one-nucleon transfer at high proton-neutron asymetry · one-nucleon transfer at high proton-neutron...

A. Gillibert1

1 IRFU/SPhN, CEA Saclay

1/23 ECT* Trento2013:

One-Nucleon Transfer at high proton-neutron asymetry

1. Brief overview of the spectroscopic factor issue

2. One-nucleon transfer on 14O measured at GANIL

3. Analysis using standard and ab-initio overlap functions

4. Conclusions / Comparison with knockout results

5. Outlook

Outline

2/23 ECT* Trento 2013

Measurement at GANIL Analysis / Interpretation Conclusion Intro: Spectroscopic Factors

Extraction of spectroscopic factors

𝜎𝜇𝑡ℎ𝑒𝑜 = 𝜑𝜇

𝐴−1 𝑎𝑝− 𝜑0

𝐴2

× 𝜎𝑝𝑝 ∈𝐻<𝐻1

reaction theory

structure theory

Theoretical cross section to populate a final state m

Comparison of experiment and theory to discuss SF + ESPEs

What should be done: Consistent approach of reaction and structure (same Hamiltonian) Clearly assess which theoretical framework is used (which Hamiltonian)

[P. Navratil and S. Quaglioni, Phys. Rev. Lett. 108, 042503 (2012)] [Th. Neff, Phys. Rev. Lett. 106, 042502 (2011)]

What is done (i.e. what can be done today): Most often highly-truncated model space (shell model) Inconsistent treatment of structure and reaction mechanism

SFs are not observable modified through Unitary Transforms

[R.J. Furnstal and H.W. Hammer, Phys. Lett. B 531, 203 (2002)] [T. Duguet and G. Hagen, Phys. Rev. C 85, 034330 (2012)]

3/23 ECT* Trento2013


Stable nuclei/target : (e,e’p)

[W. Dickhoff, Prog. Nucl. Phys. 52, 377 (2004)]


• electromagnetic probe • 30-40 % reduction • Beyond mean-field correlations

• Agreement with (d,3He) [W. Dickhoff, C. Barbieri, PNP52, 377 (2004)] [G.J. Kramer et al., NPA679, 267 (2001)]


Exotic nuclei : radioactive beams in inverse kinematics

Knockout (-1n) et (-1p)

J. Lee et al., PRC 83, 014606 (2001)


Intermediate-energy knockout

• Disagreement between theory and experiment::

sth = C2Sth ssp

2 possible sources: (structure or reaction)

ΔS = |Sn – Sp | (MeV)

Low-energy (p,d) transfer • Constant reduction~30% • Data for DS up to 12 MeV

ΔS = |Sn – Sp | (MeV)

Transfer (d,p)


B.P. Kay et al., PRL 111 (2013) 042502

ECT* Trento2013

Program

Experimental Program

14O + 9Be → 13O ou 13N + X 16C + 9Be → 15C ou15B + X

14O + d → 13O + t 14O + d → 13N + 3He 14O + d → 14O + d

53 MeV/u 75 MeV/u

@ NSCL

18 MeV/u @ SPIRAL-GANIL

Reaction Models

Transfer: Coupled-Channel calculations (FRESCO)

Use of same sp form factors for knock-out and transfer

Comparaison with ab-initio overlaps

7/23 ECT* Trento 2013

Advantages of 14O

Large value ΔS = 18.6 MeV Beam intensity : high enough for (d,3H) (d,3He) transfer measurements Beam energy

Question : Are spectroscopic factors from knockout and transfer consistent for high DS ?

F.Flavigny et al., Phys. Rev. Lett 108, 252101 (2012)

F.Flavigny et al., Phys. Rev. Lett 110, 122503 (2013)


One-nucleon transfer from 14O



Experimental Setup

SPIRAL Beam intensity: pure, 6.104 pps

CD2 targets: 0.5,1.5 and 8.5 mg.cm-2

Reactions: (d,d), (d,3H) and (d,3He)

• MUST2 10x10 cm2 300μm DSSSD + SiLi or CsI

• VAMOS spectrometer in dispersive mode

Fully exclusive measurement



Experimental data set

[M. Gaillard et al., Nucl. Phys. A 119, 161 (1968)]

One-proton pickup channel

Elastic channel One-neutron pickup channel


[M.

Published Data on 16O and 18O

[V. Bechtold et al., Phys. Lett. B 72,169 (1977)] [M. Gaillard et al., Nucl. Phys. A 119, 161 (1968)] [D. Hartwig et al., Z. Phys. 246, 418 (1971)]


Input Potential:

14O+ 2H A.J. Koning et J.P. Delaroche, NPA 713, 231 (2003)

Validated on elastic data

Output potentials:

13O + 3H and 13N + 3He D. Y. Pang et al., PRC 79, 024615 (2009)

C. M. Perey and F. G. Perey, ADNDT 17,17,1 (1976)

Form factors:

<14O | 13O + n> and <14O | 13N + p>

Two prescriptions:

Woods Saxon, Hartree Fock constrained

Ab-initio overlap (SCGF)

Coupling scheme

Coupled Reaction Channel analysis (CRC)

Coupled discretized continuum channel

(CDCC) for deuteron breakup

Reaction Framework

13N+3He

13O+3H

14O+2H



Test Case : 16O stable data

Form factors X Standard arbitrary value:

(r0 , a0) : (1.25 fm , 0.65 fm)

rrms from 16O(e,e’p)15Ngs :

rrms = 2,943 fm

WS parameters to reproduce rrms and Sp:

r0 = 1.46 fm a0 = 0.65 fm

C2Sexp = 0,93 (9) rrms from M. Leuschner et al., PRC 49, 955 (1994)

Data points from : [V. Bechtold et al., Phys. Lett. B 72,169 (1977)] [M. Gaillard et al., Nucl. Phys. A 119, 161 (1968)]

Single-particle HF w.f. with Sly4 interaction:

rrms(HF) = 2,95 fm



λV = 1.1 , λW = 0.8

14O results

C2Sexp strongly depends on radii

Ex: DC2S/C2S ≈ 6 Drrms/ rrms

Δℓ = 1



Δℓ = 1

Results with WS overlap functions

δ (RMS) δro box Error bars due to exp. Uncertainties OFs : WS (HFB constrained) C2Sth: Shell model with WBT interaction

sth(q) = C2Sth ssp(q)



48 analysis: • 2 sets of C2Sth: - WBT Interaction 0p shell + 2ħΩ - Utsuno int. 0p1s0d space • 3 HF calculations for radii

• 8 combinations of optical potentials for entrance and exit channels

c2min

Exp. Error (1 set)

Systematic error from 48 data sets

Rs = a . DS + b

a = +0.0004(24)(12) MeV-1

b = Rs(0) = 0.538(28)(18)

Results with ab-initio overlap functions

Ab-inito SFth and overlaps ( from C. Barbieri and A. Cipollone)

Single-particle Green’s function (third order diagrammatic construction method) Chiral two-body + three-body interactions (cutoff l=1.88 fm-1)

sth(q) = C2Sth ssp(q)



a = -0.0042(28)(36) MeV-1

b = Rs(0) = 0.636(24)(42)

Partial conclusion (1)

Conclusion : • Agreement between standard prescription (WS+SM) and ab-initio • Weak asymmetry dependence within the error bars

a = +0.0004(24)(12) MeV-1

b = Rs(0) = 0.538(28)(18)



a = -0.0042(28)(36) MeV-1

Partial conclusion (2)

a = +0.0004(24)(12) MeV-1

…the reduction in the SFs is due to the many-body

correlations arising from the coupling to the scattering

continuum….

[O. Jensen et al., Phys. Rev. Lett. 107 032501 (2011)]

Spec

. Fac

tor

a = -0.0039 MeV-1

between 14O points



Coupled-cluster method

Knock-out from 14O

One-nucleon removal from 14O and 16C at the NSCL

16C beam at 70 MeV/nucleon 14O beam at 53 MeV/nucleon

Stripping cross sections at intermediate energies

Probability to remove the nucleon Probability to

leave the core intact

NN cross section Core density

No explicit treatment of core excitations

Importance of core excitations for loosely-bound cores and deeply-bound nucleons?

Sudden eikonal approximation

Knockout results



Key observations:

14O and 16C fit into the Rs trend.

Strong deviations with respect to eikonal predictions

Knockout conclusions



Summary

SFs are not observables BUT useful in a given theoretical framework

Today: unconsistent treatment of structure and reactions

Transfer experiment 14O(d, 3H) (d,3He) ΔS = ± 18.5 MeV

Analysis over 48 combinations of potentials + HF radii + SM SFs

Analysis with ab-initio SFs and overlap functions consistent with standard approach

Rs = α ΔS + β, α small and consistent with 0 F. Flavigny et al., Phys. Rev. Lett 100 122503 (2013)

Discrepancy between intermediate-energy (<100 MeV/u) and low-energy transfer

Knockout: Incident energy is a problem for deeply-bound nucleons and E< 80 MeV/u

Core excitations may impact significantly the cross section F. Flavigny et al., Phys. Rev. Lett. 108, 252501 (2012)



Outlook

Transfer

Experiment performed at GANIL/SPIRAL 18Ne(d,t)(d,3He) @ 16.5 MeV/A

Knockout

More exclusive measurements on 14O (RCNP Osaka, J. Lee, A. Obertelli, Y. Lee)



CEA Saclay: A. Gillibert, A. Obertelli, N. Alamanos, A. Boudard, S. Boissinot, A. Corsi, V. Lapoux, C. Louchart, L. Nalpas, E. Pollacco, A. Signoracci. KULeuven: F. Flavigny, R. Raabe GANIL: J. Burgunder, R. Raabe, M. Rejmund, A. Shrivastava. IPN Orsay: A. Matta, D. Beaumel, N. De Séréville, S. Giron, J. Guillot, F. Hammache LPC Caen: J. Gibelin Surrey University: C. Barbieri, A. Cipollone Zoltan Institute (Warsaw): N. Keeley University of Pisa: A. Bonaccorso

Collaboration


Knockout – other work

Effect of the Pauli principle on σsp of 10% at E = 80 MeV/nucleon

Inclusion of density dependence in an eikonal approach

F. Flavigny , A. Obertelli et I. Vidana, PRC 79, 064617 (2009)

12/03/2013 26/18 FUSTIPEN 2013: The microscopicdescription of light nuclei

Knockout – other work

12/03/2013 27/18 FUSTIPEN 2013: The microscopicdescription of light nuclei

Level scheme

Measurement in GANIL Analysis / Interpretation Conclusion Intro: SpectroscopicFactors

3/2-

3/2-

1/2-

(3/2-)

Expt. SP-SM

2750

4210

6020 7853

5408 =1.2MeV

Sp = 1516 keV

13O

Input Potential:

14O+ 2H A.J. Koning et J.P. Delaroche, NPA 713, 231 (2003)

Validated on elastic data

Output potentials:

13O + 3H and 13N + 3He D. Y. Pang et al., PRC 79, 024615 (2009)

C. M. Perey and F. G. Perey, ADNDT 17,17,1 (1976)

Form factors:

<3H|d + n> and <3He |d + p> B. A. Watson et al., PR 182,977 (1969)

<14O | 13O + n> and <14O | 13N + p>

Two prescriptions:

Woods Saxon, Hartree Fock constrained

Ab-initio overlap (SCGF)

Coupling scheme

Coupled Reaction Channel analysis (CRC)

Coupled discretized continuum channel

(CDCC) for deuteron breakup

Reaction Framework

13N+3He

13O+3H

14O+2H



30

Key observations:

14O and 16C fit into the Rs trend.

Strong deviations with respect to eikonal predictions

Knockout conclusions



31

High-momentum cutoff

ef= kinetic energy of the fragments (nucleon + target) in the lab. frame Momentum threshold (CUT) for ef =0 A. Bonaccorso, Phys. Rev. C 60, 054604 (1999).

ef =0

dp

“barely visible” effect in published data

A. Gade et al., PRC 71, 051301 (2005). A. Gade et al., PRC 77, 044306 (2008). G. Grinyer et al., PRL 106, 162502 (2011).

70 MeV/u 85 MeV/u 80 MeV/u 120 MeV/u

g-ray spectroscopy of 15B: dissipative processes

Direct removal 1p from 16C expected to populate 3/2- or 1/2- states in 15B from simple SM description

Observation of 5/2- and 7/2- states suggests a more complex reaction mechanism

16C 15B

M. Stanoiu et al., EPJA 22, 5 (2004)

σ 7/2- = 0.8 (1) mb σ 5/2- = 1.3 (2) mb σ gs = 18.3 (2.2) mb

VAMOS

CSS1

CSS2

SPIRAL Target CIME

Primary beam : 16O 95 A.MeV, 1.4 kW

VAMOS

Ion Source

CSS1

CSS2

SPIRAL Target CIME

MUST2

Beam : 14O8+

•pure

• 18.1 A.MeV

• ~ 5 104pps

Beam production and acceleration



Importance of Spectroscopic Factors


Baranger’s sum rule to obtain Effective Single Particle Energies (ESPEs)

[M. Baranger, Nucl. Phys. A149, 225 (1970)]

0

Single-particle energies

Pillar of our understanding

Crucial to investigate shell evolution

[J.Holt, T.Otsuka, Jour. Phys. G39, 08111 (2012)]

Courtesy [T.Duguet]

1

21

0

A A

p

p H

SF am m + + +

= 1

21

0

A A

n n p

p H

SF a

=


one-nucleon transfer at high proton-neutron asymetry · one-nucleon transfer at high proton-neutron...

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