Transcript Transverse Spin and TMDs from SIDIS with Transversely Polarized Nucleon Jian-ping Chen, Jefferson Lab INT-10-3, EIC Program, Nov.

Transverse Spin and TMDs from SIDIS with
Transversely Polarized Nucleon
Jian-ping Chen, Jefferson Lab
INT-10-3, EIC Program, Nov. 12, 2010
 Introduction
 Longitudinal and Transverse Spin: Inclusive Scattering
Polarized Structure, OAM, g2/d2, Higher-twists
 Transverse Spin with SIDIS at JLab
Preliminary neutron (3He) results from 6 GeV experiment
12 GeV plan: 3-d mapping
 EIC simulations: 4-d (x,z,PT,Q2) projections
p/K (quark/sea TMDs) (done by Min Huang/Xin Qian)
D and D_bar (gluon TMDs) (done by Xin Qian)
 Orbital Angular Momentum
Introduction
Why EIC?
Why do we care about transverse (spin) structure?
Why EIC? Why Transverse?
•
EIC: the ultimate machine to study quark gluon structure of
nucleon/nuclear and strong interaction (QCD)?
•
WHY EIC? to our non-physics or non-nuclear physics friends:
Breakthrough in understanding strong interaction (in strong region)?
Full understanding of nucleon structure ?
• Nucleon, most of the visible matter
Dark effects also present (magnified) in strong interaction
• We do not really know where or if it will have a breakthrough
We are familiar (comfortable) with e-p (e-ion)
• Most major modern discoveries not done as major
facilities initially designed/intended for.
• Need justification(s) for EIC, guess best case for it
• What question(s) to address/to ask? Confinement?
• Spin has provided many surprises
Transverse: new ingredient to possible more surprises
Strong Interaction and QCD
•
Strong interaction, running coupling ~ 1
-- QCD: accepted theory for strong interaction
-- asymptotic freedom (2004 Nobel)
perturbation calculation works (to certain level) at high energy
-- interaction significant at intermediate energy
quark-gluon correlations
-- interaction strong at low energy (nucleon size)
as
confinement

•
theoretical tools:
pQCD, OPE, Lattice QCD, …,
models, …
A major challenge in fundamental physics:
Understand QCD in strong interaction region
 Study and understand nucleon structure
E
Nucleon Structure and QCD
•
Colors are confined in hadronic system
•
Nucleon: ideal lab to study QCD
•
Nucleon = u u d + sea + gluons
• Mass: ~1 GeV, but u/d quark mass only a few MeV each!
Spin: ½, quarks contribute ~30%
Spin Sum Rule(s)
Orbital Angular Momentum
Relations to GPDs and TMDs?
•
Quarks and gluon field are in-separable
• Spin-orbit correlations
• Multi-parton correlations
• Transverse dimension is crucial for a full understanding of nucleon
structure and QCD, help understanding confinement
•
•
Complexity vs. simplicity: beauty in physics
Precision: key to possible new understanding
Not JUST imaging as in tomography !
Nucleon Spin Structure
Spin, Orbit Angular Momentum,
Higher-Twists: quark-gluon correlations
Polarized Structure Functions and PDFs
DSSV, PRL101, 072001 (2008)
Spin Asymmetries in Valence (High-x) Region
Hall B CLAS, Phys.Lett. B641 (2006) 11
Hall A E99-117, PRL 92, 012004 (2004)
PRC 70, 065207 (2004)
pQCD with Quark Orbital Angular Momentum
F. Yuan, H. Avakian, S. Brodsky, and A. Deur, arXiv:0705.1553
Inclusive Hall A and B and Semi-Inclusive Hermes
BBS
BBS+OAM
Transverse Spin in Inclusive Scattering: g2
(Color Polarizability) or Lorentz Force: d2
• B-C Sum Rule
1
Γ 2   g 2 ( x)dx  0
0
• 2nd moment of g2-g2WW
d2: twist-3 matrix element
1
d 2 (Q )  3 x [ g 2 ( x, Q )  g 2
2
2
2
WW
( x, Q 2 )]dx
0
1
  x [2 g1 ( x, Q )  3g 2 ( x, Q )]dx
2
0
2
2
Precision Measurement of g2n(x,Q2): Search for Higher Twist Effects
• Measure higher twist  quark-gluon correlations.
• Hall A Collaboration, K. Kramer et al., PRL 95, 142002 (2005)
BC Sum Rule
1
0<X<1 :Total Integral
P
N
Γ 2   g 2 ( x)dx  0
0
Brawn: SLAC E155x
Red: Hall C RSS
Black: Hall A E94-010
Green: Hall A E97-110
(preliminary)
Blue: Hall A E01-012
(very preliminary)
BC = Meas+low_x+Elastic
“Meas”: Measured x-range
3He
“low-x”: refers to unmeasured low x part
of the integral.
Assume Leading Twist Behaviour
Elastic: From well know FFs (<5%)
d2(Q2)
E08-027 “g2p”
SANE
projected
6 GeV Experiments
Sane: recently completed in Hall C
“g2p” in Hall A, 2011
LQCD
“d2n” recently completed in Hall A
Twist-4 f2 extraction and Color Polarizabilities
•
JLab + world n data,
m4 = (0.019+-0.024)M2
•
Twist-4 term
m4 = (a2+4d2+4f2)M2/9
• extracted from m4 term
f2 = 0.034+-0.005+-0.043
•
Color polarizabilities/Lorentz force
cE = 0.033+-0.029
cB = -0.001+-0.016
• Proton and p-n
f2= -0.160+-0.179 (p),
-0.136+-0.109 (p-n)
Review: Prog. Part. Nucl. Phys. 63, 1(2009)
PLB 93 (2004) 212001
Transversity and TMDs
What have we learned?
“Leading-Twist” TMD Quark Distributions
Quark
Unpol.
Long.
Trans.
Nucleon
Unpol.
Long
.
Transversity
Trans.
Sivers
worm-gear
Pretzelocity
Pasquini, GPD2010
GTMDs
Wigner-Ds
FT   b
FT
TMDs
GPDs
spin densities
FT
PDs
Form Factors
charge densities
Separation of Collins, Sivers and pretzelocity effects
through angular dependence in SIDIS


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
Collins
AUT
 sin(h  S )
Sivers
AUT
 sin(h  S )
UT
UT
 h1  H1
 f1T  D1
AUPretzelosity
 sin(3h  S )
T
UT
 h1T  H1
Status of Transverse Spin Study
•
•
Large single spin asymmetry in pp->pX
Collins Asymmetries
- sizable for the proton (HERMES and COMPASS)
large at high x, p- and p has opposite sign
unfavored Collins fragmentation as large as favored (opposite sign)?
- consistent with 0 for the deuteron (COMPASS)
•
Sivers Asymmetries
- non-zero for p+ from proton (HERMES), smaller with COMPASS data?
- consistent with zero for p- from proton and for all channels from deuteron
- large for K+ ?
•
Collins Fragmentation from Belle
•
Global Fits/models by Anselmino et al., Yuan et al., Pasquini et al., ….
•
Very active theoretical and experimental study
RHIC-spin, JLab (6 GeV and 12 GeV), Belle, FAIR, J-PARC, EIC, …
JLab 6 GeV Neutron Transversity Experiment: E06-010
Preliminary Results
E06-010 Experiment
• First measurement on n (3He)
• Polarized 3He Target
• Polarized Electron Beam
3

He (e , ep  ) X

Luminosity
Monitor
– ~80% Polarization
– Fast Flipping at 30Hz
– PPM Level Charge Asymmetry
controlled by online feed back
• BigBite at 30º as Electron Arm
– Pe = 0.7 ~ 2.2 GeV/c
• HRSL at 16º as Hadron Arm
– Ph = 2.35 GeV/c
• 7 PhD Thesis Students (4 graduated this year)
Beam Polarimetry
(Møller + Compton)
21
JLab polarized 3He target
15 uA
longitudinal,
transverse and vertical
Luminosity=1036 (1/s)
(highest in the world)
High in-beam polarization
~ 65%
Effective polarized
neutron target
13 completed experiments
6 approved with 12 GeV (A/C)
Performance of
3He
Target
• High luminosity: L(n) = 1036 cm-2 s-1
• Record high 65% polarization (preliminary) in beam
with automatic spin flip / 20min
Preliminary Asymmetry ALT Result
To leading twist:
cos( h  s )
ALT
 FLTcos(h s )  g1qT  D1hq
• Preliminary 3He ALT
- Systematic uncertainty is still under work
- Projected neutron ALT stat. uncertainty : 6~10%
Planned JLab12 GeV Experiment: E12-10-006
Precision 3-d mapping in the valence region
Precision Study of Transversity and TMDs
• From exploration to precision study
• Transversity: fundamental PDFs, tensor charge
• TMDs provide 3-d structure information of the nucleon
• Learn about quark orbital angular momentum
• Multi-dimensional mapping of TMDs
– 3-d (x,z,P┴), limited Q2 range.
• Precision  high statistics
– high luminosity and large acceptance
Solenoid detector for SIDIS at 11 GeV
Y[cm]
Yoke
Coil
3He
Target
Aerogel
LGEMx4
LS
HG
SH
GEMx2
PS
Z[cm]
3-d Mapping of Collins/Sivers Asymmetries 12 GeV With SOLID (L=1036)
• Both p+ and p• For one z bin
(0.5-0.55)
• Will obtain 8
z bins (0.30.7)
• Upgraded PID
for K+ and K-
Power of SOLID
EIC Simulation: p/K (Min Huang/Xin Qian)
Precision 4-d mapping in the sea quark region
DIS (electron)
Electron: 2.5°< ϴe <
150°Pe > 1.0 GeV/c
Full azimuthal-angular
coverage
DIS cut:
Q2 > 1 GeV2
W > 2.3 GeV
0.8 > y > 0.05
Capability to detect high momentum
electron
Q2 > 1 GeV2
ϴe > 5°
No need to cover extreme forward
angle for electron
EIC phase space
12 GeV: from
approved SoLID
SIDIS experiment
Lower y cut, more
overlap with 12 GeV
0.05 < y < 0.8
Study both Proton and Neutron
ion momentum
PN

 z
Z/A
Not weighted by Cross
section.
Flavor separation, Combine the data
the lowest achievable x limited by the effective neutron beam and the
PT cut
Cross Section in MC
• Low PT cross section:
• A. Bacchetta hep-ph/0611265 JHEP 0702:093 (2007)
• High PT cross section:
• M. Anselmino et al. Eur. Phys. K. A31 373 (2007)
d
dx dy dz d dH dPh2
•
•
•
•
6x6 Jacobian
calculation
PDF: CTEQ6M
FF: Binneweis et al PRD 52 4947
<pt2> = 0.2 GeV2 <kt2> = 0.25 GeV2
NLO calculation at large PT
– <pt2> = 0.25 GeV2
– <kt2> = 0.28 GeV2
d
dpef d cos ef def dph d cos h dh
• 11 + 60 GeV
Projections with Proton on π+
36 days
L = 3x1034 /cm2/s
• 11 + 100 GeV
36 days
L = 1x1034/cm2/s
For both above
2x10-3 , Q2<10 GeV2
4x10-3 , Q2>10 GeV2
• 3 + 20 GeV
36 days
L = 1x1034/cm2/s
4x10-3 , Q2<10 GeV2
5x10-3 , Q2>10 GeV2
Polarization 70%
Overall efficiency 50%
z: 12 bins 0.2 - 0.8
PT: 5 bins 0-1 GeV
φh angular coverage considered
Show the average of Collins/Sivers/Pretzlosity projections
Also π-
Projections with deuteron (neutron)
• 11 + 60 GeV
72 days
• 3 + 20 GeV
72 days
D: 88% effective
polarization
Projections with 3He (neutron)
• 11 + 60 GeV
72 days
• 11 + 100 GeV
72 days
• 12 GeV SoLid
3He:
87% effective
polarization
Equal stat. for proton
and neutron (combine
3He and D)
11 + 60 GeV
11 + 100 GeV
3+20 GeV
P
36 d (3x1034/cm2/s)
36 d (1x1034/cm2/s)
36 d (1x1034/cm2/s)
D
72 d
72 d
72 d
3He
72 d
72 d
72 d
Proton π+ (z = 0.3-0.7)
D π+ (z = 0.3-0.7)
3He
π+ (z = 0.3-0.7)
Proton K+ (z = 0.3-0.7)
PT dependence (High PT) on p of π+
10 bins 1 -- 10
GeV in
log(PT)
EIC Simulation: D/D_bar (Xin Qian)
Study Tri-gluon Correlations (Gluon TMDs)?
Need update to take into account the new study
by Kazuhiro Tanaka/Yuji Koike
Simulation
• Use HERMES Tuned Pythia (From H. Avagyan)
– Thanks to E. Aschenauer for providing input file for
Charm production (Mc = 1.65 GeV)
• First try 11+60 configuration.
• Physics includes:
– VMD
– Direct
– GVMD
– DIS (intrinsic charm)
This is what
we want!!
Event Generator
•
•
•
•
Q2: 1.-1500.
y: 0.05-0.9
LUND Fragmentation.
Major decay channel of D meson is
D (cu )  p (u d ) K ( su )
0


D (cu )  p (ud ) K (u s )
0


Branching ratio: 3.8+0.07%
D meson from Different Processes
Dominated contamination is
from GVMD, and then DIS
at PT > 1 GeV
Q2 > 1 0.9 > y > 0.05
z > 0.15
At large Q2, contamination
become smaller.
Decay Products and D meson
Distribution
D
Dbar
Electron, D meson, Dbar meson
Pion vs kaon, momentum and
polar angle.
D meson Reconstruction
• Momentum res.: 0.8 % * p /10 (GeV)
• Polar angle res.: 0.3 mr
• Azimuthal angle res.: 1 mr
– Thanks to R. Ent for providing these information.
Background from
random
coincidence of
pion and kaon in
the final state.
• 1.8 MeV invariant mass resolution. A better
resolution would be desirable to reduce S/B.
Naively,
( S  B )  ( S  B )
A
S  S
1
SB

S
S
S  S  S
A 
B  B  B
144 Days @ L = 3x1034 on Proton
10 GeV > Momentum > 0.6 GeV
Polar angle > 10 degree
0.9 > y > 0.05; Q2>1GeV2,
PT > 1GeV; z > 0.15
Include decay of kaon and pion
Additional 60% efficiency
80% polarization
Sqrt(2) for angular separation.
Dilution factor due to other
processes and accidental pion and
kaons.
2x2 bins in x and Q2.
D
Dbar
Calculations from Z. B. Kang
D
Dbar
Summary
•
•
•
•
•
Spin: from longitudinal to transverse
Why transverse spin and transverse structure?
What have we learned about TMDs? A beginning, surprises
Preliminary results from 6 GeV neutron transversity experiment
Planned12 GeV
• Precision 4-d (x,z,PT, Q2)mapping of TMDs in Valence quark region
• Precision determination of tensor charge (LQCD)
• EIC simulation/projections
•
•
•
•
Ultimate coverage in kinematics, complete 4-d (x,z,PT,Q2) mapping for p/K
Initial study on D/D_bar SIDIS
Study sea and gluon TMDs
Understudy QCD dynamics, spin-orbit correlations, multi-parton correlations
• Orbital Angular Momentum
• Lead to breakthroughs in a better understanding of nucleon
structure and QCD
Quark Orbital Angular Momentum
Definitions, Indirect Evidences,
Experimental Observables, Models
Orbital Angular Momentum
 `Spin Crisis’ -> S ~ 30%; G small so far
 Orbital angular momentum important from indirect experimental evidences
Proton Form Factors
A1 (d/d ) at high-x
N-D transition
…
 Definitions:
A+=0 (light-cone) gauge
(½)S + Lq+ G + Lg=1/2
(Jaffe)
Gauge invariant
(½)S + Lq + JG =1/2
(Ji)

Ji’s sum rule -> GPDs (DVCS measurements), LQCD calculation

TMDs, Pretzelocity, Worm-gears, Sivers/Boer-Mulders.
Model calculations
What observable (more directly) corresponds to Lz~ bx X py
Model independent relations?
Orbital Angular Momentum
Pasquini, GPD2010
1/2=(½)S +Lqz+ JG
not unique decomposition
gauge invariant,
but contains interactions through
the gauge covariant derivative
[ X. Ji, PRL 78, (1997) ]
Ji’s sum rule
quark orbital angular momentum: Lq = Jq - Sq
not gauge invariant,
but diagonal in the LCWFs basis
[ R.L. Jaffe, NPB 337, (1990) ]
in the light-cone gauge A+=0,
model independent relations
of Lqz with GPDs and TMDs
Distribution in x of Orbital Angular Momentum
Pasquini, GPD2010
Definition of Jaffe and Manohar: contribution from different partial waves
TOT
up
down
Lz=0
Lz=-1
Lz=-1
Lz=+2
Comparison between the results with the Jaffe-Manohar definition and the results with the Ji
definition (total results for the sum of up and down quark contribution)
Jaffe-Manohar
Ji
Orbital Angular Momentum
 Definition of Jaffe and Manohar: contribution from different partial waves
= 0 ¢ 0.62 + (-1) ¢ 0.14 + (+1) ¢ 0.23 + (+2) ¢ 0.018 = 0.126
 Definition of Ji:
[BP, F. Yuan, in preparation]
[scalar diquark model: M. Burkardt, PRD79, 071501 (2009)]
Pasquini/Yuan
Pasquini, GPD2010
GTMDs
TMDs
GPDs
GPDs and TMDs probe the same overlap of quark LCWFs in different kinematics
nucleon
quark
at »=0
UU
UT
LL
TU
TT
TT
LT
0
TL
0