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Update of the TOF code

Update of the TOF code. F. Noferini , A. De Caro TOF group. Motivations. We collect several requests from analysis groups which focused on the possibility to improve TPC-TOF misassociation rejection (for example dielectron analysis ).

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Update of the TOF code

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  1. Update of the TOF code F. Noferini, A. De Caro TOF group Offline meeting - 13th Jan 2014

  2. Motivations Wecollectseveralrequests from analysisgroupswhichfocused on the possibility to improve TPC-TOF misassociationrejection (for exampledielectronanalysis). Werecentlyinvestigate the possibility to improve the TOF performance using information of multiple hits. • Werevisitedourframework to getbetterresults. Note that: werequiredatthis stage a complete backwardcompatibilityalso for the physicsresults (the changewill be transparent for analysisusers) Offline meeting - 13th Jan 2014

  3. From ourstudentthesis Whatismissing in the oldframework PbPbevents Run 137161 Special TOF pass1 TOF hit density (differentMRPCs). 5% multiple hit TOF hit density (same MRPC). 20-25% multiple hit Weare neglecting in the currentmatchingframework the factthat multiple hits can happen in TOF. Wewouldlike to propose a change to account for thatboth in the TOF matchingalgorithm and in the ESD/AOD structure. Offline meeting - 13th Jan 2014

  4. From ourstudentthesis Whathappens in multiple hit cases? Double and single hit caseshave a differentresidualdistribution PbPbevents Run 137161 Special TOF pass1 DOUBLE HITS SINGLE HIT Double hit case happensclose to the padborders. case iscurrentlydistorted. Time distribution in double hit Offline meeting - 13th Jan 2014

  5. From ourstudentthesis Whatwe can gain with a new approach PbPbevents Run 137161 Special TOF pass1 A recentstudyshowedthatwe are able to improve the quality of the signal in double hit cases (t1 tbest) using the information of all the matchable hit. Werevisitedour code to portsuch an information in the ESD/AOD withoutaffect the size of the files. old new Additional gain also in the identification of mismatched TPC-tracks vs TOF-hits! Offline meeting - 13th Jan 2014

  6. The main idea • In the oldframeworkthere are featureswhich are limitingour work: • Multiple hit are notported in ESD/AOD so wecannotimproveoursignal for thosecases • TPC track-TOF hit matchingisperformed in an exclusive way (11) whichmeansthatatanalysislevel: • Weloosememory of other possibile associationswhenmismatchhappens • Wecannot re-assign the TOF hit to anothertrackevenifwe are able to identify a missaciation • Information on 1N or N1 cases can help to identify high probabilitymismatchcases. •  Oursolution: • Wedisentangledthe concepts of TPC track and TOF cluster in order to allow multiple association in bothdirection • TOF matchingwindowwill be fixedat 10 cm (in PbPbwas 3 cm) so thatitcan be manageat the analysislevel (usefull to studysystematiceffect in the efficiency) • whilekTOFoutwill be switched on (for the moment) according to the matchingwindowsastillnow to guarantee no changes for the users. Offline meeting - 13th Jan 2014

  7. ESD structure OLD: All the TOF information are storedat the tracklevel (TOF branches are added to AliESDtrack ) NEW: TOF cluster (onlymatchable clusters!) will be stored in a different array (in the AliESDEvent) while in the ESD trackswill be put only the indexes of the matchable TOF clusters. The ammount of TOF information availableat the analysislevelincreased Reco trackswithoutmatchingdo notstoreany TOF information asdonetillnow  data sizeroughlythe same Multiple associationallowedin bothdirections Offline meeting - 13th Jan 2014

  8. NEW structure Many reco tracks (80-90%) willnotpointany TOF cluster. In the tracktherewill be only an array of indexes for AliESDTOFcluster. All the TOF clusters written in the ESD will be pointed from, atleast, onereco track= matchable TOF cluster (otherwisenotstored in ESD/AOD)   50% reduction The information available in the TOF clusters willbe differentin theESD and in the AOD. • AliESDTOFclusterstructure: • Some attributes for TOF standalone info: • fTOFsignal, fTOFsignalTOT, … • Some attibutesrelated to the matching with a track (array sizedependson the number of possibleassociations): • fTrackLength, fIntTimes[], fTOFsignalDz, … Offline meeting - 13th Jan 2014

  9. New classes STEER/STEERBase/AliVTOFcluster STEER/ESD/AliESDTOFcluster STEER/AOD/AliAODTOFcluster Different from AliTOFclusterused for RecPoints! Offline meeting - 13th Jan 2014

  10. Code changes in AliRoot STEER/CMakelibAOD.pkg STEER/STEERBase/ STEER/STEERBase/AliVTOFcluster.h STEER/STEERBase/AliVTOFcluster.cxx STEER/STEERBaseLinkDef.h STEER/CMakelibSTEERBase.pkg STEER/AODLinkDef.h STEER/ESD/AliESDTOFcluster.cxx STEER/ESD/AliKalmanTrack.h STEER/ESD/AliESDpid.cxx STEER/ESD/AliESDEvent.cxx STEER/ESD/AliESDtrack.h STEER/ESD/AliESDEvent.h STEER/ESD/AliKalmanTrack.cxx STEER/ESD/AliESDtrack.cxx STEER/ESD/AliESDTOFcluster.h STEER/ESDLinkDef.h STEER/CMakelibESD.pkg TOF/AliTOFtrackerV2.h TOF/AliTOFReconstructor.cxx TOF/AliTOFtrackerV1.cxx TOF/CMakelibTOFrec.pkg TOF/AliTOFtracker.cxx TOF/AliTOFtrackerV2.cxx TOF/TOFrecLinkDef.h To managerules for backwardcompatibility Changealso in the AOD dir will be done Offline meeting - 13th Jan 2014

  11. Change in AliESDtrack Int_tfTOFLabel[3]; //! TOF label Int_tfTOFCalChannel; //! Channel Index of the TOF Signal Int_tfTOFindex; //! index of the assigned TOF cluster Double32_t fTrackTime[AliPID::kSPECIESC]; //! TOFs estimated by the tracking Double32_t fTrackLength; //!Track length Double32_t fTOFsignal; //! detector's PID signal Double32_t fTOFsignalToT; //! detector's ToT signal Double32_t fTOFsignalRaw; //! detector's uncorrected time signal Double32_t fTOFsignalDz; //! local z of track's impact on the TOF pad Double32_t fTOFsignalDx; //! local x of track's impact on the TOF pad Short_tfTOFdeltaBC; //! detector's Delta Bunch Crossing correction Short_t fTOFl0l1; //! detector's L0L1 latency correction // new TOF data structure Int_tfNtofClusters; // number of matchable TOF clusters Int_t *fTOFcluster; //[fNtofClusters] // TOF clusters matchable with the track Note that, in parallel to this work, detector probabilitywillnot be written in new ESDs and integratedtimeswill be extendedalso to light nuclei (discussed with Ruben and TPC experts). Offline meeting - 13th Jan 2014

  12. Numbers from test production Werun some MC simulations(PbPb 0-5% 5.5 atTeV) to test the new framework and to estimate the impact on the ESD file: ESD size for one high multiplicityevent: -rw-r--r-- 1 noferininoferini 9176132 18 dic 11:27 AliESDsOld.root -rw-r--r-- 1 noferininoferini 9137150 20 dic 18:35 AliESDsNew.root Wealsoreconstructedonechunk on PbPb 2011 (80 events): -rw-r--r-- 1 noferininoferini 446807509 18 dic 15:57 AliESDsOld.root -rw-r--r-- 1 noferininoferini 452066800 21 dic 00:07 AliESDsNew.root *Integratedtimesextended to light nuclei also for the oldscheme Offline meeting - 13th Jan 2014

  13. Backwardcompatibility • New alirootversionswill be backword compatibile with the oldscheme (alreadytested). • Oldalirootversionswillnot be able to process the new data. • Thisis a major changewhichwillmake obsolete oldalirootversion for future TOF analyses! AliTOFtrackerclasshasbeenadaptedforthe new scheme in order to reproduceexactly the sameresultsas in the past. However more information will be availbleafter the reconstruction (TOF experts) to studypossibleclusterization, improving in the matching, mismatchrejection, … A new matchingschemewill be releasedusing the additional information to improve the performance for multiple hit cases (in developing…). AOD: Wealsoverifiedthat the old AOD filteringstillworks with the new frameworkwithoutanyadditionalaction. Howeverwewill migrate also AOD structure to the new scheme. Offline meeting - 13th Jan 2014

  14. Some QA plots Single MC ultra centralevent Wereproduced the performance obtained with the old data structure Start time generated in MC T0-TOF is the same for all the reconstructions Some minor differencesbetween OLD and NEW integratedtimes: probably due to float->double conversion Checks are stillongoingbutitisnot a big issue. Offline meeting - 13th Jan 2014

  15. Summary • TOF data structurewritten in the ESD hasbeenchanged (reco tracks and TOF clusters disentagled): • The amountof TOF information availableat the analysislevelincreased • Reco trackswithoutmatchingdo notstoreany TOF information asdonetillnow •  data sizeroughlythe same • Multiple associationallowedin bothdirections • Backwardcompatibilityisguaranted. • The changeistransparent for the analysisusers: • Weguarantee no changes for the users • However, minumum set of TOF informationswill be availableafterreconstruction for TOF experts to develop a new matchingalgorithm and clustering. • AOD change (M. Colocci service task) will be doneimmediatelyafter the commit in the ESD dir. Offline meeting - 13th Jan 2014

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