few body studies at hi g s l.
Download
Skip this Video
Loading SlideShow in 5 Seconds..
Few-body studies at HI g S PowerPoint Presentation
Download Presentation
Few-body studies at HI g S

Loading in 2 Seconds...

play fullscreen
1 / 41

Few-body studies at HI g S - PowerPoint PPT Presentation


  • 107 Views
  • Uploaded on

Few-body studies at HI g S. Sean Stave Duke 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/.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

Few-body studies at HI g S


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
few body studies at hi g s
Few-body studies at HIgS

Sean Stave

Duke 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 hi g s
Few-body experiments at HIgS

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
Overview of A=2

The Deuteron

Fundamental

Sum Rules

The BBN Importance

Ideal Laboratory for

the study of 2-body

NP system

“Baryometer”

  • Test of EFT and PM
  • Calculations

d

Target

Beam

d

understanding few nucleon systems
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 (g0)
the a 2 theoretical framework
The A=2 Theoretical Framework

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

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

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 experimental effort at hi g s
The Experimental Effort at HIgS

Few-Body Studies at TUNL are carried out at HIgS

Duke Free-Electron Laser Laboratory

(HIgS)

hi g s g ray beam generation
HIgS g-ray beam generation

RF Cavity

Optical Klystron

FEL

Booster Injector

Mirror

LINAC

High Intensity Gamma-Ray Source:

hi g s parameters
HIgS Parameters
  • Circularly and Linearly Polarized nearly monoenergetic g-Rays
  • from 2 to 60 MeV (90 MeV in the next 1 to 2 years)
  • Total Gamma-Ray Flux ~ 108 to 109g/s
a 2 experiments at hi g s
A=2 Experiments at HIgS
  • S(135°) Eg = 3.58 MeV Eric Schrieber et al., 2000
  • S(90°) Eg = 2.39 to 4.05 MeV Werner Tornow et al., 2003
  • s(q); S(q) Eg = 4 to 10 MeV Brad Sawatsky et al., 2005
  • S(90°) Eg = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2007
  • s(q); S(q) Eg = 14 and 16 MeV Matthew Blackston et al., 2007
  • s(q); stotalEg = 2.44 to 4.0 MeV Mohammad Ahmed et al., 2008

All experiments were performed using linearly polarized beams

Liquid Scintillating

Detectors in

Blowfish Array

Li-Glass

Detectors in

an Array

Liquid Scintillating

Detectors

Schreiber

Tornow

Sawatsky

Blackston

Sawatsky

Blackston

Ahmed

status of the baryometer
Status of the “baryometer”
  • Very little data in energy region for BBN
d g n p cross section expansion
d(g,n)p Cross section Expansion

Polarized beam, unpolarized target

(M1)

(E1)

Photon analyzing power measurement is proportional to

the %E1 contribution to the total cross section

a 2 results at hi g s
A=2 Results at HIgS

Tornow et al.

[PLB 574, 8 (2003)]

Excellent agreement between data and PM and EFT

4-neutron detectors at a

polar angle of 90 degrees and

azimuthal angles of

0,90,180, and 270 degrees

PRC 61, 061604 (2000)

Curves from EFT (Rupak et al.)

d g n p at hi g s ahmed et al
d(g,n)p at HIgS: Ahmed et al.

No significant

d-wave

contributions

are present

at these low

energies

4.0 MeV

3.5 MeV

2.44 MeV

sum rules for the deuteron
Sum Rules for the Deuteron

Spin-flip part of forward Compton scattering amplitude:

GDH :

Arenhoevel et al.

gdh on the deuteron theory
GDH on the deuteron: Theory

With

relativistic

corrections

Without

relativistic

corrections

Negative at

low energies

Crosses zero

at low energies

Arenhoevel et al.

[NPA 631, 612c (1998)]

cross section difference expansion
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
A=2 Global Impact

First-ever indirect determination of the GDH Sum Rule

for Deuteron at low energies: -603 ± 43 mb (Fit from thr. to 4 MeV, integrated from thr. to 6 MeV)

Remember Ds =-3s(M1)

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

a 2 gdh comparison data and theory
A=2 GDH Comparison: Data and Theory
  • Theory and Data integrated from threshold to 6 MeV
    • Data: -603 ± 43 mb
    • Arenhoevel: -627 mb
    • -3sM1: -662 mb
  • Experimentally confirmed negative value at low energy

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

a 2 results at hi g s19
A=2 Results at HIgS

Blowfish

  • 88-cell Liquid Scintillating
  • detector array
  • 25% of 4p coverage
  • q = 22.5 to 157.5 degrees
d g n p weller blackston s results
d(g,n)p: Weller/Blackston’s Results

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

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)
d g n p weller blackston s results21
d(g,n)p: Weller/Blackston’s Results

16 MeV

First-ever observation of the splittings of the

E1 (p-wave) amplitudes in low energy

deuteron photo-disintegration

[PRC 78, 034003 (2008)]

Note: d-wave results negligible and consistent with theory

Value if no

p-wave splitting

Compared with Schwamb/Arenhoevel Potential Model

a 2 global impact22
A=2 Global Impact

First-ever observation of the p-wave splittings and

confirmation of the relativistic corrections in the theory

[PRC 78, 034003 (2008)]

sum rules for the deuteron23
Sum Rules for the Deuteron

Spin-flip part of forward Compton scattering amplitude:

Forward Spin-Polarizability:

NLO, EFT calculation by X. Ji et al.

a 2 g 0 comparison data and theory
A=2 g0 Comparison: Data and Theory

First-ever indirect determination of g0 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)]

what is our understanding of few nucleon systems
What is our understanding of Few-Nucleon systems?

3He, the simplest of Few-body Systems with

3NF and no excitation spectrum

System being considered

  • 3He breakup
    • Two-body
    • Three-body
the a 3 experiments at hi g s
The A=3 Experiments at HIgS
  • 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 theoretical framework
The A=3 Theoretical Framework

Recent efforts in understanding 3-body systems

[Deltuva, Fonseca, Sauer]

  • Coulomb Interaction in the 2- and 3-body
  • photodisintegration channels
  • CD-Bonn + D, with D 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 3 he breakup cross section
Current Status of the 3He breakup cross section

Shima & Nagai

[PRC 73, 034003 (2006)]

Compared with previous data

and AV18 and AV18+Urbana IX

2-body

  • 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

3-body

total

Factor of 3

below theory

a 3 at hi g s 2 body breakup of 3 he tornow et al
A=3 at HIgS: 2-body breakup of 3He, Tornow et al.
  • High Pressure 3He/Xe cell

Data are still under analysis for absolute normalization

Two-body peaks clearly separated

3 he 3 body breakup theoretical framework
3He 3-body Breakup: Theoretical Framework

No coulomb

interaction

With coulomb

interaction

No sensitivity to

coulomb interaction

in the analyzing

power

Deltuva et al.

[PRC 72, 054004 (2005)]

weller perdue et al initial results
Weller, Perdue et al. Initial Results

From an APS talk by B. Perdue

- HIgS Data

- Deltuva

- 3-body phase space

  • Phase-Space (PS) to
  • PS + NP transition near
  • 12.8 MeV
  • About 25% below theory
summary
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 g0 sum rule for deuteron
  • Precision 3-body photodisintegration cross section for 3He
  • disagree with state-of-the-art theory at low energies
future plans at hi g s
Future plans at HIgS

New era of precision measurements at HIgS - 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 g + 3He
  • GDH Sum rule for 3He
  • Cross section measurement of g + 4He
acknowledgments
Acknowledgments
  • Calvin Howell et al.
  • Werner Tornow et al.
  • Henry Weller et al.
  • Ying Wu et al.

Thank you!

weller perdue et al initial results37
Weller, Perdue et al. Initial Results
  • Results from Gorbunov (1976) coarsely binned but consistent with current results

8-12 MeV

12-16 MeV

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

a 2 introduction
A=2 Introduction

(

(

(

(

(

(

)

)

)

)

)

)

d

d

d

n

n

p

γ

p

n

p

p

γ

,

,

,

,

,

,

Few-Nucleon Systems and BBN Network

Light-element abundances depends

on

WMAP determines

and11 nuclear reaction rates

n-p capture reaction rate becomes a “baryometer”

understanding the photodisintegration of the deuteron
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) ]

the a 2 experiments at hi g s
The A=2 Experiments at HIgS

In the near-threshold region, the photodisintegration

cross section can be expanded in terms of S and P wave

amplitudes. We can ignore the D-waves and

The P-wave splittings (evidence will be presented soon) :

Bethe, 1936

Photon analyzing power measurement is proportional to

the %E1 contribution to the total cross section

a 2 global impact ahmed et al
A=2 Global Impact (Ahmed et al.)
  • First-ever indirect determination of g0 for deuteron at low energies

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