# Presentation: 312683

## ATLAS Simulation/Reconstruction Software

**Reported by S. Rajagopalan **
**work done by most US Institutes.**
- U.S. ATLAS PCAP review
- Lawrence Berkeley National Laboratory
- January 15, 2002

## Outline

- Simulation/Reconstruction Activities:
- (mostly by physicists)
- Subsystems with US participation:
- Pixels, TRT, EM Cal, Forwad Cal, Tile Cal, Muons, Trigger
- In addition, extensive participation in combined reconstruction, test beam software and physics analysis.
- Well integrated into overall ATLAS computing effort.
- In particular, the US core efforts on Athena and DB.

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## ATLAS Subsystem/Task Matrix

-   US responsibles
-   Being vacated

|  | Offline Coordinator | Reconstruction | Simulation | Database |
| --- | --- | --- | --- | --- |
| Chair | N. McCubbin | D. Rousseau | A. Dell’Acqua | D. Malon |
| Inner Detector | D. Barberis | D. Rousseau | F. Luehring | S. Bentvelsen /
D. Calvet |
| Liquid Argon | J. Collot | S. Rajagopalan | M. Leltchouk | H. Ma |
| Tile Calorimeter | A. Solodkov | F. Merritt | V.Tsulaya | T. LeCompte |
| Muon | J.Shank | J.F. Laporte | A. Rimoldi | S. Goldfarb |
| LVL 2 Trigger/ Trigger DAQ | S. George | S. Tapprogge | M. Weilers | A. Amorim /
F. Touchard |
| Event Filter | V. Vercesi | F. Touchard |  |  |

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Software Activities Summary

- Recent simulation and reconstruction activities have been geared toward:
- High Level Trigger (HLT) Technical Design Report (due summer 2003)
- G4 physics validation
- Validation of C++ reconstruction software
- Data Challenges (DC1 ongoing)
- Test beam analysis
- Physics studies by various groups

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Geant3 simulation software

- P. Nevski (BNL) is the ATLAS coordinator for the G3 effort.
- Recent Activities include:
- First revision of geometry since Physics TDR
- Latest geometry of the Inner Detector (incertable pixels, 2/3 layer variation, strip tilt inverted to minimize cluster size, realistic R/T in TRT)
- Service Material updated
- Calorimeter: gap between barrel and endcap calorimeters introduced
- readout of calorimeters updated (including 5 sample digitization)
- dead material of the calorimeter readout updated
- Muon layout modified to latest geometry, digitization updated
- Optimised pile-up procedure allowing up to > 1k events to be added

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## G4 Simulation activities (Pixel)

- Pixel Simulation (D. Costanzo et. al., LBNL)
- Pixel Geometry: Primary numbers from MySQL database
- (used also by Geant3)
- Geometry descriptions in GeoModel
- MisAlignments handled by new Athena Services

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Material (Pixel) in G4

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## TRT Simulation

- F. Luehring (Indiana) is the ATLAS TRT software coordinator.
- (and member of the TRT steering group)
- Athena Pile-Up Requirements documentation ATL-SOFT-2001
- GEANT4 code writing
- TRT hit and digitization definitions
- Tabulation of material in the TRT detector
- And its appropriate include in G4 simulation
- Studies of effect of Pile-up in TRT detector

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## LAr Simulation

- ATLAS LAr simulation coordination: M. Leltchouk (Nevis)
- Participation in G4 EM barrel development
- Integration of the LAr Simulation code in G4 architectured by Bill  Seligman : Used as templated by EM, HEC, FCAL.
- LAr EM calorimeter hits (LArEMHit) were implemented in GEANT4 by  B.Seligman.
- Integrated with Athena Framework providing Root based persistency to G4 Hits and using them for subsequent Digitization/Reconstruction

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## GEANT 4 LAr Simulation

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## G4 Validation

- compare features of interaction models with similar features in the old Geant3.21 baseline
-  try to understand differences in applied models, like the effect of cuts on simulation parameters in the different variable space (range cut vs energy threshold...);
-  use available experimental references from testbeams for various sub-detectors and particle types to determine prediction power of models in Geant4 (and Geant3);
-  use different sensitivities of sub-detectors (energy loss, track multiplicities, shower shapes...) to estimate Geant4 performance;
-  tune Geant4 models (“physics lists”) and parameters (range cut) for optimal representation of the experimental detector signal with ALL relevant repects;

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## G4 validation comparisons

- Muon energy loss and secondaries production in the ATLAS calorimeters and muon detectors
-  Electromagnetic shower 				           simulations in calorimeters
-  Hadronic interactions in tracking                                                          devices and calorimeters
- (Different showering models
-      in Geant3 and Geant4)

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## G4 Validation (continued)

- Geant4 can simulate relevant features of muon, electron and pion signals in various ATLAS detectors, often better than Geant3;
-  Remaining discrepancies, especially for hadrons, are being addressed and progress can be expected in the near future;
-  ATLAS can has a huge amount of the right testbeam data for the calorimeters, inner detector modules, and the muon detectors to evaluate the Geant4 physics models in detail;
-  feedback loops to Geant4 team are for most systems established since quite some time; communication is not a problem;
- Few people in US involved in G4 validation studies
- I don’t think anyone from US is a member of the G4 team

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Sub-System Reconstruction

- Extensive involvement by US people, primarily in:
- LAr, Tile and Muon reconstruction
- Combined reconstruction: egamma, Jets, tau’s and MissingET
- The overall reconstruction chain is functional, a lot of the fortran code has been rewritten in C++, albeit several missing pieces and far from perfect.
- Most of the effort is focussed on:
- Validation
- Calibration issues
- Test Beam Analysis
- Standardizing the EDM and Detector Description usage

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Database/Detector Description

- Support for ROOT persistency for current Detector Description & some Event Data Objects (Hong Ma, BNL who also coordinates ATLAS LAr database activities)
- LAr Database/Detector Description activities
- Designed interfaces for accessing conditions data in Athena.  Implemented interim solution for conditions data in MySQL for MC simulation, reconstruction, and some testbeam analysis.
- Provide requirements input to ATLAS Conditions DB development
- Detector Description: 2-day workshop at BNL (12/16/02) to discuss the adoption of the new Detector Description Architecture in LAr Simu/Rec.
- Tile Database activities coordinated by Tom Lecompte (ANL)
- Similar activities as those for LAr.
**Muon database and detector description**
- XML detector description: MDTs, RPCs, TGCs implemented
- Identifier scheme for Muons implemented by Goldfarb, Assamagan

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Calorimeter Reconstruction

- Liquid Argon :        H. Ma, S. Rajagopalan (BNL),  P. Loch (Arizona)
- Tile Calorimeter  :  A. Gupta, F. Merritt (Chicago)
- Combined Calorimeter Data Classes and Algorithms

| Simulation | Online | Offline
Reconstruction | Combined
Reconstruction |
| --- | --- | --- | --- |
|  |  |  |  |

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## 1MB at t=0

- + 25 bunch crossings with
- 10 interactions each

- (E not corrected for sampling fraction)

- Expected
-  elec. noise
-  reduction
-  from
-  optimal
-   filtering

- Pile up increase
- (note: OF coeff
-  used are the
-  same
- In real life, they
-  will change with
-  luminosity

- Middle
- Sampling
- EM Barrel

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Recent Plots using LAr  recon. program

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## ATLAS Muon Software

- J. Shank (Boston U.) is the overall software coordinator
- Muon Database activities coordinated by S. Goldfarb (Michigan)
- Current activity:
**OO muon reconstruction (Moore) development**
- Contributors: G. Stavropolous (LBNL), K. Assamagan (BNL)
- Integrated into Athena; in repository; in early development
- Migration to new Event Data Model
- Clusterization for MDT and CSC completed
- Makes use of common track fitting and data classes with InDet Reco
- Material Integration Service being implemented
**Muon database and detector description**
- Conditiond DB and Athena Testbeam work for the April run. J. Rothberg (U. Wash)
- Identifers & detector description by Goldfarb, Assamagan

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## ATLAS Muon Database Contributions

- Descriptions of Barrel Toroid (left)
- and H8 test beam geometry (below).
- Both geometries were generated using
- compact AGDD syntax and both were
- developed by REU summer students,
- under the supervision of S. Goldfarb.

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Raw Data Flow

- Raw Data Flow Model established
- London Meeting: (D.Quarrie & S. Rajagopalan met with HLT to discuss their software design)
- Established strategy on use of Athena/StoreGate in HLT
- Data Converters (Hong Ma, BNL):
- Simulation of ROB data and establishing relevant services
- ByteStream  Raw Data and Calibrated Objects for use in           L2, L3 coordinated across all sub-systems by Hong Ma (and implemented for Liquid Argon)
- Being implemented for Muons (K. Assamagan, BNL)
- Efficient on demand access to data in Regions of Interest

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Validation of Athena for HLT Use

- The ATLAS EF will use selection and classification algorithms derived from the offline suite
- Offline software performance therefore has a direct impact on EF farm size and cost
- The HLT community has started “validation studies” (detailed benchmarking) of Athena, offline algorithms, and event model
- The aim is to set metrics for monitoring trends in software performance
- It is clear that the software is presently far from adequate
- Not fair to judge during development phase
- But benchmarking can (and has) helped spur improvements
- Feedback during monthly meetings with A-team and regular interactions with developers
- Software performance is also important for offline – hope that offline community will continue this work

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Combined Reconstruction

- egamma Reconstruction
- Algorithms developed by H. Ma, S. Rajagopalan (BNL)
- Algorithms to associate clusters and tracks and analyze variables necessary for e identification (shower shapes, isolation, E/p, ...)
- Calorimeter Cluster calibration (J. McDonald, Pittsburgh)
- Jet Reconstruction
- Jet Algorithms (KT and cone) developed by A. Gupta, F. Merritt (Chicago)
- Jet and Tau Calibration (F. Paige, H. Ma, S. Rajagopalan) (BNL)
- H1 style calibration adopted : Provides  weighting at a cell level.
- EM showers are denser than hadronic showers: Cells with dense energy deposition are weighted toward EM scale.
- Effective in improving linearity and resolution over standard techniques (sampling weights).
- Missing ET Reconstruction

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Physics validation

- DC1 data production includes datasets from single electrons, pions, di-jet events to full physics events with & without pile-up using G3.
- Much of this data is already being analyzed to extract the relevant calibration constants that is fed back into the process for full reconstruction.
- One of the physics signatures fully simulated is 50k SUSY events at the following msugra point : (I. Hinchliffe, F. Paige driving this effort)
-  m0=100, m1/2=300, A0=-300,  tan=6, sign() = +
- Rich in leptons (including tau’s), jets, b-jets, high multiplicity hard events which is an ideal candidate to test the software.
- Most such signatures have previously been studied only with fast simulation

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## e/Jet identification in SUSY events

-  First look at 500 events from the SUSY sample :

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003

## Summary

- New ATLAS framework, Athena, enthusiastically embraced by broad spectrum of sub-system community.
- Many US physicists active in code development
- Well integrated into overall ATLAS software effort
- Schedule:
- DC 0    12/2001
- First phase which provided a useful software continuity check
- DC 1   02/2002
- Large scale simulation/reconstruction with G3.
- Phase 1 ongoing,  Phase 2 due in March 2003.
- Athens Physics Workshop (May 2003)
- DC2 : Will use Geant4,  Scheduled for early 2004

- S. Rajagopalan     ATLAS Simulation & Reconstruction Software

- PCAP review. January 15, 2003