1. A new investigation of the Hoyle state in 12C via the
Nuclear Physics in Astrophysics VIII, Catania, June 2017
A new investigation of the Hoyle state in 12C via the
14N(d,a2) reaction
Univ. di Napoli Federico II & Université Paris-Saclay
Daniele Dell’Aquila1,2
1 Università degli studi di Napoli “Federico II” & INFN – Sezione di Napoli
2 Institut de Physique Nucléaire, CNRS-IN2P3, Univ. Paris-Sud, Université Paris-Saclay
Catania from above, 19 June 2017
Catania, June 23th 2017

2. Exotic structures in light nuclei
Complexity of nuclear force  deviation from the sphericity: axial deformation (collective behaviours), spatial re-organization of nucleons in bounded sub-units (cluster model).
12O
13O
14O
15O
16O
17O
18O
19O
20O
21O
22O
11N
12N
13N
14N
15N
16N
17N
18N
19N
20N
21N C 8C 9C
10C
11C
12C
13C
14C
15C
16C
17C
18C
19C
20C a B 8B 9B
10B
11B
12B
13B
14B
15B
17B
19B a
Univ. di Napoli Federico II & Université Paris-Saclay a Be
7Be
8Be
9Be
10Be
11Be
12Be
14Be
linear chain
10Be,13-14C,16C(?),… Li
6Li
7Li
8Li
9Li
11Li He
3He
4He
6He
8He a 1H 2H 3H a
core a a n a
core
a-cluster
8Be
neutron skin
8He,C
neutron halo
6He,11Li,11Be
dilute gas
12C 0+,16O,20Ne(?)
Daniele Dell’Aquila – Catania, June 23th 2017

3. The Hoyle state in 12C a a 12C a
In Nuclear Structure
3a process in stars
Cluster state of 12C located at MeV (0+)  quite unusual and not well understood properties  challenging question in nuclear physics. a
12C a a
7.37
7.28
Hoyle
8Be 3a
Univ. degli Studi di Napoli Federico II & INFN - Napoli
12C
N.B. Nguyen et al., Phys. Rev. Lett. 109 (2012)
D. Jenkins and O. Kirsebom, The Secret of Life,
Physics World Feb. 2013
In Nuclear Astrophysics
Proposed by Fred Hoyle in 1953  explaination to the 3a process in stars (helium burning)  production of carbon and heavier elements in the universe.
At low temperatures (T<108 K)  non-resonant processes dominates  need to know the G3a!
Daniele Dell’Aquila – Catania, June 23th 2017

4. The Hoyle state in 12C: the non-resonant decay branch
8Be ground state
O.S. Kirsebom et al.
≈5000 events  no evidence of direct decays  upper limit of 0.5% to direct branching ratios. a a a
Experiment
𝚪 𝟑𝜶 /𝚪 (%)
[1] M. Freer et al.
<4
[2] Ad.R. Raduta et al.
17.0±5.0
[3] J. Manfredi et al. …
[4] O.S. Kirsebom et al.
<0.5
[5] T.K. Rana et al.
0.91±0.14
[6] M. Itoh et al.
<0.2
[7] L. Morelli et al.
1.1±0.8
T.K. Rana et al.
≈20000 events  non-vanishing direct decay branching ratio
Γ 3𝛼 Γ =0.91±0.14
Univ. degli Studi di Napoli Federico II & INFN - Napoli
M. Itoh et al.
≈20000 events  direct decay under the sensitivity of the experimental sensitivity  <0.2%
[1] M. Freer et al., Phys. Rev. C 49, R1751 (1994). [2] Ad. R. Raduta et al., Phys. Lett. B 705, 65 (2011). [3] J. Manfredi et al., Phys. Rev. C 85, (2012). [4] O. S. Kirsebom et al., Phys. Rev. Lett. 108, (2012). [5] T. K. Rana et al., Phys. Rev. C 88, (R) (2013). [6] M. Itoh et al., Phys. Rev. Lett 113, (2014). [7] L. Morelli et al., J. Phys. G: Nucl. Part. Phys. 43, (2016).
Daniele Dell’Aquila – Catania, June 23th 2017

5. 3a correlations and the Hoyle state in 12C: our experiment
The HOYLE (Hodoscope Oriented Yield Loader Experiment) experiment at INFN-LNS  a new high statistics and low background investigation of the HOYLE state by means of the 14N(d,a2)12C(7.654) reaction.
Tandem 15MV
Istituto Nazionale di Fisica Nucleare
LNS - Laboratori Nazionali del Sud
CT-2000 chamber INFN-LNS
Univ. degli Studi di Napoli Federico II & INFN - Napoli
d beam at Ed = 10.5 MeV;
C3N6H6 target (40 mg/cm2) + 5/10 mg/cm2 backing C;
𝐼 𝑑 ≈4𝑒𝑛𝐴;
≈30 𝑑𝑎𝑦𝑠 of beam time;
𝜃 𝑙𝑎𝑏 =125° anti-telescope + superOSCAR hodoscope (31.4°).
Daniele Dell’Aquila – Catania, June 23th 2017

6. 3a correlations and the Hoyle state in 12C: our experiment
Basic idea and experimental layout
anticoincidence
telescope
SuperOSCAR
100 3α
C3N6H6 α d
Ed=10.5 MeV
Univ. degli Studi di Napoli Federico II & INFN - Napoli 3α
12C* α d
14N
Daniele Dell’Aquila – Catania, June 23th 2017

7. 3a correlations and the Hoyle state in 12C: our experiment
The superOSCAR hodoscope
64 Hamamatsu S mm silicon pads (1cmx1cm active area);
≈0.125 𝑐𝑚 ceramic frame;
4 modules 4x4 pads in 2x2 configuration;
4 pre-amplifiers Net Instruments NPA-16FE (16 chs);
3a source 
0.2% energy resolution.
Univ. degli Studi di Napoli Federico II & INFN - Napoli
100
anticoincidence
telescope
Very precise selection of Hoyle states…
Daniele Dell’Aquila – Catania, June 23th 2017

8. 3a correlations and the Hoyle state in 12C: our experiment
To select fully reconstructed (4a) good events  cuts on:
time of flights (ToFs);
Q-value;
Ex.
Univ. degli Studi di Napoli Federico II & INFN - Napoli
Invariant mass Ex spectrum  Very low background level, of the order of 0.03% of the total integral of the peak.
Narrow peak centered at MeV!!!
𝜎≈20𝑘𝑒𝑉.
Daniele Dell’Aquila – Catania, June 23th 2017

9. 3a correlations and the Hoyle state in 12C: our experiment
Study of sequential vs direct mechanism: Symmetric Dalitz Plot
𝜀 𝑖,𝑗,𝑘 = 𝐸 𝑖,𝑗,𝑘 /( 𝐸 𝑖 + 𝐸 𝑗 + 𝐸 𝑘 )
Normalized energies in the 12C emitting reference frame
𝜀 1
sequential a a a
𝜀 𝑖 ≈ 1 2
𝜺 𝟏 + 𝜺 𝟐 + 𝜺 𝟑 =𝟏
Univ. degli Studi di Napoli Federico II & INFN - Napoli
𝜺 𝒊 > 𝜺 𝒋 > 𝜺 𝒌
𝜀 1 =0.5
direct a a
𝜀 3 =0.5
𝜀 𝑖 ≈? a
𝜀 2 =0.5
𝜀 3
𝜀 2
Daniele Dell’Aquila – Catania, June 23th 2017

10. 3a correlations and the Hoyle state in 12C: our experiment
Study of sequential vs direct mechanism: Symmetric Dalitz Plot
𝜀 𝑖,𝑗,𝑘 = 𝐸 𝑖,𝑗,𝑘 /( 𝐸 𝑖 + 𝐸 𝑗 + 𝐸 𝑘 )
Normalized energies in the 12C emitting reference frame
sequential a a a
𝜀 𝑖 ≈ 1 2
𝜺 𝟏 + 𝜺 𝟐 + 𝜺 𝟑 =𝟏
Univ. degli Studi di Napoli Federico II & INFN - Napoli
𝜺 𝒊 > 𝜺 𝒋 > 𝜺 𝒌
direct a a
𝜀 𝑖 ≈? a
Daniele Dell’Aquila – Catania, June 23th 2017

11. 3a correlations and the Hoyle state in 12C: our experiment
Study of sequential vs direct mechanism
𝜀 𝑖,𝑗,𝑘 = 𝐸 𝑖,𝑗,𝑘 /( 𝐸 𝑖 + 𝐸 𝑗 + 𝐸 𝑘 )
𝜀 𝑖 > 𝜀 𝑗 > 𝜀 𝑘
𝑥= 3 ( 𝜀 𝑗 − 𝜀 𝑘 )
𝑦=2 𝜀 𝑖 − 𝜀 𝑗 − 𝜀 𝑘
simulation 100% SD
Univ. degli Studi di Napoli Federico II & INFN - Napoli
M. Itoh et al.
simulation 100% SD
Our experiment
simulation 100% DD
Experimental data
28000 counts under the sequential decay peak  compatible with fully sequential process!
Daniele Dell’Aquila – Catania, June 23th 2017

12. New upper limit DD < 0.043 % with a C.L. of 2s.
3a correlations and the Hoyle state in 12C: our experiment
Study of sequential vs direct mechanism: Symmetric Dalitz Plot
Feldman and Cousin’s approach for small signals in presence of background
G.J. Feldman and R.D. Cousins, Phys. Rev. D 57, 3873 (1998).
Univ. degli Studi di Napoli Federico II & INFN - Napoli
New upper limit DD < % with a C.L. of 2s.
D. Dell’Aquila et al., accepted on PRL
Daniele Dell’Aquila – Catania, June 23th 2017

13. Thank you for your attention.
Conclusions and Perspectives
Particle-particle and multi-particle correlations are a powerful tool to explore Nuclear Structure and Dynamics;
Correlations involving a particles  structure of self-conjugated nuclei and clustering phenomena;
We studied the Hoyle state in 12C by means of 3a correlations using the 14N(d,a2)12C(hoyle) reaction at 10.5 MeV with the aim of improving the present knowledge of its non-resonant decay branch;
For obtaining a extremely low background we used the anti-telescope technique and we developed a new modular hodoscope: superOSCAR;
We obtained no-evidence of non-resonant decays of the Hoyle state for the first time with an almost vanishing background level  New upper limit to direct decay of 0.043% C.L. 2s (about a factor 5 lower than the state of art)  consequences in low temperature helium burning astrophysical sites (T<108 K).
Univ. di Napoli Federico II & Université Paris-Saclay
Thank you for your attention.
Daniele Dell’Aquila – Catania, June 23th 2017

14. Further Slides
Univ. Napoli Federico II and INFN – Napoli

15. 12C structure via the 14N(d,a) reaction: the HOYLE experiment
Univ. degli Studi di Napoli Federico II & INFN - Napoli
Daniele Dell’Aquila – Cocoyoc (Mexico), January 6th 2017

16. 12C structure via the 14N(d,a) reaction: the HOYLE experiment
Univ. degli Studi di Napoli Federico II & INFN - Napoli
Daniele Dell’Aquila – Cocoyoc (Mexico), January 6th 2017

17. Development of new generation hodoscopes: OSCAR
OSCAR: Odoscopio di Silici per le Correlazioni e le Analisi di Reazioni
A new hodoscope for the analysis of nuclear reactions.
SSSSD (20mm, 16 strips 3mm mm interstrip) + 16 silicon pads
Univ. di Napoli Federico II & Université Paris-Saclay
Developed with the INFN-Napoli SER.
Plug-and-play connections
on-board pre-amplifiers
modular and compact detector
low cross-talk levels and high resolutions
Daniele Dell’Aquila - Napoli, November 3rd 2016

18. Development of new generation hodoscopes: OSCAR
TEST di OSCAR ai LNS: 40,48Ca+40,48Ca at 35 A MeV, 52o LAB
Ca+Ca
a source
Univ. di Napoli Federico II & Université Paris-Saclay
Good particles identification up to lithium isotopes via the DE-E technique.
Identification of very low energy particles with very good energy resolution. (a dedicated experiment has been performed at LNS for studiyng the effects of the silicon non-uniformity on the particle identifications and energy resolutions.
Daniele Dell’Aquila - Napoli, November 3rd 2016

19. Development of new generation hodoscopes: OSCAR
Energy spectra of the lightest identified fragments obtained in 48Ca+48Ca collisions at 35MeV/u
Univ. di Napoli Federico II & Université Paris-Saclay
A route to SPES  development of high segmentated detectors with low detection thresholds and high modularity (ancillary detector).
to be submitted for publication…
Daniele Dell’Aquila - Napoli, November 3rd 2016