sept. 1, 2009 1 few-body 19 bonn, germany few-body studies at hi s sean stave duke university &...

Sept. 1, 2009 1Few-Body 19Bonn, Germany

Few-body studies at HISSean StaveDuke University & Triangle Universities Nuclear Laboratory (TUNL)

And Mohammad Ahmed, Henry Weller

Supported in-part by DOE grant DE-FG02-97ER41033

www.tunl.duke.edu www.tunl.duke.edu/higs/


Few-body experiments at HIS

Exploring A=2 and 3

Photodisintegration of the Deuteron & 3He

• Importance

• Theoretical understanding of A=2,3 systems

• Global state of the experiments

• The role HIGS plays in the understanding of these systems

• What is on the horizon for HIGS


Overview of A=2

The BBN Importance

“Baryometer”

The Deuteron

Ideal Laboratory for the study of 2-bodyNP system

• Test of EFT and PM Calculations

TargetBeam

Fundamental Sum Rules

d

d


Understanding Few-Nucleon Systems

2H, the simplest of Few-Body Systems

The Theoretical Framework, A=2

• Potential Model• Effective Field Theory• Sum Rules for Deuteron: Gerasimov-Drell-Hearn (GDH) & Forward Spin Polarizability (0)


• High precision NN-potentials, MEC, RC and degrees of freedom

Potential Model Calculations [H. Arenhovel, M. Schwamb et al.]

The Pion-less Effective Field Theory Approach (EFT) [M. Savage, J-W. Chen & G. Rupak]

• E1 is computed up to N4LO and M1 is calculated up to N2LO, n-p radiative capture cross section predicted to an accuracy of 1% at CM energies ~ 1 MeV

Most accurate theory describing 2-Nucleon system, Minimal data exist to test the predictions in this energy region

The A=2 Theoretical Framework


The Experimental Effort at HISFew-Body Studies at TUNL are carried out at HIS

Duke Free-Electron Laser Laboratory(HIS)


High Intensity Gamma-Ray Source:

Booster Injector

LINAC

RF Cavity

Mirror

Optical Klystron

FEL

HIS -ray beam generation


HIS Parameters

•Circularly and Linearly Polarized nearly monoenergetic -Rays from 2 to 60 MeV (90 MeV in the next 1 to 2 years)

•Total Gamma-Ray Flux ~ 108 to 109 /s


All experiments were performed using linearly polarized beams

SchreiberTornowSawatskyBlackston

SawatskyBlackston Ahmed

Liquid Scintillating Detectors

Liquid Scintillating Detectors in Blowfish Array

Li-Glass Detectors in an Array

•(135°) E = 3.58 MeV Eric Schrieber et al., 2000•(90°) E = 2.39 to 4.05 MeV Werner Tornow et al., 2003•; E = 4 to 10 MeV Brad Sawatsky et al., 2005•(90°) E = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2007•; E = 14 and 16 MeV Matthew Blackston et al., 2007•; total E = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2008

A=2 Experiments at HIS


Status of the “baryometer”

• Very little data in energy region for BBN


d(,n)p Cross section Expansion

(M1)(E1)

Polarized beam, unpolarized target

Photon analyzing power measurement is proportional tothe %E1 contribution to the total cross section


Tornow et al.[PLB 574, 8 (2003)]

4-neutron detectors at apolar angle of 90 degrees andazimuthal angles of0,90,180, and 270 degrees

PRC 61, 061604 (2000)

A=2 Results at HIS

Curves from EFT (Rupak et al.)

Excellent agreement between data and PM and EFT


No significantd-wave contributionsare presentat these low energies

4.0 MeV

3.5 MeV

2.44 MeV

d(,n)p at HIS: Ahmed et al.


Sum Rules for the Deuteron

GDH :Arenhoevel et al.

Spin-flip part of forward Compton scattering amplitude:


GDH on the deuteron: Theory

Arenhoevel et al. [NPA 631, 612c (1998)]

Without relativistic corrections

Withrelativistic corrections

Negative at low energies Crosses zero

at low energies


Cross section difference expansion

Polarized beam, polarized target

If ignore d-waves and splitting of p-waves at low energies then

]


A=2 Global Impact

First-ever indirect determination of the GDH Sum Rulefor Deuteron at low energies: -603 ± 43 b (Fit from thr. to 4 MeV, integrated from thr. to 6 MeV)

Remember =-3(M1)

Ahmed et al. [PRC 77, 044005 (2008)]


A=2 GDH Comparison: Data and Theory

• Theory and Data integrated from threshold to 6 MeV• Data: -603 ± 43 b• Arenhoevel: -627 b

• -3M1: -662 b

• Experimentally confirmed negative value at low energy

Ahmed et al. [PRC 77, 044005 (2008)]


• 88-cell Liquid Scintillating detector array

• 25% of 4 coverage

• = 22.5 to 157.5 degrees

Blowfish

A=2 Results at HIS


Blackston et al. [PRC 78, 034003 (2008)]

d(,n)p: Weller/Blackston’s Results

16 MeV

•Cross section and analyzing power at 16 MeV as a function of angle compared with Schwamb/Arenhoevel potential model •High quality of data allowed a fit using 7 reduced transition matrix element amplitudes (phases fixed by np elastic scattering, SAID)


First-ever observation of the splittings of the E1 (p-wave) amplitudes in low energy deuteron photo-disintegration [PRC 78, 034003 (2008)]

d(,n)p: Weller/Blackston’s Results16 MeV

Compared with Schwamb/Arenhoevel Potential Model

Value if nop-wave splitting

Note: d-wave results negligible and consistent with theory


A=2 Global ImpactFirst-ever observation of the p-wave splittings andconfirmation of the relativistic corrections in the theory

[PRC 78, 034003 (2008)]


Sum Rules for the Deuteron

Forward Spin-Polarizability:

NLO, EFT calculation by X. Ji et al.

Spin-flip part of forward Compton scattering amplitude:


A=2 0 Comparison: Data and Theory

First-ever indirect determination of 0 for deuteron at low energies

Data integrated from threshold to 6 MeV• Data: 3.75 ± 0.18 fm4

• Ji-LO: 3.762 fm4

• Ji-NLO: 4.262 fm4

• Arenhoevel: 4.1 fm4

Ahmed et al. [PRC 77, 044005 (2008)]


3He, the simplest of Few-body Systems with3NF and no excitation spectrum

•3He breakup•Two-body•Three-body

System being considered

What is our understanding of Few-Nucleon systems?


• Photodisintegration of 3He between 7 and 20 MeV

• Total and differential Cross Section

• Total cross section for the 2-body breakup from 7 to 20 MeV, Tornow et al.

• Total and differential cross sections for the 3-body breakup, 12.8, 13.5, and 14.7 MeV, Perdue et al.

The A=3 Experiments at HIS


The A=3 Theoretical FrameworkRecent efforts in understanding 3-body systems[Deltuva, Fonseca, Sauer]

• Coulomb Interaction in the 2- and 3-body photodisintegration channels • CD-Bonn + , with isobar mediating an effective 3NF and 2-, 3-nucleon currents, and still consistent with 2NF

• Still has issues at low-energies (3 Nucleon Analyzing Power Puzzle still stands!)

The problem is also being worked upon by

[Witala, Glockle, Nogga, and Golak, et al.]


Current Status of the 3He breakup cross section

• No measurement that is consistent across the energy range

• Clearly calls for a set of measurements with the same experimental conditions across the energy range

2-body

3-body

total

Shima & Nagai[PRC 73, 034003 (2006)]Compared with previous dataand AV18 and AV18+Urbana IX

Factor of 3 below theory


Data are still under analysis for absolute normalization

• High Pressure 3He/Xe cell

A=3 at HIS: 2-body breakup of 3He, Tornow et al.

Two-body peaks clearly separated


12.8, 13.5, and 14.7 MeV

3He 3-body Breakup at HIS: Weller, Perdue et al.


3He 3-body Breakup: Theoretical Framework

No coulomb interactionWith coulomb interaction

No sensitivity to coulomb interaction in the analyzing power

Deltuva et al.[PRC 72, 054004 (2005)]


Weller, Perdue et al. Initial Results

From an APS talk by B. Perdue

•Phase-Space (PS) to PS + NP transition near 12.8 MeV•About 25% below theory

- HIS Data- Deltuva- 3-body phase space


Summary

What have we accomplished?

• Confirmation of PM/EFT for the deuteron near BBN region

•First determination of the splitting of the p-waves in the photodisintegration of the deuteron

• First confirmation of GDH sum rule for the deuteron•Confirmed large negative strength•Confirmed positive going above 8 MeV and that it arises fromthe splitting of the p-waves

• First determination of the 0 sum rule for deuteron

•Precision 3-body photodisintegration cross section for 3He disagree with state-of-the-art theory at low energies


New era of precision measurements at HIS - PAC-09 has approved the following experiments for the next two years:

• Continue to measure deuteron photodisintegration cross section at lower energies (below 2.4 MeV) (Using OTPC)

• Direct measurements of the GDH on deuteron

• Compton scattering on the deuteron

• Measurement of two- and three-body cross sections of + 3He

• GDH Sum rule for 3He

• Cross section measurement of + 4He

Future plans at HIS


•Calvin Howell et al.•Werner Tornow et al. •Henry Weller et al.•Ying Wu et al.

Acknowledgments

Thank you!


• Additional slides


Weller, Perdue et al. Initial Results

• Results from Gorbunov (1976) coarsely binned but consistent with current results

A. N. Gorbunov, Proc. Of the P.N. Lebedev Phys. Inst., p. 1 (1976)

8-12 MeV

12-16 MeV


A=2 Introduction

Few-Nucleon Systems and BBN Network

n-p capture reaction rate becomes a “baryometer”

WMAP determines

Light-element abundances depends on

and 11 nuclear reaction rates

(d,p)

(p,γ)(d,n)

(n,γ)

(n,p)

(d,p)


Understanding the photodisintegration of the deuteron

In 1936, H. A. Bethe and R. F. Bacher wrote …

“… the transition from the ground state to the state of positive energy . . . can be produced by a magnetic moment, this ‘magnetic dipole’ photoelectric effect is, however, small compared to the ‘electric dipole’ effect …, except for very low energies . . . the final state must be a P-state” [ Rev. Mod. Phys. 8, 82-229 (1936) ]


In the near-threshold region, the photodisintegrationcross section can be expanded in terms of S and P waveamplitudes. We can ignore the D-waves andThe P-wave splittings (evidence will be presented soon) :

Photon analyzing power measurement is proportional tothe %E1 contribution to the total cross section

The A=2 Experiments at HIS

Bethe, 1936


A=2 Global Impact (Ahmed et al.)

•First-ever indirect determination of 0 for deuteron at low energies

Ahmed et al. [PRC 77, 044005 (2008)]

sept. 1, 2009 1 few-body 19 bonn, germany few-body studies at hi s sean stave duke university &...

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