overview : high - energy computing
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Overview : high - energy computing. 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 ? - PowerPoint PPT PresentationTRANSCRIPT
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Overview: high-energy computing
• 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?
production
operations
analysis
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Analysis with ROOT
• How do I extract parameters from event records? How do I condense petabytes of data into a picture?
analysis
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Data is stored in many formats…
trigger convert
MERGE&
derive
bytestream
reconstruction
esd
aod
tag
D3PD
aod
RDO(raw)
pattern recognition
fast pattern recognitionevent sorting
more sorting
note:you’ll see these acronyms often…
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Simulation: treated the same way!
MERGE&
deriveRECO
esd
aod
tag
D3PD
aod
MONTE CARLO PRODUCTION CHAINRDO(raw)
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The event format:
muon
calorimeterclusters
tracks
electron
metadata
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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
µ tracktracktracktracktracktracktrack
jetjettau
track hittrack
hit
event
2-tuple (a,b)n-tuple (a1,a2,…aN)TTree (evt, (el.px,el.py,el.pz)[el_n],UnitVector, …)
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Condensing the information
• how can we make that “jungle” look more like a Higgs boson?
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Histograms!
Pseudocode:histo = makeHisto(nbins=50, firstbin=0*GeV, lastbin=200*GeV)for thisEvent in allEvents:
if HasZ( thisEvent ):m = recoZMass( thisEvent )
histo.FillWith( m )
• “Hello World” for HEP computing: making a histogram
TH1F::Fill(value,weight)
TH1F(“name”, “title; x title; y title”, nBins, firstBinValue,
LastBinValue)
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getting to the fun part:Are you into installing/basic histogramming?• 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!
Are you ready for processing/understanding ATLAS data?
• TTrees, tree loops, TSelectors, python tree access
• Common homework: the Duke D3PD Dictionary