# Presentation: 659144

## Reconstruction,  recent developments

- Yuri Fisyak, BNL

## Outline

**Revision of relationship between reconstruction and response simulators:****	**
**Truth information => Validation tools  to control efficiencies and fake rate.**
**Response simulators has to reproduce real data on the level of DAQ.**
**Goal: to increase robustness of embedding. **
**Main steps of propagating simulation upgrade in reconstruction **
**One more platform**
**dE/dx **
**Summary**

## Why?

- We need to revisit relationship between simulation and reconstruction because we are making right now major steps in upgrading our reconstruction:
- DAQ100 (FCF) clustering,
- ITTF as basic track reconstruction tool,
- Moving towards to Virtual Monte Carlo,
- (New) subsystems reconstruction
- ...

## The relationship includes two major items:

- Reconstruction has to be instrumented with tools which allow to propagate “Truth” information from simulation (GEANT track ID,...) to reconstructed objects.
- Simulation has to provide reliable description of real data accounting alignment, calibration, ....
**	**The goal is to provide a possibility to use the same chain for reconstruction of real and simulated data.
-       This will  simplify embedding production and analysis.

## Truth information		

- A possibility to match reconstruction with simulation based on simulated track ID (Truth) has been discussed in STAR for a number of years.
- Till now we are still using “Association” based on proximity method. This method makes essential assumption that any corrections applied during reconstruction are small.
- To access to the Truth information becomes more important now with:
- increasing statistics and  knowledge of systematical effects,
- significant increase of magnitude of applied correction, and
- New reconstruction software: ITTF,FCF, ...
- Some new software (SSD) is coming with Truth information already built in.
- As the first step we started pilot project with implementing of Truth information for TPC

## Truth in TPC

- To instrument TPC response simulator and reconstruction with Truth information it has been modified:
- 		StEvent, StMcEvent, StTrsMaker, St_tpcdaq_Maker, StMixerMaker, St_tcl_Maker,  tfs, tcl, StAssociationMaker and StAnalysisMaker.
- Main changes are:
- StHit has now 2 additional data members (with  corresponding access methods) which keep:
- IdTruth – GEANT track Id associated with this hit,
- Quality  - ratio of deposited energy (charge) produced by the above track to total reconstructed energy of the hit.
- tcl (old TPC) cluster module fills the above Truth information.
- StAssociationMaker is aware now about Truth information:
- If the information exists then it is  used to match with StMcEvent otherwise it used proximity method
- These modifications do work and now are in CVS.
- fcf  is still needed to be instrumented. Tonko promised to do this in March.

## TPC response simulator revision

- Revision of TPC response simulator (Trs) requires in order to:
- Replace dE/dx model (tss based on GEANT3) by Bichsel’s one
-  Add all known effects distorting data
- Misalignments,
- ExB, space charge, shorts, ...
- dE/dx: gain, pedestals, absorption,  ADC saturation, ..
- Development of existing StTrsMaker looks like as wasting of time. Package has already ~50 classes but most of them are not used or duplicate codes from StTpcDbMaker / StDbUtilities packages.
- The proposal is to create revised Trs, validate it and replace old one in  time scale ~ 1 month.

- 1/β2

## Truth information (cont.)

- We expect that this TPC response simulator and reconstruction revision will be used as template for all other detectors.
- I want to stress that usage of “Truth” information is very import tool for validation our reconstruction software.
- This is especially important for precise detectors : SVT, SSD and pixels.

## Upgrade simulation in root4star

- GEANT3 STAR simulation has been / being upgraded : gstar/staf => starsim (Maxim’s talk)
- A part of simulation in root4star is ~ 3 years old ( asps/agi/gst/...) and it is not synchronized with gstar/staf.
- The plan is  to have exactly the same simulation codes in starsim and root4star. It will obviously simplify development, debugging and validation of codes and data (embedding).
- This part is well under control and will move to repository just after the collaboration meeting.

## Upgrade of root4star (cont.)

- The above upgrade will open possibility to validate ROOT tracking (Virtual Monte Carlo, TGeo) with respect to one in GEANT3.
- Success of this validation
- will open avenue to use the same geometry for simulation with physics from GEANT3, FLUKA and/or GEANT4.
- will give a possibility to use the same geometry for reconstruction
- will rise the question about optimal geometry description and interface of this description with Data Base.
- Tracking within ROOT rises the question :
- How to store hits obtained during the simulation ?
- Old way i.e. in ZEBRA banks does look artificial.
- It seems that much more natural way is to store hits in ROOT objects.
- At least as the first approximation the existing StMcEvent looks very attractive to be reuse in this way. Only obstacle is absence of persistency for StMcEvent which has to be added.

## Additional platform

- In addition to RedHat 8.0 gcc 3.2 we got one more platform:
- RedHat 8.0 with Intel icc/ifort  compilers.
- The STAR offline has compiled and running.
- We are getting ~30% gain in performance of our codes.
- Processing of daq files gives the same results as gcc
- Results for simulated data is slightly different.
- This platform will  appear in dev next week.

## Once again about dE/dx

- Resolution based on fast offline for old tcl (“adc) and DAQ100 (“noadc”) is ~9%.
- The fast offline uses calibration  from dAu run.
- New data requires the new calibration. After calibration the resolution should be ~7.2%.
- A list of runs for TPC calibration has to be defined and processed at stable conditions in order to solve the issue.

- Fast offline

## Summary

- We need upgrade response simulators and reconstruction with Truth information as major step in validation software and data.
- This upgrade has been started for TPC and it expected to be completed and validated in a month.
- We have well understood road map towards to Virtual Monte Carlo.
- We have new platform for STAR software: RedHat 8.0 + icc/ifort.
- For dE/dx it is needed to select list of run for TPC calibration which have to be processed under stable condition.