Transition from direct to sequential 2p-decay in theory and in - PowerPoint PPT Presentation

Leonid Grigorenko Flerov Laboratory of Nuclear Reactions, JINR, Dubna, Russia Transition from direct to sequential 2p-decay in theory and in experiment. NUSTAR meeting, March 2-4, 2016

Limits of nuclear structure existence Dripline is studied for light nuclei Dripline is achieved for Z<32 and N<22 E T Continuous spectrum Continuum dynamics Limits of nuclear structure Quasistationary states 0 Stationary states Discrete spectrum Limits of the nuclear structure are not solidly established even for the lightest isotopes. 7 H, 12 He, 13 Li, 5 Be - ???

Few-body dynamics More than 2 First of all three-body Less than 6-7

Few-body dynamics at the driplines Modern RIB research: move towards and beyond the driplines Few-body dynamics at the driplines as consequence of (i) clusterization and (ii) paring Exotic phenomena in vicinity of driplines: Haloes (green) True 2p/2n decays (red) 4p/4n emitters (blue) NOT INVESTIGATED (gray) NOT SO EXOTIC: More or less every second isotope in vicinity of the driplines has features connected to few-body dynamics

Qualitative view of two-proton radioactivity Bound orbital No bound orbitals ! Unbound orbital Quantum mechanical case: Classical case: it could be that both particles should one particle emission is always possible be emitted simultaneously Exclusive - No deeper bound orbitals. Quantum- - The common orbital for two protons exists only when both are “inside”. Mechanical - When one of them goes out, their common orbital do not exist any phenomenon more and the second HAS to go out instantaneously

Three-body correlations. 3-body decays: 2-dimensional “internal” 3-body correlations 2-body decay: state is defined by 2 parameters - energy and width  2- dimensional “internal three - body correlations” or “energy - angular correlations” e = E x / E T cos( q k ) = ( k x , k y )/k x k y  “T” and “Y” Jacobi systems reveal different dynamical aspects  Three-body variables in coordinate and in momentum space. "T" system "Y" system   k y   k x q k  k y   X k x  1 2  k x 2 3 p q r p p p  Y  q r q k X  Y  core k y core 3 1    k y k x

Three-body decay – a lot more information than for two-body decay encrypted in the correlations Which kind of new knowledge we can decrypt from that?

45 Fe: the first found and the best studied diproton Brown, 1991 A. Brown , PRC 41 (1991) R1513. Brown 1991: energy – yes, lifetime – no Grigorenko 2001: energy – no, lifetime – yes Pfützner et al., EPJA 14 (2002) 279 Giovinazzo et al., 89 (2002) 102501 Dossat et al., PRC 72 (2005) 054315 Q 2p = 1.154 MeV Miernik et al., PRL 99 (2007) 192501  Special design Optical TPC → nuclear physics “life video”  Improved lifetime:       0.22 19 1.3 10 MeV T (2 ) p 3.5(5) ms  2 p 0.16 1/2  Complete momentum correlations provided L.Grigorenko et al., PLB 677 (2009) 30 L.Grigorenko et al., PRC 82 (2010) 014615

Common properties of correlations How can we use the correlation information?  Energy correlation in the core-p channel well 1.0 corresponds to original prediction of p - p Goldansky: energies of the emitted protons d j / d ( E x / E T ) tend to be equal.  Energy correlation in the p-p channel in the 0.5 12 O W ( s 2 ) 67% s-d shell nuclei quantitatively depend on the 16 Ne W ( s 2 ) 54% structure 19 Mg W ( s 2 ) 60%  Energy correlation in the p-p channel in the 19 Mg W ( s 2 ) 10% p-f shell nuclei qualitatively depend on the 0.0 0.0 0.2 0.4 0.6 0.8 1.0 structure E x / E T 6 Be 1.0 1.0 core - p W ( p 2 ) 98% 12 O W ( p 2 ) 43% 16 Ne d j / d ( E x / E T ) W ( p 2 ) 24% d j / d ( E x / E T ) 19 Mg W ( p 2 ) 2% 45 Fe 62 Se 0.5 0.5 p - p 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 0.0 0.2 0.4 0.6 0.8 1.0 E x / E T E x / E T

45 Fe: internal correlations 26 Fe 3/2  45 "Y" "T" dj / d e d (cos q k ) 10 10 8 8 6 6 4 4 2 2 0 0 0.00.2 1.0 0.0 1.0 0.2 0.5 0.5 0.4 0.4 cos ( q k ) 0.0 0.0 ( q ) 0.6 0.6 e e k -0.5 -0.5 s 0.8 0.8 o c 45 Fe -1.0 -1.0 1.0 1.0 Exp. data 8 10 6 8 counts 6 4 4 2 2 45 Fe "T" system 30 0 0 0.00.20.40.60.81.0 1.0 0.00.20.40.60.81.0 1.0 W ( p 2 ) = 43% 0.5 0.5 W ( p 2 ) = 24% 0.0 0.0 cos( q k ) 20 cos( q ) e counts e -0.5 k -0.5 W ( p 2 ) = 10% -1.0 -1.0 10 Miernik et al., PRL 99 (2007) 192501 0  Complete kinematics reconstructed 0.0 0.2 0.4 0.6 0.8 1.0 e  Both lifetime and correlations provide W ( p 2 ) ~ 30%

Growing sophistication of the theoretical methods

Monte-Carlo codes M.S.Golovkov et al., PRL 93 (2004) 262501. M.S.Golovkov et al., PRC 72 (2005) 064612. L.V. Grigorenko et al., PRC 82 (2010) 014615. Observables in reactions: A.S.Fomichev et al., PLB 708 (2012) 6. Nuclear structure + I.A. Egorova et al., PRL 109 (2012) 202502. Reaction mechanism + I. Mukha et al., PRL 115 (2015) 202501. Final state interaction  For studies of correlations full quantum-mechanical Monte Carlo simulations are required  Decompose experimental particle correlation data over hyperspherical amplitudes in the momentum space. HH amplitudes automatically take into account PP, angular momenta in the subsystems and spin. Calculated or parameterized.  Density matrix formalism:  Density matrix has especially simple form in the system Experimental bias: of transferred momentum for direct reactions Acceptance +  Three-body decay -> eightfold differential cross section Resolution +  People involved: Yu. Parfenova, T. Golubkova, P. Sharov Physical backgrounds

6 Be at MSU: correlations on resonance Experiment: R. Charity and coworkers, MSU 7 Be( 9 Be,X) 6 Be I. Egorova et al., PRL 109 (2012) 202502.  High statistics (~10 6 events/state)  High resolution  Nice agreement with the previous (Texas A&M, Dubna) experimental data

6 Be at MSU: energy evolution of correlations Note: the higher decay energy – the Note: when two-body states enters the more developed is low-energy p-p decay window the intensity at correlation (“ diproton ”) expected peak position is suppressed Note: above 2 + the e distribution is Note: sequential decay patterns practically insensitive to decay appears only for E T > 2E r +  energy

Long-range character of three-body 45 Fe, E T = 1.154 MeV Coulomb by example of 45 Fe r max = 1000 fm 15000  Start point for extrapolation: typical range of 1000 fm in r value Probability 10000  End point for extrapolation: typical range of 5000 100000 fm in r value  Complicated treatment of experimental 0 0.0 1.0 effects 0.2 0.5 e = E x / E T 0.4 0.0 q k ) 0.6 ( s -0.5 o 0.8 c 1.0 -1.0 40 45 Fe r ext = 100000 fm With exp. res: init. 15000 "Y" system 30 fin. Events 10000 Probability No exp. res: 20 fin. 5000 10 0 0.0 1.0 0.2 0.5 0.4 0 e = E x / E T 0.0 0.6 cos( q k ) 0.0 0.2 0.4 0.6 0.8 1.0 e -0.5 0.8 1.0 -1.0

Long-range character of three-body 16 Ne g.s., E T = 1.466 MeV Coulomb by example of 16 Ne  New level of experimental precision. MSU 2013: 16 Ne populated in n knockout from 17 Ne K. Brown et al., PRL 113 (2014) 232501  The energy distribution in “Y” Jacobi system only reproduced for extreme range of calculation

Two-proton decay of 30 Ar

S388 experiment at GSI “ Search for 2p radioactivity in 30 Ar”  2012 I. Mukha et al., PRL 115 (2015) 202501.  Primary 36 Ar beam 885 AMeV  8 g/cm 2 primary Be target “ Beta-delayed p decays of 31 Ar”  Second. 31 Ar beam 620 AMeV  50 ions s −1  4.8 g/cm 2 secondary Be target A. Lis et al., PRC 91 (2014) 064309.

EXPERT : EX otic P article E mission and R adioactivity by T racking GSI, FLNR JINR, Warsaw Uni., PTI St.-Petersburg Identification of heavy Degrade the heavy Last achromatic stage of VERY THICK A- 1 ( Z- 2) fragment excitations fragment energy fragment separator is secondary by target area g array Hi-res spectrometer for target for one- GADAST heavy decay fragment or two-nucleon 4 knockout A- 2 ( Z- 1) 5 Beam Warsaw OTPC p Radioactive particle A- 1 Z A Z emission for n stopped reaction and decay products A ( Z- 1) 1 2 3 Radiation- m Si tracking NeuRad -hard 6 detector system High-angular SSDs for light charged resolution neutron MC simulation for beam particles detector diagnostics framework to interpret the Hi-res angular measurements FRS, SuperFRS Particle unstable correlation data with one of the systems beyond both for proton and neutron dripline nuclei incomplete kinematics middle focal proton or populated on secondary target planes neutron driplines

Basic idea Z-2 X core A-2 Prof. I. Mukha: A A+1 Z X Z X p opportunity to decay p Radioactivity studies point investigate particle tracking radioactivity in fs-ns Two-proton events: lifetime range (1) Fragmentation in the target (2) exponential "tail" due to decay in the flight HOWEVER. Found to be well suited for spectroscopy Coordinate along trajectory Not an invariant mass q measurement: only transverse q max momentum distributions d q Two-body decay  ~ ( q max  q ) q d q dW/d q Better than invariant mass method! IF you understand what is happening