Yongjiang Li. Supervisor: Prof. Wang Xu Shanghai Institute of applied physics, CAS ， China Collaborator: Prof. W.M. Snow Indiana university, USA. Outline. Section 0 collaborators Section I introduction of （ the motivation, apparatus, preliminary results ） Section II Introduction of
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Supervisor: Prof. Wang Xu
Shanghai Institute of applied physics, CAS，China
Collaborator: Prof. W.M. Snow
Indiana university, USA
Section 0 collaborators
Section I introduction of
（the motivation, apparatus, preliminary results）
Section II Introduction of
（the motivation, proposed apparatus, SLEGS, systematic effect,plan）
Section III Conclusion of NPD Gamma and
J.David Bowman,1 Roger D. Carlini,2 Timothy E. Chupp,3 Wangchun Chen,4, Silviu Corvig,6 Mikayel Dabaghyan,6 Dharmin Desai,7 Stuart J. Freedman,8 Thomas R. Gentile,5 Michael T. Gericke,9 R. Chad Gillis,9 Geoffrey L. Greene,7,10
F. William Hersman,6 Takashi Ino,11 Takeyasu Ito,7 Gordon L. Jones,12 Martin Kandes,3 Bernhard Lauss,8 Mark Leuschner,4
Bill Losowki,13 Rob Mahurin,7 Mike Mason,6 Yasuhiro Masuda,11 Jiawei Mei,4 Gregory S. Mitchell,1 Suguro Muto,11 Hermann Nann,4 Shelley Page,9 Seppo Pentilla,1 Des Ramsay,9,14 Satyaranjan Santra,15 Pil-Neyo Seo,16 Eduard Sharapov,17 Todd Smith,18 W.M. Snow,4 W.S. Wilburn,1 Wang Xu,19 Vincent Yuan,1 Hongguo Zhu,6
1 Los Alamos National Laboratory, Los Alamos, NM 87545
2 Thomas Jefferson National Accelerator Facility, Newport News, VA 23606
3 Dept. of Physics, Univ. of Michigan, Ann Arbor, MI 48109
4 Dept. of Physics, Indiana University, Bloomington, IN 47408
5 National Institute of Standards and Technology, Gaithersburg, MD 20899
6 Dept. of Physics, Univ. of New Hampshire, Durham, NH 03824
7 Dept. of Physics, Univ. of Tennessee, Knoxville, TN 37996
8 Univ. of California at Berkeley, Berkeley, CA 94720
9 Dept. of Physics, Univ. of Manitoba, Winnipeg, Manitoba, R3T 2N2 Canad
10 Oak Ridge National Laboratory, Oak Ridge, TN 37831
11 High Energy Accelerator Research Organization (KEK), Tsukuba, Ibaraki, Japan
12 Dept. of Physics, Hamilton College, Clinton, NY 13323
13 Indiana University Cyclotron Facility, Bloomington, IN 47408
14 TRIUMF, Vancouver, British Columbia V6T2A3 Canada
15 Bhabha Atmoic Research Center, Mumbai, India
16 Dept. of Physics, North Carolina State University, Raleigh, NC 27695
17 Joint Institute of Nuclear Research, Dubna, Russia
18 Dept. of Physics, Univ. of Dayton, Dayton, OH 45469-2314
19Shanghai Institute of applied physics, Shanghai, China
interacts through strong NN force, mediated by mesons |m>=|qq>+…
Interactions have long (~1 fm) range, QCD conserves parity
If the quarks are close, the weak interaction can act, which violates parity. Relative strong/weak amplitudes: ~ [g2/m2] / [e2/m2W]~106
Quark-quark weak interaction induces NN weak interaction
Visible using parity violation
q-q weak interaction: an “inside-out” probe of strong QCD
~1/100 fm range
W and Z boson exchange
Nucleon interaction takes place on a scale of 1 fm -- short range repulsion. Due to the heavy exchange particles, the range of W± and Z0 is 1/100 fm, weak interaction probes quark-quark interaction and correlations at small distances.
At low energies N-N weak interaction modeled as meson exchange with one strong PC vertex, one weak PV vertex.
The weak PV couplings contribute in various mixtures and a variety of observables:
W and Z boson exchange
DDH - Model
Desplanque, Donohue, Holstein 1980
NPDGamma aims to measure the correlation between the neutron spin and the direction of the emitted photon in neutron-proton capture at low momentum transfer.
fp1 - 0.12 hr1 - 0.18 hw1 x 107
Polarized Laser Light
The rapid reversal of the neutron spin is important in the reduction of systematic effects.
drifts in detector efficiencies.
● 3π acceptance
● 48 crystals CsI (Tl) arranged in 4 rings
surrounding the LH2 target
● Current-mode experiment
● γ-rate ~100MHz (single detector)
● (15 ×15 × 15) cm3 CsI (Tl) crystals
useful range 1-15 meV
Point target and point detector:
Spin Flip Efficiency:
Gamma Energy Deposition：
The first phase of the experiment was completed in 2006 at LANSCE.
Aγ,UD = (−1.1 ± 2.1(stat.) ± 0.2(sys.)) × 10−7
Aγ,LR = (−1.9 ± 2.0(stat.) ± 0.2(sys.)) × 10−7
● activation of materials,
e.g. cryostat windows
● in magnetic field gradients
L-R asymmetries leaking into
● U-D angular distribution
(np elastic, Mott-Schwinger...)
scattering of circularly polarized
●gammas from magnetized iron
(cave walls, floor...)
→ estimated and expected to be negligible
Neutron time-of-flight from pulsed source (msec, En1/t2)
2. Scattering of polarized gamma rays by magnetized iron
Neutron Spin = +/-
•In the (polarized)n+p->D+gamma reaction, the gamma has a small circular polarization
•the scattering cross section is spin dependent.
CsI Detector Array
Liquid H2 Target
H2 Vent Line
H2 Manifold Enclosure
Magnetic Field Coils
1. The asymmetry is mainly defined by Δ I=0,2 parity-violating interactions.
2. The relationship between the asymmetry and the meson-nucleon coupling constants is energy dependent.
3.The best way to determine the ΔI=2 interaction h2ρ.
C.-P. Liu, PRC 69, 065502 (2004)
At present, there are not believable theory calculation for photon energy above12MeV.
The theory predicted value of Aγis :
3He gas ion chamber
4He gas ion chamber
Circular Polarized γ
♣ the detectors will operated in current model
♣ Graphite is used as neutron moderator.
♣ the 3He gas ion chamber Will absorb the most of neutrons, but 4He don’t. ♣ the gamma cross section on 3he and 4He is almost exactly the same.
♣ 6Li is used to prevent neutrons from going into the γ detector.
We plan to simulate the GammDNP reaction in the Geant4 code. We are building the geometry in the code.
In the near future, we will construct the SLEGS.
Using a polarized laser, a polarized γray can be generated.
When we change the polarization of the laser, the polarization of γray reverse .
▶ how close to “perfect” circular polarization
▶ beam flux
▶ frequency of helicity change
▶change of I(x, y,E, θx, θy) when switch
the polarization of the laser
▶ the polarized electrons in electron beam
▶ the efficiency of laser- electron collision
▶noise in intensity
▶ I(x, y,E, θx, θy)
▶ elliptical polarization
▶ windows laser pass through
▶the magnetic field
We preliminarily list some of the systematic effects :
★ the NPDGamma experiment have completed its first phase at LANSCE and will start its second data taking in early 2010 at ORNL.
★The GammaDNP experiment is essential to determine the constant of
h2ρ. And the relationship of parity-violating Asymmetry and coupling
constants is energy dependent.
★based on the SLEGS, it is possible to perform the GammaDNP experiment in the future.
★ The cooperation with NPDGamma group wil help us to draw valuable experience , and continue cooperation for the GammaDNP.