1. David N. Brown Lawrence Berkeley National Lab Representing the BaBar Collaboration The BaBar Mini  BaBar  BaBar’s Data Formats  Design of the Mini  Mini Performance and Status  The Mini in BaBar’s New Computing Model

2. David N. Brown LBNL BaBar 2 CHEP03 25 March, 2003 BaBar  5-layer Si Vertex tracker  40-layer Drift Chamber  DIRC Cherenkov Counter  CsI Crystal Calorimeter  Muon Chambers in Fe

3. David N. Brown LBNL BaBar 3 CHEP03 25 March, 2003 BaBar Event Data Formats (2001)

4. David N. Brown LBNL BaBar 4 CHEP03 25 March, 2003 A Gap in the Formats Raw, Reco, and ESD formats were not useful  Reading any of these required staging many large files  Time to read reco is comparable to running reconstruction A better persistent model was needed: the Mini Reco Raw Reco Track Kalman Fit … DC Hit Si Hit Cluster digi Cluster digi Kalman Fit Reco Track Kalman Fit … DC Hit Si Hit Cluster digi Cluster digi Kalman Fit ESD + Reco TransientPersistent

5. David N. Brown LBNL BaBar 5 CHEP03 25 March, 2003 Mini Design Goals Support detector studies  Provide low-level detector details to support common tasks  calibration, alignment, diagnostics, and algorithm development  Provide Reconstruction Object interfaces Support detailed Physics analysis  Provide access to the full reconstruction results  EG: track fits using Kaon mass for material effect predictions  Allow users to follow calibration and alignment changes  Allow detector-level systematic error checks  Support a detailed event display  Support the standard BaBar analysis interface Make it easy to access  A disk size of 10KBytes/event or less  A readback speed comparable to the Micro  Allow customized output to fit specific needs

6. David N. Brown LBNL BaBar 6 CHEP03 25 March, 2003 Mini Design Directly persist high-level reconstruction objects  Tracks, calorimeter clusters, PID results, … Indirectly persist lower-level reconstruction objects  Track hits, calorimeter crystals, … Store ‘raw’ detector quantities (where possible)  Digitization values, electronic channel id, … Pack data to detector precision Aggressively filter detector noise Avoid overhead in low-level ‘persistent’ classes  Used fixed-size classes  Align all data members  No virtual functions in low-level classes

7. David N. Brown LBNL BaBar 7 CHEP03 25 March, 2003 Mini Persistence Reco Track Kalman Fit … DC Hit Si Hit Cluster digi Cluster digi Kalman Fit Transient Pack data from low-level classes into compact objects Persist the entire transient tree in one persistent object  References become indices into embedded arrays Every event fully described by 13 persistent objects Persistent

8. David N. Brown LBNL BaBar 8 CHEP03 25 March, 2003 Data Packing Digitize floating point values  Eg track fit parameters and covariance matrix  Set packing precision at ~1% of detector resolution  Use locally flat, globally logarithmic packing algorithm  Packing precision depends on the value being packed  Supports histograms without binning artifacts Bitwise OR small fields into packed data words  Track Impact parameter  Pack into 17 bits  longword alignment  Pack parameter error into remaining 15 bits

9. David N. Brown LBNL BaBar 9 CHEP03 25 March, 2003 Mini Analysis Interface The BaBar Analysis Framework is entrenched  Huge investment in Physicist code after 3 years of operation The original design supported multiple data formats  But it had evolved to depend on details of the Micro  Providing Mini-compatibility was a major effort  Changes in the base classes, new subclasses, … The BaBar Mini Analysis interface is now working  Physics (Micro) objects are built from native Mini objects  Fully compatible with existing user code  Provides access to most Mini-specific features  Performance is comparable to reading the Micro

10. David N. Brown LBNL BaBar 10 CHEP03 25 March, 2003 Mini Performance Data size (after ootidy + gzip compression)  6.5 Kbytes per generic physics event  10 Kbytes per multi-hadron event (~10 tracks) Readback speed  20 mSec per generic event (1GHz pentium III Linux) Readback operation% time Transient creation + deletion35 Objectivity data read 10  30 Physics object creation20 Framework overhead10 Data field unpacking0.1

11. David N. Brown LBNL BaBar 11 CHEP03 25 March, 2003 Single Event Display- MiniSingle Event Display- Micro

12. David N. Brown LBNL BaBar 12 CHEP03 25 March, 2003 Mini Status The Mini was released for production in 2002  All components of BaBar detector represented  Trigger, MC truth matching, Particle ID, … ‘2002’ Reprocessing is nearly complete  Should finish this week!  Will provide the full Mini for BaBar’s full data sample  Reco, Raw, and ESD were not written in this processing  A Large savings in cpu, IO, tape, lock traffic, … Mini data is available at BaBar Tier-A sites  The total Mini sample will be ~10 TeraBytes  Access is through dynamic staging  Small samples can be exported to smaller sites  Physicists are starting to use it

13. David N. Brown LBNL BaBar 13 CHEP03 25 March, 2003 BaBar’s New Computing Model BaBar has recently revised its computing model  Prompted (partly) by the need to integrate the Mini The Mini will be ported to use RootIO  Allows interactive (CINT) access to production output  Embedded arrays will be converted to Root columns  Embedded object classes will be directly reused A Reduced Mini will replace the existing Micro  Cluster Mini objects used directly in analysis into New Micro  Cluster other objects separately to complete the Mini The Analysis interface will be re-implemented  Optimized for Mini access

14. David N. Brown LBNL BaBar 14 CHEP03 25 March, 2003 Conclusions BaBar has implemented a new Event format: the Mini  Replaces inefficient Raw, Reco, and ESD formats  Provides access to detector detail for average users The full BaBar data sample will soon be available in Mini format BaBar is implementing a new Computing Model  The Mini will be ported to RootIO  The Micro will be replaced with a Reduced Mini  The Analysis interface will be re-implemented  The new model will be deployed in late 2003 We are close to achieving our original goal of a flexible, unified, efficient event data format