Docstoc

Particle Identification for the PANDA detector

Document Sample
Particle Identification for the PANDA detector Powered By Docstoc
					PANDA PID Requirements:
                                                               dE/dX by TPC
Particle identification essential for PANDA
Momentum range 200 MeV/c – 10 GeV/c
Several methodes for PID needed



PID Processes:
Cherenkov radiation:
   Radiators: quartz
Energy loss: below Cherenkov threshold
   TPC or Straw Tubes
Time of flight
   Challenge: no start detector, relative timing
Electromagnetic showers: EMC for e and γ


                                 C.Schwarz, RICH 2010 Cassis                  1
                                                              GROUPS

   PANDA includes two DIRCs for PID                          GSI, Dubna

                                                               Barrel DIRC
       Barrel DIRC similar to BaBar DIRC
                                                              Giessen, Glasgow
       Endcap Disk DIRC, several designs
                                                               Endcap Disc DIRC
   R&D activities                                            Erlangen, Vienna

       radiator quality, focusing optics                      MCP-PMT, G-APD

       photon detectors, [readout electronics]
           Multi-Channel-Plate MCPs
           G-APD
       fast timing, chromatic correction
       simulation, reconstruction...

   Test experiments for small scale
    prototypes


                                C.Schwarz, RICH 2010 Cassis                      2
   Cherenkov detectors


Beam




                     Barre
                     l




                                                               Kaon distribution of the
                                                                   radiative decay
                                                                       J/ψ -> K+K- γ
       barrel DIRC           endcap disc DIRC                   (search of glue balls)‫‏‬



                                 C.Schwarz, RICH 2010 Cassis                              3
BABAR-DIRC Cherenkov angle resolution:         9.6 mrad per photon →‫ 4.2‏‏‬mrad per track

Limited in BABAR by:              Could be improved for PANDA via:
▪ size of bar image       ~4.1 mrad               ▪ focusing optics
▪ size of PMT pixel       ~5.5 mrad               ▪ smaller pixel size     PANDA
                                                                        DIRC Design
▪ chromaticity (n=n())   ~5.4 mrad               ▪ better time resolution

 9.6 mrad                 4-5 mrad per photon → 1.5–2 mrad per track




Lens design by
ZEMAX optical software                   Marcol82             NLAK33     SiO2
                                         n=1.47               n=1.78     n=1.47
                      Screen

                                    Expansion
                                    Box                                   Radiator




                                C.Schwarz, RICH 2010 Cassis                           4
                                                              air gaps
Current design of Barrel DIRC

                                                                   Photon detector &
More compact, faster, focusing optics
                                                                   electronics
96 radiator bars, synthetic fused silica
17mm (T) × 33mm (W) × 2500mm (L)‫‏‬
Focusing optics: lens system
 Compact photon detector: array of
Burle Planacon MCP-PMT
G-APD
total 7000-10000 channels.
 Fast photon detection: MCP-PMT
fast TDC/Time Over Threshold electronics                                      radiator bars

→‫ 002-001‏‬ps timing.                                                    focusing lens



Still investigating several design options:
mirror focusing, radiator plates, photon detection outside magnetic field


                                   C.Schwarz, RICH 2010 Cassis                           5
    3D-DIRC                    Time of Propagation measurement better than 100-200 ps
                               allows to partially correct dispersion
                               for‫‏‬high‫‏‬and‫‏‬low‫‏‬momenta‫‏‏‏→‏‏‬x,y,t‫3‏‏‏→‏‏‏‬D-DIRC
      kaon in
      fused silica   β=0.69c
                                                              close to threshold:
                                                              small variations in n(λ)‫‏‬
                                                              cause large δθ

                                                   cos(Θ)=1 / βn(λ)‫‏‬
Y




                     β=0.72c
                                                                  software dispersion correction




                 X
                                C.Schwarz, RICH 2010 Cassis                                        6
Endcap Dirc – Focusing Lightguide Option
                                                       LiF for dispersion correction
                                                       has smaller |dn/d| than SiO2

                                                       focussing better than 1mm
                                                       flat focal plane
       fused silica




                            LiF



                      hardware dispersion correction


                               C.Schwarz, RICH 2010 Cassis                             7
Endcap Disc DIRC - resolution




            C.Schwarz, RICH 2010 Cassis   8
    Cherenkov Radiation Dispersion
                       1
     cos    =
                  n ph ase


                different directions
                for different colours




 Dispersion correction principle:
 material with similar n
 but different dn/dlambda

                dispersive prism
                component




N.B. choice of corrector materials rather limited
                                        C.Schwarz, RICH 2010 Cassis   9
Focussing lightguide




                                 first demonstrator setup
                                 to verify proper optics
                                 of workshop machined
                                 Focusing Light Guides
                                                            CEARA




                   C.Schwarz, RICH 2010 Cassis                      10
Endap DIRC – Time Of Propagation option
                                                        dichroic mirrors as colour
                                                        filters

                                                        two wavelength bands
                                                        dispersion correction
                                                        different and longer path lengths
                                                        Hole with mirrors       Hole black
                                                                                      0
                                                                                      reflections




                             time-of-propagation [ns]
                                                                                      1 reflection
                                                                                      2
                                                                                      reflections
                                                                                      3
                                                                                      reflections




                                                                            φ [deg]

            single photon resolution t~30-50ps required
            missing start detector: relative timing between photons
                  C.Schwarz, RICH 2010 Cassis                                                        11
                                         Helps to reject
Hybrid DIRC                              photons from knock on electrons
combines strength of                     by angular measurement.
focussing option with
ToP option




                        C.Schwarz, RICH 2010 Cassis                        12
The photon detection device
                       Multi Channel Plate - PMT




 Ageing: typically 1C/cm2   ->       30% loss of QE


PANDA:
     Barrel         0.8 C/cm2/yr
     Focussing      3.8 C/cm2/yr
     TOP            9.6 C/cm2/yr

                                      ongoing developments
                                      close cooperation with companies




                                 C.Schwarz, RICH 2010 Cassis             13

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:5
posted:2/1/2012
language:
pages:13