1. Developments of the PWG3 muon analysis code
The analysis train for the muon analysis should be based on the creation of the following files:
Standard AOD
Muon - AOD
Dimuon - AOD
ESD
Standard AOD:
obtained filtering the ESD information
Muon AOD:
N  1
replica of the standard AOD, containing only events where at least one muon is present
N  2
Dimuon AOD:
replica of the standard AOD for events with N  2, adding a new branch for dimuons
Alice Offline Week, October 23rd 2008

2. Muon AOD creation Selection of muon events: Standard AOD Muon - AOD
The Muon AOD is created:
1) selecting events with N  1
2) replicating the standard AOD branches
Selection of muon events:
It’s based on the AOD tag files
Standard AOD
Muon - AOD
AOD tag
AliEventTagCuts *evCuts = new AliEventTagCuts();
evCuts->SetNMuonRange(1,10);
SetNMuonRange select muons according to the global PID
 Need to define a setter to select only muons detected in the muon spectrometer (to be implemented)

3. Replica of the AOD branches
Replica of the standard AOD branches:
The possibility of replicating the standard AOD branches is implemented in
ANALYSIS/AliAnalysisTaskSE.cxx(.h)
It is possible to choose which branches have to be replicated using some setters:
STEER/AliAODHandler.cxx(.h)
aodOutputHandler->SetNeedsHeaderReplication(); aodOutputHandler->SetNeedsTracksBranchReplication(); aodOutputHandler->SetNeedsVerticesBranchReplication(); aodOutputHandler->SetNeedsV0sBranchReplication(); aodOutputHandler->SetNeedsTrackletsBranchReplication(); aodOutputHandler->SetNeedsPMDClustersBranchReplication(); aodOutputHandler->SetNeedsJetsBranchReplication(); aodOutputHandler->SetNeedsFMDClustersBranchReplication(); aodOutputHandler->SetNeedsCaloClustersBranchReplication();
The replica of the AOD branches is of general use (i.e. not only for the Muon AOD creation)
Names of the AOD branches are the same in the standard and in the Muon-AOD
 Macros can be run on both without changes

4. Tracks belonging to events where there is at least one muon (Muon AOD)
Input: AliAODs.root, AOD.tag.root
Output: AliMuonAODs.root
Analysis Task:
PWG3/muon/AnalysisTaskFromStandardToMuonAOD.cxx
We can select the information we want to replicate in the Muon-AOD
(header of the event, tracks, vertices…)
 In principle, at this level, we should keep all the available information
3729 tracks
6 tracks
70 tracks
Tracks belonging to events where there is at least one muon (Muon AOD)
All Tracks
(Standard AOD)
Muon tracks
(Muon AOD)

5. Dimuon AOD creation The Dimuon AOD should be created:
1) selecting events with N  2, using tag cuts
replicating the interesting AOD branches
creating a dimuon object and adding it in a new Dimuon branch
Analysis Task:
PWG3/muon/AliAnalysisTaskFromMuonToDimuonAOD.cxx(.h)
Example from a generation of upsilon events
Mmm pT pT

6. Dimuon AOD creation (2) 1 Standard AOD Muon AOD 2 Muon AOD
2 possibilities can be foreseen for the Dimuon AOD creation: 1
Standard AOD
Muon AOD
N  1
1st
analysis train 2
Muon AOD
Standard AOD
N  1
1st
analysis train
Dimuon AOD
N  2
Dimuon AOD
N  2
2nd analysis train
Option 2 should be preferred
but is it possible to use two different tag selections within the same analysis train?

7. AliAODDimuon AliAODDimuon(TObject *mu1,TObject *mu2,TObject *evinfo)
The dimuon creation is based on the AliAODDimuon.cxx(.h) and AliAODEventInfo.cxx (.h) classes.
The dimuon object is created from the pointers to two AliAODTracks
AliAODDimuon(TObject *mu1,TObject *mu2,TObject *evinfo)
AliAODEventInfo  class which provides additional infos on the AliAODEvent, not included in the AOD header, namely
the beam energy (used in the calculation of the cosCS)
information on the trigger
This class should eventually be removed, because the information it contains should be retrieved from the AOD
the decoding of the trigger mask should be provided to the AOD at a higher level
the beam energy is stored in the ESD/AOD tag file, but it is not written in the AOD header  not directly accessible?

8. Files dimension Some numbers on files dimension
Typical ESD event (from PDC08/LHC08x 14TeV) :
~ 16 KB/event
compression factor ~ 5
Standard AOD :
~ 3.1 KB/event
Events with N  1 ~ 1%
Fraction of events with N  2 / N  1 ~ 1%
Size of the dimuon branch:
~ 0.02 KB/event negligible with respect to standard AOD event size (~3 KB)
Because of the small size of the files, we should create the Muon/Dimuon AODs merging several files

9. Event mixing
For the combinatorial background subtraction we should use the event mixing technique.
We can use the AliMuonAOD.root as input for the mixing, since it contains single muon tracks
Muons should be mixed if they belong to events with similar characteristics
 pools have to be defined
According with the mixing framework, pools definition can be based on the tags
Need to have tags matched to the Muon-AOD
Need to check if the information used for the pool definition (z of the vertex, centrality, reaction plane…) are contained in the tags
Output of the mixing framework should be a Mixed Dimuon-AOD containing dimuon infos and infos on the pool definition

10. Schema of the analysis train for MUON analysis
Standard AOD 1
tracks
branch
vertices
header
other
branches
Standard AOD 2
Standard AOD n …
Merging
Muon AOD
Pools
Mixed DiMuon AOD
Mixing events
dimuon
branch
Pool info for
normalization
AliAnalysisTaskME
Muon AOD
tracks
branch
vertices
header …
DiMuon AOD
tracks
branch
vertices
header
dimuon …

11. Conclusions and requirements for the Offline meeting
A proposal for the creation of the Muon/Dimuon AOD within the analysis framework has been presented
Muon/Dimuon AODs will have a smaller size with respect to standard AOD
 a merging of the files should be foreseen
The Muon-AOD will also be the input for the background estimate using the event mixing
AOD tags should be created for Muon/Dimuon AODs
The code to create Muon/Dimuon AOD, starting from the standard AOD, is ready and updated to recent developments of the analysis framework
we would like to test the Muon/Dimuon AOD production within the official analysis train
How the production of these AOD should be included?
Should it be done in the same analysis train, where the creation of the standard AOD (from ESD) is done, or in other subsequent trains?