Analysis model s in the top physics group
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Analysis model s in the top physics group. A few remarks … What people are doing now Where we are going - Top reconstruction framework Input and output formats General remarks N.B. Not official top group ‘policy’ - personal thoughts

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Analysis model s in the top physics group
Analysis models in the top physics group

  • A few remarks …

    • What people are doing now

    • Where we are going - Top reconstruction framework

    • Input and output formats

    • General remarks

  • N.B. Not official top group ‘policy’ - personal thoughts

    • … from someone who was not particularly happy with the AMF report!

Richard Hawkings

CAT physics meeting, 3/4/09

Richard Hawkings

Creative anarchy
Creative anarchy

  • March 2009 poll initiated by Nabil Ghodbane

    • Categories not discussed in advance, and not exclusive … 116 responses

  • ‘Traditional methods’ dominate (direct AOD analysis, making private ntuples)

    • SingleTop group D2PD/ntuple also popular (not only with single top group)

      • Dump of selected AOD object info, plus overlap removal and selection

    • Some use of ARA and TopPhysD3PD (successor to TopView ntuples)

    • Less than 50% use a ‘centrally-produced’ DnPD, rest are more ‘hands on’

Richard Hawkings

Common top reconstruction code framework
Common top reconstruction code / framework

  • Some negative aspects of the ‘creative anarchy’

    • Very difficult to implement, change and cross-check common object selections

    • Very difficult for groups to work together / validate each other’s work

      • Same mistakes (e.g. in truth analysis) are made again and again

  • Moving forward with common top reconstruction code (from TopReco group)

    • A pseudo-physics subgroup to provide common forum/tools/code/selections for all ATLAS top analyses - unique in the physics groups

  • TopInputs infrastructure - now ready (see AtlasProtected/TopInputs wiki)

    • Provide common object selections and overlap removal tools

      • Using ISelector interfaces ‘approved’ by PAT but largely being implemented by TopReco

      • Implementing CSC-style selections, updated to rel 14/15, as default

    • Instead of iterating over ElectronContainer, iterate over TopInput electrons

      • A bool method gives Use? Yes/No information

      • Link to more detailed overlap ‘reasoning’ information coming later

    • TopInputs has persistency - can be added to DPD files

    • Expect this object selection to be used by all top physics analyses

      • None of this is top group specific - hope it can migrate to PAT…

Richard Hawkings

Common top reconstruction code continued
Common top reconstruction code continued

  • TopEDM objects have been defined

    • Classes to represent reconstructed top and ttbar final states

      • Basically collections of ElementLinks to the constituents of the reconstructed object

      • Minimal additional functionality - don’t want to define things that don’t always make sense (e.g reconstructed mass of leptonic top quark decay)

    • Template-based approach: <lepton>+jets, <lepton><lepton> etc

    • Classes have persistency so can be added to DPD files

  • Top reconstruction algorithms are being collected/implemented in framework

    • E.g. ‘commissioning’ algorithm (3-jet hadronic), tt-bar likelihood and chisq fitters

    • These start with TopInputs and produce TopEDM objects (in containers)

  • ‘Decoration’ of TopEDM objects by specific reconstruction algorithms

    • E.g. adding masses, chisq, fit probabilities etc

    • Proposal is to make new classes deriving from TopEDM classes and adding information (e.g. TopElectronJetsChisq) … but the persistency is tricky

    • Alternatives: add <map> of extra info, egDetails-style object or use UserDataSvc

      • … best solution(s) not clear yet

Richard Hawkings

Dnpds in this model
DnPDs in this model

  • TopInputs and TopEDM have POOL persistency

    • Can write D{1,2}PDs with input objects of interest (Electrons, Jets etc) + information on top object selection and reconstruction

    • Resulting DPDs could be analysed in Athena or ARA

  • Clear need also for ntuples (D3PDs) to look at the output in ROOT

    • + Easier for newcomers, faster to read, more intuitive

    • - The disadvantages of leaving the ‘framework’

  • Need a way to write ntuples for input objects - various possibilities

    • AMA (Max Bakk already wrote AMA interface for some TopEDM objects)

    • SingleTopDPDMaker, EWPA or EventView

      • … all have modules for writing e.g. an Electron (or subset of info) to ROOT ntuple, either directly or via some intermediate transient model

      • Should be trivial to extend them to TopInput and TopEDM objects

    • … it would be desirable to have ONE officially supported way of doing this

Richard Hawkings

Input formats for top reconstruction
Input formats for top reconstruction

  • Top reconstruction code runs in Athena …

    • Can use any format where appropriate SG containers are available (e, mu, jet etc)

    • ESD, AOD, some performance DPDs which have appropriate selection

      • DPD_SINGLEEL (medium e, pT>15 GeV) and DPD_SINGLEMU (isol.  pT>20 GeV)

  • Top is a physics WG, not a performance WG

    • In principle, should be working from ‘standard’ objects on AOD provided by combined performance groups, no need for ESD access

    • But … perhaps not true in the beginning

      • E.g. not all potentially-interesting jet calibrations/algorithms available on AOD

      • E.g. may want more detailed lepton information when studying lepton efi Ztop

      • Performance DPDs may offer a good solution for this

  • Top event volumes are modest, once we understand selection basics

    • E.g. lepton+4 jet selection is ~50k events in 100 pb-1

    • Good potential for using the TAG database and making e.g. AOD skim

      • Provided TAG variables correspond to the jet/lepton definitions we actually use

      • TopMixing sample being made available in TAGs db - first real ‘physics driven’ test

Richard Hawkings

Final remarks
Final remarks

  • Working towards more commonality in the top group

    • Common inputs and reconstruction code - Athena based

    • Common DnPDs, potentially POOL and ROOT-ntuple format

      • Tool for producing the latter is not clear yet…

    • Common analysis code yet to be tackled, but needed e.g. for initial top x-sec

    • … Easier to achieve commonality across all groups in an analysis (10-20 groups in case of top cross-section) than across all analyses going on at CERN

      • … Maybe less true in case of combined performance work

  • Gratuitous remarks

    • ARA is good for validation - looking at the contents of ESD/AODs etc

      • Personally not convinced it is a viable analysis framework, esp. for less-experienced

      • Already imposing ‘requirements’ on EDM; will end up re-inventing Athena - use Athena!

    • Lots of focus on O(10) data volume reduction: DPD streams;, 100k 10k/event

    • In the case of top, final analysis will be done with much smaller samples

      • … Keep flexibility - AOD skims, dropping containers and objects, …

      • But hard to define this now until we start getting to grips with the real data

Richard Hawkings