1. Polarized 3he target and the Nucleon Transverse Spin Structure
Yi Qiang
Jefferson Lab Hall-D
Polarized 3He Target and TMD
May 21, 1020

2. Polarized 3He Target and TMD
Outline
Hall-D staff scientist since Feb 2010.
This talk covers my previous work in Jefferson Lab Hall A as a PostDoc of Duke University:
Polarized 3He Target
First Neutron Transversity Experiment
Future 3He SIDIS in Jefferson Lab
Polarized 3He Target and TMD
5/21/2010

3. Why Polarized 3He Target ?
Polarized targets bring insights into nucleon spin structure, complimentary information to the nucleon form factors and many more …
Both polarized proton and neutron targets are necessary in flavor separation of nucleon structure.
3He and Deuteron are two good candidates for a neutron target. d
~90% ~1.5% ~8% S S’ D
An Effective Polarized Neutron Target!
Polarized 3He Target and TMD
5/21/2010

4. Ways to Polarize A 3He Target
Metastability-Exchange Optical Pumping
Developed early 1960s at Rice University
Used in MAINZ, DESY, NIKHEF, MIT-Bates …
Shorter polarization time: minutes
Lower pressure: mbar, needs compression
Mostly internal target
Spin-Exchange Optical Pumping
In use since early 1990s at SLAC
Used in SLAC, MIT-Bates, JLab, HIGS …
Higher pressure: 10 bar
Longer polarization time: 10 hours
Mostly external target
Polarized 3He Target and TMD
5/21/2010

5. Spin-Exchange Optical Pumping
Polarized
D1 Laser
Alkali Optical Pumping
Hybrid Spin-Exchange
K-He efficiency is much higher than Rb-He
K-Rb strongly coupled
K only solution is limited by the laser availability
Shorter spin-up time
10  4 hours
Higher in-beam polarization
40%  50% OR
Polarized 3He Target and TMD
5/21/2010

6. Polarized 3He Target in Jefferson Lab Hall A
230 oC
Polarized Laser
795 nm
F = 3”
Pumping Chamber
10 atm 3He
Some N2, Rb, K
25 G Holding Field
The 3He target is widely used as an effective polarized neutron target. Because the two protons in the 3He nucleus will most likely form a pair, about 90% of the 3He spin is carried by the single neutron.
The 3He target we used is high pressure cell and was polarized through spin-exchange optical pumping. It has 10 atm 3He inside which allows the luminosity to be as high as 10 to the 36 level with 15 uA beam. We also put K and Rb alkali metal into the cell as the spin transfer medium.
Here is the picture of a 3He cell. It has two parts. The lower part is the 40 cm long target chamber and the electron passes through it. Top part is the 3 inch spherical pumping chamber where the optical pumping happens.
We put the pumping chamber into a oven and heat it up to 230 degrees so that we have some amount of alkali vapor in it.
The whole target was put in a uniform 25 G magnetic field, and a circular polarized high power laser was shot to the pumping chamber.
The wave length of the laser is chosen to be the D1 transition of the Rb atom, so with the existence of the external magnetic field, the Rb atom will be polarized by the laser. Then the spin of the Rb atoms will first be transferred to K and then to the 3He nuclei. Actually, the spin of the Rb atom can be directly transferred to 3He, but with K as a media, the spin exchange efficiency got greatly improved!
40 cm Target Chamber
10 atm 3He, Rb/K alkali mixture
Luminosity with 15 mA electron beam
L(n) = 1036 nuclei/cm2/s
World Record
Polarized 3He Target and TMD
5/21/2010

7. Benefit from Narrow Width Lasers
Rb D1 (S1/2  P1/2) Width
Dn = 0.3 nm
COHERENT FAP diode lasers were originally used
Dn = 2.0 nm
A lot of power wasted
Unabsorbed laser depolarizes target through thermal process
NEWPORT recently brought new COMET narrow width diode laser
Dn = 0.2 nm
Much more optical pumping efficiency
Improves target polarization to 65%
30W FAP Laser
Pumping
Laser
D2 Fluorescent
Indication of Absorption
30W COMET Laser
Much Deeper Absorption!
Polarized 3He Target and TMD
5/21/2010

8. Target System Since October 2008
New COMET lasers
Narrow line with laser make more efficiency optical pumping.
3D Holding Field Control
New vertical coil together with existing horizontal coils create holding field in any direction and cancel out any residue field.
New Oven and Optics
Better insulation, lighter weight and all three pumping directions.
A Smart Target
Automatic spin flip every 20 minutes using Adiabatic Fast Passage (AFP). Log and alarm.
Lasers
Oven
Beam
Target
For the Transversity experiment, the Hall A 3He target got upgraded mainly in the following ways
vertical coil and oven
comet lasers
spin direction
auto flip by 180 degree every 20 minutes though adiabatic fast passage to reduce the systematic error.
Holding Field Coils
Polarized 3He Target and TMD
5/21/2010

9. History of Target Performance
Reached a steady 65% polarization with 15 mA beam and 20 minute spin flip! A NEW RECORD!
A series of experiments used this target:
Neutron Transversity
Neutron structure function: d2n
Two photon exchange: Ay
3He structure: e(3He, e’d)p
History of Figure of Merit of Polarized 3He Target
Polarized 3He Target and TMD
5/21/2010

10. Nucleon Structure from Deep Inelastic Scattering
Un-polarized Nucleon Structure Function
Longitudinal Momentum Distribution.
Well probed for 50 years over very large kinematic range.
Longitudinal Polarized Nucleon Structure Functions
Since “spin crisis” in 1980s.
Plotted in fairly large range.
Transversity:
Quark transverse polarization in a transversely polarized nucleon.
Equal to g1 when there is no relativistic effect.
Chiraly Odd: Can be probed in Semi-Inclusive DIS when convoluted with Collins fragmentation function.
New business: recent measurements from HERMES and COMPASS using Hydrogen and Deuteron targets.
f1 =
g1 =
Nucleon Spin
Quark Spin
h1 =
Polarized 3He Target and TMD
5/21/2010

11. Longitudinally Polarized Transversely Polarized
Leading Twist TMDs
Nucleon Spin
Quark Spin
Quark polarization
Un-Polarized
Longitudinally Polarized
Transversely Polarized
Nucleon Polarization U L T
h1 =
f1 =
Boer-Mulder
g1 =
h1L =
Helicity
Beside the three parton distribution functions which survive the integration over the quark transverse momentum there are five more transverse momentum dependent distribution functions at leading twist.
Here is a table of all the 8 leading twist TMDs, the cartoons on the right hand side of each name tell you the meaning of each TMDs. Again, the virtual photon is supposed to go out of the paper and that’s our longitudinal direction. The red circle and arrow are the quark and it’s spin, and black circle and arrow are the nucleon and it’s spin. The blue arrow shows the momentum direction of the quark.
An important information these 5 new TMDs will tell you is the quark oribtal angular motion. They will vanish without orbital angular momentum.
In particular, the Sivers function directly tells you the quark orbital angular momentum in a transverse polarized target, Boer-Mulder tells you the correlation of the quark orbital momentum and it’s spin inside a unpolarized nucleon and Pretzelosity, in certain model context, direct measures the relativistic nature of the nucleon.
Blue: no kt dependence and T-even
Red: T-odd with kt dependence
Other: kt dependence and T-even
h1T =
f 1T =
Transversity
Sivers:
Quark orbital motion
and nucleon spin
g1T  =
h1T =
Pretzelosity
Polarized 3He Target and TMD
5/21/2010

12. SIDIS Electroproduction of Pions
Separate Sivers and Collins effects
Sivers angle, effect in distribution function:
(fh-fs): angle of hadron relative to initial quark spin.
Collins angle, effect in fragmentation function:
(fh+fs) = p+(fh-fs’): angle of hadron relative to final quark spin.
e-e’ plane q
Scattering Plane
target angle
hadron angle
Polarized 3He Target and TMD
5/21/2010

13. JLab E06-010: Neutron Transversity
E06-010: SSA in SIDIS n↑(e, e’p±) reaction on a transversely polarized 3He Target.
First measurement of the neutron Collins and Sivers asymmetries using polarized 3He target.
x =
Upgraded polarized 3He target system.
Vertical and Transverse polarization
Fast spin-flip
BigBite for e and HRSL for p and K.
Smooth run from 10/24/ /06/09
27 institutions and 7 thesis students
Preliminary results are ready to be released! e p
HRSL
16o g* e’
BigBite
30o
Polarized
3He Target
Polarized 3He Target and TMD
5/21/2010

14. Current Picture from World Data
HERMES, COMPASS, soon Jlab …
Transversity h1T :
p+: positive on proton
p -: negative on proton
Sivers distribution f 1T :
p +: positive on proton
Orbital angular motion!
Substantial contribution from sea quarks
Neutron data from 3He will bring further information to the quark flavor decomposition.
12 GeV and EIC will help on precise measurement of SIDIS asymmetries! u p d p u d
Quark-diquark model: Cloet, Bentz and Thomas PLB 659, 214 (2008), Q2 = 0.4 GeV2
CQSM: M. Wakamatsu, PLB B 653 (2007) 398. Q2 = 0.3 GeV2
Lattice QCD: M. Gockeler et al., Phys.Lett.B627: ,2005 , Q2 = GeV2
QCD sum rules: Han-xin He, Xiang-Dong Ji, PRD 52: ,1995, Q2 " 1 GeV2
Polarized 3He Target and TMD
5/21/2010

15. Polarized 3He Target and TMD
12 GeV Upgrade of JLab
A new hall, Hall-D:
Gluon-X collaboration: exotic meson spectroscopy, gluon-quark hybrid, confinement
Max beam energy upgraded to 12 GeV to Hall D, 11 GeV to Hall A, B and C.
Double cryogen capacity.
Hall A:
Dedicated devices + HRS
Polarized 3He target
Hall B
CLAS12
Polarized p/d target
Hall C
SHMS+HMS
Polarized 3He Target and TMD
5/21/2010

16. E12-10-006: 3He SIDIS with SoLID
A newly approved 12 GeV 3He SIDIS experiment using a solenoid detector.
2p azimuthal coverage will bring better separation between different angular modulations.
Polarized 3He Target and TMD
5/21/2010

17. From Exploration to Precision
Precision 4-D (pT, x, z and Q2) mapping of various SIDIS azimuthal asymmetries.
Much higher statistics, only 1/50 of data points shown
12 GeV Data
6 GeV Data
Polarized 3He Target and TMD
5/21/2010

18. Polarized 3He Target and TMD
Summary
Polarized 3He target has played an important role in probing the nucleon internal structure.
Performance being improved over the decades.
First 3He Transversity experiment was done at Jefferson Lab Hall A with 6 GeV beam.
New 12 GeV 3He SIDIS proposal with SoLID approved, precise 4-D mapping of azimuthal asymmetries in the valence quark region.
Expanded Q2 range with EIC and further into the small x region.
Polarized 3He Target and TMD
5/21/2010

19. Polarized 3He Target and TMD
Acknowledgement
JLab Polarized 3He Target Group
Jian-Ping Chen (JLab), Chiranjib Dutta (Kentucky), Joe Katich (W&M), Yi Zhang (Lanzhou), Jin Huang (MIT), Xiaohui Zhan (MIT), Huan Yao (Temple), Xiaofeng Zhu (Duke)
Polarized 3He Target Collaborators
Haiyan Gao (Duke), Todd Averett (W&M), Wolfang Korsch (Kentucky), Gordon Gates (UVa)
Thesis Students
Xin Qian (Duke), Kalyan Allada (Kentucky), Youcai Wang (UIUC)
Spokespersons of E and E
Xiaodong Jiang (LANL), Jen-Chieh Peng (UIUC), Evaristo Cisbani (INFN)
E06-010, E and Hall A Collaborations
Polarized 3He Target and TMD
5/21/2010

20. Backup Slides
Polarized 3He Target and TMD
5/21/2010

21. 3He Target Polarimetries
NMR: Nuclear Magnetic Resonance
Measures the RF signal strength radiated by 3He nuclei while being flipped.
Relative measurement.
Free NMR at pumping chamber from every auto spin flip.
Calibrated by Water NMR measurement.
EPR: Electron Paramagnetic Resonance
Measures the frequency shift of Zeeman splitting of alkali atoms with 3He spin parallel and anti-parallel to the holding field.
Absolute measurement.
Got signal from both K and Rb.
Measures pumping chamber polarization.
Both worked very well!
Water NMR
EPR
We used two polarimetries to cross calibrate the target polarization
Polarized 3He Target and TMD
5/21/2010

22. Transversity at Jefferson Lab Hall A
Newport News, Virginia
Linear accelerator provides continuous polarized electron beam
Ebeam = 6 GeV
Pbeam = 85%
3 experimental halls A B C
Polarized 3He Target and TMD
5/21/2010

23. Access TMDs through Semi-Inclusive DIS
Unpolarized
Polarized
Target
Beam and
Boer-Mulder
Sivers
Transversity
Pretzelosity
f1 =
f 1T =
g1 =
g1T  =
h1 =
h1L =
h1T =
h1T =
SL, ST: Target Polarization; le: Beam Polarization
Not just transversity and Sivers diftributions, we can actually access all the eight leading twist TMDs in semi-inclusive DIS by using different combinations of beam and target polarizations.
During the experiment we will cover in the later half of this talk, we used a transversely polarized 3He target and polarized electron beam. By forming single target spin asymmetry, we can measure Transversity, Sivers and Pretzelosity distribution functions through single target spin asymmetry.
The Pretzelosity shows the correletion of the quark transverse spin and it’s momentum inside a transversely polarized nucleon. And in certain model context, it directly measures the relativistic nature of the nucleon.
g1T tells us the chance that we find a longitudinally polarized quark inisde a transversely polarized nucleon due to the quark orbital angular momentum.
Polarized 3He Target and TMD
5/21/2010

24. Jefferson Lab Experiment E06-010
E06-010: Single Target-Spin Asymmetry in Semi-Inclusive
n↑(e, e’p±) Reaction on a Transversely Polarized 3He Target
First measurement on 3He(n) Transversity ever!
Spokespersons:
Xiaodong Jiang (Rutgers/Los Alamos, Contact Person), Jian-ping Chen (JLab), Evaristo Cisbani (INFN-Rome), Haiyan Gao (Duke), Jen-Chieh Peng (UIUC)
7 Thesis Students:
C. Dutta (Kentucky), J. Huang (MIT), A. Kalyan (Kentucky), J. Katich (W&M), X. Qian (Duke), Y. Wang (UIUC), Y. Zhang (Lanzhou U)
Finished in early February 2009, after 3 months of successful data taking
Polarized 3He Target and TMD
5/21/2010

25. Separation of SSAs through angular dependence
Rotate target spin direction to increase fs coverage
Vertical
Horizontal
Transversity
The separation of the three single spin azimuthal asymmetries will be done based on their different angular dependences.
Let me first define two important azimuthal angles around the 4 momentum transfer:
fs is the target spin direction
and fh is the hadron direction
and both angles are defined with respect to the electron scattering plane.
The transversity distribution is modulated by the sum of fs and fh, sivers distributions by the difference of fs and fh and the pretzelosity has the dependence on 3fh – fs.
Due to the small acceptance of the left HRS, in order to increase the angular coverage, we polarized the 3He spin in four directions around the beam and they are marked by the arrows: vertical up and down, horizontal left and right.
Sivers
Pretzelosity
Polarized 3He Target and TMD
5/21/2010

26. Kinematics Coverage of E06-010
x<0.25
Sivers Angle: fh-fs
Collins Angle: fh+fs y Q2 Mm z
0.6 ~ 0.9
0.6 ~ 3 (GeV/c)2
1.5 ~ 2.3 (GeV/c2)
0.4 ~ 0.6 x
0.25
0.5
Y: forwardness
Q2: momentum transfer
W’: missing mass, above main resonance region
Z: fraction of the energy transfer carried by the produced hadron, selecting leading hadron in the fragmentation
Pt: transverse momentum up to ~ 0.5 GeV
Have pretty much
x>0.25
Polarized 3He Target and TMD
5/21/2010

27. Projections of Collins Asymmetries
Based on the QCD factorization approach, Vogelsong and Yuan considered Sivers and Collins contributions to the asymmetries. They fit simple parametrizations for the Sivers and Collins functions to the HERMES data, and compare to results with COMPASS. Using the fitted parametrizations for the Sivers functions
Polarized 3He Target and TMD
5/21/2010

28. Projections of Sivers Asymmetries
Based on the QCD factorization approach, Vogelsong and Yuan considered Sivers and Collins contributions to the asymmetries. They fit simple parametrizations for the Sivers and Collins functions to the HERMES data, and compare to results with COMPASS. Using the fitted parametrizations for the Sivers functions
Polarized 3He Target and TMD
5/21/2010

29. From Exploration to Precision
SIDIS SSAs depend on 4 variables (x, Q2, z and PT ) Large angular coverage and precision measurement of asymmetries in 4-D phase space are essential.
A new 12 GeV proposal PR has been fully approved to measure SIDIS SSA on a polarized 3He target using SoLID solenoid detector with 11 GeV and 8.8 GeV electron beam in JLab hall A.
Spokenpersons: J.-P. Chen, H. Gao, X. Jiang, J.-C. Peng, and X. Qian
Over 130 collaborators, 40 institutions, 8 countries
Strong theoretical support
Polarized 3He Target and TMD
5/21/2010