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