1. Overview: high-energy computing
production
How do the raw signals become analyzable data?
How do we “fake” the LHC
(turn theoretical models into mock detector output)?
How do these analyzable events get to my workstation “so quickly?”
How are they archived?
How do I extract parameters from event records? How do I condense petabytes of data into a picture?
operations
analysis

2. Analysis with ROOT
How do I extract parameters from event records? How do I condense petabytes of data into a picture?
analysis

3. Data is stored in many formats…
trigger
bytestream
convert
RDO
(raw)
fast pattern recognition
event sorting
esd
D3PD
reconstruction
MERGE&
derive
aod
note:
you’ll see these acronyms often…
aod
pattern
recognition
more sorting
tag

4. Simulation: treated the same way!
MONTE CARLO PRODUCTION CHAIN
RDO
(raw)
esd
D3PD
RECO
MERGE
&
derive
aod
aod
tag

5. The event format:
tracks
calorimeter
clusters
electron
muon
metadata

6. The event format in software
Organized by event
(quadrillions witnessed in 2012!)
event-wide information
Examples: metadata; sum of measured transverse energy
physics object lists:
muons, electrons, taus…
tracks of charged particles
“truth” particles…
object properties:
e.g. “hits” on tracks
track
jet
tau
track hit
2-tuple
(a,b)
n-tuple
(a1,a2,…aN)
TTree
(evt, (el.px,el.py,el.pz)[el_n],UnitVector, …)

7. Condensing the information
how can we make that “jungle” look more like a Higgs boson?

8. Histograms! “Hello World” for HEP computing: making a histogram
TH1F(“name”, “title; x title; y title”,
nBins, firstBinValue, LastBinValue)
Pseudocode: histo = makeHisto(nbins=50, firstbin=0*GeV, lastbin=200*GeV) for thisEvent in allEvents: if HasZ( thisEvent ): m = recoZMass( thisEvent ) histo.FillWith( m )
TH1F::Fill(value,weight)

9. getting to the fun part:
Are you into installing/basic histogramming?
Are you ready for processing/understanding ATLAS data?
ROOT installation
The DUKE ROOT tutorial:
exercises by Al Goshaw
help from Neil, others…
The ATLAS ROOT tutorial:
also a nice way to try out your new ATLAS computing account!
TTrees, tree loops, TSelectors, python tree access
Common homework: the Duke D3PD Dictionary