent variables names (xnames) as used in HEPData. When necessary more detailed descriptions are given by clicking on the 'more'.

Observablesxnames (to be used with differential distributions)
- an xname prefixed with 'D' signifies a difference in two variables (eg DYRAP)
ObservableDescriptionxnamedescription
SIG
integrated cross section....more
M
MT
E
ET
EKIN
P
PT, PT**2
PL
XL
XT
X
THETA
OMEGA
PHI
T
TP
YRAP
ETARAP
S
W
Q, Q**2
Y
Z
CENTRALITY


THRUST
MINOR
MAJOR
SPHERICITY
PLANARITY
APLANARITY
OBLATENESS
HEAVY-JET-MASS
LIGHT-JET-MASS
WIDE-JET-BROADENING
TOTAL-JET-BROADENING
C-PARAMETER
D-PARAMETER
PTIN
PTOUT
mass
transverse mass
energy
transverse energy
kinetic energy
momentum
transverse momentum (squared)
longitudinal momentum
Feynman X
transverse X
X (in DIS)
polar angle
solid angle
azimuthal angle
momentum transfer
momentum transfer prime
rapidity
pseudorapidity
invariant mass squared
energy of system of particles
virtual momentum transfer (squared)
inelasticity (in DIS)
energy/momentum fraction
centrality

JET SHAPES
thrust
thrust minor
thrust major
sphericity
planarity
aplanarity
oblateness
heavy jet mass
light jet mass
wide jet broadening
total jet broadening
C-parameter
D-parameter
momentum projection in the event plane
momentum projection transverse to the event plane
SIG/SIG, RATIO, N/N
ratio of cross sections/distributions....more
DSIG/Dxnamesingle differential cross section
D2SIG/Dxname/Dxnamedouble differential cross section
D3SIG/Dxname/Dxname/Dxnametriple differential cross section
E*D3SIG/DP**3invariant cross section
Nnumber of events
DN/Dxnamesingle differential distribution
D2N/Dxname/Dxnamedouble differential distribution
D3N/Dxname/Dxname/Dxnametriple differential cross distribution
MULT, DISPERSION, MULT2 etc..
multiplicity measurements....more
POL, POL.POL, POL.POL.POLsingle, double and triple spin polarisations
ASYMasymmetry measurement
F1, F2, XF3, FLstructure functions
A1, A2, G1, G2spin asymmetries and structure functions
V1, V2, V3, V4, V5, V6azimuthal asymmetries (Fourier Coefficients)
V11, V22, V33, V44, V55, V66 azimuthal asymmetries (Fourier Coefficients)
ACC, EFFacceptance, efficiency measurements
CLSconfidence limits
WIDTHMeasurement of a width
RCORR, CORR(ratio of) correlation measurements
EEC, AEECenergy-energy correlation and its asymmetry
PSIJet Shape (integrated)
RHO
density matrix element....more
POL.RHO
density matrix element with a ....more
SLOPE, POWERexponential slope/power of a fit
ALPHAS, SIN2TWalpha-s, sin^2(theta-w)
GA, GVaxial-vector couplings
FORMFACTORForm Factor measurements
CONSTMeasurement of a physical constant
RAA, RPA, RCPnuclear modification factors
LEG, LEGN, LEGP, LEGPN
Legendre Coefficients (somewhat historical)....more
YLMYlm moment (somewhat historical)
AMP, REAMP/IMAMP, PHASEamplitude, real/imaginary ratio, phase (somewhat historical)