# Presentation: 831227

## Dielectron production in C+C collision with HADES

**	****	****Malgorzata Sudol**
- 	HADES experiment – setup, exp runs	Analysis strategy	Preliminary results C*+*C* *2* A*GeV	Comparison to theory
*	*Outlook

## High Acceptance DiElectron Spectrometer

_**Geometry**_
- Six sectors form a hexagonal structure:
- (azimuthal angle)
- polar angle)
_**Lepton Identification**_
- hadron-blind RICH
- Gas radiator: C4F10
- Spherical mirror
- Photon Detector: CsI photo cathode
- META
- TOF plastic scintillators
- Shower detector

_**Tracking**_
- Superconducting toroid (6 coils)
- Bmax = 0.7 T,
- Bending power 0.34 Tm
- MDC (mini drift chamber)
- Low mass design
- four modules of small cell (cm
- 	drift chambers  (6 wire planes each).
- Sophisticated trigger with real time reconstruction
- of lepton pairs
***In total about ************80.000  detector channels***

## Enhanced dilepton yields from DLS

- DLS at the Bevalac  (1987-1995)

## EXPERIMENTAL RUNS

_**November 2001**_**:** commissioning run target = 5%
**C+C 2 AGeV** LVL1 triggered events (Mch.>3) :    	**45  Mevents**
**C+C 1 AGeV** LVL1 trigger                             :    	**7.3 Mevents**
- full coverage with inner MDC chambers (Dp/p  10% at 0.7 GeV/c)
_**November 2002**_**: C+C 2 AGeV, commissioning and physics runs **
**target= 2 x 2.5%,  56% LVL1 trigger + 44% LVL2 trigger           ****220 Mevents**
**6 outer drift chambers (MDC) in 4 sectors**
_**October 2003**_**:** p+p commissioning  run  (1 GeV, 2 GeV)
- full coverage with outer MDC III (4 MDC IV) (Dp/p  1.5 % at 0.7 GeV/c)
_**January 2004**_**: **p+p 2GeV production run
- target 5 cm LH2	**400 Mevents**
_**August 2004:**_ C+C 1AGeV  production run
- 3x1.5 % target, 56% LVL1 trigger + 44% LVL2 trigger	**650 Mevents**
_**September 2005:**_ KCl+Ar 1.76AGeV  production run
- 	** ****850 Mevents**

## Electron identification

- velocity vs momentum

- +

- +

- RICH-Signal

- Track matching

- Pre-Shower Condition

**Momentum * charge [MeV/C]**

**EXP**
**Monte Carlo**

**e****+**

**e****-**

## PURITY and EFFICIENCY

**Efficiency:  ********80%**
**Purity:  ********85%**

- Contamination:
-  lepton fakes  15%
-    (mostly closed pairs)
-  hadrons  <3%

**no problem with hadron fakes!**

## REJECTION STRATEGY – Pair analysis

- 			**Pair cuts:**
- C0 = pairing
- C1 = C0 + double hit rejection
- Remove tracks with ambiguous detector hit
- C2 = C1 + opening angle > 9 deg
- Remove both tracks from sample
- C3 = C2 + close pair candidate rejection
- Remove track if incompletely reconstructed track nearby

**Relative suppression**

## Dilepton mass spectrum

- systematic errors:  +50%/-40%

**within acceptance**

- Corrected for Efficiency!
-  detector inefficiencies
-  reconstruction inefficiencies
- Not corrected for acceptance!
- Compared with a cocktail
- based on known or mt-scaled
- meson multiplicities and their
- vacuum decay properties.

- preliminary

## Comparison with transport theory

**RQMD** calculation: D. Cozma, C. Fuchs and A. Faessler, Tübingen

## Conclusions & outlook

- HADES is up and running
- First physics results obtained in low-resolution mode on C+C @ 2AGeV. To finalize:
- re-examination of low momentum efficiency,
- investigation of systematical errors
- Ongoing analysis of other data sets
- aug04 )CC 1 AGeV): calibration, alignment ready, DST production started
- jan04 (pp):  see poster A. Rustamov
- Scheduled next physics runs
- proton, deuteron and pion beams (2006)
- Upgrade of TOF subsystem with RPC (2007)
- Ni+Ni & Au+Au runs
- Feasibility studies for HADES operation at FAIR
- 2-8 AGeV runs

## G.Agakishiev9, C.Agodi2,  A.Balanda5, R.Bassini10, G.Bellia2,3, D.Belver19, J.Bielcik6, A.Blanco4, M.Böhmer14, C.Boiano10, A.Bortolotti10, J.Boyard16, S.Brambilla10, P.Braun-Munzinger6, P.Cabanelas19, S.Chernenko7, T.Christ14, R.Coniglione2, M.Dahlinger6, J.Díaz20, R.Djeridi9, F.Dohrmann18, I.Durán19, T.Eberl14, W.Enghardt18, L.Fabbietti14, O.Fateev7, P.Finocchiaro2, P.Fonte4, J.Friese14, I.Fröhlich9, J.Garzón19, R.Gernhäuser14, M.Golubeva12, D.González-Díaz19, E.Grosse18, F.Guber12, T.Heinz6, T.Hennino16, S.Hlavac1, J.Hoffmann6, R.Holzmann6, A.Ierusalimov7, I.Iori10,11, A.Ivashkin12, M.Jaskula5, M.Jurkovic14, M.Kajetanowicz5, B.Kämpfer18, K.Kanaki18, T.Karavicheva12, D.Kirschner9, I.Koenig6, W.Koenig6, B.Kolb6, U.Kopf6, R.Kotte18, J.Kotulic-Bunta1, R.Krücken14, A.Kugler17, W.Kühn9, R.Kulessa5, S.Lang6, J.Lehnert9, L.Maier14, P.Maier-Komor14, C.Maiolino2, J.Marín19, J.Markert8, V.Metag9, N.Montes19, E.Moriniere16, J.Mousa15, M.Münch6, C.Müntz8, L.Naumann18, R.Novotny9, J.Novotny17, W.Ott6, J.Otwinowski5, Y.Pachmayer8, V.Pechenov9, T.Pérez9, J.Pietraszko6, J.Pinhao4, R.Pleskac17, V.Pospísil17, W.Przygoda5, A.Pullia10,11, N.Rabin13, B.Ramstein16, S.Riboldi10, J.Ritman9, P.Rosier16, M.Roy-Stephan16, A.Rustamov6, A.Sadovsky18, B.Sailer14, P.Salabura5, P.Sapienza2, A.Schmah6, W.Schön6, C.Schroeder6, E.Schwab6, P.Senger6, R.Simon6, V.Smolyankin13, L.Smykov7, S.Spataro2, B.Spruck9, H.Stroebele8, J.Stroth8,6, C.Sturm6, M.Sudol8,6, V.Tiflov12, P.Tlusty17, A.Toia9, M.Traxler6, H.Tsertos15, I.Turzo1, V.Wagner17, W.Walus5, C.Willmott19, S.Winkler14, M.Wisniowski5, T.Wojcik5, J.Wüstenfeld8, Y.Zanevsky7, P.Zumbruch6 

1)Institute of Physics, Slovak Academy of Sciences, 84228 Bratislava, Slovakia
2)Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, 95125 Catania, Italy
3)Dipartimento di Fisica e Astronomia, Università di Catania, 95125, Catania, Italy
4)LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Departamento de Física da Universidade de Coimbra, 3004-516 Coimbra, PORTUGAL.
5)Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30059 Cracow, Poland
6)Gesellschaft für Schwerionenforschung mbH, 64291 Darmstadt, Germany
7)Joint Institute of Nuclear Research, 141980 Dubna, Russia
8)Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60486 Frankfurt, Germany
9)II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany
10)Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy
11)Dipartimento di Fisica, Università di Milano, 20133 Milano, Italy
12)Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia
13)Institute of Theoretical and Experimental Physics, 117218 Moscow, Russia
14)Physik Department E12, Technische Universität München, 85748 Garching, Germany
15)Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus
16)Institut de Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406 Orsay Cedex, France
17)Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic
18)Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden, Germany
19)Departamento de Física de Partículas. University of Santiago de Compostela. 15782 Santiago de Compostela, Spain
20)Instituto de Física Corpuscular, Universidad de Valencia-CSIC,46971-Valencia, Spain

- 1)Institute of Physics, Slovak Academy of Sciences, 84228 Bratislava, Slovakia
- 2)Istituto Nazionale di Fisica Nucleare - Laboratori Nazionali del Sud, 95125 Catania, Italy
- 3)Dipartimento di Fisica e Astronomia, Università di Catania, 95125, Catania, Italy
- 4)LIP-Laboratório de Instrumentação e Física Experimental de Partículas, Departamento de Física da Universidade de Coimbra, 3004-516 Coimbra, PORTUGAL.
- 5)Smoluchowski Institute of Physics, Jagiellonian University of Cracow, 30059 Cracow, Poland
- 6)Gesellschaft für Schwerionenforschung mbH, 64291 Darmstadt, Germany
- 7)Joint Institute of Nuclear Research, 141980 Dubna, Russia
- 8)Institut für Kernphysik, Johann Wolfgang Goethe-Universität, 60486 Frankfurt, Germany
- 9)II.Physikalisches Institut, Justus Liebig Universität Giessen, 35392 Giessen, Germany
- 10)Istituto Nazionale di Fisica Nucleare, Sezione di Milano, 20133 Milano, Italy
- 11)Dipartimento di Fisica, Università di Milano, 20133 Milano, Italy
- 12)Institute for Nuclear Research, Russian Academy of Science, 117312 Moscow, Russia
- 13)Institute of Theoretical and Experimental Physics, 117218 Moscow, Russia
- 14)Physik Department E12, Technische Universität München, 85748 Garching, Germany
- 15)Department of Physics, University of Cyprus, 1678 Nicosia, Cyprus
- 16)Institut de Physique Nucléaire d'Orsay, CNRS/IN2P3, 91406 Orsay Cedex, France
- 17)Nuclear Physics Institute, Academy of Sciences of Czech Republic, 25068 Rez, Czech Republic
- 18)Institut für Kern- und Hadronenphysik, Forschungszentrum Rossendorf, PF 510119, 01314 Dresden, Germany
- 19)Departamento de Física de Partículas. University of Santiago de Compostela. 15782 Santiago de Compostela, Spain
- 20)Instituto de Física Corpuscular, Universidad de Valencia-CSIC,46971-Valencia, Spain

- HADES collaboration

**GSI**