1. Yi Qiang Duke University for CIPANP 2009 May 27, 2009
The first measurement of neutron Transversity using a transversely polarized 3He target
Good morning… My name is Yi Qiang, from Duke University
I will talk about the first measurement of neutron transversity using a transversely polarized 3He target
Yi Qiang
Duke University
for CIPANP May 27, 2009
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

2. Outline Overview of leading twist TMDs
Jefferson Lab Experiment E06-010
First neutron Transversity experiment
Experimental configuration
Polarized 3He target
Detector performance
Current Status and Future Plan
In this talk, I will first introduce the background about the nucleon transverse momentum distributions.
Then I will talk about the details of this neutron transversity experiment performed in Jefferson Lab Hall A including …
At the end, I will summarize with the current status and the future plan.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

3. Nucleon Structure from DIS
Un-polarized Nucleon Structure Function
Longitudinal Momentum Distribution
Well probed for 50 years over very large kinematics range
Longitudinal Polarized Nucleon Structure Functions
Since “spin crisis” in 1980s
Plotted in fairly large range
Transversity:
Can be probed in Semi-Inclusive DIS
New business: recent measurements from HERMES and COMPASS using Hydrogen and Deuteron targets
f1 =
g1 =
Deep inelastic lepton-hadron scattering (DIS) has played a seminal role in the development of our present understanding of the sub-structure of hadrons.
Since the discovery of the parton from the Bjorken scaling in the late 1960s, the unpolarized structure function f1 has been measured with excellent precision over a large range of the kinematics including the longitudinal momentum fraction x and momentum transfer Q2.
Motivated by the original “spin crisis” from the EMC experiment in the 1980s, the nucleon longitudinal spin structure g1 has been determined through polarized DIS with good precision.
If we look at a nucleon from a more realistic 3D point of view, other than the unpolarized and longitudinal nucleon structure functions, the least known part is the transverse spin and momentum distributions. Transversity describes the quark transverse polarization in a transversely polarized nucleon, and its difference to the longitudinal parton distribution reveals the relativistic nature of the quarks inside the nucleon. Because Transversity is chiraly-odd, it can not be measured through inclusive DIS, but one can probe it through single target spin azimuthal asymmetries from semi-inclusive DIS processes with a transversely polarized target. In this process, it’s convoluted to the Collins fragmentation function which describes the correlation between the fragmenting quark’s transverse spin and the outgoing hadrons' transverse momentum.
The COMPASS and HERMES collaborations have recently reported first SIDIS asymmetries on transversely polarized proton and deuteron targets and the business has just started!
h1 =
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

4. Leading Twist TMDs Blue: kT independent; Red: T-odd Quark polarization
Un-Polarized
Longitudinally Polarized
Transversely Polarized
Nucleon Polarization U L T
f1 =
h1 =
g1 =
h1L =
Including the previously mentioned three distributions, totally eight transverse momentum dependent distribution functions, TMDs, are identified in the leading twist. They are listed in this table.
h1 =
f 1T =
g1T =
h1T =
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

5. Access Leading Twist Parton Distributions through Semi-Inclusive DIS
SL, ST: Target Polarization; le: Beam Polarization
Unpolarized
Polarized
Target
Beam and
Boer-Mulder
Transversity
Sivers
Pretzelosity
All the eight leading twist TMDs can be measured through semi-inclusive DIS by using different combinations of beam and target polarizations.
In this experiment, we used a transversely polarized 3He target, therefore, by only considering the target single spin asymmetry, we can measure Transversity, Sivers and Pretzelosity distribution functions. The physical meanings of Transversity has been mentioned.
The Sivers function refers to the correlation between the nucleon’s transverse spin and the quark’s transverse momentum, which involves the quark orbital motion
The Pretzelosity describes the difference between the helicity and transversity distribution and measures the relativistic effects in the nucleon.
Since the electron beam was polarized as well during the experiment, we parasitically measured the double spin azimuthal asymmetry for the g1T distribution function. g1T describes the quark longitudinal polarization in a transversely polarized nucleon and is non-vanishing only if the quark orbital angular momentum is non-zero.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

6. Transversity from JLab Hall A
Linear accelerator provides continuous polarized electron beam
Ebeam = 6 GeV
Pbeam = 85%
3 experimental halls
This is where the experiment performed: Jefferson Lab, located in Newport News Virginia.
The Jefferson Lab accelerator has two LINACs forming a circle and it can delivery electron beam up to 6 GeV with polarization around 85%.
There are three experimental Halls at the end of the beam line and they are Hall A, B and C. The neutron transversity I’m reporting was carried out in Hall A. A C B
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

7. E Collaboration
E06-010: Single Target-Spin Asymmetry in Semi-Inclusive n↑(e, e’p±) Reaction on a Transversely Polarized 3He Target
Spokespersons:
Xiaodong Jiang (Rutgers/Los Alamos, Contact Person), Jian-ping Chen (JLab), Evaristo Cisbani (INFN-Rome), Haiyan Gao (Duke), Jen-Chieh Peng (UIUC)
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)
Approved with A rating and was just finished in early February, 2009.
This experiment is supported by a world-wide collaboration and we have 7 PhD thesis student in total. In early February this year, we just finished the three months’ data taking.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

8. E06-010 Setup g* p e’ e Electron beam: E = 5.9 GeV
40 cm polarized 3He target
BigBite at 30 degrees as electron arm: P = 0.7 ~ 1.8 GeV/c
HRSL at 16 degrees as hadron arm: P0 = 2.35 GeV/c
Measure Collins, Sivers and pretzelosity asymmetries in valence range: x = 0.1 ~ 0.4 p
HRSL
16o e g* e’
BigBite
30o
The experimental is configured as following. We have 5.9 GeV polarized electron beam incident on a 40 cm polarized 3He target.
The scattered electron was detected by the BigBite spectrometer positioned 30 degrees to the beam right. And the momentum range is …
The produced hardon was detected coincidently using the left high resolution spectrometer 16 degrees to the beam left. And the momentum setting is 2.35 GeV/c.
This setup allowed us to measure the … asymmetries in the valence range …
Polarized
3He Target
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

9. Separation of Collins, Sivers and Pretzelosity effects 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
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

10. Polarized 3He Target Effective polarized neutron target
~90% ~8% ~1.5%
Effective polarized neutron target
High luminosity: L(n) = 1036 cm-2 s-1
Fast spin exchange with K/Rb hybrid cells
Oven
230 oC
Laser
795 nm
F = 3”
Pumping
Chamber
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 10 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 existance of the external magnetic field, the Rb atom will be polarized by the laser. Then the spin of the Rb atoms will be first transferred to K and then to the 3He nuclei. Actually, the spin of the Rb atom can be directly tranfered to 3He, but with K as a middle stage, the spin exchange efficiency got greatly improved!
25 G Holding Field
40 cm
Target Chamber
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

11. Target Setup for Transversity
New vertical coil together with existing horizontal coils and new oven allow 3He to be polarized in ALL three directions!
New narrow band COMET lasers make optical pumping more efficient.
3He spin pumped to horizontal and vertical directions.
Auto spin flip every 20 minutes.
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.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

12. 3He Target Polarimetries
Water NMR
NMR: Nuclear Magnetic Resonance
Free NMR at pumping chamber from every auto spin flip.
Target chamber polarization is calibrated by Water NMR measurement.
EPR: Electron Paramagnetic Resonance
Got signal from both K and Rb.
Measures pumping chamber polarization.
EPR
We used two polarimetries to cross calibrate the target polarization
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

13. Target Performance Online Preliminary
Online preliminary EPR/NMR analysis shows a stable 65% polarization with 15 mA beam and 20 minute spin flip
Cell: Astral
Cell: Maureen
The target performance is very good throughout the experiment. The …
The plot shows the polarization history from the beginning of the experiment till the Christmas shut down.
Since the first high pressure 3He cell was used in the SLAC E142 experiment in early 1990s, the effort to improve the target polarization has never been stopped. With some many technique breakthrough such as hybrid cell and narrow band laser, we just set the bar to a new height for the future 3He experiment.
Online Preliminary
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

14. BigBite Spectrometer 30 degrees to the beam right Detect electrons
A big bite of acceptance
DW = 64 msr
P : 700 ~ 1800 MeV/c
3 Wire Chambers: 18 planes
Optics is crucial for the angular dependence separation and kinematics variables
Pre-Shower and Shower for electron PID
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

15. BigBite Optics
Optics for both negative and positive charged particles have been done
Wire Chamber Spatial Resolution: 180 mm
Vertex Resolution: 1 cm
Angular Resolution: < 10 mrad
Momentum Resolution: 1%
BigBite Sieve Slit
Because of the large acceptance of the BigBite, even with a dipole magnet, both negative and positive charged particles can be detected at the same time. Therefore, the optics for both neg and pos …
Spatial resolution achieved the design goal
Vertex resolution: 1cm will allow us to do vertex coincident cut
Angular resolution: put sieve plate which is made of 1.5’’ lead in front of the BigBite magnet
Momentum resoluton
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

16. Electron Selection in BigBite
Pre-shower/Shower have been calibrated
Energy Resolution: 8%
Well separated electrons and pions
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

17. Left High Resolution Spectrometer
ep Coincidence Time
s < 400 ps p K
16 degrees to beam left with p0 = 2.35 GeV/c
Clean e/p separation with Gas Cherenkov and Pion Rejector
Vertex and TOF coincidence with BigBite will help reduce the background
Kaon asymmetry data can also be extracted:
A1: Pion rejection > 90 %
RICH: K/p separation ~ 4 s
TOF: K/p separation ~ 4 s
Cherenkov Ring
from RICH
4 s Separation 1.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

18. Kinematics Coverage x<0.25 x>0.25 y Q2 W’ z x
Pretzelosity Angle: 3fh-fs
Sivers Angle: fh-fs
Collins Angle: fh+fs y
0.6 ~ 0.9
x<0.25
0.6 ~ 3 (GeV/c)2 Q2 W’
Y: forwardness
Q2: momentum transfer
W’: missing mass, above main resonance region
Z: fraction of the energy transfer, selecting leading hadron in the fragmentation
Pt: transverse momentum up to ~ 0.5 GeV
Have pretty much
1.5 ~ 2.3 (GeV/c2)
x>0.25
0.4 ~ 0.6 z
0.25
0.5 x
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

19. Projections of Collins and Sivers Functions
This is the projection of our data with pure statistic uncertainties. If we divide x into 4 bins, both Collins and Sivers asymmetry have the statistic uncertainty from 3 to 5 percent.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

20. Projections of g1T First Neutron (3He) Measurement
With Fast Beam Helicity Flip (30Hz)
Projected Uncertainties (Stat. Only):
2.3% at low x
3.4% at high x
The statics uncertainty of g1T is very similar to Sivers uncertainty except for the addition beam polarization term and this will make the error bars slightly larger.
The plotted g1T was estimated from g1 through Lorentz Invariance Relations and Wandzuraand Wilczek Relations.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

21. The 12 GeV upgrade of Jefferson Lab will bring more lights on the future neutron transversity experiment. We are proposing a new measurement with the new Solenoid spectrometer on a transversely polarized target. Benefited of the large acceptance of the new solenoid spectrometer and higher beam energy, we can plot out the neutron transversity in a much larger kinematic range with much higher precision.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

22. Status of E06-010
The experiment was smoothly performed from Oct 2008 to Feb 2009.
Statistics exceeded the approved goal.
Detector calibrations and target analysis are ongoing.
Will start to extract physical asymmetries afterwards.
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

23. Summary
First measurement of neutron transversity from polarized 3He Target.
Data will cover valence quark range:
x = 0.1~0.4
High luminosity and statistics:
Absolute error on neutron pion asymmetries is about 3%~5%.
Preliminary results coming out really soon!
5/27/2009
Neutron Transversity in JLab Hall A CIPANP 2009

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Neutron Transversity in JLab Hall A CIPANP 2009

25. Backup Slides
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Neutron Transversity in JLab Hall A CIPANP 2009

26. Collaboration members
E Collaboration
Institutions
California State Univ., Duke Univ., Florida International. Univ., Univ. Illinois, JLab, Univ. Kentucky, LANL, Univ. Maryland, Univ. Massachusetts, MIT, Old Dominion Univ., Rutgers Univ., Temple Univ., Penn State Univ., Univ. Virginia, College of William & Mary, Univ. Sciences & Tech, China Inst. Of Atomic Energy, Beijing Univ., Seoul National Univ., Univ. Glasgow, INFN Roma and Univ. Bari, Univ. of Ljubljana, St. Mary’s Univ., Tel Aviv Univ.
Collaboration members
A.Afanasev, K. Allada, J. Annand, T. Averett, F. Benmokhtar, W. Bertozzi, F. Butaru, G. Cates, C. Chang, J.-P. Chen (Co-SP), W. Chen, S. Choi, C. Chudakov, E. Cisbani(Co-SP), E. Cusanno, R. De Leo, A. Deur, C. Dutta, D. Dutta, R. Feuerbach, S. Frullani, L. Gamberg, H. Gao(Co-SP), F. Garibaldi, S. Gilad, R. Gilman, C. Glashausser, J. Gomez, M. Grosse-Perdekamp, D. Higinbotham, T. Holmstrom, D. Howell, J. Huang, M. Iodice, D. Ireland, J. Jansen, C. de Jager, X. Jiang (Co-SP), Y. Jiang, M. Jones, R. Kaiser, A. Kalyan, A. Kelleher, J. Kellie, J. Kelly, A. Kolarkar, W. Korsch, K. Kramer, E. Kuchina, G. Kumbartzki, L. Lagamba, J. LeRose, R. Lindgren, K. Livingston, N. Liyanage, H. Lu, B. Ma, M. Magliozzi, N. Makins, P. Markowitz, Y. Mao, S. Marrone, W. Melnitchouk, Z.-E. Meziani, R. Michaels, P. Monaghan, S. Nanda, E. Nappi, A. Nathan, V. Nelyubin, B. Norum, K. Paschke, J. C. Peng(Co-SP), E. Piasetzky, M. Potokar, D. Protopopescu, X. Qian, Y. Qiang, B. Reitz, R. Ransome, G. Rosner, A. Saha, A. Sarty, B. Sawatzky, E. Schulte, S. Sirca, K. Slifer, P. Solvignon, V. Sulkosky, P. Ulmer, G. Urciuoli, K. Wang, Y. Wang, D. Watts, L. Weinstein, B. Wojtsekhowski, H. Yao, H. Ye, Q. Ye, Y. Ye, J. Yuan, X. Zhan, Y. Zhang, X. Zheng, S. Zhou.
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Neutron Transversity in JLab Hall A CIPANP 2009

27. Fermi Lab E704: p↑p→pX at 400 GeV
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Neutron Transversity in JLab Hall A CIPANP 2009