The isospin-thermometer method to determine the freeze-out temperature in fragmentation reactions D. Henzlova a, M. V. Ricciardi a, J. Benlliure b, A. S. Botvina a, T. Enqvist a, A. Keli ć a, P. Napolitani a, J. Pereira b, K.-H. Schmidt a a GSI-Darmstadt, Germany b Univ. Santiago de Compostela, Spain

Motivation phase transition of nuclear matter - investigation of caloric curve reasons: experimental mass resolution evaporation is disturbing effect -> must be corrected temperature -> isotopic thermometer isoscaling method isospin-thermometer method isospin-thermometer method -> extension to higher masses light fragments only ~ 5MeV

Full fragment identification with the Fragment Separator (FRS) at GSI Z identification – ionisation chamber ΔE ~ Z 2 A/Z identification – velocity (TOF) Bρ – magnetic rigidity full fragment identification -> /Z calculation

data do not follow the evaporation corridor What was observed in previous experiments? the higher the N/Z initial the higher the /Z of the data fragments keep the memory of the N/Z of the initial system preserve higher /Z ratio M.V.Ricciradi, et al.; proceedings of International Workshop XXXI, Hirschegg, Jan T.Enqvist, et al.; Nuc. Phys. A658 (1999) 47 T.Enqvist, et al.; Nuc. Phys. A703 (2002) 435

Understanding of the observed features evaporation I.Feature: I. Feature: manifestation of break-up in formation of heavier fragments II. Feature: II. Feature: evaporation does not remove the information on the initial N/Z evaporation chain may be used to extract additional information on the preceding stage of the reaction high E* break-up T.Enqvist, et al.; Nuc. Phys. A658 (1999) 47 T.Enqvist, et al.; Nuc. Phys. A703 (2002) 435 M.V.Ricciradi, et al.; proceedings of International Workshop XXXI, Hirschegg, Jan. 2003

The isospin-thermometer method N/Z initial /Z initial ~ /Z initial N/Z final N/Z initial - /Z final = measure of the length of the evaporation cascade possible to trace back the E* -> T at the beginning of the evaporation stage T freeze-out of the break-up stage may be deduced SMM calculation ● 238 U + Ti ● 238 U + Pb T freeze-out ~ 5MeV and constant over a wide E* range abrasionbreak-up evaporation 238 U K.H.Schmidt, et al.; Nuc. Phys. A(710) (2002) 157

Summary the obtained results provide a unified picture of nuclear reaction process both from heavy and light fragments from certain E* on all the fragments are formed in the break-up process with a universal T freeze-out ~ 5MeV the isospin-thermometer method enables an extension of nuclear thermometry to higher fragment masses