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LGS: NN2012 1 out of 25

Continuum spectroscopy of light nuclei studied via high-order correlations.

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LGS: NN2012 1 out of 25

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  1. Continuum spectroscopy of light nuclei studied via high-order correlations I. Physics overview - cartoonII. Experimental logic (TAMU & NSCL) & physics exampleIII. Technology that makes it work IV. A = 88C  6Be + (2p) a +2p + (2p) : 2p-2p & Isospin symmetry breaking 8BIAS6LiIAS + 2p : First IAS  IAS 2p decayV. A = 1212C Hoyle and 3- a decay : Exclusively through 8Beg.s.12O : A new mass and width12NIAS  10BIAS +2p : Second IAS IAS 2p decay + IMMEVI. MiscellaneousA new state in 9Li : Part of IAS analog of 9He ??VII. SummaryR. J. Charity, M. Jager, J. Manfredi, K. Mercurio, R. Shane, T. Wiser,J. Elson, L. G. Sobotka [WU]WU + NSCL + TAMU + WMU LGS: NN2012 1 out of 25 Related talk this afternoon by RJC

  2. I. Physics overview 2p decay New mass 2p decay New type A = 8 Your place or mine ? 8C 8He Multiple proton decay at the drip-line Pushing nuclear structure into the continuum Improve/complete isospin multiplets 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 re ? ? ? ? P Correlations Secrets told in mass and decay correlations

  3. From enriched Carborane C2[10B10]H12 II. Experimental logic:Example #1 TAMU using K500 cyclotron and the MARS separator ECR source Primary reaction (p,n) Secondary reaction K-500 cyc Inelastic excitation (t1/2 = 19.3 s) 2*105/s E* (parent) = “POP” – D mass A 4-particle correlation experiment ! E* = ETKE – Qgg  Time, Energy, and Particle resolving “CAMERA” with 4k pixels 

  4. 16O (150 MeV/u) 7Be (70 MeV/u)  6Be  a+p+p 9C (70 MeV/u) – n 8C  (a+ p+p) + p+p – p 8BIAS6LiIAS p+p + n 10C9.8 Menage a quatre II. Exp. Example #2  the NSCL This is 4 experiments in 1 ! scint 14 k pixels Primary target Chamber Beams 7Be (clean) > 2 * 105/s 9C (3He, 6Li,7Be,8B) ~ 5 *104/s + calibration beams (see below) Calibrations Si - 228Th(alpha source) CsI(Tl) - p,d,t,4He, 6Li beams (2 energies each)

  5. Physics Example: A new excited state in 10C at E* = 8.4 MeV. It decays through the an excited state in 9B. Three-particle Relative Energy correlation Another new state at 9.7 MeV  Menage a quatre 4-particle relative energy correlation

  6. 2,3 - particle 4-particle (aapp) intermediates Determined the decay paths for known and two new levels in 10C using….4-particle and sub event (2- and 3-particle) energy correlations. 9.7 Also disproved a level claimed by others at 4.2 MeV. The other group later retracted their claim.

  7. III. Work made possible by a CMOS signal-processing chip 6.4 mm CB 32 ch MB 512 ch FoM PRESENT Coming (dbl sh) Pulser res/range 2000 8000 Triggering/range 250 2500 ? System is now, or will soon be, in use at: WU, NSCL, TAMU, IU, LSU, FSU, ND &  RIKEN

  8. 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 12C(a,8He) [Tribble et al., PRC 13, 50 (1976)] D = 35.094 MeV G= 230 keV Sp = + 65 keV From 10B(3He,6He) D = 27.870 MeV G= 1.4 MeV Sp = -2.207 MeV OLD ~ 3 zs G= 1.23 MeV Sp = -1.966 MeV T = 2 ~ 7 zs G= 92 keV Sp = + 595 keV p p p p T = 1 a 8C  ??  a+p+p+p+p T = 0

  9. First some Combinatorics • 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 (a+2p) – Qgg  Note we can prepare 6Be cleanly from 1n removal from 7Be beam! b)E*(8C) = ETKE (a+4p) – Qgg 2. IF8C decays via 8C [6Be] + 2p[a+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 a+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, If6Be intermediate  1 correct & 5 wrong. 5 – particle correlation “like your hand” p p p p a

  10. 8C decay – as simple as 1 out of 6. Peak / bkg 1 / 5 a-p-p from a-p-p-p-p T = 2 T = 1 a-p-p from 7Be beam T = 0 6Be is the (7 zs) intermediate, i.e. 8C [6Be] + 2p + [a +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. a-p-p-p-p from 9C beam Excitation energy (MeV)

  11. DECOMPOSITION P-P relative energy (JacobyT- system) 1st [6Be]-p-p from a-p-p-p-p This time there is a “diproton”enhancement  in first step of 8C decay CTS 2nda-p-p from a-p-p-p-p 2nd Only step from 6Be decay a-p-p Clean 1-step 3-body decay Ep-p/Etot Energy variable = fraction of E in p-p rel. motion

  12. IV. A = 8 continued We just talked about the process initiated by a neutron knockout 9C 8Cg.s.(T=2, Ip=0+) [+ n]  6Beg.s.(T=1, Ip=0+) +2 p  We will now examine the process initiated by a proton knockout 9C 8BIAS(T=2, Ip=0+) [+ p]  6LiIAS (T=1, Ip=0+) +2 p  This is “identical” to the first step in 8C decay rotated in “isospace”.  It will be an isospin ALLOWED 2p decay where the 1p decay is ALLOWED by energy but FORBIDDEN by isospin. T=2 n p Tz = 0 -1-2

  13. 8B reconstruction from 6Li+p+p TOP 9C  8Cgdst (0+, T=2) +nBOT9C  8BIAS (0+, T=2) +p measure g Qgg known from D masses 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.

  14. New 8C mass and uncertainty+ since last fit new 8He mass and correct error in previous fit. • Ifisospin is a good quantum number, in the absence of Coulomb forces •  the energies of a multiplet should be independent of Tz. • 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 eTz4 terms  isospin symmetry breaking. (This statement is not invertible!) New since last fit - ours - previous fit used wrong mass uncertainty*. *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).

  15. Confirmation* of Isospin symmetry breaking in A = 8 The fit (RESIDUALS) are there 0+’s up here with small energy denominators? Classic case of isospin mixing 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*  T

  16. 12Beg.s 12CIAS 12Og.s. 12BIAS. 12NIAS TZ = 2 TZ = 1 TZ = 0 TZ = -1 TZ = -2 T=2 T=1 T=0 V. The A=12 Isobar Energy Diagram 1. Energy unknown • 4. Unusual decay of •  3- or • 0+ Hoyle ? • 12Og.s.: • Width controversy 3. Second pair of isospin clones of 2p decays: 12Og.s. And 12NIAS

  17. How does Hoyle state a decay? Our data – clean selection of Hoyle from 3a reconstruction PL B 2011 Claimed 7.5 +- 4.0 % Hoyle  3 equal-energya’s ?

  18. b) Gate on Hoyle and Construct Erms = [ <E2> - <E>2 ]1/2 Compare to simulations Equal Energy a) Gate on 3- and generate 8Be* spectrum (choose smallest E*) Hoyle8Beg.s. R-matrix Equal Energy (UPPER LIMIT) = 0.45% 17 times lower than Raduta et al. value Gated data 12C (3-) 8Beg.s. + a ~100.% The “Ghost Peak” line shape is expected from R-matrix calc. 12C (Hoyle)  8Be g.s. + a > 99.5 %

  19. 13O  -n  12O 10C + 2p 13O  -p 12N*10B*+2p T = 2  1 T = 2  1 A = 12 data onusing 13O @ TAMU Known New mass & width 12O, G < 72 keV Old 400-600 keV Complete quintet New 12N 2nd case IASIAS 2p Known Narrower 13N 12O10C +2p Narrower 12N* 10B* +2p New A = 12 No evidence (from IMME) of isospin sym. breaking. However  Some symmetry breaking effects not captured by IMME.

  20. The new class of 2p emitters IAS  IAS A = 8: NSCL 8Cgs & 8BIASIMME & correlations ? A = 16: NSCL 16Negs & 16FIAS A = 12: TAMU 12Ogs & 12NIAS IMME

  21. VI. Misc. Little known about A = 9 sextet A = 9 n p Tz = +5/2 +3/2 +1/2 -1/2 -3/2 -5/2 9He might have the (7th) last odd n in the second s state. If so the gd.st. spin is ½+ T = 5/2 ? 27 T = 3/2 36 63 T = 1/2 2nd s ? 9Li (IAS) - part of it 9He 45 54

  22. Secondary beam of 12Be (t1/2 = 24 ms)Smash it upLook in debris using particle-particle correlations Known 6Li* And 7He analog in 7LiIAS (I = 3/2-, T=3/2) Unknown 9He 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

  23. Isospin 2-state mixing for 9LiIAS pair of mixed levels* like8BeIAS pair of T = 0+1 levels? Shell-model states Physical States a) Fa(space,spin,T = 5/2, IAS) a) Fa(space,spin, T= 3/2 + 5/2) b) Fb(space,spin,T = 3/2) b) Fb(space,spin, T = 3/2 + 5/2) Same space, spin, ~ E  mix a b a b T = 3/2 + 5/2 T = 3/2 + 5/2 T = 5/2 T = 3/2 Ip = 1/2+ Ip = 1/2+ Ip = 1/2+ Ip = 1/2+ Observed ? IF the lower state were almost pure | 8Heg.s. x 1s1/2(p) > It would explain the LOW Coulomb energy ! * Suggested by John Millener

  24. Summary 1. 8C (6Be) +2p (a +2p) +2p $ First concatenated 2p decays, new 8C mass2. 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 IASIAS 2p decay 6. 12C* Hoyle & 3-a decays BOTH 99+% through 8Beg.s. 7. Part of isospin mixed analog of 9Heg.s. (~ 9LiIAS) ?? Thank you for your attention

  25. VII. Second curiosityAnother new state in 10C* at E*= 9.7 MeV17 % + 35 % boring, but the other 50 % displays a highly unusual & highly (4-body) correlated decay  1(p-p) + 4(p-a)5Li + ~1(a-a)~8Be(2+) A “menage a quatre” state. 1(a – a) X 9Bgs 0 % 35% 17% + 4(p – a) a – 6Be + 1(p – p) p– 9Be* Some correlations unavoidable ! And the rest ?

  26. Technology: G. L. Engel, et al., NIM A573, 418 (2007). HINP M. 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 = 5/211Li,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). Technology and light-nuclei continuum spectroscopy papers using HiRA (mostly) + HINP (always)

  27. PL B 2011 Claimed 7.5 +- 4.0 % Hoyle  3 equal-energya’s How does Hoyle state a decay? ? Their data Hoyle background from 3a reconstruction Our data ~ 10 % background ~ 0.2 % background

  28. Variables needed to describe 3-body decayDOF countingPrototype : 6Be  a + 2p • Total momentum variables = 3x3 =9 • Center of mass of no interest -3 • For a spin 0 (actually <=1/2) sys. Euler ang. not needed -3 • If you know the total decay energy, you can …… -1 • _______ • TOTAL 2 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”__systems Ex Ep-p/Etot Ep-core/Etot fraction of Etot in: pp p  core Q p-p to 2p-core core-p to p Energy variable = fraction E in p-p rel. motion = frac. E in core – p

  29. IV. 7Be6Be + n 3-body decay Theory gets1) 6Begs energy, 2) 6Begs widthand now  3) Jacobi maps 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 – a potential + 3-body term. Now analyzing decay from 2+…. “Coulomb holes” conspicuous in both theory and exp.

  30. Projections on Jacobi coordinates Conclusions: Reproduced by 3-body QM model Potential intermediate plays no role NO (significant) “di-protron” enhancement From Y 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.

  31. 12O Kinetic Energy Spectrum 12N Kinetic Energy Spectrum Comparison to Kryger et al. 1995

  32. 10C experiments at TAMUset of 4 dE (64 um) - E (1500 um) Si telescopes~ 400 Si ch Beam ASICs Outside vacuum

  33. 1st Dissected steps from a-p-p-p-p 2nd Clean 1-step 3-body decay

  34. What can be said about the influence of the potential Intermediates? Examine the Jacobi projections of 8C decay. IF 7B played a role it would drive Ex(Y) bimodal. It does not. From intermediate not biasing decay But now there is a “diproton” enhancement. Red 6Be ~ uniform 3-body Alex Brown can explain the width of the 8Cgs with a “diproton” R-matrix model.

  35. Reports Progress of Physics 8, 274 (1941) The beginnings in  A comment on the origin of the concept of isospin Also Wigner, E., 1937 a. Phys. Rev. 51, 106. Wigner, E., 1937 b. Phys. Rev. 51,947. Wigner, E., 1939. Phys. Rev. 56, 519. Fully developed by  After the war Feenberg  WU

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