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Dielectrons from HADES to Dielectrons from HADES to CBMCBM
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 , mB, 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,interactions
Dalitz and two-body decays, pN, N reactions dielectrons !
Dielectrons: sensing probeDielectrons: sensing probe
2sinpp2m ee
eeee
e+
e-
c10-15 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
BBeamseams@GSI@GSI for HADES for HADES
Eth
resh
[GeV
] Mx [GeV/c2]
/
pp->ppX
-p->Xn
HI beams with E2 AGeV
p beam with I<1011 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
HADES@GSIHADES@GSI
Large acceptance : 200< <800, 0< < 2
35% for pairs (m >0.2 GeV/c2, pT>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
HHADESADES in realityin reality
RICH
PreShower
Magnet RICH +MDC I
ElectronElectron identification identification
-
+
C+C, 2AGeV
p*q [MeV/c]
v/c
d
p
e- e+
Tracking+TOF
e- e+
q*p [MeV/c]v/
c
RICH +Tracking +TOF/PreShower hadron contamination <1%
p/ separation for p <1000 MeV/c
HADES electronHADES electron triggertrigger
II Second Level Trigger
Identification of electron candidates Cherenkov rings Shower hits Time-of-flight
I First Level Trigger:
TOF multiplicity (Mch>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)
Nov02(LVL2)
Preliminary
Nov01(LVL1)
Nov02 data scaled down by 10
0e+e-
Me+e- [MeV/c2]
C+C @2 C+C @2 AAGeVGeVC
ou
nts
/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
HADES @SIS200?: 8AGeV C+CHADES @SIS200?: 8AGeV C+CM o t i v a t i o n :
• d i - l e p t o n p r o d u c t i o n a t h i g h e r d e n s i t i e s a n d t e m p e r a t u r e s
• h i g h e r m e s o n p r o d u c t i o n r a t e
< M > / < B >
2 A G e V 8 A G e V
1 . 2 * 1 0 - 2 4 * 1 0 - 2
3 * 1 0 - 3 3 * 1 0 - 2
2 * 1 0 - 4 2 * 1 0 - 2
e+ e-
PLUTO
HYDRA DST
acceptance+efficiency
Leptons from eta Dalitz (theta vs mom) C8C
90
0
90
0
90
0
0 2000 0 2000
•emitted
•detected
acceptance
momentum [MeVc]
Pola
r an
gle
• Simulation of production in C+C
• even without changing HADES geometry acceptance is similar
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