1. Event Reconstruction and Data Analysis in R3BRoot Framework
D.Kresan, M.Al-Turany, D.Bertini, F.Uhlig, R.Karabowicz
GSI Helmholtzzentrum für Schwerionenforschung
Darmstadt, Germany
ACAT 2013
May 16 – 21
Beijing, China

2. Outline Introduction R3BRoot framework Multi-neutron detection
FAIR at GSI
R3B – Reactions with Rare Radioactive Beams
R3BRoot framework
Multi-neutron detection
Simulation environment
Identification matrices
Reconstruction algorithm
Spectrometer performance
Comparison vs. experimental data: s406 beam time
Summary
D.Kresan ACAT 2013, Beijing

3. Facility for Antiproton and Ion Research
D.Kresan ACAT 2013, Beijing

4. Facility for Antiproton and Ion Research
CBM
PANDA
NuSTAR
APPA
D.Kresan ACAT 2013, Beijing

5. R3B at FAIR 50 institutes from all over the world
Reaction studies with exotic nuclei far off stability
Focus on nuclear structure and dynamics
Astrophysical aspects and technical aplications
D.Kresan ACAT 2013, Beijing

6. R3BRoot Software
Mohammad Al-Turany, The FairRoot Framework Saturday, May 18-th, Track 1, 17:25
D.Kresan ACAT 2013, Beijing

7. Simulation Environment
NeuLAND
(neutrons)
DCH (protons)
GLAD
TOF (fragments)
Target
Si Tracker
CrystalBall (gammas)
D.Kresan ACAT 2013, Beijing

8. Simulation Environment (2)
Geometry: 3000 plastic scintillator bars in 30 double planes (X-Y), 2.5 x 2.5 x 3 m, at 14 or 35 m downstream the target
Input: 10k 132Sn (600 AMeV energy) reaction on hydrogen with stripping of 1, 2, 3 or 4 neutrons with 500keV (for calculation of identification matrices) and 100keV (for spectrometry) relative energy
Simulation:
TGeant3 with gcalor as transport code
Calculation of quenching in scintillator
Reconstruction
Time resolution of 150 ps
Attenuation, time decay and integration of created light
D.Kresan ACAT 2013, Beijing

9. Calorimetric Properties1n 2n
4n efficiency
with one-dimensional cut: 40%
3n to 4n misidentification: 30% 3n 4n 5n 6n
D.Kresan ACAT 2013, Beijing

10. Expanding to 2D with 2-D cuts: 60% 3n to 4n misID: 10% 4n efficiency
with one-dimensional cut: 40%
3n to 4n misidentification: 30%
with 2-D cuts: 60%
3n to 4n misID: 10%
D.Kresan ACAT 2013, Beijing

11. Identification Matrices
Cut values in the analysis can be tuned to provide necessary purity/efficiency for specific physics channel
D.Kresan ACAT 2013, Beijing

12. Reconstruction Algorithm
After the decision on the event type, neutron tracking algorithm starts
Steps of neutron tracking:
Eliminating secondary clusters (hits after elastic scattering of a neutron on proton)
D.Kresan ACAT 2013, Beijing

13. Reconstruction Algorithm
secondary
secondary
D.Kresan ACAT 2013, Beijing

14. Reconstruction Algorithm
After the decision on the event type, neutron tracking algorithm starts
Steps of neutron tracking:
Eliminating secondary clusters (hits after elastic scattering of a neutron on proton)
Sorting clusters according to the relative deviation from beam velocity (lower deviation -> higher priority) and cluster energy (higher energy -> higher priority). First cluster always stays first
Taking necessary amount of clusters from the top of the sorted list as first interactions
Calculation of relative energy from determined momentum of incident neutrons
D.Kresan ACAT 2013, Beijing

15. Spectrometer Performance
132Sn, 600 MeV/u, 1n, Erel = 100 keV
Typical resolution for
astrophysics experiments
D.Kresan ACAT 2013, Beijing

16. Tetra-neutron 132Sn, 600 MeV/u, 4n, Erel = 100 keV
Four neutrons close in space and time
Design goal resolution is reached in both extreme cases
D.Kresan ACAT 2013, Beijing

17. s406 Test Beam Time at GSI Target Magnet NeuLAND Prototype LAND
D.Kresan ACAT 2013, Beijing

18. NeuLAND Prototype
146 modules – only vertically oriented 2.5 m long 15 planes (10 modules per plane) Time resolution 150 ps
D.Kresan ACAT 2013, Beijing

19. Raw QDC Spectra Simulation Experiment 18-05-2013
D.Kresan ACAT 2013, Beijing

20. Energy per Paddle
Additional stages of reconstruction (to fit the data):
Low QDC thresholds
Energy resolution (sigma/E = 4%)
Energy saturation (hardware effect)
D.Kresan ACAT 2013, Beijing

21. Total Energy Deposit
Very good agreement of maximum value, shape and minimum ionizing peak
Slight discrepancy at lower energies: more background sources in experiment
D.Kresan ACAT 2013, Beijing

22. Multiplicity Distribution
Integration time of contributions from different tracks has the largest impact on multiplicity
This parameter in simulation has no equivalent in the experiment
D.Kresan ACAT 2013, Beijing

23. Summary
Future R3B experiment at FAIR is fully supported with the simulation software by R3BRoot framework and work is ongoing to provide the tools for data analysis
After detailed studies the performance of the neutron ToF spectrometer was significantly improved (TDR accepted by FAIR committee in Jan 2013)
After adjusting the reconstruction algorithm, R3BRoot simulations were able to fully reproduce experimental data taken in test beam time in November 2012
D.Kresan ACAT 2013, Beijing