1. Software Development for the PANDA Barrel DIRC
Dipanwita Dutta1,2 for the PANDA Cherenkov Group 1GSI Helmholtzzentrum für Schwerionenforschung GmbH, Darmstadt, Germany, 2 Bhabha Atomic Research Centre, Mumbai, India.
PANDA Experiment
BABAR DIRC Principle
Reconstruction Algorithm C
PANDA: antiProton ANnihilation at DArmstadt Future FAIR Facility for Antiproton and Ion Research at GSI
Cooled antiproton beam on proton and nuclear target
The input for the Cherenkov angle reconstruction :
Charged track parameter
Hit time (t) and position (x,y)
in photon detector plane
Possible Reconstruction Algorithms:
Babar-Like Reconstruction:
Look-up table: (PMT/Bar define angle)
Followed by likelihood method
Calculate unbiased likelihood for hypothesis e///K/p track and background Track maximum likelihood fit (track by track) individual track fit provides qc, s(qc), number of signal/background photons Event global likelihood fit
iterative process to maximize event likelihood, full correlation of all tracks
Hough Transformation
- Fit the ring directly, standard method for shape recognition
PD plane
Track
DIRC: Detection of Internally Reflected Cherenkov Light
BABAR-DIRC, first DIRC detector at SLAC B-factory
Cherenkov radiation emitted when b = v/c > 1/n(l)
Cherenkov Angle cos qc = 1/n(l) b
Radiator bar from Synthetic Fused Silica
n > 2 some photons are always totally internally reflected for
b  1 tracks
DIRC is intrinsically a 3-D device, measuring: x, y and time of
Cherenkov photons, defining qc, fc, tpropagation of photon C
Expansion medium C
PANDA Barrel DIRC
Study of QCD with Antiprotons
Charmonium Spectroscopy
Search for Exotic
Hadrons in Medium
Nucleon Structure
Hypernuclear Physics
.. and more
Photon position and time (x,y,t)
DIRC Reconstruction
Bar
Lens
Mirror
The PANDA Experiment at FAIR
Panda Barrel DIRC p
PANDA Barrel DIRC designed as a Fast Focusing DIRC
Basic approach similar to BABAR-DIRC
Improvements: Small pixel, faster timing, focusing optics
Small photon detector pixels to decrease the size of expansion region
Faster timing (~100 ps) to correct chromatic dispersion term
Use focusing optics (lens or mirror) to decrease bar size term
Fused Silica bar
Correction of Chromatic Dispersion
J. Schwiening, RICH 2007
Barrel DIRC
Cherenkov angle production is controlled by nphase ()
cos c = 1/(nphase ()×b) ; c (red) < c (blue)
(c) chromatic  5 mrad (for bialkali photo cathode)
Propagation of photons is controlled by ngroup ()
vgroup = c0 /ngroup() = c0 /[nphase() –· dnphase() /d] ; vgroup(red) > vgroup (blue)
Red photons arrive before Blue photons
Particle ID in PANDA
Particle identification essential for PANDA
Wide momentum range, 200 MeV/c -10 GeV/c
Different methods for PID needed
PID Processes:
Cherenkov radiation above 1 GeV
Barrel DIRC
Endcap Disc DIRC
Energy loss below 1 GeV : TPC/STT
Electromagnetic showers: EMC for e and 
Time of flight
K. Götzen, Troia 2009
The PANDA Experiment at FAIR
The PANDA Experiment at FAIR
PID Simulation for Barrel DIRC
kaon efficiency 2% π mis-ID
Time Of Propagation (TOP)=LPath/vgroup()
Track
Expected PID performance example from simulation
pp → J/Ψ Φ √s = 4.4 GeV/c2
C. Schwarz, RICH2007
DIRC Reconstruction
Fused silica
PANDA Barrel DIRC
=0.69 _
Aim is to partially correct chromatic dispersion of Cherenkov angle by fast timing
Realistic Hit Producer
Future Plan
Barrel DIRC Geometry
A Realistic Hit Producer is being implemented for Barrel DIRC in PandaRoot which includes following realistic detector information motivated by the expected choice of photon detector (MCP PMT or gAPD):
Pixelization of photon detector plane
Pixel size of 6.5 mm × 6.5 mm
Hits are center of pixel
Convolution with detector efficiency of photocathode
Wavelength dependent quantum efficiency of bialkali photocathode
Gaussian smearing of time (time resolution =50 ps)
Target pipe
Study reconstruction algorithms and possibility of including DIRC for trigger (look up table)
Implement chromatic dispersion correction
Incorporate DIRC into global PID likelihood
NLAK33A lens
Beam pipe
SiO2 lens
Quartz bar
Double lens structure for focusing in a plane
Barrel DIRC In PandaRoot
Results of Hit Producer
Implementation of photon detection efficiency
References
PANDA Barrel DIRC Simulation
Fused Silica Barrel
PANDA Technical Progress Report, Feb, 2005; PANDA Physics Performance Report , arXiv:0903:3905v1
Development of the PANDA barrel DIRC,
C. Schwarz , JINST 4, (2009)
3. Construction and Performance of the BaBar DIRC, J. Schwiening , JINST 4, (2009)
Radiator barrel
Lens in backward end
Cherenkov light propagation in bar QE
Expansion region
Photon ring in photon detection plane
Mirror in forward end
Photon detection plane
 (nm)
Wavelength distribution of detected Cherenkov photons
Quantum efficiency of Burle MCP PMT
Photon time distribution
Present Design of Barrel DIRC In PandaRoot
Simulation for Focusing Optics
Two lenses for flat focal plane
Detected photon hits after det. eff. and pixelization
16 fold barrel geometry of radiators (Blue)
Angular Coverage: 22-140 in  and 0-360 in 
Radial Distance: 48 cm
Each barbox is having 6 bar, total 96 bars
Quartz Bar (Fused Silica of n=1.47) dimension:1.7 cm × 3.3 cm × 250 cm
Mirror in forward end (Red)
Double lens in backward end of quartz (Yellow and Brown)
Photon Detection plane at a distance of 30 cm from the end of bar (Magenta)
Photon Propagation Medium (Green) (presently Mineral oil)
Expected number of pixels in PD plane
PANDA barrel DIRC lens combination by ZEMAX simulation
Focusing optics remove bar size contribution from Cherenkov angle resolution term
Lens or mirror focusing
Flat detection plane requires complex optics, study with ZEMAX optical system design software
Two lenses, concave-convex (NLAK33A) and plane-convex (Fused silica), designed by ZEMAX and incorporated in PandaRoot DIRC Geometry
XY distribution of MC points and detected hits in photon detection plane
PANDA Barrel DIRC Simulation
Photons directly reaching PD plane
Barrel DIRC In PandaRoot
Simulation with GEANT
in PandaRoot
BoxGen: Kaon, Mom 2 GeV, =50, =10
PANDA Barrel DIRC Prototype
Photons after a reflection on lens
MC points
C. Schwarz, RICH 2007
RICH2010, Cassis, Provence, France, 3-7 May 2010
EU FP6 grant, contract number , DIRAC secondary-Beams, and EU FP7 grant, contract number , HadronPhysics2 and HIC for FAIR.