NTuple

An NTuple, in the context of particle physics, is a simplified data structure that allows for straightforward access to the parameters of interest in an event. These files store data as rows of values, similar to an spreadsheet, where each row represents a collision event and each column a variable associated with that event.

Structure and Accessibility

The structure of NTuple files is made of a series of branches, each corresponding to a specific variable from the ATLAS detector. These branches may include information on particle types, momenta, energies, and other variables that help to the understanding the particle interactions observed in the detector. NTuple files are particularly valued in educational settings due to their ease of use. They require minimal preprocessing and can be easily accessed using standard data analysis software commonly employed in educational environments, such as ROOT.

Benefits for Education

• Simplicity: The simple, tabular format of NTuples makes them accessible for students and educators without the need for extensive background in data analysis or the complexities of particle physics detectors.
• Flexibility: Educators can easily extract specific datasets from NTuple files to tailor lessons to various educational objectives, from simple demonstrations of particle tracks to more complex analyses like identifying particle decays.
• Interactivity: NTuple files can be used in interactive environments that facilitate hands-on learning, such as Jupyter notebooks, where students can visualize and manipulate data in real-time.

Using NTuple Files

To work with NTuple files from the ATLAS Open Data

• Access: Users can download NTuple files directly from the CERN Open Data portal.
• Software: Open-source tools like ROOT can be employed to analyze the data. Tutorials and examples are provided to help users get started.
• Analysis: Users can perform a variety of analyses, from plotting simple distributions to conducting multi-variable analyses, using the structured data provided.

Details About the Published Data

8 TeV Data for Education

The resulting format of the datasets is a TTree tuple (or ROOT ntuple) with 45 branches as detailed in the table below:

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Tuple branch name	Type	Description
runNumber	int	number uniquely identifying ATLAS data-taking run
eventNumber	int	event number and run number combined uniquely identifies event
channelNumber	int	number representing leptonic channel
mcWeight	float	weight of a simulated event
pvxp_n	int	number of primary vertices
vxp_z	float	z-position of the primary vertex
trigE	bool	signifies whether event passes a standard electron trigger
trigM	bool	signifies whether event passes a standard muon trigger
passGRL	bool	signifies whether event passes a data quality assessment
hasGoodVertex	bool	signifies whether the event has at least one good vertex
lep_n	int	number of preselected leptons
lep_truthMatched	vector<bool>	indicates whether the lepton is matched to a truth lepton
lep_trigMatched	vector<bool>	indicates whether the lepton is the one triggering the event
lep_pt	vector<float>	transverse momentum of the lepton
lep_eta	vector<float>	pseudorapidity, η, of the lepton
lep_phi	vector<float>	azimuthal angle, φ, of the lepton
lep_E	vector<float>	energy of the lepton
lep_z0	vector<float>	z-coordinate of the track associated to the lepton wrt. the primary vertex
lep_charge	vector<float>	charge of the lepton
lep_flag	vector<int>	used to implement object cuts
lep_type	vector<int>	number signifying the lepton type (e, mu, tau) of the lepton
lep_ptcone30	vector<float>	used to ensure tracking isolation of the lepton
lep_etcone20	vector<float>	used to ensure calorimeter isolation of the lepton
lep_trackd0pvunbiased	vector<float>	d0 of the track associated to the lepton at the point of closest approach (p.c.a.)
lep_tracksigd0pvunbiased	vector<float>	d0 significance of the track associated to the lepton at the p.c.a.
met_et	float	Transverse energy of the missing momentum vector
met_phi	float	Azimuthal angle of the missing momentum vector
jet_n	int	number of selected jets
jet_pt	vector<float>	transverse momentum of the jet
jet_eta	vector<float>	pseudorapidity, η, of the jet
jet_phi	vector<float>	azimuthal angle, φ, of the jet
jet_E	vector<float>	energy of the jet
jet_m	vector<float>	invariant mass of the jet
jet_jvf	vector<float>	fraction of the total momentum of tracks in the jet
jet_trueflav	vector<int>	true flavor of the jet
jet_truthMatched	vector<int>	information whether the jet matches a jet on truth level
jet_SV0	vector<float>	weight from algorithm that reconstructs secondary vertices associated with a jet
jet_MV1	vector<float>	weight from algorithm based on multi variate technique
scaleFactor_BTAG	float	scalefactor for btagging
scaleFactor_ELE	float	scalefactor for electron efficiency
scaleFactor_JVFSF	float	scalefactor for jet vertex fraction
scaleFactor_MUON	float	scalefactor for muon efficiency
scaleFactor_PILEUP	float	scalefactor for pileup reweighting
scaleFactor_TRIGGER	float	scalefactor for trigger
scaleFactor_ZVERTEX	float	scalefactor for z-vertex reweighting

13 TeV Data for Education

The full list of ROOT branches and variables contained within the this dataset is presented in the list below:

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Tuple branch name	C++ type	Variable description
runNumber	int	number uniquely identifying ATLAS data-taking run
eventNumber	int	event number and run number combined uniquely identifies event
channelNumber	int	number uniquely identifying ATLAS simulated dataset
mcWeight	float	weight of a simulated event
XSection	float	total cross-section, including filter efficiency and higher-order correction factor
SumWeights	float	generated sum of weights for MC process
scaleFactor_PILEUP	float	scale-factor for pileup reweighting
scaleFactor_ELE	float	scale-factor for electron efficiency
scaleFactor_MUON	float	scale-factor for muon efficiency
scaleFactor_PHOTON	float	scale-factor for photon efficiency
scaleFactor_TAU	float	scale-factor for tau efficiency
scaleFactor_BTAG	float	scale-factor for b-tagging algorithm at 70% efficiency
scaleFactor_LepTRIGGER	float	scale-factor for lepton triggers
scaleFactor_PhotonTRIGGER	float	scale-factor for photon triggers
trigE	bool	boolean whether event passes a single-electron trigger
trigM	bool	boolean whether event passes a single-muon trigger
trigP	bool	boolean whether event passes a diphoton trigger
lep_n	int	number of pre-selected leptons
lep_truthMatched	vector<bool>	boolean indicating whether the lepton is matched to a simulated lepton
lep_trigMatched	vector<bool>	boolean indicating whether the lepton is the one triggering the event
lep_pt	vector<float>	transverse momentum of the lepton
lep_eta	vector<float>	pseudo-rapidity, $\eta$, of the lepton
lep_phi	vector<float>	azimuthal angle, $\phi$, of the lepton
lep_E	vector<float>	energy of the lepton
lep_z0	vector<float>	z-coordinate of the track associated to the lepton wrt. primary vertex
lep_charge	vector<int>	charge of the lepton
lep_type	vector<int>	number signifying the lepton type (e or µ)
lep_isTightID	vector<bool>	boolean indicating whether lepton satisfies tight ID reconstruction criteria
lep_ptcone30	vector<float>	scalar sum of track pT in a cone of R=0.3 around lepton, used for tracking isolation
lep_etcone20	vector<float>	scalar sum of track ET in a cone of R=0.2 around lepton, used for calorimeter isolation
lep_trackd0pvunbiased	vector<float>	d0 of track associated to lepton at point of closest approach (p.c.a.)
lep_tracksigd0pvunbiased	vector<float>	d0 significance of the track associated to lepton at the p.c.a.
met_et	float	transverse energy of the missing momentum vector
met_phi	float	azimuthal angle of the missing momentum vector
jet_n	int	number of pre-selected jets
jet_pt	vector<float>	transverse momentum of the jet
jet_eta	vector<float>	pseudo-rapidity, $\eta$, of the jet
jet_phi	vector<float>	azimuthal angle, $\phi$, of the jet
jet_E	vector<float>	energy of the jet
jet_jvt	vector<float>	jet vertex tagger discriminant of the jet
jet_trueflav	vector<float>	flavor of the simulated jet
jet_truthMatched	vector<float>	output of the multivariate b-tagging algorithm of the jet
photon_n	int	number of pre-selected photons
photon_truthMatched	vector<bool>	boolean indicating whether the photon is matched to a simulated photon
photon_trigMatched	vector<bool>	boolean indicating whether the photon is the one triggering the event
photon_pt	vector<float>	transverse momentum of the photon
photon_eta	vector<float>	pseudo-rapidity of the photon
photon_phi	vector<float>	azimuthal angle of the photon
photon_E	vector<float>	energy of the photon
photon_isTightID	vector<bool>	boolean indicating whether photon satisfies tight identification reconstruction criteria
photon_ptcone30	vector<float>	scalar sum of track pT in a cone of R=0.3 around photon
photon_etcone20	vector<float>	scalar sum of track ET in a cone of R=0.2 around photon
photon_convType	vector<int>	information whether and where the photon was converted
largeRjet_n	int	number of pre-selected large-R jets
largeRjet_pt	vector<float>	transverse momentum of the large-R jet
largeRjet_eta	vector<float>	pseudo-rapidity of the large-R jet
largeRjet_phi	vector<float>	azimuthal angle of the large-R jet
largeRjet_E	vector<float>	energy of the large-R jet
largeRjet_m	vector<float>	invariant mass of the large-R jet
largeRjet_truthMatched	vector<int>	information whether the large-R jet is matched to a simulated large-R jet
largeRjet_D2	vector<float>	weight from algorithm for W/Z-boson tagging
largeRjet_tau32	vector<float>	weight from algorithm for top-quark tagging
tau_n	int	number of pre-selected hadronically decaying $\tau$-lepton
tau_pt	vector<float>	transverse momentum of the hadronically decaying $\tau$-lepton
tau_eta	vector<float>	pseudo-rapidity of the hadronically decaying $\tau$-lepton
tau_phi	vector<float>	azimuthal angle of the hadronically decaying $\tau$-lepton
tau_E	vector<float>	energy of the hadronically decaying $\tau$-lepton
tau_charge	vector<int>	charge of the hadronically decaying $\tau$-lepton
tau_isTightID	vector<bool>	boolean indicating whether hadronically decaying $\tau$-lepton satisfies tight ID reconstruction criteria
tau_truthMatched	vector<bool>	boolean indicating whether the hadronically decaying $\tau$-lepton is matched to a simulated $\tau$-lepton
tau_trigMatched	vector<bool>	boolean signifying whether the $\tau$-lepton is the one triggering the event
tau_nTracks	vector<int>	number of tracks in the hadronically decaying $\tau$-lepton decay
tau_BDTid	vector<float>	output of the multivariate algorithm discriminating hadronically decaying $\tau$-leptons from jets
ditau_m	float	di-$\tau$ invariant mass using the missing-mass calculator
lep_pt_syst	vector<float>	single component syst. uncert. (lepton momentum scale and resolution) affecting lep_pt
met_et_syst	float	single component syst. uncert. ($E_T^{miss}$ scale and resolution) affecting met_pt
jet_pt_syst	vector<float>	single component syst. uncert. (jet energy scale) affecting jet_pt
photon_pt_syst	vector<float>	single component syst. uncert. (photon energy scale and resolution) affecting photon_pt
largeRjet_pt_syst	vector<float>	single component syst. uncert. (large-R jet energy resolution) affecting largeRjet_pt
tau_pt_syst	vector<float>	single component syst. uncert. ($\tau$ lepton reconstruction and energy scale) affecting tau_pt

Evolution from the 8 TeV release (2016) to the 13 TeV release (2020)

The evolution of the ATLAS Open Data and the tuple structure from the 8 TeV release in 2016 to the [13 TeV release].(./files.md) in 2020 are depicted below: