How to open session: use static method AliRunLoader::Open("galice.root","AlicE","update") or just AliRunLoader::Open() for defaults. Returns pointer to AliRunLoader on success or fatal termination on error How to get total number of events in galice.root: AliRunLoader::GetNumberOfEvents() (or AliRun::GetEventsPerRun() using f.e. gAlice deprecated) How to get pointer to HMPID: AliRunLoader()->GetAliRun()->GetDetector("HMPID") but before one needs to AliRunLoade()->Set How to avoid using gAlice: detector->GetLoader()->GetRunLoader()->GetAliRun() returns gAlice global pointer. How to retrieve pointer to alice run loader: use pHMPID->GetLoader()->GetRunLoader() (all detector classes inherit from AliDetector which has GetLoader()) use method AliRun::GetRunLoader for gAlice (deprecated) How to get pointers to different root trees: TreeE belongs to AliRunLoader, available after AliRunLoader::LoadHeader() TreeK belongs to AliRunLoader, available after AliRunLoader::LoadKinematics() TreeH belongs to AliLoader , available after AliLoader::LoadHits() TreeS belongs to AliLoader , available after AliLoader::LoadSDigits() TreeD belongs to AliLoader , available after AliLoader::LoadDigits() TreeR belongs to AliLoader , available after AliLoader::LoadRecPoints() all methods return 0 on success. How to get event of interest: AliRunLoader::GetEvent(event_number) returns 0 on success How to deal with the stack of particles? - first of all, the stack includes primary as well as secondary particles - pointer to the stack is taken: AliRunLoader::Stack() but before one needs to load event header by AliRunLoader::LoadHeader() otherwise both methods return 0. Moreover loading header gives the information about number of particles only. To retrieve the list of particle one also needs to load kinematics by AliRunLoader::LoadKinematics() - total amount of particles in stack for a given event: AliStack::GetNtrack() - total amount of primary particles in stack for a given event (after LoadHeader()): AliStack::GetNprimary() How to retrieve hits: Hits are stored on primary by primary basis. Hits for the given primary is TClonesArray. To retrieve all hits one needs to do: -initialize the root tree and containers: pRich->GetLoader()->LoadHits(); (AliLoader::LoadHits() returns 0 on success) -read number of entries in TreeH: pRich->GetLoader()->TreeH()->GetEntries() -then for each entry: pRich->GetLoader()->TreeH()->GetEntry(i) How to retrieve sdigits? Sdigits stored in tree S with the branch of TClonesArray, all sdigits in a single TClonesArray So the tree has only one entry. One needs to say: -pRich->GetLoader()->LoadSDigits(); this one open file, get the tree and invoke AliHMPID::SetTreeAddress() How to retrieve digits? Digits stored in tree D with the 7 branches of TClonesArray, one per chamber, all digits of a given chamber in a single TClonesArray So the tree has only one entry. -One needs to say: pRich->GetLoader()->LoadDigits(); this one opens file, gets the tree and invoke AliHMPID::SetTreeAddress() which in turn corresponds branches of the tree to the digits containers in memory. There are 7 containers, one per chamber, all of them belong to AliHMPID. -Then one needs to take the tree entry (only one) to the memory: pRich->GetLoader()->TreeD()->GetEntry(0) -Finally pRich->Digits(chamber_number) returns the pointer to TClonesArray of AliHMPIDdigit What are the debug methods avail: AliLog::SetGlobalDebugLevel(AliLog::kDebug) How to get info for a given particle number: Header and Kinematics trees must be loaded, then possible to retrieve pointer to Stack of particles Int_t AliRunLoader::LoadHeader(); Int_t AliRunLoader::LoadKinematics() AliStack *AliRunLoader::Stack() TParticle *AliStack::Particle(tid) TParticle::Print() How to deal with AliRunDigitizer: AliRunDigitizer::Exec() just call AliRunDigitizer::Digitize() What are the meanings of different VMC flags: gMC->IsTrackAlive() gMC->IsTrackStop() gMC->IsTrackDisappeared() How to get pad number for a local position: use static TVector AliHMPIDParam::Loc2Pad(TVector2 position); Why list of chambers belongs to AliHMPIDParam: How to check if a given stack particle is primary: Stack is TClonesArray of TParticle. TParticle::GetMother(0) returns -1 if it's primary (no mother) How to loop over all possible object: for(Int_t iEventN=0;iEventN < GetLoader()->GetRunLoader()->GetAliRun()->GetEventsPerRun();iEventN++){//events loop for(Int_t iEntryN=0;iEntryN < GetLoader()->TreeH()->GetEntries();iEntryN++){//TreeH loop GetLoader()->TreeH()->GetEntry(iEntryN);//get current entry (prim) for(Int_t iHitN=0;iHitNGetEntries();iHitN++){//hits loop AliVHMPIDHit *pHit=(AliVHMPIDHit*)Hits()->At(iHitN);//get current hit }//hits loop }//TreeH loop }//events loop HMPID full simulation-reconstruction sequence hits->sdigit: Responsible method is AliHMPID::Hits2SDigits One hit may affect one or more pads. Hit position is taken on the anode wires plane as the most of avalanche is developed there. This position is not directly available, track intersections with entrance and exit of amplification gap are only stored. So the position in the middle of the gap is calculated as average out of pHit->In() and pHit->Out() positions. Then, total charge collected for this hit is calculated by AliHMPIDParam::Hit2Qdc. Area of disintegration is a list of pads affected by current hit. This is a parameter of Mathienson sdigits->digits: The necessety of sdigits is dictated by the fact that transport engine transports tracks in a continuous sequence track by track. It means that it may happen that the same pad is affected by few tracks. But this might be known only after the transport of full event is finished. digits->clusters A set of neighboring digits compose cluster. The aim of this transformation is to construct a list of clusters out of digits list. The calling sequence is: AliReconstruction::Run() AliHMPIDReconstructor::Reconstruct() creates an empty clusters list, loops on chambers, retrieves a list of digits for a given chamber, gives it to the method Dig2Clu() and finally serializes the list AliHMPIDReconstructor::Dig2Clu() which knows no details about clusters+tracks->theta cerenkov How to get correct magnetic field: mag field is needed for simulation as well as reconstruction Generalized structure of AliReconstruction: Run() { if(there is galice.root) <-| AliRunLoader::Open(....) | else | this is done in InitRunLoader() if(raw data process requested) | create galice.root on the base of AliRawReader::NextEvent <-| for(all detectors){ <-| if(detector not selected to run) skip this detector | this is done in RunLocalReconstruction() reconstructor=get detector's reconstructor | | if(detector HasLocalReconstruction) skip this detector | IMPORTANT! if HasLocalReconstruction() returns YES use RunLocalEventReconstruction instead if(run upon raw data) | reconstructor->Reconstruct(fRunLoader, fRawReader); | else | <- this approach is currently used by HMPID as all branches are mounted in AliHMPID.cxx reconstructor->Reconstruct(fRunLoader); | } <-| for(all events){ for(all detectors){ | if(detector not selected to run) skip this detector | reconstructor=get detector's reconstructor | loader=get detector's loader | this is done in RunLocalEventReconstruction() if(raw data process requested and detector HasDigitConversion){ | loader->LoadDigits("update"); | open file and invoke detector->SetTreeAddress(); loader->CleanDigits(); | loader->MakeDigitsContainer(); | create tree reconstructor->Reconstruct(fRawReader,loader->TreeD()); | expected to fill TreeD out of raw reader loader->WriteDigits("overwrite"); | loader->UnloadDigits(); | } | if(detector do not HasLocalReconstruction) skip this detector | IMPORTANT! assumed that this detector is already processed in RunLocalReconstruction() loader->LoadRecPoints("update"); | loader->CleanRecPoints(); | loader->MakeRecPointsContainer(); | if(fRawReader && reconstructor do not HasDigitConversion()){ | reconstructor->Reconstruct(fRawReader, loader->TreeR()); | expected to fill TreeR out of raw reader }else{ | loader->LoadDigits("read"); | reconstructor->Reconstruct(loader->TreeD(),loader->TreeR()); | the only operations inside are pDigTree->GetEntry(0) and pCluTree->Fill(); loader->UnloadDigits(); | } | loader->WriteRecPoints("OVERWRITE"); | loader->UnloadRecPoints(); | }//detectors loop | }//events loop } HMPID calibration and alignment. Abstract HMPID calibration and alignment strategy is described with emphasis put on those aspects of the procedure which are relevant for reconstruction and thus the final detector figure of merit. In particular, the refractive index calibration technique based on mass plot shifts analysis and chamber alignment with respect to core detectors are explained in details. External sources of calibration and alignment data are also mentioned as well as the way HMPID intends to handle those data, including initial CDB creator. Calibration. Looking on HMPID chamber structure, full description of which is available elsewhere (ref RichTDR), easy to compile the table of all possible parameters affecting reconstruction. The first one of major importance is a freon refractive index. Although the full optical path visible by photons includes freon vessel, proximity and amplification gaps filled with methane and quartz window separating above mentioned volumes, only freon refractive index is subject for calibration. Refractive index of SiO2 window is not practically affected by any external parameters, while influence of methane temperature to it's refractive index is negligible. So it's enough to measure there optical curves just once. In the rest, the only changeable parameter is refractive index of freon. Temperature influence on freon refractive index was measured experimentally. The parametrization found to be: n=n0-0.0005(T-20) where T is freon temperature in degrees Celsius n0=Sqrt(1+ 0.554*lamda^2/(lamda^2-5796)) where lamda is photon wavelength in nm taken at 20 degrees Celsius Preliminary, the parametrization itself is considered to be permanent one. The only parameter to store and retrieve is freon temperature. Since this value is available from DCS DB and expected to be served by a SHUTTLE program which is not yet ready, the following temporarily solution has been adopted. In local CDB storage (default directory is $ALICE_ROOT) two versions of freon refractive index are written by external macro RichCdb.C : Run0_0_v0_s0.root contains DiMauro's parametrization and the temperature is set to 20 degrees. To be used as default for simulation and reconstruction. Run0_0_v0_s1.root contains DiMauro's parametrization and the temperature is set to 50 degrees. To be used in special uncalibrated reconstruction to test calibration procedure. Both of them are valid in run range from run number 0 to run number 0, thus in no way affecting any normal operations. Refractive index of freon (C6F14) is taken in AliHMPIDRecon for 3 different photon energies by means of 2 methods: Set Alignment. Information about detector position and orientation is needed during reconstruction phase. This information affects track-cluster matching procedure, the relevant peace of code comes to AliHMPIDTracker::PropogateBack(). Matching procedure consists in prolongation of the track reconstructed in core detectors up to each HMPID chamber plane in a sequence. The plane used is the entrance to HMPID radiators. If the intersection exists and inside the sensitive area, the point of intersection is to be transformed to HMPID local reference system. Note, that in this check, the dead zones in-between radiators are not taken into account. This operation requiring MARS to LORS transformations is done in AliHMPIDHelix::RichIntersection(). Plane to be intersected is defined by a point belonging to that plane served by AliHMPIDParam::Center(ChamberNumber) and a vector normal to the plane served by AliHMPIDParam::Norm(ChamberNumber). Transformations itself are done in AliHMPIDParam::Mars2Lors() and AliHMPIDParam::Lors2Mars(). Internaly in AliHMPIDParam, each chamber is represented by TGeoHMatrix. It's worth to stress again that geometry related operations are needed to be done for 3 different planes per chamber, namely entrance to radiator, anode wires plane and photocathode plane. So AliHMPIDParam sustains 7*3=21 planes. Also important to say, that direct usage of TGeoHMatrix::MasterToLocal() and vice versa is not possible due to special nature of HMPID LORS. According to the decision made about 3 years ago, HMPID local reference system is centered in low left hand corner of the chamber if one looks from outside to direction pointing to intersection point. So the most obvious candidate for alignable objects to be stored are these 21 TGeoHMatrix objects. The approach suggested in AliAlignObj is not quite feasible mainly due to the fact it relays on incrementing procedure using import from geometry.root. HMPID geometry is defined in a way that there is no volumes exactly corresponding to the HMPID planes. Geometry of HMPID chambers. After the decision to rotate the whole HMPID setup from 12 o'clock position to 2 o'clock position we have the following situation: Theta = 109.5 degrees for chambers 1,3 Theta = 90.0 degrees for chambers 2,4,6 Theta = 70.5 degrees for chambers 5,7 Phi = 50.0 degrees for chambers 6,7 Phi = 30.0 degrees for chambers 3,4,5 Phi = 10.0 degrees for chambers 1,2 Old parametrization by AliHMPIDChamber: HMPID chamber 1 (454.877118 , 80.207109 , -163.565361)(rho,theta,phi)=(490.0,109.5,10.0) HMPID chamber 2 (482.555799 , 85.087607 , 0.000000)(rho,theta,phi)=(490.0, 90.0,10.0) HMPID chamber 3 (400.012224 , 230.947165 , -163.565361)(rho,theta,phi)=(490.0,109.5,30.0) HMPID chamber 4 (424.352448 , 245.000000 , 0.000000)(rho,theta,phi)=(490.0, 90.0,30.0) HMPID chamber 5 (400.012224 , 230.947165 , 163.565361)(rho,theta,phi)=(490.0, 70.5,30.0) HMPID chamber 6 (314.965929 , 375.361777 , 0.000000)(rho,theta,phi)=(490.0, 90.0,50.0) HMPID chamber 7 (296.899953 , 353.831585 , 163.565361)(rho,theta,phi)=(490.0, 70.5,50.0) New parametrization by TGeoHMatrix: perfect geometry, no misalignment HMPID 0 -0.328736 -0.173648 0.928321 Tx = 454.877118 -0.057965 0.984808 0.163688 Ty = 80.207109 -0.942641 0.000000 -0.333807 Tz = -163.565361 HMPID 1 0.000000 -0.173648 0.984808 Tx = 482.555799 0.000000 0.984808 0.173648 Ty = 85.087607 -1.000000 0.000000 0.000000 Tz = 0.000000 HMPID 2 -0.289085 -0.500000 0.816351 Tx = 400.012224 -0.166903 0.866025 0.471321 Ty = 230.947165 -0.942641 0.000000 -0.333807 Tz = -163.565361 HMPID 3 0.000000 -0.500000 0.866025 Tx = 424.352448 0.000000 0.866025 0.500000 Ty = 245.000000 -1.000000 0.000000 0.000000 Tz = 0.000000 HMPID 4 0.289085 -0.500000 0.816351 Tx = 400.012224 0.166903 0.866025 0.471321 Ty = 230.947165 -0.942641 0.000000 0.333807 Tz = 163.565361 HMPID 5 0.000000 -0.766044 0.642788 Tx = 314.965929 0.000000 0.642788 0.766044 Ty = 375.361777 -1.000000 0.000000 0.000000 Tz = 0.000000 HMPID 6 0.214567 -0.766044 0.605918 Tx = 296.899953 0.255711 0.642788 0.722105 Ty = 353.831585 -0.942641 0.000000 0.333807 Tz = 163.565361