What Can be Learned Studying the Distribution of the Biggest Fragment - Nuclear ExperimentReport as inadecuate

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Abstract: In the canonical formalism of statistical physics, a signature of a firstorder phase transition for finite systems is the bimodal distribution of anorder parameter. Previous thermodynamical studies of nuclear sources producedin heavy-ion collisions provide information which support the existence of aphase transition in those finite nuclear systems. Some results suggest that theobservable Z1 charge of the biggest fragment can be considered as a reliableorder parameter of the transition. This talk will show how from peripheralcollisions studied with the INDRA detector at GSI we can obtain this bimodalbehaviour of Z1. Getting rid of the entrance channel effects and under theconstraint of an equiprobable distribution of excitation energy E*, we usethe canonical description of a phase transition to link this bimodal behaviourwith the residual convexity of the entropy. Theoretical with and without phasetransition and experimental Z1-E* correlations are compared. This comparisonallows us to rule out the case without transition. Moreover that quantitativecomparison provides us with information about the coexistence region in theZ1-E* plane which is in good agreement with that obtained with the signal ofabnormal uctuations of configurational energy microcanonical negative heatcapacity.

Author: Eric Bonnet IPNO, GANIL, Francesca Gulminelli LPCC, Bernard Borderie IPNO, Nicolas Le Neindre IPNO, Marie-France Rivet IPNO

Source: https://arxiv.org/

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