JINR-LHE-0983-7 (NA49 Project)
· Data approved: 1998 · Data started: 1998 · Data completed: 2002
Status: ongoing experiment
Accelerator: CERN SPS
Detector: NA49 setup with time projection chambers, time-of-flight walls, calorimetry and beam defining counters, target stations
Beams: Pb-ions of 158, 80 and 40 A GeV; protons and pions; C- and Si-secondary fragments of 158 A GeV
Targets: nuclei (Pb, Al, Si, C) and liquid H2


Project NA49: Large Acceptance Hadron Detector for an Investigation of Pb-Induced Reactions at the CERN SPS

[1]S.Afanasiev, N.Agababyan, B.Batar, S.Chatrchyan, A.Isupov, V.Kolesnikov, A.Malakhov, G.Melkumov, A.Semenov
[1] Joint Institute for Nuclear Research, Dubna

Also participating:

[2] Department of Physics, University of Athens, Greece.
[3] Lawrence Berkeley National Laboratory, University of California, Berkeley, USA.
[4] Birmingham University, Birmingham, England.
[5] KFKI Research Institute for Particle and Nuclear Physics, Budapest, Hungary.
[6] CERN, Geneva, Switzerland.
[7] Institute of Nuclear Physics, Cracow, Poland.
[8] Gesellshaft für Schwerionenforschung (GSI), Darmstadt, Germany.
[9] University of California at Davis, Davis, USA.
[10] Fachbereich Physik der Universität, Frankfurt, Germany.
[11] University of California at Los Angeles, Los Angeles, USA.
[12] Fachbereich Physik, der Universität, Marburg, Germany.
[13] Max-Planck-Institut für Physik, Munich, Germany.
[14] Institute for Nuclear Studies, Warsaw, Poland.
[15] Institute for Experimental Physics, University of Warsaw, Warsaw, Poland.
[16] Nuclear Physics Laboratory, University of Washington, Seattle, WA, USA.
[17] Yale University, New Haven, CT, USA.
[18] Rudjer Boskovic Institute, Zagreb, Croatia.
[19] Comenius University, Bratislava, Slovakia.
[20] University of Houston, TX, USA.


Spokesman: P.Seyboth

Contactman from JINR: G.Melkumov


The NA49 experiment is being performed to search for the phase transition from hadrons to deconfined quarks and gluons in Pb+Pb collisions at the SPS predicted by Lattice QCD. Such reactions provide the largest energy density of a collision system for a controlled study at the laboratory. The NA49 was optimized to study hadronic observables in strong interactions of nucleons and nuclei, with a specific aim at obtaining large acceptance for momentum reconstruction and for the identification of most produced particles.

The JINR has been taking an active part in the NA49 since 1995. A 900-channel Time-of-Flight (TOF) detector is the main contribution of Dubna to the experiment. In this activity, the Dubna group has focussed on the design and construction, the maintenance and running of the whole TOF system on the beam, as well as on its callibration and test, and finally on data taking and analysis.



The experimental NA49 setup (fig.1) comprises four Time Projection Chambers (TPC) for tracking and energy loss measurements; four Time-of-Flight (TOF) walls; an array of PesTOF counters for additional particle identification; calorimetry for neutral particle detection and triggering; a system of beam detectors.

Two medium size TPCs (VTPC-1/2) are located inside the Vertex-Magnets (VTX-1/2) with up to 1.5T field strengths each. Two large size TPCs (MTPC-L/R) are positioned downstream the magnet for high-precision dE/dx measurements and acceptance coverage in the forward direction.

The TOF scintillator systems supply an additional particle identification in the region of minimum ionization. A Ring Calorimeter (RCAL) offers a photon and neutral particle measurement as well as a transverse energy determination over the full azimuth. A Veto Calorimeter (VCAL) covering an extreme forward direction is used for central event triggering in Pb+Pb interactions.

The position and direction of each beam particle is measured by a system of proportional chambers with cathode readout (BPD-1.2.3). Metal foil targets are used for Pb+Pb and p+A running (fig.1a and c). A liquid hydrogen target is available for p+p running (fig.1b). The acceptance coverage amounts to about 80% of all charged particles. For central Pb+Pb interactions, this means that 1200 are detected out of about 1500 produced charged particles.

Figure 1: Set-up of NA49 experiment with different target arrangements for a) Pb+Pb, b) p+p and c) p+A collisions. The target position is at the front face of the first Vertex Magnet (VTX-1).



In its initial phase, the NA49 collaboration has been concentrating on an exploratory investigation of central Pb+Pb interactions at the highest SPS energy. The analysis makes use the unique capability of the NA49 detector to combine the study of particle yields with correlation analysis and physics at the event-by-event level.

First results shed new light on the salient question concerning the behaviour of matter at large energy density.

The following was shown for central Pb+Pb collisions at 158 A GeV:

  • Large baryon stopping

  • High energy density

  • Strangeness enhanced production

  • Pion enhancement

  • Large transverse flow

  • Small event-by-event fluctuations



The status and future program of the NA49 experiment were submitted to the SPS Committee in Addenda 2 and 3 to Proposal SPSLC/P264.

This report advocates a comprehensive and consistent study of hadronic interactions with the NA49 detector, ranging from elementary hadron + nucleon processes via hadron + nucleus interactions with controlled centrality to heavy ion collisions at a variety of nuclear masses and energies.

Primary items of the NA49 experimental program are the following:

  • to obtain more statistics for Pb+Pb collisions at 158 A*GeV as needed for rare processes requiring clean TOF identification, such as PHI, lambda(1520) and KK, pp interferometry,

  • to study Pb+Pb collisions at lower beam energies (40 A*GeV and 80 A*GeV) in order to establish the collision energy dependence of QGP signals and to locate the QGP phase transition potentially,

  • to study collisions of lighter ions (C+C and Si+Si and Ag+Ag) in order to investigate how the properties of matter depend on the size of colliding objects (the level of equilibration, creation of QGP),

  • to continue the investigation of proton(meson)-nucleon and nucleus reactions with sufficient statistics for relating to nucleus-nucleus collisions and for studying soft hadronic phenomena in a simpler environment.


NA49 original Proposal - CERN/SPSLC 91-31, SPSLC/P264, May 1991

Addendum 2 - CERN/SPSC 98-4, January 1998

Addendum 3 - submitted to the SPS Committee in January 1999



  1. Proceedings of QM96, QM97, QM99, SQM97, SQM98 Conf: in Nucl.Phys. A610, A638, and J.Phys.G: Nucl.Part.Phys. 23(1997).
  2. NIM A409(1998).
  3. PRL 80,(1998)4136.
  4. Eur.Phys.J.C2(1998)661, Eur.Phys.J.A2,(1998)383.
  5. PRL 82,(1999)2471.
  6. PL B444(1998)523.
  7. NIM CERN-EP/99-01, nucl-ex/9810005, IKF-HENPG/1-99.


E-mail contact: melkumov@moonhe.jinr.ru

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