1. First step to Reconstruction of PANDA Barrel DIRC in PandaRoot
Dipanwita Dutta
GSI, Darmstadt
(Also at Bhabha Atomic Research Centre, Mumbai, India)
PANDA Collaboration Meeting, GSI
Mar

2. Panda Collaboration Meeting, Mar 2010
Outline
Reconstruction Algorithm for DIRC
Introduction
What is Look-up Table
What we are doing and why?
Results
Summary and Outlook
D. Dutta
Panda Collaboration Meeting, Mar 2010 2

3. Panda Collaboration Meeting, Mar 2010
PANDA barrel DIRC
DIRC Barrel
Target Beam Pipe
Cherenkov Photons
Propagated in bar
Beam Pipe
Photons hits in the Photon Detector (Cherenkov Ring)
Mirror
Photon Detection Plane
Photon Propagation Medium ( Marcol82 )
Lenses
D. Dutta
Panda Collaboration Meeting, Mar 2010 3

4. Reconstruction Algorithm
Reconstruction Input:
(1) Charged track parameter
(2) Hit time and position (x,y) in Photon Detector plane
Possible Reconstruction Algorithms:
Babar-Like Reconstruction:
(Ref. DIRC NIM paper for BaBar Experiment, NIMA 538(2005)281)
Look-up Table: (PMT/Bar define angle)
Likelihood method
- Track maximum likelihood fit (track by track)
- Event global likelihood fit
Hough Transformation
- Fit the ring directly, standard method for shape recognition
CosC=1/n
D. Dutta
Panda Collaboration Meeting, Mar 2010 4

5. What is Look up Table?
Provides Average kBar vector for each pixel in PD for (pixel, bar) combination
Very fast decision: useful for triggering
Track Dir Vector (trx,try,trz)
PD plane
Photon Dir Vector at exit
(kx, ky, kz)
Photon Dir Vector at creation
(phx, phy, phz)
kBar vector
(pixel bar)
in bar co-ordinate system y ky x kx z kz
8 fold ambiguity
Focussing Lens
D. Dutta
Panda Collaboration Meeting, Mar 2010 5 5

6. What we are doing and why?
Reconstruction : Step1
Look-up table and getting the average kBar vector for each (pixel,bar) combination
Already a test model implemented in drcprop dir by Roland (talk in PID)
Has to be implemented in PandaRoot framework with proper DIRC geometry
Problem of implementation due to double ring structure in PD plane ( talk dec09)
Instead start with average k vector ( a simplified approach to test reco.)
Option 1: Take the momentum direction vector at the PD hits
Option2: Take the Direction vector of the connecting vector of PD hit and the middle of bar
Step2: Estimate ThetaC taking account all possible ambiguity of k vector y ky
Option 1 x kx z kz 1 3 2
Option 2
8 fold ambiguity
Focussing Lens
D. Dutta
Panda Collaboration Meeting, Mar 2010 6 6

7. Results on Cherenkov Angle Reconstruction
Kaon (Box Generator): Mom =2 GeV, =50,  =10, nEvents=100, Mag Field :off
ThetaC at creation point
c (rad)
D. Dutta
Panda Collaboration Meeting, Mar 2010 7

8. Results of Cherenkov Angle Reconstruction
Kaon (Box Generator): Mom =2 GeV, =50,  =10, nEvents=100, Mag Field :off
Option 1: kDir from photon mom.
Mean=
=0.034
ThetaC estimated from all possible combination of k vector
c (rad)
Good News: Get a peak at expected ThetaC
Bad News: The resolution ~34mrad instead of expected ~10mrad
(understood due to simplified approach of k vector)
D. Dutta
Panda Collaboration Meeting, Mar 2010 8

9. Results on Cherenkov Angle Reconstruction
Kaon (Box Generator): Mom =2 GeV, =50,  =10, nEvents=100, Mag Field :off
Option 2: kDir from connecting vector of photon hit in PD and middle of bar
ThetaC with all possible combination
Splitting due to two rings
Further splitting due to pixelization
c (rad)
ThetaC after putting detection efficiency and pixelization
c (rad)
D. Dutta
Panda Collaboration Meeting, Mar 2010 9

10. Results on Cherenkov Angle Reconstruction
Kaon (Box Generator): Mom =0.6 GeV, =50,  =10, nEvents=100, Mag Field :off
ThetaC at creation point
c (rad)
D. Dutta
Panda Collaboration Meeting, Mar 2010 10

11. Results on Cherenkov Angle Reconstruction
Kaon (Box Generator): Mom =0.6 GeV, =50,  =10, nEvents=100, Mag Field :off
Option 1: kDir from photon mom.
ThetaC with all possible combination
c (rad)
ThetaC after putting detection efficiency and pixelisation
c (rad)
D. Dutta
Panda Collaboration Meeting, Mar 2010 11

12. Panda Collaboration Meeting, Mar 2010
Summary and Outlook
Reconstruction with average kVector:
Reconstruction of Cherenkov Angle (ThetaC),
a first test version has been implemented
All possible ambiguity for k vector considered to estimate ThetaC
Shows peak at expected thetaC
Poor Sigma due to simplified approach of k vector
Splitting of ThetaC peak if k vector is taken from hit to bar middle connecting vector (due to double ring)
Outlook
kBar vectors in bar co-ordinate system should be implemented
Average k vector should be replaced by the kBar from look-up table
Studying the source of double ring structure in PD plane (talk dec09) -
D. Dutta
Panda Collaboration Meeting, Mar 2010 12

13. Panda Collaboration Meeting, Mar 2010
Thank you
D. Dutta
Panda Collaboration Meeting, Mar 2010 13

14. Patterns in Photon Detector Plane
Kaon (Box Generator): Mom =2 GeV, =50,  =10, nEvents=100, Mag Field :Off
Putting Graphical Cuts
band1 (cut1) and band2 (cut2)
D. Dutta
Panda Collaboration Meeting, Mar 2010 14