FIAS Scientific Report 2010 - Frankfurt Institute for Advanced Studies ...

Production of multi-hyper-nuclei in peripheral heavy-ion collisions
Collaborators: I.N. Mishustin 1 , J. Steinheimer 1 , M. Bleicher 1 , A. Botvina 1,2 , K. Gudima 3
1 Frankfurt Institute for Advanced Studies, 2 Institute for Nuclear Research, RAS, Moscow, 3 Institute of Applied Physics,
Moldavian Academy of Sciences
We study a new mechanism of hyper-nuclei production in peripheral collisions of relativistic nuclei when hyperons
are produced in secondary reactions and can be captured by spectators. In this way, a piece of relatively
cold (multi-)strange nuclear matter can be formed in the laboratory under conditions similar to the interiors
of neutron stars. In the following this excited strange matter will disintegrate into several ordinary and
hyper-fragments. Experiments on production of hyper-nuclei in relativistic nucleus-nucleus collisions are now
under-way at GSI (HypHI collaboration) and are also planed for FAIR. Within this project we have developed
a hybrid approach for description of hyper-fragment production in such reactions. The first dynamical stage of
the reaction is described by the Quark Gluon String Model (QGSM) or by Ultra-relativistic Quantum Molecular
Dynamics (UrQMD), which have demonstrated previously a very good description of strange hadron production.
We have applied a new criterion for the absorption of produced hyperons, e.g. Λ is captured when its
kinetic energy is less than the hyperon potential generated by surrounding nucleons. The characteristics of
the hyperonic spectator matter and probability of producing multi-strange systems were also investigated. For
reliable predictions we need to generate about 10 6 events. The calculations are performed at the CSC using
a vectorization algorithm. Our calculations show that double- and even triple-Λ-hypernuclei can be produced
by the proposed mechanism. This project is a very good example of the close cooperation of different FIAS
groups.
X 20
15
10
5
0
-5
-10
Au(20 GeV/A)+Au → Λ abs + x
P
T
Y+N=Λ+N
AK+N=Λ+π
N+N=Λ+K+N
π+N=Λ+K
-10 -7.5 -5 -2.5 0 2.5 5 7.5 10
Y
Projections of the Λ-hyperon absorption points on the X-Y plane perpendicular to the beam axis. The counters of the
projectile (P) and target (T) nuclei are shown by the circles. The various processes leading to the hyperon production
are shown by different symbols. One can clearly see the accumulation of the absorbed Λ’s in the spectator parts of the
colliding nuclei. Presented results correspond to 10000 events.
Related publications and talks in 2010:
1. A.S. Botvina, K.K. Gudima, J. Steinheimer, M. Bleicher and I.N. Mishustin, Production of spectator
hypermatter in relativistic heavy-ion collisions, paper in preparation;
2. Igor Mishustin, Production of hypernuclei in relativistic heavy-ion collisions, invited talk at the International
Workshop “Strangeness in Nuclei” (ECT*, Trento, November 3-7, 2010).
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