1. Semi-Inclusive DIS with SoLID on a polarized 3He target
Yi Qiang
for JP. Chen, H. Gao, X. Qian

2. 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 =

3. 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
g1T  =
h1T =
Sivers
Pretzelosity
10/30/2009
Transverse Momentum-dependent Sturecutre of the Nucleon

4. SIDIS electroproduction of pions
Separate TMDs with different angular dependences
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
Pretzelosity angle: 3fh-fs
Scattering Plane
target angle
hadron angle
e-e’ plane q
No like the pp scattering, you have both Sivers and Collins effects mixed, we can clearly identify the Sivers and Collins effects in the SIDIS pion production based on their different azimuthal distributions.
Here is a figure for the SIDIS kinematics. We defined two important azimuthal angles about the Q-vector here, one is the target angle fs, which is the angle of the target spin to the scattering plane and another one is fs, which is the angle of produced hadron to the scattering plane. Here is the projection of the angles if we look into the virtual photon.
For the Sivers function, because it is an effect in the distribution function, it has a dependence on the angle between the produced hadron and the initial quark spin. And this angle is fh – fs.
For the Collins function, since it’s an effect in the fragmentation process, it will a dependence on the angle between the hadron and the final quark spin. So we got the Collins angle as fh + fs.
10/30/2009
Transverse Momentum-dependent Sturecutre of the Nucleon

5. Access Leading Twist Parton Distributions through Semi-Inclusive DIS
SL, ST: Target Polarization; le: Beam Polarization
f1 =
f 1T =
g1 =
g1T  =
h1 =
h1L =
h1T =
h1T =
Unpolarized
Polarized
Target
Beam and
Boer-Mulder
Sivers
Transversity
Pretzelosity
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.
10/30/2009
Transverse Momentum-dependent Sturecutre of the Nucleon

6. SIDIS with SoLID Modification based on PVDIS setup
Coil
Yoke GC HG A C
Collimator
Polarized 3He Target LC
GEMx4
GEMx5
LC: Large angle Calorimeter
GC: Gas Cherenkov
HG: Heavy Gas Cherenkov
A: Aerogel Detector
C: Calorimeter
TOF

7. Polarized 3He Target 40 cm polarized 3He target
10 amg: 3x1036 nuclei/s/cm2 with 15 mA beam
Successfully run during 6 GeV Hall A transversity experiment
65% polarization with 15 mA beam and 20 min auto spin flip (~ 0.5% relative AFP loss per flip)
Faster flipping speed can be achieved by doing field rotation
<5s flip time, 1 flip per minute
~0% polarization loss
Tread in: real time polarization monitoring
Require special treatment for fringe field
Shielding
Correction coil

8. Target Collimator
Shield high energy electron and photons, which are generated from the target glass wall for the forward angle detector.
Target
Collimator
Large Angle
Forward Angle
Acceptance Comparison with or without target collimator

9. Tracking with GEM detectors
5 planes reconfigured from PVDIS GEM detectors
Total surface ~ 18 m2
Need to build the first plane
Electronics can be shared

10. Rates and Random Noise on GEM
Background rates simulated using GEANT3, with all physics processes (Moller/Mott ... etc).
50 ns ADC gate 1
0.1
0.01
Chamber Rate (kHz/mm2)
Radius (cm)
LF2 L1
LF3
LF4 F5 F6 L1
LF2
LF3 11 51 40
LF4 F5 F6 49 36 40

11. “Progressive” Tracking Algorithm
The tracking is based on “progressive” method.
Starts from a seed, normally a hit in the first chamber.
Then it looks for match in the second chamber based on designed momentum and angular coverage.
With the two hits, narrow down the search range.
Then we look for a smaller region in chamber-3 and same procedure until we goes to the last layer of chamber.
After the coarse tracking, a global fitting is implemented to judge the tracks so that we can order tracks by c2/DOF.
Then the “similar tracks” will be merged (de-ghosting).

12. Tracking Performance
Assume 200mm spatial resolution and 98% hit efficiency
Require 3/4 chambers firing for large angle and 4/5 for small angle
Performance with real tracks:
Large angle side: (Tracking efficiency > 99%)
Multi-tracks: 0.32%
No-tracks: 0.49%
Small angle side: (Tracking efficiency > 99%)
Multi-tracks: 0.28%
No-tracks: 0.31 %
Performance with pure background (false track):
Large angle side: 0.30%
Small angle side: 0.29%
Speed: (preliminary) 100 Hz with single CPU, can be improved.

13. Particle Identification
Large angle side: 14.5o – 22o
Electron only
Momentum: 3.5 – 6.0 GeV/c
p/e < 1.5
Shashlyk calorimeter
Forward angle side: 6.6o – 12o
Electron and pion
Momentum: 0.9 – 7.0 GeV/c
Calorimeter: Pre-shower/Shower splitting
Cherenkov and TOF detectors for hadron identification

14. Hadron Identification
Momentum range: 0.9 – 7.0 GeV/c
Configuration for only pion identification
P (GeV)
Gas Cherenkov: atm
n = , 200 cm
N.P.E. ~ 17.4
Heavy Gas Cherenkov:
atm
n = , 30 cm
N.P.E ~ 9.3
Aerogel Cherenkov:
n = 1.015, 10 cm
N.P.E ~ 13.6

15. Hadron Identification (continued)
Configuration for pion and kaon
Require TOF to identify kaon below 3.5 GeV/c
P (GeV)
Gas Cherenkov: atm
n = , 200 cm
N.P.E. ~ 13.2
Heavy Gas Cherenkov:
atm
n = , 30 cm
N.P.E ~ 18.5
Aerogel Cherenkov:
n = 1.012, 15 cm
N.P.E ~ 16.4

16. Time-of-Flight K/p separation up to 3.5 GeV
assume 8 meter pathlength: sT < 150 ps (4s separation)
Can also help to suppress photon events
Scintillator
MRPC
Multi-Resistive
Plate Chamber
s < 90ps
No PMT, can
live with field
Rates > 25 kHz/cm2
TK-Tp
Tp-TK

17. Table of Rates 15 uA beam and 40 cm target@10 amg w/ collimator
Models for rate estimation have been adjusted based on real rates measured in E06-010
Only momentum cut: 3.5 GeV/c on large angle.

18. Trigger Setup Divide the azimuthal angle into 10 sectors.
Level 1 trigger: Electron Trigger
Large side: Calorimeter (11 kHz/10 = 1 kHz), OR
Small side: coincidence between Pre-Shower/Shower Signal and Gas Cherenkov (140 kHz/10 = 14 kHz)
Total rate of 10 sectors: 10 x (1+14) = 150 kHz
Level 2 trigger: Electron Pion Coincidence Trigger
Pion Trigger: Coincidence signal between Aerogel counter and Pre-Shower VETO (5MHz/10 = 500kHz)
Coincidence of electron and pion triggers from different sectors: 45 total combinations.
Assuming 50 ns coincidence window, total rate of all 45 combinations is: 45 x 500kHz x 50ns x 15 kHz + 3 kHz = 30 kHz
Level 3 trigger:
Online track cleaning up.

19. Data transfer rate to tape
Size of single event is about 3kB.
If we use Level 2 trigger, the total data transfer rate is about 3kB x 20 kHz = 60 MBps = 480 Mbps. Already pretty reasonable.
With Level 3 trigger, probably will be able to further reduce the recording rate by a factor of 2.

20. Kinematic Coverage
Precision 3-D (x, pT and z) mapping of Collins, Sivers and pretzelosity.
Coverage with 11GeV beam plotted here.
xB: 0.1 ~ 0.6
PT: 0 ~ 1.3 GeV/c
W: 2.3 ~ 4 GeV
z: 0.3 ~ 0.7
Mm: 1.6~ 3.3 GeV

21. Huge advantage from Angular Coverage
2p fS coverage and very large fh coverage:
Impact of fh coverage on uncertainties of extracting different SSAs: Sivers, Collins and Pretzelosity.
An example of fh coverage

22. Preliminary Beam Time Request

23. Projected Data
Total 500(300) bins in x, Pt and z for 11(8.8) GeV beam.
z ranges from 0.3 ~ 0.7, only a sub-range of 11 GeV shown here.

24. Coordinate with PVDIS collaboration
Work together with PVDIS
Yoke design
Pre-Shower/Shower design
Single Gas Cherenkov setup for both experiments?
Try to optimize the way of switching over:
Reallocation of baffles, GEMs and various detector
Electronics, DAQ

25. Backup Slides

26. Multi-Resistive Plate Chamber
Time resolution: < 90 ps
Efficiency: > 95 %
Gain: ~ 105