1. Particle Identification@PANDA: Recipes and Physics Applications
Concettina Sfienti, GSI Darmstadt
Hypernuclear Physics
Double Hypernuclei in PANDA
Particle IDentification in PANDA
Cherenkov R&D
Conclusions & Outlook
XII International Conference on Hadron Spectroscopy October 2007, INFN- Laboratori Nazionali di Frascati, Frascati (Roma) - Italy

2. Baryon-Baryon Interaction
Takahashi et al.
1963: Danysz et al. 10LLBe
1966: Prowse LLHe
1991: KEK-E LLB
2001: KEK-E LLHe
2001: AGS-E LLH (~15)
Hypernuclear Physics

3. Strange baryons in nuclear systems
S=1: L-, S-hypernuclei
nuclear structure, new symmetries
The presence of a hyperon may modify
the size, shape… of nuclei
New specific symmetries
hyperon-nucleon interaction
strange baryons in nuclei
weak decay
S=2: X-atoms, X-, 2L-hypernuclei
nuclear structure
baryon-baryon interaction in SU(3)f
H-dibaryon
S=3: W-atom, (W-,LX-,3L-hypernuclei)
Hypernuclear Physics

4. Birth, Life and Death of a Hypernucleus
target nucleus
p,n  L g
electromagnetic decays
nonmesonic weak decay
mesonic decays
hadronic decay in emulsion
strangeness deposition
FINUDA
strangeness production (p+, K+), (p-, K0) BNL,KEK,(GSI)
strangeness exchange (K_, p-) ,(K_, p0)
BNL,KEK,JPARC
electroproduction (e,e´K+) , (g,K+) Jlab, MAMI-C
Required energy resolution
K,p: MeV
Kstopped: 1 MeV
e: MeV
g-transitions: 5 keV
Hypernuclear Physics

5. Production of LL-Hypernuclei
simultaneous implantation of two L is not feasible
reaction with lowest Q-value: X-pLL: 28MeV
direct implantation of a X- via a two-body reaction difficult because of large momentum transfer
X- capture:
X- p  LL + 28 MeV X- L
+28MeV g
in most cases two-step process
production of X- in primary nucleus
slowing down and capture in a secondary target nucleus
spectroscopic studies only possible via the decay products
Double Hypernuclei in PANDA

6. Production of X- X- production PANDA@HESR X- conversion in 2 L:
p(K-,K+)X-
needs K- beam (c·t=3.7cm)
recoil momentum >460 MeV/c
KEK-E176:
 E373: stopped X per week
AGS-E885: 104
X- capture:
X- p  LL + 28 MeV X-
3 GeV/c
Kaons _ X L
trigger p
+28MeV g
few times 105 stopped X per day
 g-spectroscopy feasible
Double Hypernuclei in PANDA

7. Strategy Universal detector for high luminosity
tag primary reaction by X+ or 2K+ in forward direction  trigger
measure incoming track of X- by active secondary target  reduce BG
measure emitted g-rays with high resolution  spectroscopy
Antiproton momentum close to threshold (3GeV/c)
only few open channels with double strangeness production:
Low mass secondary targets (Li,Be,B,C) in four separated sections
identification can rely on existing information on single hypernuclei
low g-ray absorption
no x-ray background  B Li Be C
Double Hypernuclei in PANDA

8. Integration in the Setup
θlab < 45° X+, K trigger
θlab = 45°-90°, X- capture , Hypernucleus formation
θlab > 90°, g-detection at backward angles
Neutron background (16000 n s-1 per HPGe Crystal )
Der polarwinkel theta.
Der nachweiss des antihyperon und seine assoziierten kaonen erfolgt unter dem winkelbereich von 0-45grad.
2. Geschieht zwischen 45-90
3. Wird bei ruckswartswinkeln nachgewiesen wo der hadronische untergrund geringer ist.
The PANDA Detector

9. PANDA Spectrometer Muon Detectors Forward RICH Barrel DIRC Barrel TOF
Endcap DIRC
Forward TOF
The PANDA Detector

10. Particle Identification
dE/dX by TPC
PANDA PID Requirements:
Particle identification essential for PANDA
Momentum range 200 MeV/c – 10 GeV/c
Different process for PID needed
PID Processes:
Cherenkov radiation: above 1 GeV
Radiators: quartz, aerogel, C4F10
Energy loss: below 1 GeV
Best accuracy with TPC
Time of flight
Start detector: fibre detector
Electromagnetic showers: EMC for e and γ
Forward ToF
Particle IDentification in PANDA

11. Detection of Internally Reflected Cherenkov light
A Textbook Example: the BABAR DIRC
Detection of Internally Reflected Cherenkov light
Different Cherenkov angles give different reflection angles
The task is to separate p’s and K’s in the range: 0.7<p< 3.5 GeV/c
The Barrel DIRC
Measure angle of Cherenkov cone
Transmitted by internal reflection (typ. # light bounces = 300)
Detected by PMTs

12. A Textbook Example: the BABAR DIRC
The Barrel DIRC

13. The Barrel DIRC@PANDA (I)
Babar Design for PANDA
96 Fused silica bars, 2.6m length
Water tank & 7000 PMTs
K eff.
K eff.
Fulfills physics requirements...
Number of required photon detectors
Water tank
Overall size of DIRC
Bar-size uncertainties
Chromatic uncertainty
 miss-id.
 miss-id.
The Barrel DIRC

14. The Barrel DIRC@PANDA (II)
Smaller sized photon-detector
with focusing optics:
Get rid of water tank with different
imaging (reduced background,
maintenance)
Focusing removes bar-size
uncertainty in the focusing
plane:
Improved geometrical (Cherenkov
angle) resolution
Smaller detectors have better
transit time spread
Improved timing resolution
(sDt = ps)
Reduces chromatic uncertainty
The Barrel DIRC

15. 3D imaging X-Y and TOP [B. Ratcliff NIMA502(2003)211]
Ultimate Focusing-TOP DIRC
(t)
3D imaging X-Y and TOP [B. Ratcliff NIMA502(2003)211]
X proximity focusing with wide bar
Y focused by mirror
Time-Of-Propagation Measurement
A.Lehmann, Erlangen 2006
Photodetector requirements....
DT < 100ps
DY~1-2 mm DX ~ 5 mm
Single photon counting
Efficiency (QE, gain, S/N) > 20%
Magnetic field immunity T
Effective area > 70%
Operational Lifetime
The Barrel DIRC

16. Quick summary on ongoing activities
Many sub projects have started
Radiator
radiation hardness
surface polishing
Photon detector
Gain and time resolution tests
Coupling to radiator
Three forward-endcap Cherenkov options
Focussing disk (x-y image)
TOP disk (x-t image)
Proximity Imaging RICH
liquid radiator + CsJ-photon det.
tracking capabilities
R&D around the DIRCs

17. ….more about PID Detectors
Central Tracker: TPC option
Goal
dp/p ~1% dE/dx resolution ~6%
Challenges
Space charge build-up
Continuous sampling
Particle IDentification in PANDA

18. Conclusions & Outlook
Antiproton collisions with nuclei offer many opportunities to study strange baryon in cold nuclei
Baryon-baryon interaction
Weak decay
Spectroscopy of baryonic atoms
....
These studies are made possible by a unique combination of experimental facilities at FAIR
 spectroscopy with Ge detectors  PANDA  antiproton beams
Particle identification (PID) is an essential requirement for such a unique physics program.
The DIRC detectors will play a key role
A wide R&D program is ongoing
Conclusions & Outlook

19. The PANDA Collaboration
www-panda.gsi.de
Conclusions & Outlook

20. ….more about PID Detectors
EMC Barrel and Endcaps
Approx crystals
LAAPDs readout
Challenges
High rate capability: 2 x 107 interactions/s
High resolution & low threshold (10 MeV)
Compact design: EMC inside solenoid
Operation in magnetic field of ~ 2T
Proto60
Particle IDentification in PANDA

21. ….more about PID Detectors
Central Tracker: ST option
Total number of tubes - ~5000
Radial dimensions – 16-42cm
Length – 1.5m
Tube diameters – 10mm
Tube wall material – Mylar, 30μm
Anode wire – W/Re, 20μm
Spatial resolution – σrφ≈150μm, σz≈3-10mm
Gas filling – Ar+10%CO2
Gas absolute pressure – 2 bar
Thickness - ~1% X0.
more details in T. Stockmanns talk
Particle IDentification in PANDA

22. ….more about PID Detectors
TOF system
Low momentum kaons
Scintillator fibers (START)
~2000 fibers placed in two rings  Readout with SiPMT
Tof barrel (STOP)
Time Resolution ~ 80ps
16 Slabs ~6 bars
Particle IDentification in PANDA