Investigation of the freeze-out configuration in the 197 Au + 197 Au reaction at 23 AMeV

1. Investigation of the freeze-out configuration in the 197Au + 197Au reaction at 23 AMeV Rafał Najman for CHIMERA collaboration M. Smoluchowski Institute of Physics Jagiellonian University The theoretical analysis of properties of superheavy nuclei do not predict any long living nuclei with compact shapes beyond the island of stability (N ~ 184, Z ~ 114).

2. Search for superheavy nuclei Liquid drop model with shell corrections and Hartree – Fock – Bogoliubov theory with the Gogny D1S force calculations have shown that metastable islands of nuclear bubbles can exist for nuclei in the range A=450-3000 K. Dietrich, K.Pomorski Phys. Rev. Lett. 80, 37 (1998) J. Decharge et al. Nucl. Phys.A 716, 55 (2003 )‏ • The energy of the toroidal minimum decrease relatively to the potential energy of the spherical configuration with increase of the mass of the system • For Z>140 , the global minimum of potential energy corresponds to the toroidal shape M. Warda, Int. J. of Mod. Phys. E 16,452 (2007)

3. BUU simulations for central collisions of Au + Au Calculations predict that a threshold energy for toroidal freeze-out configuration is at about 23 MeV / nucleon A.Sochocka et al., Int. J. Mod. Phys. E17, 190 (2008)

4. Results of ImQMD simulation Prolate spheroid E = 5.4 – 7.4 AMeV Flat shape Time evolution of quadrupole moment for 238U + 238U Time evolution of 238U + 238U at Ecm=3570 MeV and b=0 fm E = 30 AMeV Tian et al., Phys. Rev. C77, 064603 (2008)‏ 4

5. Macroscopic droplet collisions Formation the toroidal-shapes configurations can beobserved in binary droplet collision at high velocity V=3.89 m/s V=9.1 m/s 5 Phys.Rev.E 80, 036301 2009

6. CHIMERA – Charged Heavy Ion Mass and Energy Resolving Array 17 rings CHIMERAs advantage: • 1192 telescopes: Si and CsI • Low detection threshold - 1MeV/A • Covering almost 94% of 4 • Z and A identification 687 telescopes on 9 wheels

7. ΔE-E technique

8. Time of Flight Techinique

9. Global properties of experimental data from 197Au+197Au reaction at 23 AMeV well defined events TLF PLF IVS Fission fragments from PLF decay

10. Multiplicity distribution for well defined events Nfrag≥ 5

11. Shape analysis δ parameter measures the shape of the events in momenta space. Zfrag > 9

12. Shape analysis Δ2 parameter measures the flatness of the events in velocity space. For toroids it is much smaller than for sphere or bubble. A, B, C, D - plane parameters

13. Observables distributions Flat events conditions: One can see that for both observables the biggest differencebetween experimental distribution and model predictions is observedfor the Ball 8V0, and Bubble 8V0 configurations. In contrast to that, the experimentaldata seem to be more consistent with the simulations assuming toroidal freeze-out configurations.

14. Location of toroidal events on the ϴplane vs ϴflow plane

15. Efficiency factor: Efficiency factor – ratio of number of events fulfilling the selection conditions to the total number of events with 5 heavy fragments Flat events conditions: EF is: • Very low for spherical freeze-out configurations in respect to the corresponding values for toroidal configuration • For QMD calculations is strongly dependent on the ϴplane range • For experimental data the value of the EF is about 50% for events located in the reaction plane (ϴplane > 750 ) • Is reduced by factor 2 for events perpendicularto the reaction EF values for experimental data are very close to the model predictions for toroidal configurations. This observation may indicate the formation of toroidal/flat freeze-out configuration created in the Au + Au collisions at 23 MeV/nucleon.

16. Other observables In order to get additional evidence to support the hypothesis that toroidal objects are created, the behavior of other observables was investigated: • mass standard deviations of fragments, • relative angles of fragment pairs, • mean velocities of fragments as a function of their mass • relative velocities of fragments pairs

17. Other observables A standard deviation of masses for flat events with 5 fragments

18. Other observables New observables: θflow< 20 θplane< 75 θflow > 20 θplane < 75 θflow > 20 θplane> 75 Vij is mean value of relative velocities for flat events with 5 fragments θflow< 20 θplane> 75 Inside reaction plane Outside reaction plane Inside reaction plane Outside reaction plane Outside reaction plane region where observation of toroidal freeze-out configuration is expected region dominated noncentral collisions For Vij distributions the mean values for class of events located outside the reaction planeare smaller in comparison to the case of events located in the reaction plane. This observation may be used as an indication that for events located outside the reaction plane freeze-out configuration is more extended in comparison withthat for events located inside reaction plane.

19. Road Map Search for toroidal freeze-out configurations in events with smaller number of fragments (3 and 4) Isotopic identification of light fragments ( 3 ≤ Z ≤ 9 ) Investigation of isotopic composition of IVS

20. Summary and outlook The experimental data for well defined events have been shown. The experimental data are compared with ETNA and QMD model predictions. Efficiency factor is used as indication of formation of exotic freeze-out configuration. Comparison between experimental data and model predictions may indicate the formation of flat/toroidal nuclear system. Distribution of vij indicatesthat toroidal freeze-out configuration may be created outside reaction plane Additional analysis of experimental data

21. Breakup Collaboration F.Amorini1,2, L.Auditore3, A.Bubak4, T.Cap5, G.Cardella6, E. De Filippo6, E.Geraci2,6, L.Grassi2,6, A.Grzeszczuk4, E.La Guidara7, J.Han1, D.loria3, S.Kowalski4, T.Kozik8, G.Lanzalone1,9, I.Lombardo2,9, Z.Majka8, R.Najman8, N.G.Nicolis10, A.Pagano6, E.Piasecki11, S.Pirrone6, R.Płaneta8, G. Politi2,6, F.Rizzo1,2, P.Russotto1,2, K.Siwek-Wilczyńska5, I.Skwira-Chalot5, A.Sochocka12, A.Trifirò3, M.Trimarchi3, J.Wilczyński13, G.Verde6, W.Zipper4 1) INFN, Laboratori Nazionali del Sud, Catania, Italy 2) Dipartimento di Fisica e Astronomia Universitá di Catania, Catania, Italy 3) Dipartimento di Fisica Universitá di Messina and INFN Gruppo Collegato di Messina, Italy 4) Institute of Physics,University of Silesia, Katowice, Poland 5) Faculty of Physics,University of Warsaw, Warsaw, Poland 6)INFN,Sezione di Catania, Italy 7)Centro Siciliano di Fisica Nucleare e Struttura della materia 8) M.Smoluchowski Institute of Physics, Jagiellonian University, Kraków, Poland 9)Università Kore, Enna,Italy 10)Department of Physics, The University of Ioannina,Ioannina,Greece 11) Heavy IonLaboratory,University of Warsaw, Warsaw, Poland 12) Department of Physics, Astronomy and Applied Informatics, Jagiellonian University, Kraków, Poland 13) A.SołtanInstitute for Nuclear Studies,Świerk, Poland

22. Reconstruction results

23. Estimation of collision centrality One can see on this plot that noncentral events are located at small θflow angles (> 20 degree) and big θplane angles (< 75 degree). As an impact parameter estimator for experimental data we used total transverse momentum

24. CHIMERA – Charged Heavy Ion Mass and Energy Resolving Array

25. ToF Techinique E- particle energy [MeV] calculated from: E=aL· Channeldesilpg + bL m- ion mass [u] R – distance from target to detector [cm] t0 – time offset calculated for each detector [ns] α= 3·T / d T- cyclotron period [ns] d- distance between two beam bursts [channels] For calibration data the following 8-parametres function is fitted:

26. ToF Techinique

28. CM Klasteryzacja b) 300 Czas[ fm/c ] 0 QMD – model dynamiczny LAB Zimne fragmenty Rozpad gorących frgmentów i przyśpiesznie w polu kulombowskim Czas [ fm/c ] Kod GEMINI QMD + GEMINI Nukleony są przedstawione w formie paczek falowych o stałej szerokości w czasie - układ ewoluuje zgodnie z równaniem Hamiltona. detektor

29. ETNA – Expecting Toroidal Nuclear Agglomeration + GEMINI kod Opisuje rozpad obiektu tworzonego w fazie wymrażania. Obiekt taki tworzy się po emisji nukleonów przedrównowagowych z systemu złożonego, który powstaje w wyniku połączenie się jądra wiązki z jądrem tarczy. ACN = AT + AP ZCN = ZT + ZP -minus nukleony emitowane w początkowej fazie(preequilibrium) reakcji Eava = ECM + Q –ECOULOMB - dostępna energia Podział dostępnej energii: Eava= E* + E th = NaT2 +3/2k(N-1)T ; zakladając równą temperaturę, N – liczba fragmentów Losowanie fragmentów: • Rozkład Gaussa < Zfrag > = Ztot / N N =5 – liczba fragmentow Dynamiczny kod GEMINI: • rozpad wzbudzonych fragmentów • przyśpieszanie w polu kulombowskim Detekcja cząstek w detektorze CHIMERA Wszystkie fragmentysą umieszczanew konfiguracji “wymrożenia” w kształcie kuli, bańkii toroidu warunek przekrywania: Rij > Ri + Rj + 2fm , numer detektorarand ,rand Próg energetyczny Ethr= 1 MeV/A Uwzględnienie niecentralnych kolizji dla zadanego parametru zderzenia b Z FWHM = 1 ch.u. A=2.08* Z ( przewidywania kodu GEMINI )

30. Definition of sphericity and coplanarity From the cartesian components of fragment Z 5 momenta in the centre of mass may construct the tensor where p(n)iis the i-th Cartesian momentum component of the n-th particle, and is the n-th fragment momentum vector. The diagonalization of the momentum tensor gives the eigenvalues: ti, (t1 < t2 < t3).