JINR-LHE-1020, JINR-BLTP (HADES Project)
· Date approved: 1995 · Date started: 1996 · Date completed: 2005
Accelerator: SIS at GSI
Detector: High Acceptance Di - Electron Spectrometer (HADES) consisting of a fast RICH, a toroidal superconducting magnet, a system of low - mass Mini Drift Chambers (MDC), a time of flight system and a shower detector

 

High Acceptance Di - Electron Spectrometer

1S.Chernenko, V.Chepurnov, O.Fateev, A.Petrov, L.Smykov, Yu.Zanevsky, G.Agakishiev, Yu.Panebratsev, V.Pechenov, A.Titov, V.Toneev
1 Joint Institute for Nuclear Research, Dubna, Russia

Also participating:

2 Istituto Nazionale di Fisica Nucleare - LNS, Catania, Italy
3 Lab. de Physique Corpusculaire, Universite Blaise Pascal Clermont II, Aubiere, France
4 Smoluchowski Inst. of Physics, Jagiellonian University of Cracow, Poland
5 Gesellschaft fur Schwerionenforschung (GSI), Darmstadt, Germany
6 Inst. fur Kern-und Hadronenphysik, FZ Rossendorf, Dresden Germany
7 Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia
8 Inst. fur Kernphysik, Joh. Wolfgang Goete Univ., Frankfurt, Germany
9 Physik Department E12, Techn. Univ. Munchen, Garching, Germany
10 II. Physikalisches Institut, Justus Liebig Universitat Giessen, Germany
11 Istituto Nazionale di Fisica Nucleare, Milano, Italy
12 Institute of Theoretical and Experimental Physics, Moscow, Russia
13 Institute for Nucl. Research, Russ. Academy of Sciences, Moscow, Russia
14 Moscow State Engineering Physics Institute, Moscow, Russia
15 Department of Natural Sciences, University of Cyprus, Nicosia, Cyprus
16 Institut de Physique Nucleaire d'Orsay, Orsay, France
17 Nuclear Physics Inst., Czech Academy of Sciences, Rez, Czech Republic
18 Depart. de Fisica de Particulas, Univ. of Santiago de Compostela, Spain
19 Instituto de Fisica Corpuscular, University of Valencia, Spain

 

Spokesman: J. Friese

Contactman from JINR: Yu.V. Zanevsky

 

The physics goal of the HADES collaboration is to investigate in-medium modifications of light vector mesons (r, w, j), as well as to study dilepton continuum below the r/w - region in hot and dense hadronic matter. Attractive extensions of this program include the investigation of r/w interference and the measurement of electromagnetic formfactors of baryons and neutral mesons via dilepton and Dalitz decays, respectively. The HADES detector is specially designed to provide an excellent mass resolution and a very large acceptance for comprehensive studies of the behaviour of r, w and j mesons in a nuclear medium.

Schematic cross section of HADES spectrometer. MDC - low mass multilayer drift chamber.

 

Spatial resolution of full scale Prototype (MDC-2), which has been constructed at LHE JINR and successfully tested at GSI, Darmstadt.

HADES is designed to measure the dilepton yield at invariant masses below 1 GeV/c2 in p - nucleus, p - nucleus and heavy nucleus - nucleus collisions. The detector has a geometric acceptance of almost 50% for e+ e- pairs and a mass resolution of 0.8% for r and w mesons. Presently, the HADES collaboration consists of about 100 physicists from 19 institutes and 9 countries. JINR responsibilities are concentrated on the following: full responsibility for the design of a system of six Multilayer Drift Chambers (MDC, plane - II), carrying out R&D on analogue readout electronics for all Macs (plane I - IV, totally 24 modules), preparation of software for fast finding and reconstructing charged particle tracks in the MDC system and participation in data analysis.

 

Main results in 1995 - 1999

  1. The R&D, design and construction of full-scale Prototype I of new generation low - mass multilayer drift chambers (MDC) have been carried out at JINR for a central part of the HADES spectrometer of 1.2 x 1.0 m2 dimensions and six anode planes with different wire orientation. Prototype I was successfully tested under laboratory conditions in Dubna and for two beam times on SIS and GSI in 1997. This detector operated on a helium-based gaseous mixture and showed very stable parameters under conditions very close to a real experiment for all testing times. The spatial resolution (s) was better than < 70 mm at a high rate and multiplicity. Taking into account the test results of Prototype I, the mass production of drift chamber modules started. Six modules were constructed and tested with good results under laboratory conditions. Two modules fully equipped with analogue and digital readout electronics have been tested on a beam at GSI in 1999.

  2. Technological equipment needed for the development, production and test of high precision drift chambers has been developed.

  3. The R&D of analogue readout electronics (amplifier - shaper - discriminator) has been performed at LHE JINR, the mass - production of about 30.000 channels has been fulfilled after testing these cards in detail.

  4. The program for fast finding and reconstructing tracks in the system of drift chambers has been developed.

  5. Theoretical investigations for the HADES physical program have been carried out by the physicists from JINR and FZ-Rossendorf.

Main results of the common activity were presented at the Wire Chamber Conference (Vienna, Feb. 98), at the XIV International Seminar on High Energy Physics Problems (Dubna, August 98), at the Int. Nuclear Physics Conference (Paris, August 98), at the Workshop on Scientific Co-Operation between JINR and German Research Centres (Dubna, November 98) and the Position - Sensitive Detector Conference PSD-99 (London, Sept. 99)

 

The Research Program

The physics program of HADES is rather broad and includes the study of lepton pair emission in relativistic heavy ion collisions, dilepton production in elementary reactions and experiments aimed at studying the structure of hadrons:

  1. Investigation of properties of dense and hot nuclear matter in heavy ion collisions at SIS (up to 2 AGeV):

    1. Investigation of in-medium modifications of light vector mesons’ (r, w, j) properties (masses, widths). The spectrometer HADES has a geometric acceptance of almost 50% for electron pairs and a mass resolution of 0.8% in the r/w region.

    2. Investigation of dilepton continuum below the r/w - region.

  2. Investigation of r/w interference and measurement of electromagnetic form-factors of baryons and neutral mesons via dilepton and Dalitz decays, respectively.

  3. Study of dilepton productions with pion and proton beams.

 

References:

  1. A.I.Titov, T.I. Gulamov, B.Kaempfer "Neutral Mr-meson properties in an isospin - asymmetric pion medium", J. Nucl. Phys. (Russ.), 59, 1996, p.727.;

  2. S.Chernenko, O.V.Fateev, Yu.V.Zanevsky "Octal channel amplifier-discriminator based on ASD-8 (ASIC) for timing measurements with drift chambers", Preprint JINR, Dubna, E13-97-60, 1997, p.11;

  3. C.Garabatos, W.Karig, C.Muentz, A.Steigerwald, J.Stroth, J.Wustenfeld, A.Zentek, K.Bethge, S.Chernenko, O.Fateev, L.Glonti, L.Smykov, Yu.Zanevsky, P.Zumbruch, H. Bokemeyer, W. Koenig, H.Stelzer "Optimization of low-mass drift chambers for HADES", Nuclear Instr. and Meth. in Phys. Res., A412(1998) 38 - 46;

  4. C.Garabatos, for the HADES collaboration "The HADES dilepton spectrometer" Nucl.Phys. B61, 607c(1998).

 

E - mail contact:

friese@mailhost.bl.physik.tu-muenchen.de (J. Friese)

zanevsky@lhedl.jinr.ru (Yu.V. Zanevsky)


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