Upload
ledien
View
216
Download
2
Embed Size (px)
Citation preview
INPC2016 M.Itoh 1
INPC2016 M.Itoh 2
INPC2016 M.Itoh 3
INPC2016 M.Itoh 4
INPC2016 M.Itoh 5
INPC2016 M.Itoh 6
INPC2016 M.Itoh 7
INPC2016 M.Itoh 8
INPC2016 M.Itoh 9
INPC2016 M.Itoh 10
INPC2016 M.Itoh 11
INPC2016 M.Itoh 12
INPC2016 M.Itoh 13
INPC2016 M.Itoh 14
INPC2016 M.Itoh 15
INPC2016 M.Itoh 16
INPC2016 M.Itoh 17
Energy distribution of decay alpha particles
● “εi” : Highest normalized energy among three decay-α particles
M.I et al, Phys. Rev. Lett. 113, 102501 (2014)
Hoyle
8Be
α
εi ~ 0.506
Sequential Decay
SD
DDEDDΦ
Direct Decay?
Normalized energy distribution for the highest energy α particles
INPC2016 M.Itoh 18
12C(α,α'3α) experiment in India
● The non-zero direct components of the decay from the Hoyle state have been reported using the 12C(α,α'3α) reaction.T.K .Rana et a l,PRC88,021601(R)(2013)
0.91(14) %
INPC2016 M.Itoh 19
● The 10C+ C(Be) experimentThey obtained the upper limit of 3.9% for the direct 3α decay from the Hoyle state.J.Manfredi et al,PRC85,037603(2012).
● The 11B(3He,d3α) experimentThey improved the upper limit of the direct 3α decay to be 5 x10-3.O.S.Kirsebom et al,PRL108,202501(2012).
Recent experiments
INPC2016 M.Itoh 20
Experimental situation on the direct 3α decay
● Experiment of the 12C(12C,3α)12C reactionM.Freer et al, PRC49(1994)R1751
– Upper limits of 4% for the contribution of the direct decay process to Γα
● In 2011, the direct decay branch of 17±5% had been reported by Catania group. Among them, the direct decay with three α particles of equal energies was 7.5±4.0%.Ad.R.Raduta et al,PLB705(2011)65.
Evidence for α condensation of the Hoyle state??
INPC2016 M.Itoh 21
Algebraic Cluster Model in 12C
● Hoyle state: the A symmetric stretching vibration ( breathing mode) of the triangular configuration
D.J.Marín-Lámbarri et al, Phys.Rev.Lett.113, 012502 (2014)
12C(4He,α)4He experiment at Birmingham
they found 5- state at 22.4 MeV
R.Bijker and F.Iachello, PRC61(2000)067305
INPC2016 M.Itoh 22
Structure of the Hoyle state
● Root mean square radius
A
B
C
2.5fm
2.2fm
3.3fm
4.2fm
5.3fm
1.9fm
Rrms
~ 3.43 fm
B=C
10%
20%
10%
S.Ishikawa, Phys.Rev.C90, 061604(R)(2014)
INPC2016 M.Itoh 23
Misassignment of decay alpha particles
Why do the shoulders appear? … Misassignment of decay alpha particles
EX1
≈ EY1
→ α1 (X1,Y1)
Eα1
≈ Eα2
α1(X1,Y2), α2(X2,Y1)
α1(X2,Y1), α2(X1,Y2)
Misassignment
INPC2016 M.Itoh 24
Energy spectrum for the decay 3α particles
Einv
= Erecoil12C
+ Eα1
+ Eα2
+ Eα3
Total 3α energy spectrum in the 12C* rest frame
Invariant Mass spectrum
~103 MeV
INPC2016 M.Itoh 25
Accidental coincidence
● There was no accidental 3α coincidence.
Recoil 12C + 1-α Recoil 12C + 3-α
TDC TDC
accidental coincidence true coincidence
INPC2016 M.Itoh 26
Kinematics and Recoil 12C spectrum
● Particle Identification:TOF method
● Excitation energy is determined from the energy of the recoil 12C.
TOF spectrum of SD12C α
p
d
12C(2+)+12C(2+)12C(02+)
12C(2+)
3α coincidence
INPC2016 M.Itoh 27
Decay and structure of Hoyle state
INPC2016 M.Itoh 28
Structure of the Hoyle state 1
● Density distribution
A
B
C
2.5fm
2.2fm
3.3fm
4.2fm
5.3fm
1.9fmS.Ishikawa, Phys.Rev.C90, 061604(R)(2014)