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AliZDC

ZDC Status Report. AliZDC. AliZDCMerger. AliZDCHit. AliZDCMergedHit. AliZDCDigit. AliZDCReco. 18 March 2002 – ALICE Week C. Oppedisano. AliGenZDC. AlZDCFragment. AliZDCv2. Outline. ZDC classes in AliRoot. Event merging: motivation and “strategy” Reconstructed quantities

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AliZDC

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  1. ZDC Status Report AliZDC AliZDCMerger AliZDCHit AliZDCMergedHit AliZDCDigit AliZDCReco 18 March 2002 – ALICE Week C. Oppedisano AliGenZDC AlZDCFragment AliZDCv2 Outline • ZDC classes in AliRoot • Event merging: motivation and “strategy” • Reconstructed quantities • Avalaible macros

  2. Merging “strategy” • Procedure adopted togenerate only oncea sample of spectators (n and p) • 2 TNtuple containing hits for 104 neutrons and 104 protons: ZNsignalntu.root and ZPsignalntu.root (~ 600 Kb each). Time required for simulations is minimized; Fast merging and digitization procedures. Energy deposited in ZP by 104p of 2.7 TeV Energy deposited in ZN by 104n of 2.7 TeV

  3. Class for event merging and digitization AliZDCMerger Only digitization (fMerge = kDigitize) Merging and digitization (fMerge = kMerge) –> default Background (full HIJING simulation) + Signal (spectators) Event merging Initialization Background opens background file and reads generated b, Nspec from event header;  Fragmentation applies fragmentation alghoritm, providing Nspec “free”. Merging  from background hits to “merged hits”  Mixing adds signal to background hits, creating a TCA of AliZDCMergedHit;  ExtractSignal used to extract signal from the stored spectator distributions. Digitization Digitize  from “merged hits” to digits  Phe2ADCch taking into account PMT gains and resolutions computes the light yield;  AddPedestal add a pedestal to the ADC spectrum.

  4. Background hits Signal hits Energy Energy SDigits Digits Energy ADC spectrum Structure of the ZDC branches Hits  hits generated by background (AliGenHijing without spectators); SDigits background + signal hits  “merged hits”; Digits  ADC spectra of the PMTs for the merged event;

  5. Calculated Estimated EZN+EZP vs. b b reconstructed (fm) Npart reco vs. Npart sim b reco vs. b sim b simulated (fm) • Class for reconstructed quantities • Reconstructed quantities provided by AliZDCReco: • energy detected in ZN, ZP and ZEM; • number of detected spectator protons and neutrons; • number of “true” spectator protons and neutrons; • impact parameter and number of participants. • 103 HIJING events merged with signal and reconstructed

  6. Merging and digitization Loop over the events Reconstruction • Macros avalaible in CVS server • Digitization  ZDCHits2Digits.C (# events, merge mode) • Default (mode = 1) -> merging and digitization • Reconstruction  ZDCDigits2Reco.C (# events) • b, Npart are written in ZDC branch of TreeR • AliZDCMerger *merger = new AliZDCMerger(); • merger->SetBackgroundFileName(“file.root”); • ZDC->SetMerger(merger); • merger->SetBackgroundEventNum(iev); • gAlice->Hits2SDigits(“ZDC”); • gAlice->SDigits2Digits(“ZDC”); • gAlice->Digits2reco(“ZDC”);

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