SoLID-Spin Program at 12 GeV JLab
Xin QianKellogg Radiation Lab
CaltechFor SoLID Collabration
1Weihai Workshop
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
2Weihai Workshop
Nucleon Spin Structure• Understand Nucleon Spin in terms of quarks and
gluons (QCD).
– Small contribution from quarks and gluons’ intrinsic spin
~30% from data “spin crisis”
Nucleon’s spinJi’s Sum Rule
J q
Orbital angular momentum is important!Parton transverse motion + Spin-orbit correlations
Weihai Workshop 3
Transverse Momentum Dependent PDFs
TMD f1u(x,kT)
Longitudinal Direction zTransverse
Plane x-y4Weihai Workshop
A Unified Picture of Nucleon Structure (X. Ji) Wp
u(x,kT,r ) Wigner distributions
PDFs f1
u(x), .. h1u(x)
d2kT
d3r
TMD PDFs f1
u(x,kT), .. h1u(x,kT)
X. Ji PRL 91 (03)
3D imaging
6D Des.
Form FactorsGE(Q2), GM(Q2)
GPDs/IPDs
d2kT drz
d2rT
dx &Fourier Transformation
1D5Weihai Workshop
Leading-Twist TMD PDFs
f1 =
f 1T =
SiversSivers
HelicityHelicity
g1 =
h1 =TransversityTransversity
h1 =
Boer-MuldersBoer-Mulders
h1T =
PretzelosityPretzelosity
g1T =
Worm GearWorm Gear
h1L =
Worm GearWorm Gear(Kotzinian-Mulders)(Kotzinian-Mulders)
Nucleon Spin
Quark Spin
Spin-orbital (trans. mom.) correlation is important!
Very well known
Reasonably known
Weihai Workshop 6
Semi-Inclusive DIS• A DIS reaction in which a hadron h, produced in the
current fragmentation region is detected coincidently with scattered electron (k’).
Parton distribution function (PDF)
Fragmentationfunction (FF)
DXs ~ PDF X FF
h tags struck quark’s flavor, spin andtransversemomentum
Current Fragmentation
h
XhkPk '
Weihai Workshop 7
Access TMDs through SIDIS
SL, ST: Target Polarization; e: Beam Polarization
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Sh
Sh
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h
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FS
FS
F
F
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F
F
y
xyQdPdzddxdyd
d
Unpolarized
PolarizedTarget
PolarizedBeam andTarget
Boer-Mulder
Sivers
Transversity/Collins
Pretzelosity
Weihai Workshop 8
Separation of Collins, Sivers and pretzelocity effects through angular dependence
1( , )
sin( ) sin( )
sin(3 )
l lUT h S
h SSiverCollins
Pretzelosi
UT
tyU
sUT h S
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N NA
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A
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PretzelosityU
SiversUT
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T h S T
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TU
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TA
H
f
A
D
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h
Weihai Workshop
UT: Unpolarized lepton + Transversely polarized nucleon
9
Collins effect• Access to transversity– Transversity links
quak’s spin tonucleon spin
– Collins FF links quark’s spin to hadron transverse momentum
• Artru model– Based on LUND
fragmentation picture.
Weihai Workshop
11 HhA TCollins
10
Rich Physics in TMDs (Sivers Function)• Correlation between nucleon spin with quark orbital
angular momentum
Burkhardt : chromodynamic lensing
Final-State-InteractionYD
qTSIDIS
qT ff
11Important test forFactorization
11 DfA TSivers
Weihai Workshop 11
Current Status on TMD• Collins Asymmetries - Sizable for proton (HERMES and COMPASS)
Large at high x, large for - but with opposite signUnfavored 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 …
12Weihai Workshop
E06010: arXiv: 1106.0363, PRL in press
Weihai WorkshopSee X. Jiang’s talk 13
• High 1036 N/cm2/spolarized luminosity
• Achieved Performance:– Transverse/Vertical and
Longitudinal PolarizedTarget
– >60% polarization– Fast Spin Flip
• Large acceptanceenables 4-D mappingof asymmetries
• Full azimuthal-angle coverage -> smaller systematic uncertainties
SoLID Setup for SIDIS on 3He
~90% ~1.5% ~8%
Effective pol. neutron target
14Weihai Workshop
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 Chamber)
• Fast pipeline DAQ (Similar to Hall D)
• See Z. W. Zhao’s talk for simulation
Progressive Tracking, Mom. res. 1%, polar angular res. 0.3 mr, azimuthal angular res. 5 mr, 0.8 cm vertex res with realistic magnetic field simulation and 200 um GEM pos. res. Shoot for 100 ps TOF resolution, (60 ps intrinsic resolution from MRPC) 15Weihai Workshop
SIDIS L.-G. Cherenkov: Optical system
)11
(cos
2
rxix
R
Focusing optimized for central ray: for SIDIS kinematics (BaBar) => (9.3 + 14.3)/2 = 11.8 deg
mirror the tonormal and
ray incident between angle
ray reflected
mirroron ray incident
rxix
One spherical mirror
Slide from S. Malace16Weihai Workshop
SIDIS L.-G. Cherenkov: Focusing “-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
Collection efficiency dependence of : small effect at isolated kinematics
Slide from S. Malace 17Weihai Workshop
• Two main choices– 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
Weihai Workshop 18
Choice of CalorimeterTypical Pb SciFi
Hertzog, NIM, 1990
Typical ShashlikPolyakov, COMPASS Talk, 2010
Talk from J. Huang
Weihai Workshop 19
Scan for best shower and preshower thickness
Reach Best rejection @ 3~5rad
length
Reach Best rejection @ 3~5rad
length
Total rad length
Total rad length
No
pres
how
er s
epar
ation
Electron Efficiency
1/ (Pi rejection)Minimal is best
Reach Best rejection @ ~20
rad length
Reach Best rejection @ ~20
rad length
Total rad length
Can not contain
EM shower More hadron shower
Electron Efficiency
Talk from J. Huang
• L2: additional detector, simple pattern matchhttps://www.jlab.org/exp_prog/electronics/trigdaq/PipelineTriggerElectronics_S&T09.pdf
Ben Raydo Talk
20Weihai Workshop
ROCROC
ROCROC
ROCROC
ROCROC
ROCROC
ROCROC
ROCROC
ROCROC
ROCROC
Front-End
Crates
Read O
ut
Con
trolle
rs
~60 crates~50MB/s out
per crate
EB1Event Builder
stage 1
EB1Event Builder
stage 1
EB1Event Builder
stage 1
EB2Event Builder
stage 2
EB2Event Builder
stage 2
Staged Event Building
blocked event fragments
partially recombined event fragments
N x M array of nodes (exact number to be determined by available hardware at time of
purchase)
Level-3 Trigger
and monitori
ng
full events
L3 FarmL3 Farm
nodenode
nodenode
nodenodenodenode
nodenodenodenode
nodenode
Raid
Dis
k
EREvent Recorder
Event Recording
300MB/s in300MB/s out
• All nodes connected with 1GB/s links
• Switches connected with 10GB/s fiber optics
L3 Farm (slide from A. Camsonne)
Weihai Workshop21
Natural Extension of E06-010
• 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 channels.
11
11
11
)cos(
)sin(
)sin(
DgA
DfA
HhA
TshLT
TshSiversUT
TshCollinsUT
22Weihai Workshop
Transversity• 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
h1T =
23Weihai Workshop
Map Collins, Sivers and Pretzlosity asymmetries in a 4-D (x, z, Q2, PT)
24Weihai Workshop
Sivers Function• Correlation between nucleon spin with quark angular momentum• Important test for factorization• 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)
f 1T =
YD
qTSIDIS
qT ff
11
UUT
UUUTTTJUT
dP
APJdPA
Sh
Sh
)sin(
)sin()(
Also in x
25Weihai Workshop
Pretzlosity:• Direct measurement of relativistic effect of quark?
PRD 78, 114024 (2008)• Direct measurement of OAM? PRD 58, 096008 (1998)• First non-zero pretzlosity asymmetries?
h1T =
26Weihai Workshop
Worm-gear functions:• 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
• Connections with Collinear PDFs through WW approx. and LIR.
h1L =
g1T =
Worm Gear
Cent
er o
f poi
nts:
)()(~ 11 zDxgA TLT )()(~ 11 zHxhA LUL
27Weihai Workshop
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.
28Weihai Workshop
A New Proposal of TSSA Measurement of a Transversely Polarized Proton (NH3)
• PAC report for 3He SoLID-Spin Proposal
Weihai Workshop 29
• 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
Projections @ 120 days
Weihai Workshop 30About a factor of 4-5 worse than neutron measurement due to lower 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. 31Weihai Workshop
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)
32Weihai Workshop
Weihai Workshop 33
Weihai Workshop
Quark Tagging Technique
)9
2()
9
4()
9
1()
9
1()
9
4(
)9
1()
9
8()
9
1()
9
4()
9
4(
..
pp
SC
nnn
ppppp
uddduN
duduuP
u quark dominated
Sensitive to d quark
)( du )( du
duudunfav
uddufav
DDDDD
DDDDD
favunfavn
unfavfavn
favunfavp
unfavfavp
DuDd
DuDd
DdDu
DdDu
24
24
8
8
u quark dominatedu quark dominatedSensitive to d quarkSensitive to u quark
34