Is the caloric curve a robust signal of the phase transition in hot nuclei ? E.Vient IWM-EC 2016 Thursday, April 12th 2016

INDRA systematic study of caloric curves of QP With the different campaigns of the INDRA collaboration, we can build different caloric curves of QP for different symmetric or quasi symmetric systems With the same multidetector array and an only one experimental protocol [2] E.Legouée, Ph.D Thesis, Université de Caen-Basse Normandie (2013) [1] E. Vient, Mémoire d’habilitation à diriger des recherches, Université de Caen -Basse Normandie (2006). With a new calorimetry called “3D calorimetry of the QP” [1,2] With measured temperatures from the slopes of kinetic energy spectra of protons, deuterons and tritons [1,2] [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie]

Necessity to do certain event selections Use of an event generator like HIPSE and an INDRA Software Filter to understand and to control our experimental work [3] [3] D. Lacroix, A. Van Lauwe, D. Durand, Phys. Rev. C 69 (2004) 054604. Event selections with a correct detection of the QP products We lose an important cross section at all impact parameters Completeness in the forward hemisphere of the c.m. [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 3

Necessity to do certain event selections Event selections of the collision violence and centrality Selection according to the Normalized Etr12, dividing its distribution in ten slices of the same cross section Etr12 Normalized Counts b (fm) 12 6 3,75 2 1,75 0,5 Ni + Ni 52 A.MeV [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 4

Reminders on the 3D Calorimetry The QP frame is built with IMF and fragments located in the forward hemisphere of the c.m. In the QP frame the whole space is divided in six spatial zones [INDRA-FAZIA workshop on Symmetry Energy and Isospin physics, 20/04/2016, Vient Emmanuel] 5

Reminders on the 3D Calorimetry HIPSE Data Counts Counts  [120°,180°] [60°,120°] QP HIPSE Others HIPSE Ekin (MeV) Ekin (MeV) Counts Counts  [0°,60°]  [-60°,0°] Ekin (MeV) Ekin (MeV) Counts Counts [-180° ,-120°]  [-120°,-60°] Ekin (MeV) Ekin (MeV) [INDRA-FAZIA workshop on Symmetry Energy and Isospin physics, 20/04/2016, Vient Emmanuel]

Reminders on the 3D Calorimetry Principle of the 3D calorimetry of the QP All the particles emitted in the angular domain [0° ; -60°] in the QP frame are assumed solely evaporated by the QP Estimate of an evaporation probability according to the kinetic energy for an angular domain by comparison with this reference domain : [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 7

Reminders on the 3D Calorimetry Use the probabilities Probn(Ek, 𝜃SPIN, 𝜑,Etr12) to be emitted by the QP to do a calorimetry of the QP event by event In the reconstructed QP frame [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 8

Application of this 3D Calorimetry to obtain caloric curves Observed breaks of slope seeming to correspond to a change of the mode of de-excitation of the nuclei. [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 9

Limits of existence of hot nuclei Does it mean that we have reached the limiting temperature of existence of hot nuclei ? Lines correspond to calculations of limiting temperatures due to Coulomb instability extracted from two theoretical models [4] et [5]. [4] Y. Zhang, Physical Review C 54 (1996) 1137 [5] L. Zhang, Physical Review C 59 (1999) 3292 [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 10

Limits of existence of hot nuclei Understand what happens with HIPSE? There is an effect due to a pollution by the others contributions [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 11

Possible signals of phase transition : Rise and fall [6] What do we observe for the QP contribution in the angular domain of reference ? LCP × 6 Li × 6 IMF×6 [6] P. Kreutz , Nucl. Phys. A556, 672 (1993) [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 12

Possible signals of phase transition : ∆-scaling in the liquid [7] ∆= 1 ∆= 1/2 central Very peripheral [7] J.D.Frankland, Physical Review C 71 (2005) 034607 [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 13

Conclusions and outlooks The response is no for the moment ! Improve the calorimetry of the QP Determine the efficiency of the multi detector array with an event generator and correct its effec Optimize the separation criteria between the different contributions (QP, QT, mid-rapidity) with the help of an event generator or a model Take into account the entrance channel by a selection according to the QP mass Try to ameliorate the thermometry of the QP by the same recipes and correct well the cooling of the hot nucleus. Correlate the evolution of the correct caloric curves with the others signals of phase transition [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 14

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Influence of the entrance channel [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 16

Different caloric curves [7,8] What happens with another thermometer ? A/8 A/8 [7] S.Albergo, Il Nuevo Cimento A, Vol 89, Issue 1 (1985) 1 [8} J. Pochodzalla, Phys. Rev. Lett., 75 (1995), p. 1040 [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 17

Possible Signals of phase transition : Evolution and fluctuations of the largest fragments Evolution of <Zmax2> Evolution of <Zmax > [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 18

Possible signals of phase transition : ∆-scaling in the liquid [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 19

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Possible signals of phase transition : ∆-scaling in the liquid [IWM-EC 2016 GANIL (Caen), 9/05/2016, Vient Emmanuel, LPC Caen ENSICAEN-Université Caen Normandie] 21

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