1. Dielectrons from HADES to CBM Bratislava (SAS, PI), Catania (INFN - LNS), Cracow (Univ.), Darmstadt,(GSI), Dresden (FZR), Dubna (JINR), Frankfurt (Univ.),Giessen (Univ.), Milano (INFN, Univ.), Moscow (ITEP, INR, MEPhI), Munich (Tech. Univ.), Nicosia (Univ.), Orsay (IPN),Rez (CAS, NPI), Sant. de Compostela (Univ.), Valencia (Univ.) Properties of hadrons in strong int. matter: M,  vs , m B, T, V SIS / GSI accelerator facility :heavy ion, proton, pion beams 0   3   0  T  80 MeV Vector meson , ,  spectral functions measurements Hadron’s structure: em form-factors, vector meson-nucleon,inter actions Dalitz and two-body decays, pN,  N reactions dielectrons !

2. Dielectrons: sensing probe e+ e- cc 10-15 fm/c dielectron two-body decays   1.3fm 4.4x10 -5  23fm 7.1x10 -5  44fm 3.1x10 -5      e+ e-..and Dalitz decays    e+ e- BR ! ! HI collisions Figure of merit

3. Beams@GSI for HADES E thresh [GeV] M x [GeV/c 2 ]   //  pp->ppX  - p->Xn HI beams with E  2 AGeV p beam with I<10 11 E<4.6 GeV secondary  beams study elementary dielectron sources from pN and  N reactions Study in-medium vector meson properties in pA,  A reactions

4. HADES@GSI Large acceptance : 20 0 <  <80 0, 0<  < 2   35% for pairs (m >0.2 GeV/c 2, p T >0.1 GeV/c) e -,e +,p,  identification real-time lepton triggering  M=1-2% @  /  ( 2003-> ) operation with p, , HI beams (<2AGeV) 4.5m beam RICH MDC I/II coils META

5. HADES in reality RICH PreShower Magnet RICH +MDC I

6. Electron identification -- ++ C+C, 2AGeV p*q [MeV/c] v/c d p e-e- e+e+ Tracking+TOF e-e- e+e+ q*p [MeV/c] v/c RICH +Tracking +TOF/PreShower hadron contamination <1% p/  separation for p <1000 MeV/c

7. HADES electron trigger II Second Level Trigger Identification of electron candidates Cherenkov rings Shower hits Time-of-flight I First Level Trigger: TOF multiplicity (M ch >3) 60 VME boards decision ~ 10  s process ~3 GByte/s raw data Trigger Condition: 1 electron : (1 ring matched by TOF / Shower) Event Suppression: only 8% selected events (LVL2) Trigger Condition: 1 electron : (1 ring matched by TOF / Shower) Event Suppression: only 8% selected events (LVL2)

8. Nov02(LVL2) Preliminary Nov01(LVL1) Nov02 data scaled down by 10  0  e + e - M e+e- [MeV/c 2 ] C+C @2 AGeV C+C @2 AGeV Counts/MeV 10 times more pair statistics in the same running time No bias on pair distributions High resolution tracking with outer MDC’s Not acceptance corrected

9. HADES @SIS200?: 8AGeV C+C emitted detected acceptance momentum [MeVc] Polar angle Simulation of  production in C+C even without changing HADES geometry acceptance is similar