nuclear structure now (precision and discovery) c.j.(kim) lister [email protected] [email protected]

Nuclear Structure Now (precision and discovery)

C.J.(Kim) [email protected]

mailto:[email protected]

2C.J. (Kim) Lister:- Frontiers In Gamma Spectroscopy 2009, Mumbai INDIA

Our Nuclear Domain


RIBF@RIKEN

FAIR@GSI

FRIB@MSU


A different view of our nuclear world


Ab-initio Greens Functional Monte Carlo Calculations

Pieper and Wiringa (ANL)

Described in

NP A751 516c (2005)


Neutron Stars


Testing Ab-Initio Calculations


RMS Radii of 6,8He

6He

P.Mueller et. al (ANL)


RMS Radii of 6,8He

L.-B. Wang et al., PRL 93, 142501 (2004)

P. Mueller et al., PRL 99, 252501 (2007).

After some convergence issues were resolved, predictions of charge radii very good, ~ 1%

…..matter radii not quite so good.


Transfer ReactionsANL-UWM CollaborationA. H. Wuosmaa et. al. PRL94 082592 and PRC72 061301(R) 2005

Example: 6He(d,p)7He

Issues: How reliable are calculations of unbound states?

Is there a low lying state below 1MeV?

Sn=0.533 l=1 p3/2

No renormalization

to QMC calculations

Data

Fit to g.s. and Ex=2.25,=3.0 MeV state


Transfer ReactionsCompare: 6He(d,p)7He and 8Li(d,3He)7He

Issues: Is spectroscopy of broad resonances possible?

Yes!!Using selective in both population and decay

channels

1/2 -

5/2-


The Special Case of Beryllium Nuclei


Key Issues: Microscopically, how do the neutrons really form a potential to bind the nucleus? Is it the same for all states?


Investigating 8Be

Upshot: Test of electromagnetic decay from unbound resonance

Experiment

Ab-Initio Theory

4211 825)24:2( fmeEB

424.02.18)24:2( fmeEB

…..Here in Mumbai!!


The Bound States of 10Be

0+

2+

2+1-

10Be

5958

2589

25905960

3367E2

E1E1E2

M1/E2

2- 62632895

0+ 61792811

219E1

6812 9Be+n


4211 )10(5.10)02;2( fmeEB

4211 )30(89.7)02;2( fmeEB

4212 )26(08.2)02;2( fmeEB

10Be Data Compilation

GFMC TheoryQ ≤ 0

Q ≥ 04212 )10(9.6)22;2( fmeEB

A=10 nuclei provide a sensitive test of GFMC

S.C. Pieper, K. Varga and R.B. Wiringa, Phys. Rev. C 66, 044310 (2002).

Very sensitive to the effects

of 3-body correlations.

8.3)02:2(

)02:2(

12

11

EB

EBR


Ken Nollett (ANL) and Brent Graner (UC) visulization of 10Be J=21 state (2008)

The Ab-Initio projection of T=0 and T=1 density


The Traditional Shell Model (1956+++)

Kurath, Cohen and Kurath, Millener and Kurath, Millener and Warburton

R=11.3


10Be : A popular nucleus)02;2( 11

EB )02;2( 12 EB

(e2fm4)RatioAuthor

Okabe MO 11.26 0.44 25.6

Caurier NCSM 6.58 0.13 49.5

Itagaki TMO 11.8 0.70 16.9

Navratil NCSM 5.4 0.17 32.7

Arai MCM 4.8 0.10 48.0

Wiringa GFMC 7.89(30) 2.08(26) 3.8

EXPT 10.5(1.0) ?? ??

NCSM : No-core shell model, E. Caurier et al., Phys. Rev. C 66, 024314 (2002). MO : Molecular orbit model, N. Itagaki and S. Okabe, Phys. Rev. C 61, 044306 (2000).

MCM : Microscopic cluster model, K. Arai, Phys. Rev. C 69, 014309 (2004). TMO : Triaxial Molecular Orbital, N. Itagaki et al., Phys. Rev. C 65, 044302 (2002).

GFMC : Greens Functional Monte Carlo, R. Wiringa and S. Pierper et al., Private Communication.

(e2fm4) Calc.


E.K. Warburton et al., Phys. Rev. 129, 2180 (1963).

E.K. Warburton et al., Phys. Rev. 148, 1072 (1966).

G.C. Morrison et al., - unpublished (1965).

T.R. Fisher et al., Phys. Rev. 176, 1130 (1968).

Evaluated = 180(18) fsAll DSAM measurements

Previously measured DSAM J=21 lifetime in 10BeSystematic problems of:-

•Initial recoil velocity ill-defined

•Stopping powers poorly known

•Very slow recoils

•State feeding poorly known

•Detector angle poorly defined

At the time these measurements WERE cutting edge and provided discriminating tests of the (new) intermediate-coupling shell model (Kurath et al 1958) .

But now we need better!


F. Sarazin et al., Phys. Rev. C 70, 031302(R) (2004)….-decay at ISAC / TRIUMF

11Li β-delayed 1-n emissionLine shape depends on

Energies and intensities of all neutron branches feeding the level

Lifetime of the level

Angular correlation between gamma ray and neutron

Y. Hirayama et. al. Phys Lets B611 239 (2005)…..polarized -decay at ISAC/TRIUMF (high stats)


The Doppler Shift Attenuation Method

(DSAM)


The Doppler Shift Attenuation Method

v0

E = Eo {1 + (v0/c)Cos}

v(t)

Free Space

Stopping E = Eo {1 + F(t)Cos}

log(

F()

1

0Actually, recoils are sufficiently swift (v/c ~6%) that 2nd order relativistic is correction needed


What SRIM shows us

J.F. Ziegler, J.P. Biersack and M.D. Ziegler http://www.srim.org

SLOW Ions…. 1 MeV 10Be in 100g/cm2 Li on 6mg/cm2 Au

FAST Ions…. 15 MeV 10Be in 100g/cm2 Li on 6mg/cm2 Au

(99.99% electronic stopping)


DSAM*

DSAM done properly:-

2-body kinematics

High recoil velocity

Well defined recoil direction

Well defined gamma direction

Control of state population

7Li(7Li,)10Be at 10 MeV

α 10Be

10Be (g.s) = 18.2 MeV10Be* (3.3) = 16.5 MeV10Be* (5.9) = 15.0 MeV

E.A. McCutchan et. al. (ANL)


Etot in Ion Chamber

ΔE

Recoil - Gated Data3 mg/cm2 Cu backing

12

A=10 q=3 selected with FMA

Recoil-gamma time


Extracting the lifetime from mean

N

1 2 3

time

time

’s weighted by # of decays at given time t

determines weight

Ideally you want all decays in the stopping material

But…• Need some finite thickness of production material

• Need nuclei to recoil out of target

1

Cou

nts

Energy

3

2C

ount

s

Energy

2


Results (1): First excited State with J=2+ at 3367 keV7Li

7Li

7Li

66g/cm2 7Li on 6.95mg/cm2 Au

115g/cm2 7Li on 2.69mg/cm2 Au

288g/cm2 7LiF2 on 2.48mg/cm2 Cu

fs

fs

+200-100

fs

+100-60


Traditional DSAM analysis……and GS alignment

cos1

1 2

oEE

100 g/cm2 7Li on 2.33 mg/cm2 Au


Results so far for 3369keV J=2 state


The Bound States of 10Be

0+

2+

2+1-

10Be

5958

2589

25905960

3367E2

E1E1E2

M1/E2

2- 62632895

0+ 61792811

219E1

6812 9Be+n


Some Detective Work Required

I1 11-

I2 22+

I2 22+

Is it possible to untangle the two-line J=1-,2+ mess?

The states are only 1.8keV apart and have similar, short lifetimes


What we have learned so far


First J = 2+ state in 10Be

4211 )10(5.10)02;2( fmeEB

NNDC transition strength was

4211 )5(2.9)02;2( fmeEB

Our new transition strength

sysstat )8()5(205

4211 )30(89.7)02;2( fmeEB

Ab-initio transition strength

4221 )40(97.9)022:2( fmeEB

Note: The predicted ab-initio summed E2 decay strength is:


Second J = 2+ state in 10Be

NoneNNDC lifetime

fs)10(59This work

Theory seems to have much too much mixing of J=2+ states. The original GFMC with V18 and IL2 three body force predicted R=3.8

fs(??)89Sarazin et. al.

422 )3(11.0)02:2( fmeEB

)16(78)02:2(

)02:2(

2

1

EB

EBRatio

Much smaller than GFMC which initially predicted 2.08(26) e2fm4


Lessons Learned

We set out to test a model that was thought to be good at the <10% level.

Tests were for calc. stability & validating 3-body forces.

We Found:

Good agreement in absolute binding energy of the ground state. Modest agreement in the binding energies of the excited states (correct ordering, too close in energy)

Good agreement in the total collectivity, without resorting to any effective charges. Modest agreement in the distribution of strength.


Conclusions for 10Be In Experiment

We have made a precise measurement of the lifetime of the first excited state in 10Be. Reliable <5% DSAM IS possible.

We have determined the ratio R, which shows there is very little mixing between first and second J=2 states.

In Theory

We need to reconcile the differences:

Does the experimental distribution of B(E2) strength allow us to constrain the models of 3-body forces?

YES, but reveals more work is needed

nuclear structure now (precision and discovery) c.j.(kim) lister [email protected] [email protected]

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