IWHSS09, Apr 11

Harut Avakian (JLab)Harut Avakian (JLab)

Mainz, April 1, 2009

SIDIS results from JLAB

IWHSS09, Apr 12

Outline

Describe the complex nucleon structure in terms of partonic degrees of freedom of QCD

•Physics motivation–Transverse Momentum Distributions (TMDs) of quarks and spin-azimuthal asymmetries in semi-inclusive DIS

•SIDIS results from JLab at 6 GeV –Tests of the applicability of the partonic picture–Studies of spin-orbit correlations with CLAS

•Measurements of TMDs at 6 GeV–Longitudinally polarized proton target measurements (E05-113) –Transversely polarized 3He (E06-010/011) and proton targets (E08-015)

•Summary

IWHSS09, Apr 13

z

sin2moment of the cross section for unpolarized beam and longitudinal target

U unpolarizedL long.polarizedT trans.polarized

SIDIS kinematical plane and observables

Transverse spin effects are observable as correlations of transverse spin and transverse momentum of quarks.

IWHSS09, Apr 14

Structure of the Nucleon

GPDs/IPDs

d2kT

d2kT

TMD PDFs f1

u(x,kT), .. h1u(x,kT)

Gauge invariant definition (Belitsky,Ji,Yuan 2003)Universality of kT-dependent PDFs (Collins,Metz 2003)Factorization for small kT. (Ji,Ma,Yuan 2005)

Wpu(k,rT) “Mother” Wigner distributions

d2 r T

PDFs f1u(x), .. h1

u(x)

quark polarization

IWHSS09, Apr 15

CLAS at JLAB

Electron beam energy 6 GeV Lumi ~1034cm-2sec-1

IWHSS09, Apr 16

Scattering of 5.7 GeV electrons off unpolarized and polarized proton and deuteron targets

SIDIS with CLAS 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

e

1) Polarized NH3/ND3 (~5 days)2) Polarized H 30+30 days (2001/2005)

IWHSS09, Apr 17

multiplicities in SIDIS ep→e’X

+/- multiplicities at large z diverge from SIDIS predictions0 multiplicities less affected by higher twists0.4<z<0.7 kinematical range, where higher twists are expected to be small

DSS (Q2=2.5GeV2)

DSS (Q2=25GeV2)

M.AghasyanHall-C

IWHSS09, Apr 18

Rpd-

Both ratios agree with PDF models for z<0.7 (Mx>1.4 GeV)

Tests of partonic picture with ratios

Hall-C @ 6 GeV

Rpd+

IWHSS09, Apr 19

A1 PT-dependence in SIDIS

M.Anselmino et al hep-ph/0608048

+ ALL can be explained in terms of broader kT distributions for f1 compared to g1

02=0.25GeV2

D2=0.2GeV2

In perturbative limit predicted to be constant

Como-2005

constituent quark model (Pasquini et al).

IWHSS09, Apr 110

BBS/LSS no OAM

BBS/LSS with OAM

Quark longitudinal polarization

JMR model

q

DqMR , R=s,a

For given x the sign of the polarization is changing at large kT

Effect of the orbital motion on the q- may be significant (H.A.,S.Brodsky, A.Deur,F.Yuan 2007)

u/u

(dipole formfactor), J.Ellis, D-S.Hwang, A.Kotzinian

IWHSS09, Apr 111

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

IWHSS09, Apr 112

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

IWHSS09, Apr 113

A1 PT-dependence

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

AnselminoCollins

IWHSS09, Apr 114

Collins Effect: azimuthal modulation of the fragmentation function

D(z,PT)=D1(z,PT)+H1┴(z,PT) sin(hS’)

spin of quark flips wrt y-axisS’ = -S sin(hS)

C

S

STy

x

h

PT sT

S’

C

FUT∞h1H1┴ sT(q×PT)↔ H1┴

x

PT

hS=h

y

y

x

S h

PTS = +h

x

PT

h

S=y

hadronizing quark

Intial quark polarization

IWHSS09, Apr 115

SIDIS (*p->X) x-section at leading twist

•Measure Boer-Mulders distribution functions and probe the polarized fragmentation function•Measurements from different experiments consistent

TMD PDFs

IWHSS09, Apr 11616

Kotzinian-Mulders asymmetryKotzinian-Mulders asymmetry

•Data indicate that spin-orbit correlations with long.pol. target may be significant•Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995)

curves, QSM from Efremov et al

Transversely polarized quarks in the longitudinally polarized nucleon

More data needed to clarify the situation with negative pions

IWHSS09, Apr 11717

What comes nextWhat comes next

Hall-A Transversely polarized 3He target measurement (E06-010/011)

Hall-B Longitudinally polarized proton (NH3) target measurement (E05-113)

Hall-B Transversely polarized proton target measurement (E08-015)

Currently runningCalibrating September 2011

Sivers asymmetry

Collins asymmetry with transverse (neutron)target

Correlations of transverse and longitudinal momenta (PT-dependences) in ALL

Collins asymmetry with longitudinally polarized (proton) target

Exclusive asymmetries as background

Sivers asymmetry

Collins asymmetry with transverse proton target

Shape of proton studies

Exclusive asymmetries as background

Fixed bins in x/Q2 Wide kinematical coverage , multiple hadronic states

IWHSS09, Apr 118

Cell: Astral Cell: Maureen

e

e’

HRSL

BigBite

16o

30o

Polarized3He Target

Target Single-Spin Asymmetry in Semi-Inclusive n↑(e, e’+/-)

pt ~ 65% (proposal 42%)

• First measurement of the neutron Collins and Sivers asymmetries in SIDIS.

• High density polarized 3He target. • Run in Hall A from 10/24/08-2/5/09. 110 shift workers, 7 Ph.D. students.

Reaction on a Transversely Polarized 3He TargetE06-010:

IWHSS09, Apr 119

Experimental Setup

Inner Calorimeter (424 PbWO4 crystals) to detect high energy photons at forward lab angles.

Polarized target (NH3/ND3)

13o

50o

IC

1) Polarized NH3 with IC 60 days 2) Polarized HD-Ice (no IC, 25 days)

IWHSS09, Apr 12020

AALLLL P PTT-dependence in SIDIS-dependence in SIDIS

M.Anselmino et al hep-ph/0608048

• study the PT-dependence for different quark helicities and flavors for bins in x, 2 (x) • flavor decomposition in PT-bins.

02=0.25GeV2

D2=0.2GeV2

0.4<z<0.7

E05-113

IWHSS09, Apr 12121

Kotzinian-Mulders asymmetryKotzinian-Mulders asymmetry

•Provide measurement of SSA for all 3 pions, extract the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995) •Study Collins fragmentation with longitudinally polarized target

curves, QSM from Efremov et al

60 days of CLAS L=1.5.1034cm-2s-1

Transversely polarized quarks in the longitudinally polarized nucleon

E05-113

IWHSS09, Apr 122

Pros1. 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

much better FOM, especially for deuteron Cons

1. HD target is highly complex and there is a need for redundancy due to the very long polarizing times (months).

2. Need to demonstrate that the target can remain polarized for long periods with an electron beam with currents of order of 1-2 nA

3. Additional shielding of Moller electrons necessary (use minitorus)

CLAS transversely polarized HD-Ice target

Heat extraction is accomplished with thin aluminum wires running through the target (can operate at T~500-750mK)

HD-Ice target at ~2nA ~ NH3 at 5 nA

HD-Ice target vs std nuclear targets

IWHSS09, Apr 12323

Collins SSAsCollins SSAs

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

Anselmino et al (2007) Boffi et al (2009)

helicity-transversity=pretzelosity

CLAS E08-015

IWHSS09, Apr 12424

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

IWHSS09, Apr 125

Summary

Significant azimuthal moments in pion production in SIDIS are measured using CLAS with longitudinally polarized target.

Measurements of azimuthal dependences of double and single spin asymmetries indicate that correlations between spin and transverse motion of quarks may be significant.

PT-dependences of the double and single-spin asymmetries provide important input for studies of flavor and helicity dependence of quark transverse momentum dependent distributions.

Upcoming CLAS SIDIS experiments at 6 GeV will significantly improve the statistical precision of longitudinally polarized target data, and will provide new data on transversely polarized target

IWHSS09, Apr 126

Support slides….

IWHSS09, Apr 127

IWHSS09, Apr 128

Factorization studies

Rpd+ for any z, pt (if d and u have same pt dependence)!

Simple LO picture in valence region:

Rpd- for any z, x!

IWHSS09, Apr 129

The CLAS Detector

~ 200 physicists37 institutions

large kinematical coverage high luminositymulti-particle final states

charged particles:p>0.2 GeV/c8o<<140o

p/p~0.5% (<30o)p/p~1-2%(>30o)=1mrad=4mrad

IWHSS09, Apr 13030

Sivers effect: protonSivers effect: proton

•CLAS will provide a superior measurements of Sivers asymmetry at large x, where the effect is large and models unconstrained by previous measurements. •Measure also asymmetries in target fragmentation region and for exclusive channels (background)

Vogelsang & YuanSchweitzer et al

CLAS E08-015

IWHSS09, Apr 131

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.

IWHSS09, Apr 132

Collins Effect: azimuthal modulation of the fragmentation function

D(z,PT)=D1(z,PT)+H1┴(z,PT) sin(hS’)

spin of quark flips wrt y-axisS’ = -S sin(hS)

C

S

STy

x

h

PT sT

S’

C

FUT∞h1H1┴

S

y

x

h

PT

sT(p×kT)↔ h1┴

FUU∞h1 ┴ H1┴

S = +h

sT(q×PT)↔ H1┴

x

sin(2h)

PT

h

S=h

y

FUL∞h1L H1┴┴

(sTkT)(pSL)↔ h1L┴sin(h+S)

cos(2h)

IWHSS09, Apr 133

JLab, Nov 2533

Hall A E06-010Hall A E06-010: Neutron (3He) Transversity : Neutron (3He) Transversity

Collins: transversity Sivers: Orbital Angular Momentum

First JLab transverse SSA measurement: running now to 2/09 First world neutron(3He) measurement

IWHSS09, Apr 134

Contributions to in Double Polarized SIDIS

TMDsMulders et al

IWHSS09, Apr 135

Spin densities in transverse proton from Lattice(QCDSF/UKQCD)

G.Miller/”pretzelosity”

u-quark

d-quark

Spin of quark

Boer-Mulders TMD

IWHSS09, Apr 136

SSA with unpolarized target

quark polarization

IWHSS09, Apr 137

SSA with unpolarized target

quark polarization

IWHSS09, Apr 138

SSA with long. polarized target

quark polarization

IWHSS09, Apr 139

SSA with long. polarized target

quark polarization

IWHSS09, Apr 140

CLAS: Fraction from baryonic decays in SIDIS

Significant fraction from target fragmentation at pion momenta below 2 GeV

IWHSS09, Apr 141

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

-

IWHSS09, Apr 142

Collins Effect: from asymmetries to distributions

Combined analysis of Collins fragmentation asymmetries from SIDIS and e+e- (BELLE) would allow separation of transverse spin distributions (Anselmino et al., arXiv:0707.1197 )

need

Brodsky & Yuan (2006)

CLAS12

IWHSS09, Apr 143

JLab@12GeV: Inclusive DIS

BBS/LSS no OAM

PDF measurements at large x provide additional information on OAM

BBS/LSS with OAM

IWHSS09, Apr 144

Azimuthal Asymmetries in SIDIS

Due to color coherence the configuration with gluon inside the quark cone is more probable

Why <cos> < 0 ? Chay,Ellis,Stirling-1991

x

=180

=0

IWHSS09, Apr 145

HT and Semi-Exclusive Pion Production E. Berger, S. Brodsky 1979 (DY), E.Berger 1980,A.Brandenburg, V. Khoze, D. Muller 1995

A.Afanasev, C.Carlson, C. Wahlquist Phys.Lett.B398:393-399,1997

+

Fragmentation +

0

• Azimuthal asymmetries with opposite sign from HT effects

• Effect may be suppressed for semi-exclusive 0 compared to +/-