SoLID-Spin Program at 12 GeV JLab
Xin Qian
Kellogg Radiation Lab
Caltech
For SoLID Collabration
Weihai Workshop
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Outline
• Nucleon Spin
– Transverse Momentum Dependent Parton
Distribution Functions (TMDs)
– Semi-Inclusive Deep Inelastic Scattering
(SIDIS)
• Current Status of Single Spin Asymmetry
(SSA) Measurements
• Overview of SoLID-Spin Program
• Summary
Weihai Workshop
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Nucleon Spin Structure
• Understand Nucleon Spin in terms of quarks and
gluons (QCD).
Nucleon’s spin
Ji’s Sum Rule
Jq
~30% from data
“spin crisis”
– Small contribution from quarks and gluons’ intrinsic spin
Orbital angular momentum is important!
Parton transverse motion + Spin-orbit correlations
Weihai Workshop
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Transverse Momentum
Dependent PDFs
3-D
Tomogr
aphy
TMD f1u(x,kT)
Transverse
Plane x-y
Models
TMD
QCD
Dyna
mics
Longitudinal
Direction z
Nucleon
Spin
Lattice
QCD
Weihai Workshop
QCD
Factoriz
ation
Quark
OAM/
Spin
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A Unified Picture of Nucleon Structure (X. Ji)
6D Des.
Wpu(x,kT,r ) Wigner distributions
d2kT drz
d3r
TMD PDFs
GPDs/IPDs
f1u(x,kT), .. h1u(x,kT)
3D imaging
d2k
T
PDFs
f1u(x), .. h1u(x)
dx &
Fourier Transformation
d2rT
1D
Weihai
X. Ji PRL
91Workshop
(03)
Form
Factors
GE(Q2),
GM(Q2)
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Leading-Twist TMD PDFs
Nucleon Spin
Quark Spin
Quark polarization
Unpolarized
(U)
Nucleon Polarization
U
Longitudinally Polarized
(L)
h1 =
Very well
known
f1 =
Boer-Mulders
Reasonably known
g1 =
L
Transversely Polarized
(T)
Helicity
h1L =
Worm Gear
(Kotzinian-Mulders)
h1 =
T
f 1T =
Transversity
g1T =
Sivers
h1T =
Worm Gear
Pretzelosity
Spin-orbital (trans. mom.) correlation is important!
Weihai Workshop
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Semi-Inclusive DIS
• A DIS reaction in which a hadron h, produced in the
current fragmentation region is detected coincidently
with scattered electron (k’).
k  P  k 'h  X
DXs ~ PDF X FF
Fragmentation
function (FF)
Parton distribution
function (PDF)
h tags struck quark’s
flavor, spin and
transverse
momentum
h
Current
Weihai Workshop
Fragmentation
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Access TMDs through SIDIS
d
2
y2


2
2
dxdydS dzdh dPh  xyQ 2(1   )
{FUU ,T  ...
Boer-Mulder
cos( 2h )
UU
  cos(2h )  F
 ...
Unpolarized
 S L [ sin( 2h )  FULsin( 2h )  ...]
Transversity
/Collins
Sivers
Pretzelosity
 ST [ sin(h  S )  FUTsin(h S )
 sin(h  S )  ( FULsin(h S )  ...)
Polarized
Target
  sin(3h  S )  FUTsin( 3h S )  ...]
 S L e [ 1   2  FLL  ...]
Polarized
Beam and
cos(h  S )
2
 ST e [ 1   cos(h  S )  FLT
 ...]} Target
SL, ST: Target Polarization; e: Beam Polarization
Weihai Workshop
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Separation of Collins, Sivers and pretzelocity effects
through angular dependence


1
N

N
AUT (hl ,  Sl ) 
P N  N
Collins
Sivers
 AUT
sin(h  S )  AUT
sin(h  S )
ty
 AUPretzelosi
sin(3h  S )
T
UT: Unpolarized lepton + Transversely polarized nucleon
Collins
UT
A
 sin(h  S )
Sivers
AUT
 sin(h  S )
UT
UT
 h1  H

1
 f1T  D1
AUPretzelosity
 sin(3h  S )
T
UT
 h1T  H1
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Collins effect
ACollins  h1T  H

1
• Access to transversity
– Transversity links
quak’s spin to
nucleon spin
– Collins FF links
quark’s spin to
hadron transverse
momentum
• Artru model
– Based on LUND
fragmentation
picture.
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Rich Physics in TMDs (Sivers Function)
• Correlation between nucleon spin with quark orbital
angular momentum
Sivers

A
 f1T  D1
Burkhardt :
chromodynamic
lensing
f1Tq
SIDIS
  f1Tq
D Y
Important test for
Factorization
Weihai
Workshop
Final-State-Interaction11
Current Status on TMD
• Collins Asymmetries
- Sizable for proton (HERMES and COMPASS)
Large at high x, large for - but with opposite sign
Unfavored Collins fragmentation as large as favored (opposite
sign) Also see Belle's data.
- consistent with 0 for deuteron (COMPASS)
- small for neutron (JLab Hall A)
• Sivers Asymmetries
- non-zero for + from proton (HERMES), consistent with COMPASS
results at high Q2?
- consistent with zero for - from proton and for  and - from
deuteron
- negative values for neutron + , small for - (Hall A)
• Very active theoretical and experimental study
• RHIC-spin, JLab (CLAS12, HallA/C 12 GeV), Belle, FAIR (PAX)
Future EIC
• Global Fits/models by Anselmino et al., Yuan et al. and …
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E06010: arXiv: 1106.0363, PRL in press
See X. Jiang’s talk
Weihai Workshop
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SoLID Setup for SIDIS on 3He
• High 1036 N/cm2/s
polarized luminosity
• Achieved Performance:
– Transverse/Vertical and
Longitudinal Polarized
Target
– >60% polarization
– Fast Spin Flip
~90%
~1.5% ~8%
Effective pol. neutron target
• Large acceptance
enables 4-D mapping
of asymmetries
• Full azimuthal-angle
coverage -> smaller systematic uncertainties
Weihai Workshop
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SoLID Setup for SIDIS on 3He
• Tracking: GEM Tracker.
– Shared R&D with Super
BigBite
• Electron Identification:
– E&M calorimeter for large
angle and high momentum
– E&M calorimeter and light gas
Cerenkov for forward angle
• Pion identification:
– Heavy Gas Cerenkov and TOF
(Multi-Resistive Plate
Progressive Tracking, Mom. res. 1%, polar
Chamber)
angular res. 0.3 mr, azimuthal angular res. 5 mr,
• Fast pipeline DAQ (Similar to Hall 0.8 cm vertex res with realistic magnetic field
D)
simulation and 200 um GEM pos. res.
Shoot for 100 ps TOF resolution, (60 ps intrinsic
• See Z. W. Zhao’s talk for
resolution from MRPC)
Weihai Workshop
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simulation
SIDIS L.-G. Cherenkov: Optical system
One spherical mirror
xi  incident ray on m irror
2
R
x r  reflectedray
1
1
cos  (

)   angle between incident ray
xi
xr
and norm alto the m irror
 Focusing optimized for central ray:
for SIDIS kinematics (BaBar) => (9.3 + 14.3)/2
= 11.8 deg
Slide from S. Malace
Weihai Workshop
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SIDIS L.-G. Cherenkov: Focusing
 “F-scan”: at fixed polar
angle check collection
efficiency as a function of
the azimuthal angle
Example: 14.3 deg & 3.5 GeV
Example: 14.3 deg & 1.5 GeV
Slide from S. Malace
 Collection efficiency dependence of
F:Workshop
small effect at isolated kinematics
Weihai
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Choice of Calorimeter
• Two main choices
Typical Pb SciFi
Hertzog, NIM, 1990
– High resolution, radiation hardness, 100ps timing
• SciFi ECal
– Simulation shown in last meeting
• W-Ecal resolution is not enough
• Pb-Ecal (with >50% SciFi ratio) works
– Require large area light readout
– Not cheap
• Shashlik Type
– Pickup/Readout photon with wave-length shifting fiber, small light
read out area
Typical Shashlik
Polyakov, COMPASS Talk, 2010
Talk from J. Huang
Weihai Workshop
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Scan for best shower and preshower thickness
Electron
Efficiency
Reach Best
rejection @ ~20
rad length
No preshower separation
1/ (Pi rejection)
Minimal is best
Electron Efficiency
Total rad length
Talk from J. Huang
Total rad length
Reach Best rejection
@ 3~5rad length
Total rad length
Weihai Workshop
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Ben Raydo
Talk
• L2: additional detector, simple pattern match
https://www.jlab.org/exp_prog/electronics/trigdaq/PipelineTriggerElectronics_S&T09.pdf
Weihai Workshop
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L3 Farm (slide from A. Camsonne)
blocked event
fragments
ROC
• Switches connected
with 10GB/s fiber optics
Event Builder
stage 1
EB2
Event Builder
stage 2
ROC
EB1
EB2
ROC
ROC
node
node
node
L3 Farm
Event Builder
stage 1
ROC
ROC
• All nodes connected
with 1GB/s links
EB1
ROC
ROC
full events
Event Builder
stage 2
node
node
node
node
Raid Disk
Read Out Controllers
ROC
partially recombined
event fragments
ER
Event Recorder
EB1
Event Builder
stage 1
Front-End
Crates
Staged Event
Building
~60 crates
~50MB/s out
per crate
N x M array of nodes (exact number
to be determined by available
hardware at time of purchase)
Level-3
Trigger
and
monitoring
Event
Recording
300MB/s in
300MB/s out
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Weihai Workshop
Natural Extension of E06-010
Collins
AUT
 sin( h  s )  h1T  H1
Sivers
AUT
 sin( h  s )  f1T  D1
ALT  cos(h  s )  g1T  D1
• Both transverse and
longitudinal polarized
target.
• Attack 6/8 leading twist
TMDs
• Much wider phase space
– Also data at low and high
z value to access target
frag. and exclusive
Weihai Workshop
channels.
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Transversity
h1T =
• The third PDFs in addition to f1
and g1L
• 10% d quark tensor charge with world data
• Test Soffer’s inequality |h1T| <= (f1+g1L)/2 at large x
Weihai Workshop
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Map Collins, Sivers and Pretzlosity asymmetries in a 4-D (x, z,
Q2, PT)
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Sivers Function
f 1T =
• Correlation between nucleon spin with quark angular momentum
q
q
f


f
• Important test for factorization
1T SIDIS
1T D Y
• Different sign with twist-3 quark-gluon corr. dis. at high PT?
– Kang, Qiu, Vogelsang and Yuan: arxiv: 1103.1591
– Search for sign change, also PT weighted moments (Boer, Gamberg, Musch)
Also in x
dP J ( P ) A


 dP 
sin(h S )
J sin(h S )
UT
A
T
T
UT
T
UU
  UU
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Pretzlosity:
h1T =
• Direct measurement of relativistic effect of quark?
PRD 78, 114024 (2008)
• Direct measurement of OAM? PRD 58, 096008 (1998)
• First non-zero pretzlosity asymmetries?
Weihai Workshop
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Worm-gear functions:
h1L =
g1T =
Center of points:
• Dominated by real part of interference
between L=0 (S) and L=1 (P) states
• No GPD correspondence
• Lattice QCD -> Dipole Shift in mom. space.
• Model Calculations -> h1L =? -g1T
Worm Gear
• Connections with Collinear PDFs through WW approx. and LIR.
ALT ~ g1T ( x) D1 ( z)
Weihai Workshop
AUL ~ h 1L ( x) H 1 ( z )
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SIDIS Factorization Test at 11 GeV
– With proton/deuteron/3He unpolarized data in a large
phase space coverage.
• Understand SIDIS process (Factorization , PT dependence)
• Complementary to Hall C RSIDIS, PT dependence studies.
• Complementary to Hall B SIDIS, PT dependence studies.
• Understand the Nuclear effect in the light nuclei.
Weihai Workshop
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A New Proposal of TSSA Measurement of a
Transversely Polarized Proton (NH3)
• PAC report for 3He SoLID-Spin Proposal
• 3 cm long NH3 target
• 1035 N/cm2/s polarized luminosity
• 5 T holding field
• line of flames
• Optics property of magnetic
field
70% Polarization
Weihai Workshop
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Projections @ 120 days
About a factor of 4-5 worse than neutron measurement due to lower
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luminosity and larger dilution, but
asymmetry is also larger with proton
Bright Future for TMDs
• Golden channel of Electron-Ion Collider
– See Abhay Despande’s talk
• Sea quark TMDs Gluon Sivers? What happened
at very low x? SIDIS vs. dipole model
• Test Collins-Soper Evolution for high vs. low Q2
at large x.
Weihai Workshop
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Summary
• SIDIS is a powerful tool to study Parton dynamics
in the amplitude level (TMDs)
– Spin-OAM correlation, flavor dependence etc.
• SoLID is an ideal device to study SIDIS
– High luminosity, large acceptance and full azimuthal
coverage
– Will provide ultimate precision (4-D) of SSA/DSA, at
high-x (valence), low Q2 region, which is crucial input
to global analysis.
– Test SIDIS factorization, PT dependence at JLab12
(complementary to SIDIS programs in Hall B/C)
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Weihai Workshop
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Quark Tagging Technique
4
4
1
8
1
P  up ( )  up ( )  d p ( )  up ( )  d p ( )
9
9
9
9
9
4
1
1 C .S .
4
2
N  un ( )  d n ( )  d n ( )  d p ( )  u p ( )
9
9
9
9
9
 (u d )

u quark dominated
Sensitive to d quark
D fav  Du   Dd   Dd   Du 
 (ud )

Dunfav  Dd   Du   Du   Dd 
 p   8u  D fav  d  Dunfav
 p   8u  Dunfav  d  D fav
 n   4d  D fav  2u  Dunfav
 n   4d  Dunfav  2u  D fav
u quark dominated
u quark dominated
Sensitive to d quark
Sensitive to u quark
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