Update timestamps for new AMANDA simulation (17/02/2015)
[u/mrichter/AliRoot.git] / HMPID / api.txt
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d3da6dc4 1How to open session:
2 use static method AliRunLoader::Open("galice.root","AlicE","update") or just AliRunLoader::Open() for defaults.
3 Returns pointer to AliRunLoader on success or fatal termination on error
4How to get total number of events in galice.root:
5 AliRunLoader::GetNumberOfEvents() (or AliRun::GetEventsPerRun() using f.e. gAlice deprecated)
6How to get pointer to HMPID:
7 AliRunLoader()->GetAliRun()->GetDetector("HMPID") but before one needs to AliRunLoade()->Set
8How to avoid using gAlice:
9 detector->GetLoader()->GetRunLoader()->GetAliRun() returns gAlice global pointer.
10How to retrieve pointer to alice run loader:
11 use pHMPID->GetLoader()->GetRunLoader() (all detector classes inherit from AliDetector which has GetLoader())
12 use method AliRun::GetRunLoader for gAlice (deprecated)
13How to get pointers to different root trees:
14 TreeE belongs to AliRunLoader, available after AliRunLoader::LoadHeader()
15 TreeK belongs to AliRunLoader, available after AliRunLoader::LoadKinematics()
16 TreeH belongs to AliLoader , available after AliLoader::LoadHits()
17 TreeS belongs to AliLoader , available after AliLoader::LoadSDigits()
18 TreeD belongs to AliLoader , available after AliLoader::LoadDigits()
19 TreeR belongs to AliLoader , available after AliLoader::LoadRecPoints()
20 all methods return 0 on success.
21How to get event of interest:
22 AliRunLoader::GetEvent(event_number) returns 0 on success
23How to deal with the stack of particles?
24 - first of all, the stack includes primary as well as secondary particles
25 - pointer to the stack is taken:
d3da6dc4 26 AliRunLoader::Stack() but before one needs to load event header by AliRunLoader::LoadHeader() otherwise both methods return 0.
27 Moreover loading header gives the information about number of particles only.
28 To retrieve the list of particle one also needs to load kinematics by AliRunLoader::LoadKinematics()
29 - total amount of particles in stack for a given event:
30 AliStack::GetNtrack()
d3da6dc4 31 - total amount of primary particles in stack for a given event (after LoadHeader()):
32 AliStack::GetNprimary()
33How to retrieve hits:
322b6a67 34 Hits are stored on primary by primary basis (hits corresponding to primary particles stored in a single entry; total number of entries in hits tree equals
35 to number of primaries; order of primaries is not preserved). Hits for the given primary is TClonesArray.
d3da6dc4 36 To retrieve all hits one needs to do:
37 -initialize the root tree and containers: pRich->GetLoader()->LoadHits(); (AliLoader::LoadHits() returns 0 on success)
38 -read number of entries in TreeH: pRich->GetLoader()->TreeH()->GetEntries()
745cdf23 39 -then for each entry: pRich->GetLoader()->TreeH()->GetEntry(i)
d3da6dc4 40How to retrieve sdigits?
41 Sdigits stored in tree S with the branch of TClonesArray, all sdigits in a single TClonesArray
42 So the tree has only one entry.
43 One needs to say:
44 -pRich->GetLoader()->LoadSDigits(); this one open file, get the tree and invoke AliHMPID::SetTreeAddress()
45How to retrieve digits?
46 Digits stored in tree D with the 7 branches of TClonesArray, one per chamber, all digits of a given chamber in a single TClonesArray
47 So the tree has only one entry.
48 -One needs to say:
49 pRich->GetLoader()->LoadDigits(); this one opens file, gets the tree and invoke AliHMPID::SetTreeAddress() which in turn corresponds
50 branches of the tree to the digits containers in memory. There are 7 containers, one per chamber, all of them belong to AliHMPID.
51 -Then one needs to take the tree entry (only one) to the memory:
52 pRich->GetLoader()->TreeD()->GetEntry(0)
53 -Finally pRich->Digits(chamber_number) returns the pointer to TClonesArray of AliHMPIDdigit
54What are the debug methods avail:
55 AliLog::SetGlobalDebugLevel(AliLog::kDebug)
56How to get info for a given particle number:
57 Header and Kinematics trees must be loaded, then possible to retrieve pointer to Stack of particles
58 Int_t AliRunLoader::LoadHeader(); Int_t AliRunLoader::LoadKinematics()
59 AliStack *AliRunLoader::Stack()
60 TParticle *AliStack::Particle(tid)
61 TParticle::Print()
62How to deal with AliRunDigitizer:
63 AliRunDigitizer::Exec() just call AliRunDigitizer::Digitize()
64What are the meanings of different VMC flags:
65 gMC->IsTrackAlive()
66 gMC->IsTrackStop()
67 gMC->IsTrackDisappeared()
68How to get pad number for a local position:
69 use static TVector AliHMPIDParam::Loc2Pad(TVector2 position);
d3da6dc4 70
71How to check if a given stack particle is primary:
72 Stack is TClonesArray of TParticle. TParticle::GetMother(0) returns -1 if it's primary (no mother)
73How to loop over all possible object:
74 for(Int_t iEventN=0;iEventN < GetLoader()->GetRunLoader()->GetAliRun()->GetEventsPerRun();iEventN++){//events loop
75 for(Int_t iEntryN=0;iEntryN < GetLoader()->TreeH()->GetEntries();iEntryN++){//TreeH loop
76 GetLoader()->TreeH()->GetEntry(iEntryN);//get current entry (prim)
77 for(Int_t iHitN=0;iHitN<Hits()->GetEntries();iHitN++){//hits loop
322b6a67 78 AliHMPIDHit *pHit=(AliHMPIDHit*)Hits()->At(iHitN);//get current hit
d3da6dc4 79
80 }//hits loop
81 }//TreeH loop
82 }//events loop
83
84
85HMPID full simulation-reconstruction sequence
86
322b6a67 87hits creation:
88 HMPID uses 2 types fo hits: MIP hit and photon hit. Both types are implemented in the same class AliHMPIDHit.
89 The difference in ctor patterns is only in energy variable: for photon it is full energy, whereas for MIP it's energy lost in amplification gap gas.
90 Hit for photon is created when photon enters the volume representing a single pad of segmeneted photocathode and survives QE test.
91 Hit for MIP is created when MIP exits amplification gap (or disappired for whatever reason). The responsible code is AliHMPIDv1::StepManager().
92 Internally in ctor, the energy is converted to the total charge accamulated for this hit expressed in QCD channels. This is done in a honest manner for photon:
93 photon always produces a single electron, and the response of the chamber to a single electron pulse is parametrized out of test beam data for few HV sets.
94 For MIP the same procedure is generally wrong: the total energy lost by particle is devided by ionization potential, this value is interpreted as number of electrons
95 created, then each electon contribution is sampled according to puasonian distribution with the same single electron pulse mean as fro photons. The final charge is
96 then a sum of all single electon's contributions, it substitutes the value of energy.
d3da6dc4 97hits->sdigit:
322b6a67 98 Due to segmented photocathode, single hit might affect few neighboring pads (up to 9 in our default parametrization). The total charge collected by a single pad
99 is the answer to electrostatic problem solved in article by Mathieson (see ref ???). Actual disintegration is implemented in AliHMPIDHit::Hit2Sdi().
100 The implementation creates by default sdigits only for closest neighbours of a pad containing hit positon (further neighbours might also be checked subject to
101 parameterization flag ?????? but the contribution to them from single hit is such a tiny that only large nubmer of close hits may provide something not negligable).
d3da6dc4 102sdigits->digits:
103 The necessety of sdigits is dictated by the fact that transport engine transports tracks in a continuous sequence track by track.
322b6a67 104 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.
105 So the task of this convertion is to collect all the sdigits for the same pad and sum them up. This is done in AliHMPIDDigitizer::Exec(). This technique also provides
106 the possibility to mix events from seperate simulations facilitating studies of rare signals on top of huge background.
d3da6dc4 107digits->clusters
322b6a67 108 The aim of this conversion is to try to reconstruct the initial position of hits.
109 This it done by 2 steps procedure. On first step so called raw cluster is formed as a composition of all neighboring pads (diagonal pads are not allowed).
110 Then center of gravity of the cluster is calculated and used as a naive estimate of hit position.
111 On second step, the code tries to improve the hit position knowledge by fitting by local maxima number of Mathieson shapes. If the procedure failes, the cog
112 position is preserved as hit position.
d3da6dc4 113clusters+tracks->theta cerenkov
114
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117
745cdf23 118How to get correct magnetic field:
119 mag field is needed for simulation as well as reconstruction
120
d3da6dc4 121
122
123
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125
126
127Generalized structure of AliReconstruction:
128
129Run()
130{
131 if(there is galice.root) <-|
132 AliRunLoader::Open(....) |
133 else | this is done in InitRunLoader()
134 if(raw data process requested) |
135 create galice.root on the base of AliRawReader::NextEvent <-|
136
137 for(all detectors){ <-|
138 if(detector not selected to run) skip this detector | this is done in RunLocalReconstruction()
139 reconstructor=get detector's reconstructor |
140 |
141 if(detector HasLocalReconstruction) skip this detector | IMPORTANT! if HasLocalReconstruction() returns YES use RunLocalEventReconstruction instead
142 if(run upon raw data) |
143 reconstructor->Reconstruct(fRunLoader, fRawReader); |
144 else | <- this approach is currently used by HMPID as all branches are mounted in AliHMPID.cxx
145 reconstructor->Reconstruct(fRunLoader); |
146 } <-|
147
148 for(all events){
149
150 for(all detectors){ |
151 if(detector not selected to run) skip this detector |
152 reconstructor=get detector's reconstructor |
153 loader=get detector's loader | this is done in RunLocalEventReconstruction()
154 if(raw data process requested and detector HasDigitConversion){ |
155 loader->LoadDigits("update"); | open file and invoke detector->SetTreeAddress();
156 loader->CleanDigits(); |
157 loader->MakeDigitsContainer(); | create tree
158 reconstructor->Reconstruct(fRawReader,loader->TreeD()); | expected to fill TreeD out of raw reader
159 loader->WriteDigits("overwrite"); |
160 loader->UnloadDigits(); |
161 } |
162 if(detector do not HasLocalReconstruction) skip this detector | IMPORTANT! assumed that this detector is already processed in RunLocalReconstruction()
163 loader->LoadRecPoints("update"); |
164 loader->CleanRecPoints(); |
165 loader->MakeRecPointsContainer(); |
166 if(fRawReader && reconstructor do not HasDigitConversion()){ |
167 reconstructor->Reconstruct(fRawReader, loader->TreeR()); | expected to fill TreeR out of raw reader
168 }else{ |
169 loader->LoadDigits("read"); |
170 reconstructor->Reconstruct(loader->TreeD(),loader->TreeR()); | the only operations inside are pDigTree->GetEntry(0) and pCluTree->Fill();
171 loader->UnloadDigits(); |
172 } |
173 loader->WriteRecPoints("OVERWRITE"); |
174 loader->UnloadRecPoints(); |
175 }//detectors loop |
176
177 }//events loop
178}
179
180
181HMPID calibration and alignment.
182
183Abstract
184HMPID 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
185figure of merit. In particular, the refractive index calibration technique based on mass plot shifts analysis and chamber alignment with respect to core detectors
186are 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
187creator.
188
189Calibration.
190Looking on HMPID chamber structure, full description of which is available elsewhere (ref RichTDR), easy to compile the table of all possible parameters affecting reconstruction.
191The 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
192with methane and quartz window separating above mentioned volumes, only freon refractive index is subject for calibration. Refractive index of SiO2 window is not practically
193affected 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.
194In the rest, the only changeable parameter is refractive index of freon. Temperature influence on freon refractive index was measured experimentally. The parametrization
195found to be:
196 n=n0-0.0005(T-20) where T is freon temperature in degrees Celsius
37bac312 197 n0=Sqrt(1+ 0.554*lamda^2/(lamda^2-5769)) where lamda is photon wavelength in nm taken at 20 degrees Celsius
8c2afcb4 198Preliminary, the parametrization of refractive index versus temperature and photon energy is considered to be permanent.
199As the reconstruction itself is only interested in mean refractive index Nmean C6F14, the most elegant solution is to store in OCDB this value, prcalculated in
200AliHMPIDPrecprocessor. 2 measurements of temperature is avaiable from DCS: for inlet and outlet. They come in form of TObjArray of AliDCSValue, where AliDCSValue
201holds the value of temperature plus a time stamp at wich the value was taken. Due to organization of DCS, it's not possible to implay that all the points are taken at the same
202time, hence marked with the same time stamp. So the mean temperature are not calculable from inlet-outlet pair. Instead each sperate temperature data points are fitted.
203The resulting functions provide mean temperature function.
204
205
206
d3da6dc4 207In local CDB storage (default directory is $ALICE_ROOT) two versions of freon refractive index are written by external macro RichCdb.C :
208Run0_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.
209Run0_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.
210Both of them are valid in run range from run number 0 to run number 0, thus in no way affecting any normal operations.
211
212Refractive index of freon (C6F14) is taken in AliHMPIDRecon for 3 different photon energies by means of 2 methods: Set
213
214
215
216Alignment.
217Information about detector position and orientation is needed during reconstruction phase. This information affects track-cluster matching procedure, the relevant peace of
218code comes to AliHMPIDTracker::PropogateBack(). Matching procedure consists in prolongation of the track reconstructed in core detectors up to each HMPID chamber plane in
219a 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
220local 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
221in AliHMPIDHelix::RichIntersection(). Plane to be intersected is defined by a point belonging to that plane served by AliHMPIDParam::Center(ChamberNumber) and a vector normal
222to the plane served by AliHMPIDParam::Norm(ChamberNumber). Transformations itself are done in AliHMPIDParam::Mars2Lors() and AliHMPIDParam::Lors2Mars(). Internaly in AliHMPIDParam,
223each 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
224to radiator, anode wires plane and photocathode plane. So AliHMPIDParam sustains 7*3=21 planes. Also important to say, that direct usage of TGeoHMatrix::MasterToLocal()
225and 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
226hand corner of the chamber if one looks from outside to direction pointing to intersection point.
227So the most obvious candidate for alignable objects to be stored are these 21 TGeoHMatrix objects.
228The 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
229in a way that there is no volumes exactly corresponding to the HMPID planes.
230
231Geometry of HMPID chambers.
232After the decision to rotate the whole HMPID setup from 12 o'clock position to 2 o'clock position we have the following situation:
233
234Theta = 109.5 degrees for chambers 1,3
235Theta = 90.0 degrees for chambers 2,4,6
236Theta = 70.5 degrees for chambers 5,7
237
238Phi = 50.0 degrees for chambers 6,7
239Phi = 30.0 degrees for chambers 3,4,5
240Phi = 10.0 degrees for chambers 1,2
241
242
243Old parametrization by AliHMPIDChamber:
244HMPID chamber 1 (454.877118 , 80.207109 , -163.565361)(rho,theta,phi)=(490.0,109.5,10.0)
245HMPID chamber 2 (482.555799 , 85.087607 , 0.000000)(rho,theta,phi)=(490.0, 90.0,10.0)
246HMPID chamber 3 (400.012224 , 230.947165 , -163.565361)(rho,theta,phi)=(490.0,109.5,30.0)
247HMPID chamber 4 (424.352448 , 245.000000 , 0.000000)(rho,theta,phi)=(490.0, 90.0,30.0)
248HMPID chamber 5 (400.012224 , 230.947165 , 163.565361)(rho,theta,phi)=(490.0, 70.5,30.0)
249HMPID chamber 6 (314.965929 , 375.361777 , 0.000000)(rho,theta,phi)=(490.0, 90.0,50.0)
250HMPID chamber 7 (296.899953 , 353.831585 , 163.565361)(rho,theta,phi)=(490.0, 70.5,50.0)
251
252New parametrization by TGeoHMatrix: perfect geometry, no misalignment
253HMPID 0
254 -0.328736 -0.173648 0.928321 Tx = 454.877118
255 -0.057965 0.984808 0.163688 Ty = 80.207109
256 -0.942641 0.000000 -0.333807 Tz = -163.565361
257HMPID 1
258 0.000000 -0.173648 0.984808 Tx = 482.555799
259 0.000000 0.984808 0.173648 Ty = 85.087607
260 -1.000000 0.000000 0.000000 Tz = 0.000000
261HMPID 2
262 -0.289085 -0.500000 0.816351 Tx = 400.012224
263 -0.166903 0.866025 0.471321 Ty = 230.947165
264 -0.942641 0.000000 -0.333807 Tz = -163.565361
265HMPID 3
266 0.000000 -0.500000 0.866025 Tx = 424.352448
267 0.000000 0.866025 0.500000 Ty = 245.000000
268 -1.000000 0.000000 0.000000 Tz = 0.000000
269HMPID 4
270 0.289085 -0.500000 0.816351 Tx = 400.012224
271 0.166903 0.866025 0.471321 Ty = 230.947165
272 -0.942641 0.000000 0.333807 Tz = 163.565361
273HMPID 5
274 0.000000 -0.766044 0.642788 Tx = 314.965929
275 0.000000 0.642788 0.766044 Ty = 375.361777
276 -1.000000 0.000000 0.000000 Tz = 0.000000
277HMPID 6
278 0.214567 -0.766044 0.605918 Tx = 296.899953
279 0.255711 0.642788 0.722105 Ty = 353.831585
280 -0.942641 0.000000 0.333807 Tz = 163.565361
281
282
da08475b 283
322b6a67 284Manual:
285Diclaimer: We call the operator any persons who wants "to operate" HMPID that is to do something reasonalbe to understand current perfomance coming from the detector.
286This person is not necesarelly an expert in HMPID hardware and or software.
287Be also aware that analysis of HMPID data can only be perfomed from AliESD (taking also into acount some info which is not specific to HMPID). The task to plot something from
288hits, digits or clusters is called quality assesment.
da08475b 289
322b6a67 290From operator point of view, one needs to do 3 different tasks with HMPID: simulation, reconstruction and QA.
da08475b 291
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d3da6dc4 295