Neutron Spectroscopic Factors from transfer reactions for Z=3-28 - - PowerPoint PPT Presentation

The National Superconducting Cyclotron Laboratory

@Michigan State University

Betty Tsang

Neutron Spectroscopic Factors from transfer reactions for Z=3-28 isotopes

Kernz08 Dec 1-5, 2008

 Spectroscopic factor (SF)

measures the orbital configuration of the valence nucleons.

Independent Particle Model (IPM), SF represents how good can we describe the nucleus as a single particle plus a core.

Properties of valence nucleons

RM EX gs

d d d d S ) ( ) (     

Experimental SF :

1

exp



IPM

S S Orbital description is accurate

1

exp



IPM

S S

Valence nucleon

• ccupies more

than one orbit LBSM.

 Spectroscopic factor (SF)

measures the orbital configuration of the valence nucleons.

Large Basis Shell Model (LB- SM), SF can be used to test the interactions used in SM.

Properties of valence nucleons

RM EX gs

d d d d S ) ( ) (     

Experimental SF :

1

exp



SM LB

S S Orbital description is accurate

1

exp



SM LB

S S

Improvement in interactions?

Problems with previous experimental SF

Important to have systematic approach  consistent spectroscopic factors

Example: 1f 7/2 neutron SF in 41Ca = 40Ca+n SFSM=1.00

• No. of papers

100 200 300 400 500 600 1 2 3 4 5 6

50’s 60’s 70’s 2000- 90’s 80’s Decade 600 300 Measurements in (d,p) and (p,d) reactions

Spectroscopic factor  reflects the properties of valence neutron  constant value independent of incident energy Large fluctuations : Consequence of using different codes, optical model potentials and parameters in the reaction model  cannot constrain the physics

Murillo, NPA579, 125 (1994)

SF=0.99

Ed=16 MeV 14C(d,p)15C Goss, PRC12,1730 (1975) Ed=14 MeV

SF=0.88

Cecil, NPA255,345 (1975) Ed=17 MeV

SF=1.03

The data differ by factor

• f 2 but SF’s are nearly

the same by varying the input parameters!!

Discrepancies between data sets

• J. P. Schiffer et al., Phys. Rev. 164, 1274 (1967)
• Z. H. Liu et al., Phys. Rev. C 64, 034312 (2001).
• J. Lang et al., Nucl. Phys. A477, 77 (1988).

U.Schmidt-Rohr et al., Nucl. Phys. 53, 77 (1964).

• J. P. Schiffer et al., Phys. Rev. 164, 1274 (1967).
• Z. H. Liu et al., Phys. Rev. C 64, 034312 (2001).

D.Fick, J,NUK,19,693 (1974) (EXFOR).

Quoted experimental uncertainties are 6-20% Quality control from independent measurements

Theo EXP EXP

d d SF d d                 

ADWA

 Johnson- Soper (JS) Adiabatic Approximation to take care of d-break-up effects Use global p and d optical potential with standardized parameters (CH89)  Include finite range & non- locality corrections  n-potential : Woods-Saxon shape ro=1.25 & ao=0.65 fm; depth adjusted to reproduce experimental binding energy.

Systematic methods for consistent spectroscopic factors

TWOFNR from Jeff Tostevin (University of Surrey)

• J. Lee et al, Phys. Rev. C75 (2007) 064320

Compute with TWOFNR code

Compare with LB-Shell Model (Oxbash, B.A. Brown)

Good agreement with most isotopes Austern’s values were predicted 40 years ago

M.B. Tsang, et al, PRL95, 222501 (2005).

Ground State Neutron Spectroscopic Factors for Ni isotopes

• 56Ni core, in fpg model

space

• New T=1 effective

interaction (derived for heavy Ni isotopes) --XT

• 40Ca core, in fp model

space

• GXPF1A, KB3G

interaction

• No 56Ni shell closure

requirement

Ground-state SFs for Ni

• calculations with

truncated basis are wrong.

• GXPF1A + complete basis

calculation is in best agreement with the data

*Linear lines are the least square fits of the linear correlations between data and predictions.

Change in light curve by 10% if rate of 27P(p,g) 28S is changed by factor of 2. X-ray burst light curves from GS 1826-24 – observation uncertain --10%

• F. Montes, MSU

Biggest uncertainty: excited-state SF

SF determinations need to be better than a factor of 2

17O, 18O, 21Ne, 24Na, 25Mg , 27Mg, 29Si, 31Si, 33S, 35S, (32P, 36Cl, 37Ar)

g.s.

S.C. Su (Chinese University of Hong Kong) – 06’ SURE program paper in preparation

Agreement with Shell Model better than 30%

17O, 18O, 21Ne, 24Na, 25Mg , 27Mg, 29Si, 31Si, 33S, 35S, (32P, 36Cl, 37Ar)

g.s. Ex.

Analyzed ~ 794 angular distributions

N Z

Excited-state SFs of rare nuclei:

• rp process calculations
• X-ray burst simulations

Not available in experiment from SM predictions  SFs for excited states are very small (< 0.1) Test the predictive power of Shell Model Use nuclei in sd shell where the interaction (USDA/USDB) is well understood.

Excited-state Spectroscopic Factors of sd shell nuclei

5.627;3/2+

(5/2)

Application: Determination of Spin assignments from Systematics 3.491;3/2+ 4.15;5/2+

Jπ assignment

27Mg (NUDAT):

(3/2,5/2)+

Expt SM

5.627 (3/2,5/2) 5.454, 3/2 5.404, 5/2

S.C. Su (Chinese University of Hong Kong) – 06’ SURE program, Paper in preparation

Comparison with Large-Basis Shell Model (Oxbash) and Independent Particle Model (IPM) for Ca isotopes, 40Ca – 48Ca

IPM predictions: Assume Spherical core + Maximal pairing

n S 

1 2 1 1     j n S

for even n for odd n  SF’s of 40Ca-48Ca isotopes agree very well with IPM  Good agreement with LB-SM  The 1f7/2 valance neutrons in Ca isotopes are good single particles with spherical 40Ca core.

M.B. Tsang, et al, PRL95, 222501 (2005).

N Z

g.s.

Phoenix Dai (Chinese University of Hong Kong) – 07’ SURE program

Agreement with shell model generally better than a factor of 2

Neutron Spectroscopic Factor – Ca, Ti, Cr isotopes Large fragmentation of states spreading over the energy space in experiment, but shell model predicts mainly single particle states

The fragmentation is more

• bvious when we compare the

N=27 and N=29 isotones Fragmentation of the levels increases when more protons are added Calculations of SFs for Ti and Cr  Time consuming

• using FPD6PN in MSU_HPC

by Hang Liu (Oxbash)

• using GXPF1A by M. Horoi

(m-matrix code -- Antoine)  similar results

Fragmentation of the single particle strength for N=27 and N=29

Phoenix Dai – DNP 07’-- CEU poster section (DA00017)

Neutron Spectroscopic Factors for Ni isotopes

• M. Horoi

GXPF1A Complete basis

SF values agree to factor of 2  cannot distinguish between two interactions Data uncertainties: 20-30 % Interactions for gfp shell still need improvements

XT

• GXFP1A with full fp model space

does not require 56Ni shell closure  CPU intensive

• XT interaction provides a fast

way to predict the spectroscopic properties of these nuclei.

states predicted < 3MeV

Nucleon knockout Measurements of Spectroscopic Factors (e,e’p)

Lapikas, NPA 553, 297c (1993) Gade, PRL 93, 042501 (2004) Tsang et al, PRL 95, 222501 (2005)

(e,e’p): Proton SF values deduced from nuclei near closed shells are suppressed by 30-40% compared to IPM

G.J.Kramer et al., Nucl. Phys. A 679, 267 (2001)

Quenching observed from (e,e’p) and knockout reactions

• J. Lee et al, Phys. Rev. C 73 , 044608 (2006)

As long as a systematic approach is used, relative SF can be obtained reliably over a wide range of nuclei  Correlation is beyond the residual interactions employed in the shell model.

p-rich n-rich

Reduced spectroscopic factors from transfer reactions

• Consistent with proton SF

studied with (e,e’p) reactions

34Ar

p(34Ar,d)33Ar & p(46Ar,d)45Ar

Inverse kinematics at 35MeV/u:

Neutron transfer reactions for neutron rich and proton rich Ar isotopes

NSCL Expt 05133 (Oct19-30, 2007)

p-rich n-rich

• J. Lee et al, Phys. Rev. C 73 , 044608 (2006)

Schematics of setup with HiRA and S800

Expt 05133 : Neutron transfer reactions for neutron rich and proton rich Ar isotopes

p(34Ar,d)33Ar & p(46Ar,d)45Ar

Inverse kinematics at 33 MeV/A:

4x CsI(Tl) 4cm

32 strips v. (front)

Beam Si-DE 65 mm

32 strips v (front)

Si-E 1.5 mm pixel

32 strips h. (back)

• 20 Telescopes
• 62.3 x 62.3 mm2 Active Area
• strip pitch 1.8 mm
• 1024 Pixels per telescope

High resolution in energy, position and dE-E.

PID from previous experiment

HiRA collaborators

NSCL Bill Lynch; Betty Tsang; Vladimir Henzl; Daniela Henzlova; Andy Rogers; Micha Kilburn; Sun Zhiyu; Alisher Sanetullaev; Daniel Coupland; Mike Youngs; Jenny Lee; Daniel Bazin; Mauricio Portillo; Marc Hausmann; Len Morris WU in St. Louis Lee Sobotka; Bob Charity; Jon Elson Indiana University Romualdo Desouza; Sylvie Hudan Western Michigan University Mike Famiano; Alan Wousma LANL Mark Wallace ORNL Dan Shapira Rutgers University Jolie Cizewski; Bill Peters; Patrick O'Malley University of Tennesee Kate Jones; Kyle Schmitt; Andy Chae; Brian Moazen INFN, Catania, Italy Giuseppe Verde

NSCL experiment by Paul Mantica’s group: Small magnetic moment of 57Cu suggests significant shell- breaking at N=28  56Ni core is not doubly-magic

(PRL 96, 102501 (2006))

Is 56Ni doubly magic ? (Shell-breaking at N=28 subshell)

Two shell structures with different interactions for unstable 56Ni nucleus:

• 56Ni as an inert core
• All 28 protons and

28 neutrons are inside the core

• 40Ca as an inert core
• 8 valence protons

and 8 neutrons are

• utside the core

Use SF to test SM Interactions:

Use transfer reactions (d,p) and (p,d) to study neutron SF for Ni isotopes with neutron outside 56Ni  Comparison of the data to model

predictions may distinguish the two interactions.

Analyzed ~ 381 angular distributions

N Z

A national user facility for rare isotope research and education in nuclear science, astro-nuclear physics, accelerator physics, and societal applications 282 employees, incl. 51 undergraduate and 50 graduate students, 24 faculty

(as of March 05)

User group of over 600 CCF users

The National Superconducting Cyclotron Laboratory

@Michigan State University

ADWA via TWOFNR

(Tostevin)

Soper-Johnson Adiabatic Approximation to take care of d-break-up effects. Use global p and n

• ptical potential with

standardized parameters (CH89) n-potential : Woods- Saxon shape ro=1.25 fm & ao=0.65; depth adjusted to experimental binding energy. Include finite range & non-locality corrections

12C(d,p)13Cgs

SF=0.75+0.10; SF(SM) = 0.62

Liu et al, PRC 69, 064313 (2004)

Apply the technique to a large data set

Deduced Spectroscopic factors constrained by Hartree-Fock calculations

No a priori justification to adopt fixed geometry for n-bound states with ro=1.25 fm and ao=0.65 fm  Constrain the transferred neutron orbital rms radii with Hartree-Fock (HF) calculations

• 1. Change the rms radius of the transferred neutron

 15 % reduction in the spectroscopic factors

 Constrain the geometry of the nucleon optical potential with the target by HF calculations through target density

• 2. Adopt the global potentials derived from nuclear matter

effective nucleon-nucleon potential (JLM)

 Another 15 % reduction in the spectroscopic factors

p-rich n-rich

Reduced spectroscopic factors from transfer reactions

46Ar 34Ar

NSCL experiment (done in Oct 2007) Neutron transfer reactions for neutron rich and proton rich Ar isotopes

Obtain spectroscopic factors

• f 46Ar(ΔS= -10.63 MeV) and

34Ar(ΔS=13.9 MeV)

SF values and trends should be the same independent of measurement methods, i.e. (e,e’p), nucleon knockout and transfer reactions should give same SF values.

Measurements of Spectroscopic Factors

Approved experiments : p(46Ar, d)45Ar; p(34Ar, d)33Ar – to study possible quenching effects in strong and weakly bound neutrons in rare isotopes.

Lee, PRC73, 044608 (2006); Gade, PRL 93, 042501 (2004)