1. The HADES experiment @GSI
Collaboration:
18 Inst members
Motivation
Detector description
Performance
outlook

2. Motivation Dalitz and two-body decays, pN, N reactions
Properties of hadrons in strong int. matter: M, G vs r, mB, T, V
Vector meson , ,  spectral functions measurements
Hadron’s structure: VDM, Form factors, vector meson-nucleon inter.
Dalitz and two-body decays, pN, N reactions
SIS / GSI : heavy ion, proton,pion beams
0  r  3 r  T  80 MeV
HADES: systematic dielpton spectroscopy
meson prod. in pp / pp : r = 0 , T = 0 MeV
meson prod. in pA / pA : r = r0 , T = 0 MeV
meson prod. in AA : r = 1-3r0 , T = 80 MeV

3. High Acceptance DiElectron Spectrometer
Magnet
SC. toroid ( 6 coils)
2p in f o < J < 85o
Lepton Identification
RICH C4F gas Phot. Det CsI - cathode
META TOF scintillator wall +
Pre-Shower detector
p/ identification
META and tracking
Tracking
p – measurement, vertex reconstruction
MDC Drift chambers dx ~ 80 mm (s)

4.
PreShower
Magnet
Coils
RICH
RICH +MDC I
Back view

5. HADES S.C. Magnet ILSE SC Toroid Beam operation Imax = 3465 A
Bmax = T
Bmax = T
Dp (q=25°) = 103 MeV/c
Dp (q=80°) = 60 MeV/c
Beam operation
I = 2500 A
Dp (25°) = 74 MeV/c
coil
air

6. Ring Imaging CHerenkov Detector
e+e- - identification
Cherenkov light
cos qc= 1/ ß.n(l)
N = N0. lrad .1/ gt ( lrad = 40 cm )
N0 det. characteristics
Radiator (hadron blind!)
3 ~ ghad < gt < glep
C4F10 : gt = 18.3
pp> 3 GeV/c
VUV - Mirror Poly-C substr. (2 mm) x/X < 2% Al + MgF2 coating R > 80%
Photon detector (MWPC) CsI - cath.
CaF2 window

7. RICH in parts
Photon detector with
CaF2 window
&
CFK radiator shell

8. RICH rings g e+ p0 Q ~ 2.20 e- g Q ~ 0.70 Strong sources lead to large
Dalitz
Strong sources
lead to large
comb. backgr.!!! g e+ e-
Q ~ 0.70
Conversion

9. Multiwire Drift Chambers
0.7 % mass resolution in the r/w - region
Combinatorial background reduction – e+,e- close pair rejection

10. Multiwire Drift Chambers
IPN Orsay
FZR
LHE Dubna
GSI
4 layer/sector.
total 33 m3 active area, cells
y<100 m plane resolution
He-iC4H10 [60-40] gas mixture and low Z material
GSI plane
ORSAY plane
MDC: participating Institutions:
I: GSI,
II: LHE/JINR Dubna,
III: FZ Rossendorf,
IV: IPN Orsay

11. MDC module
x/X0 
Cell characteristic
6 [mm]

12. Performance of MDC Intrinsic spatial resolution:
Proton beam, silicon tracker
“In-beam” (C+C 1.8 AGeV)
Layer
efficiency:
> 98%
Orsay
FZR
Dubna
GSI
Chamber Number
Spatial Resolution (microns)

13. MDC Read-out Daughterboards ASD8 LVL1-connector FPC- connector TDC
Motherboard
Analog Read-out:
Differential amplifier, ASD8 chip, 8 channels,
1 fC intr. Noise, 30 mW/channel
adjustable threshold (one for 16 channels)
TDC Features: (8 channels per chip)
8 channels per chip
250/500 ps/channel
“2 times (t1, t2) – multi-hit capable
Zero & spike (t1-t2 < 20ns) suppression
Calibration Mode (…mixed trigger
“Time above threshold” (…signal shape, charge):
Efficient Offline noise suppression!

14. TOF >450 dt : 90 – 140 ps Ch. p. distribution for C+C @ 1.5 AGeV
Outer TOF wall >450:
6 * 64 scint. Installed.
T line fully operational
dt : 90 – 140 ps
dE/dx measurement
tracking
J. Friese, TU München

15. TOF-hadron identification
Preliminary
p [MeV/c] b
Mass [MeV/c2]
counts
Tof [ns]
Energy loss [MeV]
Mass [MeV/c2]
counts
Deuteron peak:
m0 = 1890 MeV
sm = 551 MeV
deuterons
protons

16. TOF-RICH lepton identification

17. Pre-Shower/TOF system <450
Pre-conv
Post1-conv Post2-conv.
esingle80%
Pads
TOFINO
tof measurement
t0.35 ns
Field
Sense
wires
2 radiation lengths Pb converter
target
Pre-Shower detector side view
beam
3 pad chambers (20000 pads)
em. showers in Pb converters

18. C+C 1.5 AGeV p beam e- beam Shower candidate
One event: detector response
Pre-converter
Post1-converter
Post2-Converter
p beam
e- beam
Shower
candidate
Pre-Conv
Pre-Conv
Post1-Conv
Post1-Conv

19. RICH-MDC-META lepton identification
Data: Nov01 C-C 2.0 AGeV magnetic field
preliminary
q* momentum
Log z!
tof [ns]
tof [ns]
q*momentum

20. RICH-MDC-META lepton identification
Data: Nov01 C-C 2.0 AGeV magnetic field
preliminary
Full HADES simulation and data analysis
RQMD ev.generator
simul.
Ne/N+
RICH-Track(MDC-META)
RICH & fast tof &shower
MDC I/II (inner ) e- e+
q* momentum [e*MeV/c]

21. HADES Trigger System Needs level 2 trigger: 107- 108 paricles/s
Ring recognition in RICH
Hit finding and tof calculation in TOF
El. Shower search in Pre-Shower
RICH and META candidate matching via azimuthal correlations
Selection of e+e--pairs (momentum and invariant mass analysis)
High rates (105 Hz)
10ms max. LVL2 trigger decision time)
Parallel- und Pipeline architecture FPGAs, CPLDs and DSPs
paricles/s
105-6 interactions/s (1% target)
Level 1 Trigger:
Multiplicity in TOF
104 _105 central events/s
Large data rate 3 GByte/s

22. Second Level trigger flow
dilepton
1:100

23. Trigger distribution system
Trigger distribution: LVL1 (TOF Mult.) and LVL2 (MU) via CTU
DAQ synchronized via event number distribution
Total: 50 VME-Modules

24. RICH IPU 1 ring search mask (13x13 pads)
Pattern reconstruction (96x96 pad plane)
Ring recognition
fixed 80 pads mask ( ring/ veto region)
local maximum search
IPU-algorithm X correlation
Hits found by the IPU
and not by
the algorithm
Hits found by the
algorithm and not
by the IPU
0.2%
X ALGO (pads)
X IPU (pads)
uncorrelated emulation rings
X (pads)
Y (pads)
Data: Nov01 C-C 1.5 AGeV full field
Discrepancy: 0.4%

25. Matching Unit Preliminary lepton
Data: Nov01 C-C 1.5 AGeV magnetic field
Reference System: offline analysis leptons
LVL2 conditions in the MU:
1 hit in RICH
1 hit in TOF
Df < 15°
lepton
Trigger condition % evts
evt >= 1 ring 10.5%
evt >= 1 lepton 2.9%
evt >= 2 rings 4.6%
evt >= 2 leptons 1.7%
evt >= 1 dilepton 0.3%
Efficiency
RICH IPU LVL2
integrated eff 85.3% 84.7%
event eff 87.3% 86.6%
N. fakes ele/evt

26. Outlook HADES comes into operation(e/p/p sep., LVL2 trig., tracking)
3 MDC layer will be completed this summer (p3% for /)
DAQ and LVL2 trigger commisioning
Phase I (2002 – 2003) : (acc. proposals S200 ,S262)
Continuum below M inv < 600 MeV/c2 ; 0 Dalitz in C+C
High statistics e+,e- production in HI reactions C+ C @ 1 – 2 AGeV (compare to DLS)
e+e- production in p- p p- p @ 0.8 – 1.3 GeV/c (below and above threshold for r/w
e+e- pair acceptances pp  pp h  pp e+e-

27. e+e- pairs in C + C collisions
Ebeam = 1A GeV/c
Simulation
for 3 MDC setup :
needs
2 * 109 events
~ 5 days
89000 e+e-
Ebeam = 2A GeV/c

28. e+e- pairs in -+p reactions
Pbeam = 0.8 GeV/c
Simulation
for 3 MDC setup :
7 days of
p- beam
@ 1 * 106 s-1 !!
Pbeam = 1.3 GeV/c

29. Collaboration Bratislava (SAS, PI) Catania (INFN - LNS)
Clermont-Ferrand (Univ.)
Cracow (Univ.)
Darmstadt (GSI)
Dresden (FZR)
Dubna (JINR)
Frankfurt (Univ.)
Giessen (Univ.)
Milano (INFN, Univ.)
Moscow (ITEP, MEPhI, RAS)
Munich (Tech. Univ.)
Nicosia (Univ.)
Orsay (IPN)
Rez (CAS, NPI)
Sant. de Compostela (Univ.)
Valencia (Univ.)