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The isospin-thermometer method to determine the freeze-out temperature in fragmentation reactions

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

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The isospin-thermometer method to determine the freeze-out temperature in fragmentation reactions

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  1. The isospin-thermometer method to determine the freeze-out temperature in fragmentation reactions D. Henzlovaa, M. V. Ricciardia, J. Benlliureb, A. S. Botvinaa, T. Enqvista, A. Kelića, P. Napolitania, J. Pereirab, K.-H. Schmidta aGSI-Darmstadt, Germany bUniv. Santiago de Compostela, Spain

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

  3. Full fragment identification with the Fragment Separator (FRS) at GSI Z identification – ionisation chamber ΔE ~ Z2 A/Z identification – velocity (TOF) Bρ – magnetic rigidity full fragment identification -> <N>/Z calculation

  4. What was observed in previous experiments? 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 • data do not follow the evaporation corridor preserve higher <N>/Z ratio • fragments keep the memory of the N/Z of the initial system the higher the N/Z initial the higher the <N>/Z of the data

  5. Understanding of the observed features evaporation 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 I.Feature:manifestation of break-up in formation of heavier fragments high E* break-up 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

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

  7. Summary • the isospin-thermometer methodenables anextension of nuclear thermometry to higher fragment masses • the obtained resultsprovide 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 Tfreeze-out ~ 5MeV

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