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H.Avakian, JLab, Oct 29 1
Studies of spin-orbit correlations
H.Avakian (JLab)H.Avakian (JLab)
Transverse Spin Phenomena and Their Impact on QCD a Workshop in Honor of Gary Goldstein's 70th
BirthdayOctober 28-29, 2010
Thomas Jefferson National Accelerator Facility
H.Avakian, JLab, Oct 29 2
Outline
Transverse structure of the nucleon and partonic correlations
•Physics motivation•kT-effects in double spin asymmetries•Physics with transversely polarized hadrons and quarks
–kT-effects and SSA in pion production –Higher twist effects–Kaon puzzle
•Future studies of 3D PDFs at CLAS at 6 GeV •Transverse structure & CLAS12•Summary
H.Avakian, JLab, Oct 29 33
Cross section is a function of scale variables x,y,z
z
SIDIS kinematical plane and observablesSIDIS kinematical plane and observables
U unpolarized
L long.polarized
T trans.polarizedBeam polarizationTarget polarization
sin2moment of the cross section for unpolarized beam and long. polarized target
H.Avakian, JLab, Oct 29 44
Structure of the Nucleon
d2kT
PDFs q(x), q(x)…
d2rT
d2k T
Wpu(k,rT) “Mother” distributions (Wigner, GTMDs,..)
d2r T
TMD PDFs q(x,kT), q(x,kT)…
GPD/IPDs H(x,rT), H~(x,rT)…
H.Avakian, JLab, Oct 29 5
DIS vs SIDIS → additional hadron detection.
H.Avakian, JLab, Oct 29 6
Acceptances and efficiencies
How acceptance in and PT affect the A1 and s extractions in SIDIS?
HERMES
H.Avakian, JLab, Oct 29 777
Quark distributions vs kQuark distributions vs kTT: and b : and b
Higher probability to find at large kT u-quarks anti-aligned with proton spin and d-quarks
B.Musch arXiv:0907.2381
B.Musch arXiv:0907.2381 B.Pasquini et al
H.Avakian, JLab, Oct 29 88
CLAS configurationsCLAS configurations
e
ep→e’X
Polarizations:Beam: ~80%NH3 proton 80%,ND3 ~30%HD (H-75%,D-25%)
1) Polarized NH3/ND3 (no IC, ~5 days)2) Unpolarized H (with IC ~ 60 days)3) Polarized NH3/ND3 with IC 60 days
10% of data on carbon 4) Polarized HD-Ice (no IC, 25 days)
Inner Calorimeter
Unpolarized, longitudinally and transversely polarized targets
Unpolarized and longitudinally polarized targets
H.Avakian, JLab, Oct 29 99
Scattering of 5.7 GeV electrons off polarized proton and deuteron targets
SIDIS with JLab at 6 GeVSIDIS with JLab at 6 GeV
DIS kinematics, Q2>1 GeV2, W2>4 GeV2, y<0.85 0.4>z>0.7, MX
2>2 GeV2
2
eX
Large PT range and full coverage in azimuthal angle crucial for studies
H.Avakian, JLab, Oct 29 1010
coscos moment in A moment in ALLLL-P-PTT-dependence-dependence
PT-dependence of cos moment of double spin asymmetry is most sensitive to kT-distributions of quarks with spin orientations along and opposite to the proton spin.
hep-ph/0608048
02=0.25GeV2
D2=0.2GeV2
CLAS PRELIMINARY
H.Avakian, JLab, Oct 29 11
A1 PT-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
+ A1 suggests broader kT distributions for f1 than for g1
- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors
02=0.25GeV2
D2=0.2GeV2
0.4<z<0.7
arXiv:1003.4549
H.Avakian, JLab, Oct 29 12
A1
A1 PT-dependence
CLAS data suggests that width of g1 is less than the width of f1
AnselminoCollins
Lattice
New CLAS data would allow multidimensional binning to study kT-dependence for fixed x
PT
PT
arXiv:1003.4549
H.Avakian, JLab, Oct 29 13
Beam SSA: ALU from CLAS @ JLab
0.5<z<0.8
Beam SSA from hadronization (Collins effect) by Schweitzer et al.
Photon Sivers Effect Afanasev & Carlson, Metz & Schlegel, Gamberg et al.
Beam SSA from initial distribution (Boer-Mulders TMD) F.Yuan using h1
┴ from MIT bag model
Collins contribution should be suppressed → g┴ wanted !!!
H. Avakian, Frascati, Oct 2114
No x-dependence?
Change the sign at low z?
Beam SSA: ALU from COMPASS & HERMES
CLAS @4.3GeV
Beam SSA for exclusive pions
Sign flip at z ~ 0.5
At z>0.5 struck quark in pion
W2>4 GeV2,Q2>1 GeV2
4.3 GeV
5.7 GeV
LUND-MC
-t < 0.5GeV2
15H.Avakian, JLab, Oct 29
H.Avakian, JLab, Oct 29 16
Kaon <cos2> @ HERMES
H.Avakian, JLab, Oct 29 17
Collins asymmetry - proton
Is there a link between HERMES and BRAHMS Kaon vs pion moments (K- has the same sign as K+ and pi+, comparable with K+)?
“Kaon puzzle” in spin-orbit correlations
H.Avakian, JLab, Oct 29 18
Collins effect
Simple string fragmentation (Artru model)
Leading pion out of page ( - direction )
If unfavored Collins fragmentation dominates measured - vs +, why K- vs K+ is different?
L
z
kicked in the opposite to the leading pion(into
the page)
Sub-leading pion opposite to leading (double kick into the
page)
L
18
H. Avakian, Frascati, Oct 2119
Kotzinian-Mulders Asymmetries
B.Musch arXiv:0907.2381B.Pasquini et al, arXiv:0910.1677
HERMES
CLAS (5 days)
Worm gear TMDs are unique (no analog in GPDs)
Cisbani
Griffioen
H.Avakian, JLab, Oct 29 2020
1. Small field (∫Bdl~0.005-0.05Tm)2. Small dilution (fraction of events
from polarized material)3. Less radiation length4. Less nuclear background (no nuclear
attenuation)5. Wider acceptance
CLAS transversely polarized HD-Ice targetHD-Ice target vs std nuclear targets
H.Avakian, JLab, Oct 29 2121
Collins SSAsCollins SSAs
CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function
Anselmino et al H.A.,A.Efremov,P.Schweitzer,F.Yuan
helicity-transversity=pretzelosity
CLAS E08-015 (2011)
H.Avakian, JLab, Oct 29 2222
Measurement of Sivers function and GPD-E
DVCS Transverse asymmetry (function of momentum transfer to proton) is large and has strong sensitivity to GPD-E
CLAS will provide a measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements.
Meissner, Metz & Goeke (2007)
GPD-E=0
(DVCS) (SIDIS) CLAS E08-015
TMDs program @ 12 GeV in Hall B
Nq
ULT
H.Avakian, JLab, Oct 29 23
E12-06-112:E12-06-112: Pion SIDIS E12-09-008: E12-09-008: Kaon SIDIS
E12-07-107:E12-07-107: Pion SIDIS E12-09-009: E12-09-009: Kaon SIDIS
LOI12-06-108: LOI12-06-108: Pion SIDISLOI12-09-004: LOI12-09-004: Kaon SIDIS
PAC approved experiments & LoI
Complete program of TMDs studies for pions and kaons
Kaon measurements crucial for a better understanding of the TMDs “kaon puzzle”
Kaon SIDIS program requires an upgrade of the CLAS12 detector
PID RICH detector (Project under development)
CLAS12CLAS12
H.Avakian, JLab, Oct 29 24
Collins fragmentation: Longitudinally polarized target
•Study the Collins function of kaons•Provides independent information on the RSMT TMD
Kotzinian-Mulders Asymmetry
proton deuteron
Pasquini et al.
H.Avakian, JLab, Oct 29 25
Some questions to address in future
• What is the shape of kT-distributions?• Can kT-distributions be flavor dependent?• Are kT-distributions the same for different spin orientations?• How spin-orbit correlations change the momentum
distributions?• How big are quark-gluon correlations?• How nuclear medium changes kT-distributions?• What is the fraction of kT-generated in FSI?• How gluons and sea are distributed in kT
How spin-orbit correlations are related to the longitudinal structure and nuclear effects?
H.Avakian, JLab, Oct 29 26
Summary
•CLAS longitudinally polarized NH3 and ND3 target data provides superior sample of events allowing detailed studies of single and double spin asymmetries using multidimensional bins
Measurements of spin and azimuthal asymmetries with unpolarized, longitudinally polarized and transversely polarized targets in semi-inclusive processes at CLAS/CLAS12 will :
•Measure TMDs of partons in the valence region•Provide detailed info on partonic spin-orbit correlations •Study quark-gluon correlations (HT)•Study nuclear modification of 3D PDFsWe’ll try hard to keep you busy next 10-15 years!
H.Avakian, JLab, Oct 29 27
Support slides….
M.Osipenko
H.Avakian, JLab, Oct 29 29
HERMES/COMPASS
Berger
H.Avakian, JLab, Oct 29 3030
~10% of E05-113 data
30
Longitudinal Target SSA measurements at CLAS Longitudinal Target SSA measurements at CLAS
p1sin+p2sin2
0.12<x<0.48
Q2>1.1 GeV2
PT<1 GeV
ep→e’X
W2>4 GeV2
0.4<z<0.7
MX>1.4 GeV
y<0.85 p1= 0.059±0.010p2=-0.041±0.010
p1=-0.042±0.015p2=-0.052±0.016
p1=0.082±0.018p2=0.012±0.019
CLAS-2009 (E05-113)CLAS PRELIMINARY
CLAS-2000
Data consistent with negative sin2 for +
H.Avakian, JLab, Oct 29 31
Kotzinian-Mulders Asymmetries
B.Musch arXiv:0907.2381B.Pasquini et al, arXiv:0910.1677
HERMES
CLAS (5 days)
Worm gear TMDs are unique (no analog in GPDs)
H.Avakian, JLab, Oct 29 323232
Single hadron production in hard scattering
xF - momentum
in the CM frame
xF>0 (current fragmentation)
xF<0 (target fragmentation)
h
h
Target fragmentation
Current fragmentation
Fracture Functions
xF
M
0-1 1
h
h
TMD GPD
kT-dependent PDFs Generalized PDFs
hFF
DA DA
exclusivesemi-inclusive semi-exclusive
You think you understand something? Now check your target fragments!
H.Avakian, JLab, Oct 29 333333
Quark distributions at large kQuark distributions at large kTT
Higher probability to find a hadron at large PT in nuclei
kT-distributions may be wider in nuclei?
PT = p┴ +z kT
bigger effect at large z
Understanding of modification of kT widths in nuclei is important also for nucleon TMDs
H.Avakian, JLab, Oct 29 3434
kT and FSI
l l’
x,kT
proton
spectator system
•The difference is coming from final state interactions (different remnant)•Studies of DIS and SIDIS with nuclear targets provide info on kT
Tang,Wang & Zhou
Phys.Rev.D77:125010,2008
BHS 2002Collins 2002Ji,Yuan 2002
lT
l l’
x,k’T l’T
spectator systemnucleus
total transverse momentum broadening squared
~4 n, with ~4-6 MeV
soft gluon exchanges included in the distribution function (gauge link)
35H.Avakian, JLab, Oct 29
H.Avakian, JLab, Oct 29 36
CHL-CHL-22
Beam Current: 90 µAMax Pass energy: 2.2 GeVMax Enery Hall A,B,C: 11 GeV
May 2012
6 GeV Accelerator Shutdown starts
May 2013 Accelerator Commissioning starts
2013-2015
Pre-Ops (beam commissioning)
Solenoid 5T
DC R1, R2, R3 LTCC
HTCC
FTOF
PCAL
EC
CLAS12
L = 1035 cm-2s-1
Primary goal of experiments using CLAS12: study of the internal nucleon dynamics by accessing GPDs &
TMDs detector tuned for studies of exclusive and semi-inclusive
reactions in a wide kinematic range. Large acceptance detector and high luminosity capabilities
CEBAF @ 12 GeV and CLAS12
Structure of the nucleon
H.Avakian, JLab, Oct 29 37
You think you understand something? Now go 3D!
You think you understand something? Check the nuclear targets!
You think you understand something? Now add the strange!
You think you understand something? Now add the spin!
You think you understand something? Now check your target fragments!
H.Avakian, JLab, Oct 29 38
Sivers effect in the target fragmentation
A.Kotzinian
High statistics of CLAS12 will allow studies of kinematic dependences of the Sivers effect in target fragmentation region
xF>0 (current fragmentation)
xF<0 (target fragmentation)
Fracture Functions
Mh
H.Avakian, JLab, Oct 29 393939
Jet limit: Higher Twist azimuthal asymmetriesJet limit: Higher Twist azimuthal asymmetries
No leading twist, provide access to quark-gluon correlations
T-odd
H.A.,A.Efremov,P.Schweitzer,F.Yuan Phys.Rev.D81:074035,2010
“interaction dependent”
Twist-2
Twist-3
H.Avakian, JLab, Oct 29 4040
AALLLL P PTT-dependence in SIDIS-dependence in SIDIS
M.Anselmino et al hep-ph/0608048
•New experiment with 10 times more data will study the PT-dependence for different quark helicities and flavors for bins in x to check if 0< 2
02=0.25GeV2
D2=0.2GeV2
0.4<z<0.7
E05-113
H.Avakian, JLab, Oct 29 41
H. Avakian, JLab, May 34141
SIDIS: partonic cross sections
kT
PT = p┴ +z kT
p┴
Ji,Ma,Yuan Phys.Rev.D71:034005,2005
Is the info on x-kT correlations accessible in kT integrated observables?
H.Avakian, JLab, Oct 29 42
Extracting widths from A1
Assuming the widths of f1/g1 x,z and flavor independent
Anselmino et al
Collins et al
Fits to unpolarized data
EMC
H.Avakian, JLab, Oct 29 43
Dilution factor in SIDIS
Multiple scattering and attenuation in nuclear environment introduces
additional PT-dependence for hadrons
Fraction of events from polarized hydrogen in NH3
Nu,Np -total counts from NH3 and carbon normalized by lumi
u, p -total areal thickness of hydrogen (in NH3), and carbon target
Cn=Nitr/Carbon ratio (~0.98)Diff. symbols for diff x-bins
-
H.Avakian, JLab, Oct 29 44
EMC Effect
I. Cloet (Argonne-2010)
NJL-model In medium quarks are more relativisticq more sensitive to angular momentumLower components of wavefunctions more enhancedLower components carry more angular mom.
44H. Avakian, JLab, May 3
In medium modificationMass, magnetic moment, sizeForm factors, PDFs, GPDs, TMDs, etc
How sensitive are inclusive measurements to the transverse structure of nucleon and nucleus ?