Sept. 1, 2009 1 Few-Body 19 Bonn, Germany Few-body studies at HI S Sean Stave Duke University &...
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Transcript of 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/
Sept. 1, 2009 2Few-Body 19Bonn, Germany
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
Sept. 1, 2009 3Few-Body 19Bonn, Germany
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
Sept. 1, 2009 4Few-Body 19Bonn, Germany
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)
Sept. 1, 2009 5Few-Body 19Bonn, Germany
• 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
Sept. 1, 2009 6Few-Body 19Bonn, Germany
The Experimental Effort at HISFew-Body Studies at TUNL are carried out at HIS
Duke Free-Electron Laser Laboratory(HIS)
Sept. 1, 2009 7Few-Body 19Bonn, Germany
High Intensity Gamma-Ray Source:
Booster Injector
LINAC
RF Cavity
Mirror
Optical Klystron
FEL
HIS -ray beam generation
Sept. 1, 2009 8Few-Body 19Bonn, Germany
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
Sept. 1, 2009 9Few-Body 19Bonn, Germany
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
Sept. 1, 2009 10Few-Body 19Bonn, Germany
Status of the “baryometer”
• Very little data in energy region for BBN
Sept. 1, 2009 11Few-Body 19Bonn, Germany
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
Sept. 1, 2009 12Few-Body 19Bonn, Germany
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
Sept. 1, 2009 13Few-Body 19Bonn, Germany
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.
Sept. 1, 2009 14Few-Body 19Bonn, Germany
Sum Rules for the Deuteron
GDH :Arenhoevel et al.
Spin-flip part of forward Compton scattering amplitude:
Sept. 1, 2009 15Few-Body 19Bonn, Germany
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
Sept. 1, 2009 16Few-Body 19Bonn, Germany
Cross section difference expansion
Polarized beam, polarized target
If ignore d-waves and splitting of p-waves at low energies then
]
Sept. 1, 2009 17Few-Body 19Bonn, Germany
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)]
Sept. 1, 2009 18Few-Body 19Bonn, Germany
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)]
Sept. 1, 2009 19Few-Body 19Bonn, Germany
• 88-cell Liquid Scintillating detector array
• 25% of 4 coverage
• = 22.5 to 157.5 degrees
Blowfish
A=2 Results at HIS
Sept. 1, 2009 20Few-Body 19Bonn, Germany
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)
Sept. 1, 2009 21Few-Body 19Bonn, Germany
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
Sept. 1, 2009 22Few-Body 19Bonn, Germany
A=2 Global ImpactFirst-ever observation of the p-wave splittings andconfirmation of the relativistic corrections in the theory
[PRC 78, 034003 (2008)]
Sept. 1, 2009 23Few-Body 19Bonn, Germany
Sum Rules for the Deuteron
Forward Spin-Polarizability:
NLO, EFT calculation by X. Ji et al.
Spin-flip part of forward Compton scattering amplitude:
Sept. 1, 2009 24Few-Body 19Bonn, Germany
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)]
Sept. 1, 2009 25Few-Body 19Bonn, Germany
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?
Sept. 1, 2009 26Few-Body 19Bonn, Germany
• 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
Sept. 1, 2009 27Few-Body 19Bonn, Germany
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.]
Sept. 1, 2009 28Few-Body 19Bonn, Germany
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
Sept. 1, 2009 29Few-Body 19Bonn, Germany
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
Sept. 1, 2009 30Few-Body 19Bonn, Germany
12.8, 13.5, and 14.7 MeV
3He 3-body Breakup at HIS: Weller, Perdue et al.
Sept. 1, 2009 31Few-Body 19Bonn, Germany
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)]
Sept. 1, 2009 32Few-Body 19Bonn, Germany
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
Sept. 1, 2009 33Few-Body 19Bonn, Germany
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
Sept. 1, 2009 34Few-Body 19Bonn, Germany
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
Sept. 1, 2009 35Few-Body 19Bonn, Germany
•Calvin Howell et al.•Werner Tornow et al. •Henry Weller et al.•Ying Wu et al.
Acknowledgments
Thank you!
Sept. 1, 2009 37Few-Body 19Bonn, Germany
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
Sept. 1, 2009 38Few-Body 19Bonn, Germany
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)
Sept. 1, 2009 39Few-Body 19Bonn, Germany
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) ]
Sept. 1, 2009 40Few-Body 19Bonn, Germany
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