Studies of spin-orbit correlations

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


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


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


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)…


DIS vs SIDIS → additional hadron detection.


Acceptances and efficiencies

How acceptance in and PT affect the A1 and s extractions in SIDIS?

HERMES


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


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


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


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


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


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


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


Kaon <cos2> @ HERMES


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


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


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


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)


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


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


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.


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?


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!


Support slides….

M.Osipenko


HERMES/COMPASS

Berger


~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 +


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)


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

PDF

hFF

DA DA

exclusivesemi-inclusive semi-exclusive

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


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


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


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


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!


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


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


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, 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?


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


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

-


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 ?

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Studies of spin-orbit correlations

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