Neutron-Neutron Correlations in the Dissociation of Halo Systems: 6He Group "Exotiques" LPC-Caen Collaboration LPC-CHARISSA-DEMON

Neutron-Neutron Correlations in the Dissociation of Halo Systems: 6He Motivation + History Principles of neutron-neutron interferometry 6He breakup Limitations – coherence, theory… Conclusions & Perspectives

Two-Neutron Halo Systems  “Borromean”

n-n interaction in field of core binds the system ... Two-Neutron Halo Systems  n-n interaction in field of core binds the system ...

Halo neutron correlations … ? Two-Neutron Halo Systems  rnn Halo neutron correlations … ?

Halo n-n Spatial Configuration 6He “cigar” “dineutron” RNBT Collaboration – 3-body Faddeev

3-body Model Calculations * : 6He = a + n +n ground state wavefunction “cigar” “dineutron” r1 = r2 = rc-nn = 3.6 fm ; rnn = 4.6 fm * Hagino, Sagawa, Phys Rev C72 (2005)

A History of Probes … dissociation: pcore v’s pn [Hansen] dissociation: pnn [Ieki et al.] very high EB dissociation: s-2n v’s s-1n [Bertsch et al.] see also JA Tostevin (today) 2n transfer [Oganessian et al.] see also T Roger, N Keeley (yesterday) radiative capture [Sauvan et al.] dissociation: E1 strength + Rrms [Hagino, Sagawa] Rrms charge [Mueller et al.] ……

“That was the beginning, and the idea seemed so obvious to me and so elegant that I fell deeply in love with it. And, like falling in love with a woman, it is only possible if you do not know much about her, so you cannot see her faults. The faults will become apparent later, but after the love is strong enough to hold you to her." Richard Feynman Nobel Lecture (1965)

Correlation Function - Cnn Intensity Interferometry - HBT Effect* : Source Size Correlation Function - Cnn FM Marqués et al., PLB (2000) Cnn dominated by n-n FSI * incoherent emission

Cnn(r,t) : r0 = 3 fm ; t = 0, 100, 300*, 1000 fm/c * 5Hegs G ~ 0.7 MeV Group Exotiques - G. Normand et al.

3-Body Breakup: “Complete Kinematics” vn1 vn2 v0 vcore Target pn-n = pn1 - pn2 Erel = m(vcore- vnn)2/2

Intensity Interferometry - HBT Effect U. of Sydney Stellar Interferometer, Narrabri, NSW “Hanbury-Brown’s Steamroller“ D Kleppner, Physics Today, August 2008

Setup: Kinematically “Complete” Measurement DEMON 90 modules (NE213)  ToF & position en ~ 10% enn ~ 1% FM Marqués et al., NIMA450 (2000) + Cross-talk Rejection !!

n-n Separation : EMD + Cnn + Gaussian Source* * R Lednicky, VL Lyuboshits, Yad. Fiz. (1982) Event mixing – residual correlations FM Marqués et al., PLB (2000)

* * * rnn  average of n-n configurations of 6He breakup states C/Pb(6He,a+n+n)X @ 30 MeV/u : Cnn + Gaussian Source * * * rnn  average of n-n configurations of 6He breakup states Group Exotiques - G. Normand et al.

C/Pb(6He,a+n+n)X @ 30 MeV/nucleon 2+ 2+ (1-, … ) Group Exotiques - G. Normand et al.

C/Pb(6He,a+n+n)X @ 30 MeV/nucleon 2+ 2+ Ed(6He) after subtraction of uncorrelated distribution Groupe Exotiques - G. Normand et al.

Three-body continuum spatial correlations in 6He * * B Danilin et al., PRC69 (2004)

Effects of a coherent n-n source * * Yamashita et al., PRC72 (2005), NUPA735 (2004) [ Data: FMM et al. PLB (2000) ]

Conclusions & Perspectives Neutron-neutron correlations … breakup + “interferometry˝ (Cnn) as a possible tool to explore halo n-n correlations in unbound Ex/continuum Improvements … First step : account for coherence in emission Ideally : realistic structure + reaction + FSI to generate pnn, Cnn, pcore, ds/dE, …

Pb(11Li,9Li+n+n)X @ 28 MeV/nucleon 3-body model wave function + EMD + FSI (c-n et nn) H Esbensen et al., PRC48 (1993)

C/Pb(6He,a+n+n)X @ 30 MeV/nucleon Group Exotiques - G. Normand et al.

C/Pb(6He,a+n+n)X @ 240 MeV/nucleon GSI/LAND – T. Aumann et al.