Nuclear Structure@
KVI
A.M. van den Berg, M.N. Harakeh, H.J. WörtcheKernfysisch Versneller Instituut (KVI)
Groningen
Title
Nuclear Structure @ KVI
spin and isospin selective nuclear structure studies with high precission
unique combination
AGOR & Big Bite Spectrometer & EuroSuperNova detector& variety of detection systems
driven by vivid international collaborations !!!
KVI - ion accelerator AGOR
0 0.2 0.4 0.6 0.8 1.0charge / A
ener
gy /
A [M
eV] 100
10
AGORoperating diagramme
variable acceleratorbroad spectrum of beamswith high quality
proton beamsup to 190 MeVpolarized
deuteron - &alpha beams35 - 90 MeV / n
deuteronsvector- &tensor polarized
KVI - experimental facilities
TRIµP - Trapped Radioactive Isotopesµicro Laboratories forFundamental Physics
radio biology
irradiation setup
few-body physics
Big-Bite Spektrometer (BBS) &EuroSuperNova detection system(ESN detector)
KVI - BBS & ESN detector
Big-Bite Spektrometer large acceptance (momentum & angle), moderate resolution
EuroSuperNova detector light-ion detector equipped with real-time data processinghigh rate capabilities
KVI - BBS & ESN Detektor
Focal Plane Detector:(FPDS)2 VDCs
Focal Plane Polarimeter:(FPP)4 MWPCs &graphite analyzer
features a.o.:- fast readout-VDC readout by pipeline TDCs -VDC decoding using imaging technics-DSP based online analysis
BBS (mode B):
dΩ < 9.2 msrdΘ < 66 mraddΦ < 140 mradΔp/p < 19 %ΔE/E > 4 · 10-4
0o - operation
BBS - program (in part)
•(pol(p), p’) cross sections, analyzing powers Ay, polarization transfer Dnn11B, 12C, 48Ca, 58Ni, 116,124Snspectroscopy of M1, M2 strength
•(d, 2He) cross sectionsd, 6,7Li, 12C, 14N, 28,30Si, 32S, 48Ti, 50,51V, 58,61,64Ni, 56Fe, 70,72,74Ge, 116Sn spectroscopy of GT+ strength, double (0νββ) decayn-n scattering length spin entanglement
•(pol(d), 2He), (d, 2He n) cross sections, tensor analyzing powers Ayy, Azz12CJπ = 0-, 1-, 2- components spin-dipole
•(α, 2He) production rate12Cspin entanglement
•(t, 3He) cross-sections12C, 48Ca, 58Ni, 90Zr, 208Pb(no spin-flip) isovector modes
•(α, α’ γ), (α, α’ p), (α, α’ n)48Ca, 58Ni, 90Zr, 140Ce, 208Pbisospin low-lying dipole, isoscalar electric dipole (ISGDR)
BBS - selection of highlights
ISGDR + ??? in 208PbM. Hunyadi et al, PLB 576 (2003) 253, NPA 731 (2004) 49
nn - scattering lengthC. Bäumer et al., PRC 71 (2005) 044003
matrix elements 2νββRakers et al.PRC 71 (2005) 054313
BBS & ESN Detektor - 2He
d
2He
A, Z
A, Z-1
pp
target nucleusremainingnucleus
deuteron diproton (2He)
• charge exchange reaction equivalent (n,p)• close to 100% spin-flip (Gamow-Teller transition) if: protons in 1S0 state 2He detected at 0°
but enormous (!) backgrounddue to deuteron break up104 - 105 larger cross section !
(d,2He) - principle
BBS
Target
focal-plane detector:
momentum (energy), arrival time
2He protons in coincidence
BBS acceptancelimits relativekinetic energy protons < 1 MeVfor Ed < 180 MeV
2He filter
d
2He
A, Z
A, Z
pp
target nucleusremaining nucleus
internal energy [MeV]
focal-plane arrival time difference [ns]
kinetic energydeuterons: < 180 MeV 1S0
Playing with spin and isospin
14N(d,2He)14C in comparison 14N(3He, t)14O
12C((pol)d,2He)12B
(12C(d, pol(2He))12B)
2He spin-flip filter
2He spin-flip filter &ΔS, ΔL coupling
spin correlations
14C , isospin symmetrie,shell model vs cluster model
matrix elements double β-decay, parity breaking
quantum correlations in nuclear systems
(d,2He) - structure A=14 / A.L. Negret PhD, Gent 2005
14N(d,2He)14C
(d,2He) Gamow-Teller filter (time-reversed β--decay)
(d,2He) - structure A=14 / A.L. Negret PhD, Gent 2005
stability 14C againts β--decay (14C → 14N)( 14C dating, τ1/2 = 5730 years)
• ground-state transitions
• comparison with large scale shell-model calculations
• structure & strength of transitions to excited states
• nuclear-strcuture classics!
(d, 2He) - structure A=14 / A.L. Negret PhD, Gent 2005
Coulomb
KVI, 14N(d,2He)14CEd = 170 MeV (n,p) - equivalent
RCNP, Osaka, 14(3He,t)14OEHe = 420 MeV(p,n) - equivalent
(d,2He) - structure A=14 / A.L. Negret PhD, Gent 2005
complexity
Gamow-Tellertransition strength in 14C
shell-model calculationsS. Aroua et al.,Nucl. Phys. A720, 71 (2003)
(d,2He) - structure A=14 / A.L. Negret PhD, Gent 2005
GT strength distribution experiment vs theory
strength 2+ states notreproduced by shell-model!
triple α-cluster +2 nucleon structure /molecular states ?
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
12C((pol)d,2He)12B
(pol(d),2He) filtering Jπ components spin dipole (time reversed first forbidden β--decay)a testcase !
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
spin dipole: ΔS = 1 (spin flip), ΔL = 1 (momentum transfer)time reversed, first forbidden β--decay
• starting from 0+ ground state: Jπ = 0-, 1-, 2- final states
• angular separation of transitions not possible, identical for Jπ = 1-, 2-
• predicted differences in cross-section depending on tensor polarisation - but: subtile effect !!! • relevant for analysis 0ν2β-decay
• high lying, collective 0- states relevant parity mixing of ground state (for 0+ ground state)
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
• vector polarisedpZ = N+ - N-
• tensor polarisedpZZ = N+ + N- - 2N0
withN+ + N_ + N0 = 1
extrema:pZZ = 1 , N+ = N_ = 1/2pZZ = -2, N0 = 1
• KVI deuteron beam, E0 = 171 MeVpZZ = 0.57 ± 0.03, pZ = 0.06 ± 0.01pZZ = -1.24 ± 0.05, pZ = -0.01 ± 0.01
N- N+
N0
z
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
Separation of 0-,1-,2- spin-dipole strengthfor scattering close 0°
z
q (ΔL)
ΔS
q
ΔS
PZZ = -2transversal orientationfavours natural parityπ = (-1)J
i.e. Jπ = 1-
PZZ = 1longitudinal orientationfavours non-natural parityπ = (-1)J+1
i.e. Jπ = 0- , 2-
tensor analysing powers: Ayy = 1, Azz = -2 for 0-
Ayy = -1/2, Azz = 1 for 1- (natural parity)
(ΔL)
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
1+
2+2-
1-
2-
1+
3+
1-1-
0-, 1-, 2- ?
12C(d, 2He)12B E0 = 171 MeV, θ = 0° - 4° ∆E ≈ 130 keV
first time verificationof predictions Ayy, Azz !
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
PZZ = -1.24
PZZ = 0.57
12C((pol)d,2He)12Bθlab = 0° - 1.7°Ed = 172 MeV
n-threshold quasi-free backgroundsubtracted
background verificationthrough n-decay data
differences forpolarisation modes
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
Low Lying Transitions
2-
1.67 MeV
1-
2.62 MeV
2- + ?4.4 MeV
angular dependencyof cross-sectiondoesn’t allow 1-, 2- separation
1- transition nicely fit Ayy , Azz close 0°(also 2+ at 0.96 MeV)unique fingerprint !
2- exhibit indifferent asymmetries
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
(PZZ = 0.57) - (PZZ = -1.24)
AZZ
naturalparity
naturalparity
indicationslocalized 0- strengthat 9.5 MeV(H. Okamura et al., Phys. Rev. C66 054602 (2003))
(d,2He) - spin dipole in 12B / M.A. de Huu PhD, KVI 2003
first time verificiation of Ayy , Azz predictions
selection of 0-, 1-, (2-) excitations possible
extension to heavier nuclei i.e. range relevant for 0νββ, A > 48
extraction transition strength ?
(α, α’ γ) structure Pigmy/ D. Savran PhD, TuD
(α, α’ γ) 48Ca, 58Ni, 140Ce
isospin structure of the electrical dipole (E1) strengthjust below the particle threshold-Pigmy resonance -
combining hadronic probeswithhigh resolution γ - spectroscopy
(α, α’ γ) structure Pigmy/ D. Savran PhD, TuD
48Ca, 58Ni, 140Ce (α,α’γ)
2 years of experimentalstudies
Ge-setup extremelysensitive to backgrounds
change up to factor 10hadron / γ trigger rateany AGOR fine tune
• unique way of linking hadronic/electromagnetic probes• (p,p’ γ) under investigation
58Ni E = 136 MeV θ = 3 - 8 deg
(α, α’ γ) structure Pigmy/ D. Savran PhD, TuD
Pigmy resonance
140Ceconcentration of E1below particle threshold-Pigmy resonance - :
a new collective mode ?
correlated to neutron/proton excess ?
αscattering indicatessplitting of strength inisoscalar - isovector component
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