I. Physics overview - cartoonII. Experimental logic (TAMU & NSCL) & physics exampleIII. Technology that makes it work IV. A = 8 8C 6Be + (2p) +2p + (2p) : 2p-2p & Isospin symmetry breaking

8BIAS6LiIAS + 2p : First IAS IAS 2p decayV. A = 12 12C Hoyle and 3- decay : Exclusively through 8Beg.s. 12O : A new mass and width 12NIAS 10BIAS +2p : Second IAS IAS 2p decay + IMMEVI. Miscellaneous A new state in 9Li : Part of IAS analog of 9He ??VII. Summary

R. J. Charity, M. Jager, J. Manfredi, K. Mercurio, R. Shane, T. Wiser, J. Elson, L. G. Sobotka [WU]

WU + NSCL + TAMU + WMULGS: NN2012

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Continuum spectroscopy of light nuclei studiedvia high-order correlations

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Related talk this afternoon by RJC

I. Physics overview

1. Multiple proton decay at the drip-line Pushing nuclear structure into the continuum

2. Improve/complete isospin multiplets

3. Hopefully peering in at nucleon-nucleon correlations (in the medium) by “pushing” Fermi surface to (or into) the continuum.

? ???

N Correlations ??Secrets told in mass and e

P CorrelationsSecrets told in mass anddecay correlations

Your place or mine ?

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8He 8C

A = 8 2p d

ecay

New

type

2p d

ecay

New

mas

s

Momentum Achromat Recoil Separator (MARS)

Scale (meters)

0 5

15 MeV/amu

B10

H GasTargetP = 1.7 atmT = 77 K

2

Velocit

y Filter

10.7 MeV/amu > 99.5%

10C Emittance

Slits

DP SlitsFaraday Cup

Q5Q4

D3

V1

D2S1 Q3 D1 Q2

Q1T

SW2 QY QX

SW1

From enriched CarboraneC2[10B10]H12

II. Experimental logic: Example #1 TAMU using K500 cyclotron and the MARS separator

ECRsource

K-500 cyc

E* = ETKE – Qgg

(t1/2 = 19.3 s)

2*105/s

A 4-particle correlation experiment !

E* (parent) = “POP” – mass

(p,n)

Inelastic excitation

Primary reaction

Secondary reaction

Time, Energy, and Particle resolving “CAMERA” with 4k pixels

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16O (150 MeV/u) 7Be (70 MeV/u) 6Be +p+p 9C (70 MeV/u) – n 8C (+ p+p) + p+p – p 8BIAS 6LiIAS p+p

+ n 10C9.8 Menage a quatre

scint Chamber

Beams7Be (clean) > 2 * 105/s9C (3He, 6Li,7Be,8B) ~ 5 *104/s+ calibration beams (see below)

CalibrationsSi - 228Th(alpha source)CsI(Tl) - p,d,t,4He, 6Li beams

(2 energies each)

Primary target

II. Exp. Example #2 the NSCL

This is 4 experiments in 1 !

14 kpixels

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Physics Example: A new excited state in 10C at E* = 8.4 MeV. It decays through the an excited state in 9B.

Three-particleRelative Energycorrelation

4-particle relative energy correlation

Another new state at 9.7 MeV Menage a quatre

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Determined the decay paths for known and two new levels in 10C using….

4-particle and sub event (2- and 3-particle)

energy correlations.

2,3 - particle 4-particle (pp) intermediates

9.7

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Also disproved a level claimedby others at 4.2 MeV. The other group later retracted their claim.

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III. Work made possible by a CMOS signal-processing chip

6.4

mm

CB32 ch

MB

512

ch

System is now, or will soon be, in use at:WU, NSCL, TAMU, IU, LSU, FSU, ND & RIKEN

FoM PRESENT Coming (dbl sh)Pulser res/range 2000 8000Triggering/range 250 2500 ?

8C ?? +p+p+p+p

From 12C(,8He)[Tribble et al.,PRC 13, 50 (1976)] = 35.094 MeV= 230 keVSp = + 65 keV

IV. A = 8 A 5-particle correlation study.QUESTION: What is dynamical path for 8C decay? Is 6Be a “rest stop”? Correlations between p’s?

From 10B(3He,6He) = 27.870 MeV= 1.4 MeVSp = -2.207 MeV

= 1.23 MeVSp = -1.966 MeV

= 92 keVSp = + 595 keV

T = 2

T = 1

T = 0

~ 3 zs

~ 7 zs

OLD

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p p

p p

1. The excitation of any unbound species can be reconstructed from the relative energy of the fragments corrected for the decay Q-value.

a) E*(6Be) = ETKE (+2p) – Qgg

Note we can prepare 6Be cleanly from 1n removal from 7Be beam!

b) E*(8C) = ETKE (+4p) – Qgg

2. IF 8C decays via 8C [6Be] + 2p[+2p]+2p

there will be two protons from the first step and two from the second.

There are 6 ways to choose two protons from a set of four protons,

6 = 4!/(2!2!).

Construct E*(6Be) from ETKE of +2p, from all 6 combinations

ONE combination will be correct and FIVE will be wrong.

Increment a histogram once for EACH combination.

i.e. six increments/event, If 6Be intermediate 1 correct & 5 wrong.

pp p

p

5 – particle correlation “like your hand”

First some Combinatorics

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-p-p-p-pfrom 9C beam

-p-pfrom 7Be beam

-p-pfrom -p-p-p-p

Peak / bkg 1 / 5

8C decay – as simple as 1 out of 6.

6Be is the (7 zs) intermediate, i.e.8C [6Be] + 2p + [ +2p] +2p

Now on to correlations between p’s in first and second steps.

In ~ 1/3 of the events only ONE of the six combinations lies in the 6Be peak. For these events we can assign protons to first and second steps.

T = 2

T = 1

T = 0

Excitation energy (MeV)

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Only step from 6Be decay-p-p

2nd -p-p from -p-p-p-p

[6Be-p-p from -p-p-p-p

DECOMPOSITIONP-P relative energy(JacobyT- system)

Energy variable = fraction of E in p-p rel. motion

Clean 1-step 3-body decay

CT

S

2nd

1st

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This time there is a “diproton”enhancement in first step of 8C decay

Ep-p/Etot

We just talked about the process initiated by a neutron knockout9C 8Cg.s.(T=2, I=0+) [+ n] 6Beg.s.(T=1, I=0+) +2 p

We will now examine the process initiated by a proton knockout9C 8BIAS (T=2, I=0+) [+ p] 6LiIAS (T=1, I=0+) +2 p

This is “identical” to the first step in 8C decay rotated in “isospace”.

It will be an isospin ALLOWED 2p decaywhere the 1p decay is ALLOWED by energy but FORBIDDEN by isospin.

T=2

Tz = 0 -1 -2

n p

IV. A = 8 continued

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TOP 9C 8Cgdst (0+, T=2) +nBOT 9C 8BIAS (0+, T=2) +p

8B reconstruction from 6Li+p+p

Qgg known from masses

measure

Energy “spot on” ~ 1 ppt for IAS.

1p decay is ALLOWED by energy but FORBIDDEN by isospin.

1p and 1n isospin ALLOWED decays are energy FORBIDDEN.

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New 8C mass and uncertainty+ since last fit

new 8He mass and correct error in previous fit. 1. If isospin is a good quantum number, in the absence of Coulomb forces

the energies of a multiplet should be independent of Tz.2. In first-order perturbation theory or if charge dep. forces only two-body

the masses should if fit with a quadratic IMME.

3. The need for dTz3 and eTz

4 terms isospin symmetry breaking. (This statement is not invertible!)

New since last fit - ours - previous fit used wrong mass uncertainty*.

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*NOTE:Previous work suggested isospin symmetry breaking in A = 8, but they used an uncertainty of the 8LiIAS energy 10x too small. Confirmed with authors.J. Britz, A. Pape, and M.S. Antony, Atomic Data and nuclear Data Tables 69, 125 (1998).

Confirmation* of Isospin symmetry breaking in A = 8

Needs d(Tz)3 term (as do A = 9 & 32)Does not need an e4 term.

? Reason ?

Perhaps isospin mixing in T = 2 like T = 0 + 1 in 8Be*

The fit (RESIDUALS) are there 0+’s up here with small energy denominators?

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TClassic case of isospin mixing

V. The A=12 Isobar Energy Diagram

T=2

T=1

T=0

TZ = 2 TZ = 1 TZ = 0 TZ = -1 TZ = -2

12Og.s.12NIAS

12CIAS12BIAS.

12Beg.s

1. Energy unknown

2. 12Og.s.:

Width controversy

4. Unusual decay of

3- or

0+ Hoyle ?

3. Second pair of isospin clones of 2p decays:

12Og.s. And 12NIAS

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How does Hoyle state decay?

PL B 2011Claimed 7.5 +- 4.0 %Hoyle 3 equal-energy ’s

Our data – clean selection of Hoyle from 3 reconstruction

?

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12C (3-) 8Beg.s. + The “Ghost Peak” line shape is expected from R-matrix calc.

b) Gate on Hoyle and ConstructErms = [ <E2> - <E>2 ]1/2 Compare to simulations

Equal Energy

Hoyle8Beg.s.

Equal Energy (UPPER LIMIT) = 0.45% 17 times lower than Raduta et al. value

a) Gate on 3- and generate 8Be* spectrum (choose smallest E*)

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Gat

ed d

ata R-matrix

12C (Hoyle) 8Be g.s. +

A = 12 data onusing 13O @ TAMU

12O10C +2p

12N* 10B* +2p

New mass & width 12O, < 72 keV Old 400-600 keV

Complete quintet

A = 12No evidence (from IMME) of isospin sym. breaking.However Some symmetry breaking effects not captured by IMME.

13O -n 12O 10C + 2p 13O -p 12N*10B*+2p T = 2 1 T = 2 1

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Known

Known

New

Narrower

New

Narro

wer 2nd case IASIAS 2p

12N

13N

The new class of 2p emitters IAS IAS

A = 8: NSCL 8Cgs & 8BIAS IMME & correlations

?

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A = 16: NSCL16Negs & 16FIAS A = 12: TAMU

12Ogs & 12NIAS IMME

A = 9

9He might have the (7th) last odd n in the second s state. If so the gd.st. spin is ½+

n p

Tz = +5/2 +3/2 +1/2 -1/2 -3/2 -5/2

9He9Li (IAS) - part of it

T = 1/2

T = 3/2

T = 5/2

3 6 6 3

2 7

4 55 4

VI. Misc.Little known about A = 9 sextet

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?

2nd s ?

Known

6Li*

And 7He analog in 7LiIAS

(I = 3/2-, T=3/2)

Unknown9He analog in 9LiIAS (I = 1/2+, T = 5/2) ?Its ~600 keV lower than “expected”. from 6,7,8He - 6,7,8Li*.

Could be of mixed isospin: T = 5/2 + 3/2 With almost pure 8He x p (1s1/2 character)

with s- Coulomb shift. John Millener

Secondary beam of 12Be (t1/2 = 24 ms)Smash it up

Look in debris using particle-particle correlations

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Isospin 2-state mixing for 9LiIAS pair of mixed levels* like

8BeIAS pair of T = 0+1 levels?

Shell-model states Physical States

a) aspace,spin,T = 5/2, IAS) ) space,spin, T= 3/2 + 5/2)

b) bspace,spin,T = 3/2) ) space,spin, T = 3/2 + 5/2)

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T = 5/2

T = 3/2

I = 1/2+

I = 1/2+

I = 1/2+

I = 1/2+

T = 3/2 + 5/2

T = 3/2 + 5/2

IF the lower state were almost pure| 8Heg.s. x 1s1/2(p) >

It would explain the LOW Coulomb energy !

Observed ?

a

b

Same space, spin, ~ E mix

* Suggested by John Millener

Summary1. 8C (6Be) +2p (+2p) +2p

$ First concatenated 2p decays, new 8C mass

2. 8BIAS 6Li IAS + 2p $ First example of IAS IAS 2p decay

3. Evidence for isospin symmetry breaking in A = 8 but not A =12

4. New mass & width for 12O. $ Width (UL!) much smaller

5. 12NIAS 10B IAS + 2p $ Second IASIAS 2p decay

6. 12C* Hoyle & 3- decays BOTH 99+% through 8Beg.s.

7. Part of isospin mixed analog of 9Heg.s. (~ 9LiIAS) ?? Thank you for your attention

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+ 1(p – p)

–

+ 4(p – 0 %

35%

17%

And the rest ?

Some correlations unavoidable !

A “menage a quatre”state.

– 6Be

p– 9Be*

VII. Second curiosityAnother new state in 10C* at E*= 9.7 MeV

17 % + 35 % boring, but the other 50 % displays a highly unusual & highly (4-body) correlated decay

1(p-p) + 4(p-5Li 8Be(2

9Bgs X

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Technology and light-nuclei continuum spectroscopy papers using HiRA (mostly) + HINP (always)

Technology: G. L. Engel, et al., NIM A 573, 418 (2007). HINPM. S. Wallace et al., NIM A 583, 302 (2007) HIRA

G. L. Engel, et al., NIM A 612, 161 (2009). PSD improvements ported to HINP G. L. Engel, et al., NIM A 652, 462 (2011). HINP + PSD

6Be: L.V. Grigorenko, et al., Phys. Rev. C 80, 034602 (2009). L.V. Grigorenko, et al., Phys. Lett. B 677, 30 (2009).

8C and 8BIAS : R. J. Charity, et al., Phys. Rev. C 82, 041304(R) (2010). + misc R. J. Charity, et al., Phys. Rev. C 84, 014320 (2011).  10C: R. J. Charity, et al., Phys. Rev. C 75, 051304(R) (2007). K. Mercurio, et al., Phys. Rev. C 78, 031602(R) (2008). R. J. Charity, et al., Phys. Rev. C 80, 024306 (2009).

T = 5/211Li,11Be,11B R.J. Charity, et al., in preparation (2012).

12C (Hoyle) J. Manfredi, et al., Phys. Rev. C 85, 037603 (2012). 12O + 12NIAS M. Jager, et al., Phys. Rev. C in press (R) (2012). 12Be: R. J. Charity, et al., Phys. Rev. C 76, 064313 (2007).

Misc (inc. 9Li”IAS”): R. J. Charity, et al., Phys. Rev. C 78, 054307 (2008).

Isospin symmetry breaking: R. J. Charity, et al., Phys. Rev. C. 84, 051308 (R) (2011).

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How does Hoyle state decay? PL B 2011Claimed 7.5 +- 4.0 %Hoyle 3 equal-energy ’s

Their data Hoyle background from 3 reconstruction Our data~ 10 % background ~ 0.2 % background

?

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Variables needed to describe 3-body decayDOF counting

Prototype : 6Be + 2p1. Total momentum variables = 3x3

=92. Center of mass of no interest -33. For a spin 0 (actually <=1/2) sys. Euler ang. not needed -3 4. If you know the total decay energy, you can …… -1

_______

TOTAL

2

Energy variable = fraction E in p-p rel. motion = frac. E in core – p

Mind-set / physics perspective “T” “Y” “2p” decay sequential

There are two physically instructive sets of variables. The Jacobi …… (A matter of perspective)

“T” and “Y”__systemsEx Ep-p/Etot Ep-core/Etot

fraction of Etot in: pp p core

p-p to 2p-core core-p to p

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7Be 6Be + n 3-body decay Theory gets

1) 6Begs energy, 2) 6Begs widthand now 3) Jacobi maps

“Coulomb holes” conspicuous in both theory and exp.

Energy variable = fraction of E in p-p rel. motion

= frac. E in core – p

Theory (Grigorenko et al.) nicely reproduces data.Theory has …. p – p potential, p – potential + 3-body term.

Now analyzing decay from 2+….

IV.

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Projections on Jacobi coordinates

Conclusions:1.Reproduced by 3-body QM model2.Potential intermediate plays no role3.NO (significant) “di-protron” enhancement

FromY intermediate not biasing decay (if sequential bimodal) Thus NOT sequential but 3-body.(Some call decays with very wide intermediates “democratic”.)

T little “diproton” enhancement.

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Comparison to Kryger et al.

1995

Nucleus 12O (1) 12O (2) 12N (1) 12N (2)

ET [MeV] 1.638(24) 3.606(60) 1.165(29) ~3.17

E* [MeV] 0 1.968(52) 12.196(29) ~14.20

ΔM [MeV] 31.914(24) 33.872(6) 29.534(29) ~31.54

Γ [keV] <72 475(110) <110

Jπ 0+ (2+,0+) 0+

12O Kinetic Energy Spectrum

12N Kinetic Energy Spectrum

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32

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10C experiments at TAMUset of 4 dE (64 um) - E (1500 um) Si telescopes

~ 400 Si ch

ASICsOutside vacuum

Beam

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1st

2nd

Clean 1-step 3-body decay

Dissected steps from -p-p-p-p

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What can be said about the influence of the potentialIntermediates?

Examine the Jacobi projections of 8C decay.

IF 7B played a role it would drive Ex(Y) bimodal.It does not.

Red 6Be~ uniform 3-body

Fromintermediate not biasing decay

But now there is a“diproton” enhancement.

Alex Brown can explain the width of the 8Cgs with a “diproton” R-matrix model. 36

Reports Progress of Physics 8, 274 (1941)

A comment on the origin of the concept of isospin

The beginnings in

Fully developed by

After the war Feenberg WU

Also Wigner, E., 1937 a. Phys. Rev. 51, 106. Wigner, E., 1937 b. Phys. Rev. 51,947. Wigner, E., 1939. Phys. Rev. 56, 519.

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