1. Probing the Structure of the Most Neutron-rich Isotopes Carbon … Anatomy of a dripline Nucleus (22C)
Motivation: haloes & structure N~14-16
S2n, sR, momentum distributions
Invariant mass spectroscopy: 21C
Search for 22C*(2+)
Conclusions & Perspectives
“Groupe Structure Nucléaire”: S Leblond, FM Marqués, J Gibelin, NAO, et al.
+TokyoTech & the SAMURAI Collaboration
‟Formless Continuum” – Jack Haas

2. 21,22C: neutron haloes & structural evolution with Tz
n2s1/2 + n1d5/2
n2s1/2 + n1p1/2
n1p3/2
N=8
N=14
N=16

3. 21,22C: structure in the region of N~14 – 16 (n2s1/2 – n1d5/2)
N=14 16
WBT Shell Model Interaction: M Stanoiu et al., PRC (2008)

4. structure in the region of N ~ 16 - 20 …
Z=8
DISCUSSION: how do we disentangle 3N, continuum, tensor effects [based on exp’tal observations] ??
ESPE O isotopes - Otsuka et al., PRL (2010)

5. 22C: total reaction cross section & matter radius
p + 40 MeV/nucleon: K Tanaka et al., PRL (2010)

6. Valence/halo neutronS binding energies (S2n) …
S2n [19B] = 0.140.39 MeV
S2n [22C] = < 0.32 MeV (1s)
-0.140.46 MeV
SPEG TOF: L Gaudefroy, WM, NAO et al., PRL (2012)

7. Matter radius & valence neutron configuration …
L Gaudefroy, WM, NAO et al., PRL (2012)

8. Precise High EB [240 MeV/nucleon] measurement of 22C sR …
All 22C 3-body wavefunctions*: dominately (>90%) neutron [2s1/2]2 configurations ~
sR  rm = 3.44 ± 0.08 fm S2n = /-0.20 MeV
* 20C(0+) x [nlj] Y Kucuk, JAT PRC (2014)
Y Togano et al., PLB (2016)

9. 20,22C core momentum distributionS @ 240 MeV/nucleon …
C(20C,18C)
C(22C,20C)
ln=0
ln=2
INCLUSIVE Measurement (ZDS): N Kobayashi et al., PRC (2012)

10. Spectroscopy of 21C: high-energy direct reactionS …
Neutron removal/knockout *
 halo “hole” states core n nlj2  core  n nlj
p(core+n) distribution  ln halo
* ~10% of observed yield via 3-body continuum: eg., (22C,22C* 20C+n+n)

11. Spectroscopy of 21C: high-energy direct reactionS
Neutron removal/knockout
 halo “hole” states core n nlj2  core  n nlj
p(core+n) distribution  ln halo
Proton removal/knockout
 projectile valence n nlj unperturbed
[ Dln  0 ]

12. Invariant mass spectroscopy beyond the dripline …Vf Vn
Vf - Vn
target
RNB
f + n
… nucleon “knockout” or breakup(b  0.6) + in-flight decay
 fragment – n FSI
Ed = 1 m (vf - vn)2 2
NOTE: excited state of core also should be included where populated… g-ray decay

13. 21C: C(22N,20C+n) @ 245 MeV/nucleon …
uncorrelated f+n events / non resonant continuum *
* generated via event mixing
S Leblond et al., NP1106-SAMURAI04

14. n 22N  21C 21C: C(22N,20C+n) @ 245 MeV/nucleon … C(22N,20C+n) l=0
1d3/2
2s1/2
1d5/2
1p1/2
1p3/2
1s1/2 n
22N  21C
l = 0 (R-Matrix) ER =0.900.10 MeV; G = 0.80 0.50 MeV + non resonant continuum
S Leblond et al., NP1106-SAMURAI04

15. 21C: C(22C,20C+n) @ 245 MeV/nucleon …
non resonant continuum
S Leblond et al., NP1106-SAMURAI04

16. 21C: C(22C,20C+n) @ 245 MeV/nucleon – 20C+n MOMENTUM DISTRIBUTIONS …OR
1d3/2
2s1/2
1d5/2
1p1/2
1p3/2
1s1/2 n
22C  21C
S Leblond et al., NP1106-SAMURAI04

17. Ex Ex 21C: C(22C,20C+n) @ 245 MeV/nucleon … C(22C,20C+n) l=0 l=2
Er=0.750.20 MeV
Er=1.500.10 MeV
l=0
l=2 Ex Ex
Eikonal + shell model C2S
S Leblond et al., NP1106-SAMURAI04
JA Tostevin
S Leblond et al., NP1106-SAMURAI04

18. ? N=14 16 Magicity of N=16 below 24O: 22C(2+) …
N=14 16
ESPE O & C isotopes WBT Shell Model Interaction: M Stanoiu et al., PRC (2008)

19. N=14 16 Magicity of N=16 below 24O: 22C(2+) …
WBP Shell Model & Coupled Cluster [ GR Jansen et al., PRL (2014) ]

20. N=16 22C(2+) : C(23N,20C+n+n) … <23N|22C> Shell model- WBP
Ex [MeV] Jp C2S
[Bound]
J Gibelin et al., NP1106-SAMURAI04

21. Conclusions & Perspectives …
Knockout analyses being finalised but ...
22C : very weakly bound (<~0.32 MeV) & very well developed halo (rm = 3.44 ± 0.08 fm)
22C : valence/halo configurations n (2s1/2)2 + n (1d5/2)2
21C : 1/2+ – 5/2+ “inversion” ; 3/2+ located
In Progress…
C(19C,17B+n) & C(19B,17B+n) – interpretation in progress
Reaction calculations – momentum distributions C(22C,20C+n) & C(19B,17B+n)
Remeasurement of C(23N,20C+n+n) – 22C*(2+) – run Nov-Dec 2016
Perspectives …
20,21B (N=15, 16)
23C (N=17)
24,25N (N=17,18)
Charge exchange to go neutron beyond dripline ~