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Studies of spin-orbit correlations

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Studies of spin-orbit correlations

H.Avakian (JLab)

Transverse Spin Phenomena and Their Impact on QCD a Workshop in Honor of Gary Goldstein's 70th BirthdayOctober 28-29, 2010Thomas Jefferson National Accelerator Facility

H.Avakian, JLab, Oct 29

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

Target polarization

Cross section is a function of scale variables x,y,z

U unpolarized

L long.polarized

T trans.polarized

z

Beam polarization

sin2f moment of the cross section for unpolarized beam and long. polarized target

3

H.Avakian, JLab, Oct 29

TMD PDFs

q(x,kT), Dq(x,kT)…

GPD/IPDs

H(x,rT), H~(x,rT)…

Wpu(k,rT) “Mother” distributions (Wigner, GTMDs,..)

d2rT

d2kT

d2kT

d2rT

PDFsq(x), Dq(x)…

4

H.Avakian, JLab, Oct 29

DIS vs SIDIS → additional hadron detection.

H.Avakian, JLab, Oct 29

HERMES

How acceptance in f and PT affect the A1 and Ds extractions in SIDIS?

H.Avakian, JLab, Oct 29

B.Musch arXiv:0907.2381

B.Pasquini et al

B.Musch arXiv:0907.2381

Higher probability to find at large kT u-quarks anti-aligned with proton spin and d-quarks

7

7

H.Avakian, JLab, Oct 29

CLAS configurations

ep→e’pX

Inner Calorimeter

e

p-

p+

Unpolarized and longitudinally polarized targets

Unpolarized, longitudinally and transversely polarized targets

- Polarized NH3/ND3 (no IC, ~5 days)
- Unpolarized H (with IC ~ 60 days)
- Polarized NH3/ND3 with IC 60 days
- 10% of data on carbon

- Polarized HD-Ice (no IC, 25 days)

- Polarizations:
- Beam: ~80%
- NH3 proton 80%,ND3 ~30%
- HD (H-75%,D-25%)

8

H.Avakian, JLab, Oct 29

2

SIDIS with JLab at 6 GeV

Scattering of 5.7 GeV electrons off polarized proton and deuteron targets

- DIS kinematics,
Q2>1 GeV2, W2>4 GeV2, y<0.85

- 0.4>z>0.7, MX2>2 GeV2

epX

Large PT range and full coverage in azimuthal angle f crucial for studies

9

H.Avakian, JLab, Oct 29

hep-ph/0608048

m02=0.25GeV2

mD2=0.2GeV2

CLAS PRELIMINARY

PT-dependence of cosf moment of double spin asymmetry is most sensitive to kT-distributions of quarks with spin orientations along and opposite to the proton spin.

10

H.Avakian, JLab, Oct 29

arXiv:1003.4549

0.4<z<0.7

M.Anselmino et al hep-ph/0608048

m02=0.25GeV2

mD2=0.2GeV2

p+ A1 suggests broader kT distributions for f1 than for g1

p- A1 may require non-Gaussian kT-dependence for different helicities and/or flavors

H.Avakian, JLab, Oct 29

Lattice

Anselmino

Collins

arXiv:1003.4549

A1

PT

PT

CLAS data suggests that width of g1 is less than the width of f1

New CLAS data would allow multidimensional binning to study kT-dependence for fixed x

H.Avakian, JLab, Oct 29

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

0.5<z<0.8

Beam SSA from hadronization (Collins effect) by Schweitzer et al.

Collins contribution should be suppressed → g┴ wanted !!!

H.Avakian, JLab, Oct 29

CLAS @4.3GeV

No x-dependence?

Change the sign at low z?

H. Avakian, Frascati, Oct 21

W2>4 GeV2,Q2>1 GeV2

Sign flip at z ~ 0.5

4.3 GeV

-t < 0.5GeV2

5.7 GeV

At z>0.5 struck quark

in pion

LUND-MC

H.Avakian, JLab, Oct 29

H.Avakian, JLab, Oct 29

“Kaon puzzle” in

spin-orbit correlations

Is there a link between HERMES and BRAHMS Kaon vs pion moments (K- has the same sign as K+ and pi+, comparable with K+)?

H.Avakian, JLab, Oct 29

kicked in the opposite to the leading pion(into the page)

L

Sub-leading pion opposite to leading (double kick into the page)

Simple string fragmentation (Artru model)

p+

Leading pion out of page ( - direction )

z

L

p-

If unfavored Collins fragmentation dominates measured p- vs p+, why K- vs K+ is different?

18

H.Avakian, JLab, Oct 29

B.Musch arXiv:0907.2381

B.Pasquini et al, arXiv:0910.1677

HERMES

Griffioen

CLAS (5 days)

Cisbani

Worm gear TMDs are unique (no analog in GPDs)

H. Avakian, Frascati, Oct 21

HD-Ice target vs std nuclear targets

- Small field (∫Bdl~0.005-0.05Tm)
- Small dilution (fraction of events from polarized material)
- Less radiation length
- Less nuclear background (no nuclear attenuation)
- Wider acceptance

20

H.Avakian, JLab, Oct 29

CLAS E08-015 (2011)

H.A.,A.Efremov,P.Schweitzer,F.Yuan

Anselmino et al

helicity-transversity=pretzelosity

CLAS with a transversely polarized target will allow measurements of transverse spin distributions and constrain Collins fragmentation function

21

H.Avakian, JLab, Oct 29

Measurement of Sivers function and GPD-E

CLAS E08-015

(DVCS)

(SIDIS)

GPD-E=0

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)

22

H.Avakian, JLab, Oct 29

U

CLAS12

L

T

q

N

PAC approved experiments & LoI

E12-06-112:Pion SIDIS

E12-09-008: KaonSIDIS

E12-07-107:Pion SIDIS

E12-09-009: KaonSIDIS

LOI12-06-108: Pion SIDIS

LOI12-09-004: KaonSIDIS

- 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)

H.Avakian, JLab, Oct 29

Kotzinian-Mulders Asymmetry

proton

deuteron

Pasquini et al.

- Study the Collins function of kaons
- Provides independent information on the RSMT TMD

H.Avakian, JLab, Oct 29

- 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

- 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 PDFs

We’ll try hard to keep you busy next 10-15 years!

H.Avakian, JLab, Oct 29

H.Avakian, JLab, Oct 29

M.Osipenko

Berger

H.Avakian, JLab, Oct 29

~10% of E05-113 data

CLAS-2009 (E05-113)

CLAS PRELIMINARY

ep→e’pX

p1sinf+p2sin2f

CLAS-2000

W2>4 GeV2

Q2>1.1 GeV2

y<0.85

p1= 0.059±0.010

p2=-0.041±0.010

p1=-0.042±0.015

p2=-0.052±0.016

p1=0.082±0.018

p2=0.012±0.019

MX>1.4 GeV

PT<1 GeV

0.12<x<0.48

0.4<z<0.7

Data consistent with negative sin2f for p+

30

30

H.Avakian, JLab, Oct 29

B.Musch arXiv:0907.2381

B.Pasquini et al, arXiv:0910.1677

HERMES

CLAS (5 days)

Worm gear TMDs are unique (no analog in GPDs)

H.Avakian, JLab, Oct 29

Target fragmentation

h

Current fragmentation

TMD

semi-inclusive

exclusive

semi-exclusive

h

FF

h

DA

DA

h

GPD

M

1

-1

xF

0

Fracture Functions

kT-dependent PDFs

Generalized PDFs

You think you understand something? Now check your target fragments!

xF>0 (current fragmentation)

h

xF<0 (target fragmentation)

xF- momentum in the CM frame

32

32

H.Avakian, JLab, Oct 29

bigger effect at large z

PT = p┴+zkT

Higher probability to find a hadron at large PT in nuclei

kT-distributions may be wider in nuclei?

Understanding of modification of kT widths in nuclei is important also for nucleon TMDs

33

33

H.Avakian, JLab, Oct 29

kT and FSI

l’

l

total transverse momentum broadening squared

x,k’T

l’T

spectator system

nucleus

Tang,Wang & Zhou Phys.Rev.D77:125010,2008

l

l’

BHS 2002

Collins 2002

Ji,Yuan 2002

x,kT

lT

~4 n, with ~4-6 MeV

spectator system

proton

soft gluon exchanges included in the distribution function (gauge link)

- The difference is coming from final state interactions (different remnant)
- Studies of DIS and SIDIS with nuclear targets provide info on kT

34

H.Avakian, JLab, Oct 29

H.Avakian, JLab, Oct 29

LTCC

DC R1, R2, R3

CHL-2

PCAL

CLAS12

Beam Current: 90 µA

Max Pass energy: 2.2 GeV

Max Enery Hall A,B,C: 11 GeV

Solenoid 5T

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

EC

HTCC

FTOF

L = 1035 cm-2s-1

May 2012

6 GeV Accelerator Shutdown starts

May 2013 Accelerator Commissioning starts

2013-2015

Pre-Ops (beam commissioning)

H.Avakian, JLab, Oct 29

You think you understand something? Now add the spin!

You think you understand something? Now go 3D!

You think you understand something? Now add the strange!

You think you understand something? Check the nuclear targets!

You think you understand something? Now check your target fragments!

H.Avakian, JLab, Oct 29

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)

h

M

Fracture Functions

H.Avakian, JLab, Oct 29

H.A.,A.Efremov,P.Schweitzer,F.Yuan Phys.Rev.D81:074035,2010

Twist-2

Twist-3

T-odd

“interaction dependent”

No leading twist,

provide access to quark-gluon correlations

39

39

H.Avakian, JLab, Oct 29

E05-113

M.Anselmino et al hep-ph/0608048

m02=0.25GeV2

mD2=0.2GeV2

0.4<z<0.7

- 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 m0< m2

40

H.Avakian, JLab, Oct 29

kT

p┴

PT = p┴+zkT

Ji,Ma,Yuan Phys.Rev.D71:034005,2005

Is the info on x-kT correlations accessible in kT integrated observables?

41

41

H.Avakian, JLab, Oct 29

H. Avakian, JLab, May 3

Fits to unpolarized data

Anselmino et al

Collins et al

Assuming the widths of f1/g1 x,z and flavor independent

EMC

H.Avakian, JLab, Oct 29

Fraction of events from polarized hydrogen in NH3

Nu,Np -total counts from NH3 and carbon normalized by lumi

ru, rp -total areal thickness of hydrogen (in NH3), and carbon target

Cn=Nitr/Carbon ratio (~0.98)

Diff. symbols for diff x-bins

p-

Multiple scattering and attenuation in nuclear environment introduces additional PT-dependence for hadrons

H.Avakian, JLab, Oct 29

I. Cloet (Argonne-2010)

- In medium modification
- Mass, magnetic moment, size
- Form factors, PDFs, GPDs, TMDs, etc

- In medium quarks are more relativistic
- Dq more sensitive to angular momentum
- Lower components of wavefunctions more enhanced
- Lower components carry more angular mom.

NJL-model

How sensitive are inclusive measurements to the transverse structure of nucleon and nucleus ?

44

H.Avakian, JLab, Oct 29

H. Avakian, JLab, May 3