Berthier, B

Cerruti, C

Hisleur, J M

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52530991191 Gif sur yvette cedex (France) OCR Output2— Laboratoire national Saturne91191 Gif sur yveite cedex (France)1- Centre d’études nucléaires de Saclay, DPHN/MF,bat.34contactmanz Berthier Bernard (tel: 33 1 6 908 350Q)Spokesman : NGO Christian (tel:33 1 6 908 QMYO)C.Mazur1, C.NgO1 et M.Ribrag1B.Berthierl, C.Cerruti2, J.M.His1eur1, J.Julien1, R.Luces1SACLAY-SATURNE COLLABORATIONSEARCH FOR NUCLEI IN HEAVY ION COLLISIONS AT ULTRARELATIVISTIC ENERGIESADDENDUM TO PROPOSAL P2238% · HYA fiV;.<.LSC00000527P20 February @867)THg#z§} SPSC/P223-ADP1»E? 5;CERN LIBRARIES, CENEVA - CERN/SPSC/87 llcJ5R 4/EUROPEAN ORGANIZATION FOR NUCLEAR RESEARCHvery likely to be an indication that the multifragmentation mechanism is OCR Outputresults are therefore different from those associated to protons and arewith the data is not as good as with the exponential. The experimentalbest fit with a Z‘" function which leads to T Z 1.9. However the agreementwhere A is the mass of the fragment, with T = 2.6. The figure also shows aae exp(-0.3hZ)i 2-1.9YieldO + Au 226 GeV/usame energy range, it has been found that the mass yield1’ varies like A`T,is shown at 226 GeV/u in the figure. In proton induced collisions, in theefficiency). Their atomic number distribution decreases as Z increases andnuclei with atomic numbers up to Z ~ 13 (even up to Z = 18 but with a small1*between a very energetic 20 projectile and a 3gAu target. We detectedWe wanted to see if nuclei are still present at large angles in a collisionOur experiment with the 120 beam at 226 GeV/u has been successful.1- we would like to decrease our energy detection threshold because the OCR Outputprevious experiment with the following modificationsThe experimental set up we would like to use is the same as in theprojectile would therefore be useful to study this evolution.of fact one observes more collectivity in heavy ion collisions. A biggerat very large bombarding energies compared to the proton case. As a mattermultifragmentation of the projectile spectators is different for heavy ionsThis difference indicates that the process inducing aike e‘°·3°Z..¤ield has been found to vary like Z'T with T = 2.6 whereas here it variesand if it is even steeper. Indeed in proton induced reactions the masswe would like to check if a similar behaviour of the mass yield is observedcan still survive in an ultrarelativistic heavy ion collision. Furthermore,16 8. The aim is the same as in the previous experiment, i.e. see if nucleiexperiment, which is parasitic to NA38, using a heavier projectile likeIn view of the above results, we would like to pursue thelarger by a factor of the order of two.the SPS give similar results but the production cross section seems to beThe results obtained at 60 GeV/u during the few shifts provided bypercolation approach,·a critical phenomenon, and in particular can be explained within aseveral pieces (multifragmentation). These results could be interpreted asbetween the nucleons. As a final result the spectator nucleus break up intocascade through the spectator volume, create holes and weaken the bondsinduced reactions, fast particles coming from the participant region mightcompressional energy might also be present. Furthermore, as in protondegrees of freedom) is converted into thermal excitation. Littlesystem reorganizes, the deformation energy (essentially in the surfaceshape due to the projectile which gouge a hole through the target. When theafter the collision. These spectators are expected to have a very distortedspectators which are left practically at rest in the laboratory systemThis fragment production is expected to originate from the targetrepulsion between the fragments.below 30-MO MeV which indicates that it comes essentially from the coulombdifferent in both cases. The kinetic energy of most of the products is2) J.Nemeth et al Z. Phys. éjgj (1986) $#71) A.S.Hirsch et al Phys. Rev. QQQ (198H) 508processors which are working in parallel.2- We shall use a faster acquisition system based on several 8088stops the gas circulation, will be installed in case of any leak.a few hundred of cmj and is at a low pressure. An automatic set up, which(an inert gas). The volume of the gas in each telescope is of the order of10 cm depth and will be operated under a pressure of about 50 Torrs of CFfollowed by 2 silicon AE detectors (150 um and 500 um). The gas AE part hasreason we would like to use two telescopes consisting of 2 gas—AE sectionskinetic energy of the nuclei emitted at large angles is small. For this

Search for nuclei in heavy ion collisions at ultrarelativistic energies

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