P12 Tornow

Recent Few-Body Activities
at TUNL and HIγS
Werner Tornow
Duke University & Triangle Universities Nuclear Laboratory

Content
A. TUNL: Polarized Neutrons
1. n-p A y
(θ) at E n
=12 MeV
2. n-d A y
(θ) between E n
=19 and 22.5 MeV
3. n- 3 He A y
(θ) between E n
=2.26 and 5.54 MeV
B. HIγS: Linearly Polarized Gamma-rays
1. γ-d breakup photon analyzing power Σ L
(θ) from 2.4 to 10 MeV
2. γ- 3 He three-body breakup photon analyzing power Σ L
(θ) at 15 and 12.8 MeV

Nijm PWA
n-p

2
R. Machleidt: πNN coupling constant g / π
π
4
≥14.0
to correctly reproduce
the quadrupole moment Q of the deuteron [0.276(2) fm 2 ].
Nijmegen:
VPI:
2
2
g / π 0 =13.47+-0.11 / π
π
4
g =13.54+-0.05
π 4
2
π / 4
2
g / π ≈13.3 π
4
π 0
g ≈ 13.9
g
2
π
/ 4π
≥14.0
creates problems for the 3 P 0
NN phase shifts (too large!) at low
energies.
2
Assume charge splitting of πNN: /4π
13. 6
3
P 0
and Q are o.k.
2
g and g π
+ − / 4π
= 14. 4
π
0 =

Nijm PWA
CD Bonn
2
2
g / 4π g / 4π
π /
0
π +−
13.6 / 13.6
13.6 / 14.0
13.6 / 14.4
2
All low-energy n-p A Y
(θ) data require g π
+ − / 4π
≥14.
0

n-d
Witala
n-d
n-d

.… Fit
AV18 Witala
A y
θ c.m.

AV18 Witala
…. Fit

TUNL data
Pisa calc.
p- 3 He p- 3 He

TUNL data
Pisa calc.
p- 3 He p- 3 He

NN Interactions in 3N and 4N Systems
d
d
3N:
p +
n
p
1 pn + 1pp
n +
n
p
1 pn + 1 nn
3
He
3
He
p +
p
p
n
1 pn + 2 pp n +
p
p
n
2 pn + 1 nn
4N:
3
H
3
H
n +
n
n
p
1 pn + 2 nn p +
n
n
p
2 pn + 1 pp

Fonseca
…. Hale RM
A y
θ c.m.
180

HIγS (High-Intensity Gammaray
Source) at Duke/TUNL
early Mono-energetic γ-rays
unable Energies
nergy resolution selected by collimator size
inearly and Circularly Polarized γ-rays
igh Beam Intensities

Upgraded Facility
(3a) Building extension
+ booster radiation shielding
(2) 1.2-GeV Booster Injector
(3b) LTB Transfer Line
(3c) BTR Transfer Line
(1) RF System with HOM Damping
(3e) Radiation shielding
over SR east arc
3(d) Modifications to SR NSS

pgrade Schedule
Commissioning of Booster July-August 2006
Commissioning of Booster and Ring with OK-4—September-November
Nuclear Physics Program begins-December, 2006
Dec. 06 May 07 Linear Pol.- Below 65 MeV, >2x10 8 γ/s
Sept. 07 Circ. Pol. Up to 110 MeV, >10 8 γ/s
These are TOTAL intensities. Beam on target is:
TOTAL x 1.5 x % resolution (ex. 5% res. at 100 MeV: 7.5 x 10 6 γ/s)
Expect to have energies up to 160 MeV by Spring 09

Few-Body Physics @ ΗΙγS
esolve long standing cross section
problems.
erform Precision tests of few-body theory
including EFTs and 3-body force models
using polarized beams and targets.
easure fundamental properties such as the
electric polarizabilities for 3 He and 4 He via

Two-Body System
• Gamma-Deuteron Breakup at Low Energies

Detector Geometry
: 3 He scintillator
: neutron detector
o
θ = 90
(lab)
2
1
ε (θ )
: Asymmetry
N
H
− NV
( θ ) = = p Σ ( θ )
N + N
ε
γ L
H
p : γ-ray linear polarization
y
Σ
L
( ) θ
V
: Analyzing power
3
4

W. Tornow, C. Howell, V. Litvinenko, J. Kelley, et al.

The cross section and the linear analyzing power

Blowfish Detector Array
Norum/Weller

The Gerasimov-Drell-Hearn (GDH) Sum Rule for Deuteron
σ P/A
(E) are the total cross sections for the absorption of circularly polarized
photons on a target with spin Parallel/Antiparallel to the spin of the photon;
κ = anomalous magnetic moment (of the deuteron).
κ d
= -0.143 μ m
I GDH Predicted = 0.65 μb

THE GDH INTEGRAND FOR THE DEUTERON NEAR
PHOTODISINTEGRATION THRESHOLD
Contributions are expected from s-waves and p-waves (notation 2S+1 L J
)
M1 terms: 1 S 0
and 3 S 1
E1 terms: 1 P 1
, 3 P 0
, 3 P 1
, and 3 P 2
Expect the “spin-flip” E1 term 1 P 1
~ 0.
Then σ P
- σ A
= π/2k 2 { - 1 S 02
–3/2 3 S 12
- 3 P 02
–3/2 3 P 12
+ 5/2 3 P 22
}
Expect 3 P 0
~ 3 P 1
~ 3 P 2
, and 3 S 1
~ 0.
So that σ P
- σ A
= π/2k 2 { - 1 S 02
}
Also, with 3 S 1
~ 0 we have:
σ(M1) = π/6k 2 { 1 S
2
0
}
Which gives the result:
σ P
- σ A
= -3 σ(M1)

Tornow’s Group
Norum/Weller’s Group

Three-Body Photodisintegration
of 3 He
• Reaction: γ + 3 He p+ p + n
Q
= −7.72
MeV
• E γ =15 MeV
• Tornow’s Group

Detector Geometry
: 3 He scintillator
: neutron detector
o
θ = 90
(lab)
2
1
ε (θ )
: Asymmetry
N
H
− NV
( θ ) = = p Σ ( θ )
N + N
ε
γ L
H
p : γ-ray linear polarization
y
Σ
L
( ) θ
V
: Analyzing power
3
4

Deltuva et al.
γ+ 3 He n+p+p

Photon Analyzing Power for
3
He(γ,pp)n

Time-of-Flight vs. ΣE p Spectra
γ
n
γ
n

Time-of-Flight Spectra

Photon Analyzing Power for
3
He(γ,pp)n
• For neutrons in the energy range 1.23 to
4.80 MeV, σ-weighted average of the
photon analyzing power:
– Theoretical prediction: Σ L (θ n =90°) = 0.949
– Experimental result: Σ L (θ n =90°) = 0.95 ± 0.01

Three-Body Photodisintegration
of 3 He
• Target: 3 He-Xe gas scintillator
– 47 atm 3 He, 3 atm Xe
• Not enough stopping power for highenergy
protons: they don’t deposit all of
their energy: Edge effects:
Scintillator housing
γ-ray beam

Three-Body Photodisintegration
of 3 He
• Reaction: γ + 3 He p+ p + n
Q
= −7.72
MeV
• E γ =12.8 MeV
• Weller’s Group

The upgraded BLOWFISH array and a 6.5 cm gas cell
containing 2500 psi of 3 He was used to measure the
3
He(γ,n)pp reaction with 12.8 MeV linearly polarized γ
rays.

Two-Body Photodisintegration
of 3 He
• Reaction: γ + 3 He p + d
– Q = -5.49 MeV
• Observable: Total cross section
– Measured at E γ = 8.0, 9.0, 9.5, 10.0, 10.5,
11.0, 11.5, 12.0, 12.5, 13.0, 14.0, 15.0, and
16.0 MeV (13 energies)
– Previously measured using a variety of
techniques (bremsstrahlung photons, virtual
photons from e- 3 He scattering, pd capture via
detailed balance); results in disagreement

Cross Section for 3 He(γ,p)d

Cross Section for 3 He(γ,p)d
Deltuva et al.
with Coulomb
Naito et al.

Three- and Two-Body Signal
Distinction

Two-Body Photodisintegration
of 3 He
• Target: 3 He-Xe gas scintillator
– 34 atm 3 He, 14 atm Xe
• Increased Xe content to increase stopping
power for protons:
– Edge effects:
Scintillator housing
γ-ray beam

Setup for Flux Determination

γ-ray Production at HIγS
W
N
S
E
Electron beam for FEL
LINAC
Optical Klystron
γ-rays
Collimato
Electron beam for
Compton scattering
Optical beam reflected from
downstream cavity mirror
wo modes of operation:
o electron loss (E γ < 20 MeV)
lectron loss (E γ > 20 MeV)