Javier Castillo 1 Muon Embedding Status & Open Issues PWG3 - CERN - 15/02/2011

Motivation A quite complicated environment like high multiplicity Pb-Pb collisions could alter the particle reconstruction efficiency – Efficiency in Pb-Pb will differ from the p-p one – Efficiency could depend on centrality The best possible simulation of a high multiplicity event is the high multiplicity event himself! Embedding: embed a simulated particle into a real event and re-reconstruct the embedded event Javier CastilloPWG3 - CERN - 15/02/2011 2

The ALICE Approach Perform the embedding at the SDigits level Signal – Simulate your preferred particle (pure J/ψ) Background – Convert raw data to SDigits (AliSimulation::ConvertRaw2SDigits) Embedding – Merge Signal and Background SDigits (AliSimulation::MergeWith) Reconstruction – From merged SDigits Javier CastilloPWG3 - CERN - 15/02/2011 3

What it means Javier CastilloPWG3 - CERN - 15/02/ SDigits DigitsClusters Embedding Hits Geant hitDeposited charge Detector reading RawDigits Reco. charge none ADC FC SDigits Reco. charge Raw FCADC calibrate decalibrate* decalibrate Calibrate: Remove pedestal and apply gain correction Decalibrate: uncorrect gain and add pedestal Signal Background Charge unit: ADC: ADC channel FC: fempto coulomb

MUON embedding All pieces existed but Merging of 2 simulations not tested recently Merging of simulation and real data never tested Many problems related to containers, formats, units, decalibration and calibration Thanks to Laurent for his help in fixing all the problems All fixes in trunk, request to port to the release will follow Javier CastilloPWG3 - CERN - 15/02/2011 5

Testing MUON embedding Simulation – Parameterized J/psi – Default OCDB: raw:// – Specific OCDBs: MUON/Calib/Gains: Ideal MUON/Align/Data: Second alignment residual on top of second alignment Reconstruction – Default OCDB: raw:// Thanks to Philippe & all for the very useful document! Global features – Test on grid on runs , – 1 signal per event in raw file – signal is generated at the real event reconstructed vertex – ITS (vertex), V0 (centrality) and ZDC (phys. Sel.) used as “black boxes” Javier CastilloPWG3 - CERN - 15/02/2011 6

Does it work? Javier CastilloPWG3 - CERN - 15/02/ Christophe S. 0-10%

Quick look at charges Javier CastilloPWG3 - CERN - 15/02/ Simulated clustersBackground clusters Charges in fc

Open issues (MUON) MUON trigger information from real data is not propagated down in the embedding chain – Conversion of raw to SDigits is disabled – If one requires the trigger matching only simulated tracks are left J/ψ width is to large – Vertex! Detailed checks to be performed – Are real and simulated charges similar enough? – Tracking: Is the embedded event equivalent to the original? Javier CastilloPWG3 - CERN - 15/02/2011 9

Open Issues (global) Generation at vertex from real event – Generator headers in galice are shifted by one event: Two possible approaches to perform embedding – First select the events to embed into (phys. sel., centrality…) and then embed – Embed into all raw events and then select ITS (vertex), V0 (centrality), ZDC (phys. sel.) – Is the calibrate, decalibrate and calibrate sequence equivalent to calibrate? Central trigger – Fired Trigger Classes are those from simulation! Can we keep those from real events instead? Physics selection: can it work on embedding? – Need right fired trigger classes – ZDC timing seems to be lost Centrality framework – Must check we get the same centrality in embedded and real event Copy some branches from original ESDs? Javier CastilloPWG3 - CERN - 15/02/

Outlook Keep on working Javier CastilloPWG3 - CERN - 15/02/

The simple embedding chain Javier CastilloPWG3 - CERN - 15/02/ SDigits Digits Clusters Simulation Hits Geant hitDeposited chargeDetector reading RawDigits Reco. charge none ADC FC Clusters Real Data RawDigits Reco. charge ADCFC SDigits DigitsClusters Embedding Hits Geant hitDeposited charge Detector reading RawDigits Reco. charge none ADC FC SDigits Reco. charge Raw FCADC decalibrate calibrate decalibrate* decalibrate calibrate

Other quick checks … Javier CastilloPWG3 - CERN - 15/02/ Christophe S. Embedding Pass1_4plus − Mainly background tracks − Signal tracks matching the trigger − No trigger matching − Trigger matching