JLab, Jan 20101

Studies of Partonic Structure using SIDISStudies of Partonic Structure using SIDIS

H.Avakian (JLab)H.Avakian (JLab)

Hall-C collaboration meeting, JLab, Jan 22Hall-C collaboration meeting, JLab, Jan 22

JLab, Jan 201022

Outline

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

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

– Tests of partonic description

– Spin-azimuthal asymmetries

– Double spin asymmetries– Future measurements– From JLab12 → EIC

•Summary

JLab, Jan 20103

Transverse Momentum Dependent (TMD) Distributions

Quark polarization

Nucleon polarization

Real and imaginary parts of the L≠0 interference contributions

Factorization of kT-dependent PDFs proven at low PT of hadrons (Ji et al)

Twist-2

Twist-3

f1u(x,kT)

JLab, Jan 20104

SIDIS kinematical plane and observables

Beam polarization Target polarization

U unpolarized

L long.polarized

T trans.polarized

sin2moment of the cross section for unpolarized beam and longitudinal target

JLab, Jan 201055

s

x

h

PT

Fragmenting quark polarization

C

C

y

x

S h

PTS = +h

x

PT

h

S=y

HT function related to force on the quark. M.Burkardt (2008)

Collins mechanism for SSACollins mechanism for SSAfragmentation of transversely polarized quarks into unpolarized hadrons

JLab, Jan 201066

Sivers mechanisms for SSASivers mechanisms for SSA -Correlation between quark transverse momentum and the proton spin

S

x

kT

PT

Proton polarization

S

HT asymmetries (T-odd)

No leading twist, provide access to quark-gluon correlations

JLab, Jan 201077

SIDIS: partonic cross sections

kT

PT = p┴ +z kT

p┴

JLab, Jan 20108

Double spin asymmetries and flavor decomposition

Anti-parallel electron & quark spins

Parallel electron & quark spins

u-quarks are mainly aligned with proton spin (u>0)

HERMES

JLab, Jan 201099

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

JLab, Jan 201010

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:

JLab, Jan 20101111

CLAS configuration: EG2000CLAS configuration: EG2000

e

Polarizations: Beam: ~70% NH3 proton ~70%

Target position -55cmTorus +/-2250Beam energy ~5.7 GeV

1) Polarized NH3/ND3 ( ~5 days)2) Polarized NH3/ND3 with IC 60 days

Longitudinaly polarized target

ep→e’X

JLab, Jan 201012

Closed (open) symbols reflect data after (before) events from coherent production are subtracted

GRV & CTEQ,@ LO or NLO

E00-108: Leading-Order x-z factorization

Good description for p and d targets for 0.4 < z < 0.65

Hall-C

JLab, Jan 201013

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

(2004)

constituent quark model (Pasquini et al).

0.790.740.74

JLab, Jan 20101414

Quark distributions at large kQuark distributions at large kTT: models: models

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

JMR model

q

DqMR , R=s,a

Higher probability to find a quark anti-aligned with proton spin at large kT

u+<u-

JLab, Jan 20101515

Quark distributions at large kQuark distributions at large kTT: lattice: lattice

Higher probability to find a d-quark at large kT

Higher probability to find a quark anti-aligned with proton spin at large kT

B.Musch arXiv:0907.2381

JLab, Jan 201016

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

JLab, Jan 201017

A1

A1 PT-dependence

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

AnselminoCollins

Lattice

New eg1dvcs data allow multidimensional binning to study kT-dependence for fixed x

JLab, Jan 20101818

kkT T -distributions-distributions in nuclei in nuclei

Higher probability to find a hadron at large PT in nuclei

kT-distributions may be wider in nuclei?

PT = p┴ +z kT CLAS

Hall-C

bigger effect at large z

JLab, Jan 20101919

~10% of E05-113 data

19

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 +

JLab, Jan 20102020

Kotzinian-Mulders asymmetryKotzinian-Mulders asymmetry

•Measurement of SSAs for pions, provides access to the RSMT TMD (Ralston-Soper (1979), Mulders-Tangerman (1995) •Study Collins fragmentation with longitudinally polarized target

Transversely polarized quarks in the longitudinally polarized nucleon

curves, QSM from Efremov et al

CLAS 2009 (projected)

Wormgear

JLab, Jan 20102121

What we know about What we know about ??

Boffi et al, Phys. Rev. D 78 (2008) 034025

JLab, Jan 201022

Intrinsic transverse momentum densities of the nucleon

genuine effectof intrinsic transversemomentum of quarks

genuine effectof intrinsic transversemomentum of quarks

GPDs

up down

PhH, B. Musch et al.arXiv:0908.1283

PhH, B. Musch et al.arXiv:0908.1283

Ph. Haegler et alarXiv:0908.1283

JLab, Jan 201023

Trento, Nov 1223

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

JLab, Jan 20102424

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

JLab, Jan 201025

Electroproduction kinematics: JLab12→EIC

JLab 0.1<xB<0.7 JLab@12GeV

Study of high x domain requires high luminosity, low x higher energies

EIC

JLab12

Q2

EIC

collider experiments

H1, ZEUS 10-4<xB<0.02

EIC 10-4<xB<0.3gluons (and quarks)

fixed target experiments

COMPASS 0.006<xB<0.3

HERMES 0.02<xB<0.3

gluons/valence and sea quarks

valence quarks

JLab, Jan 201026

CLAS12LTCC

FTOF

PCAL

ECHTCC

Lumi = 1035cm-2s-1

High beam polarization 80%High target polarization 85%NH3 (30 days) ND3 (50 days)

Wide detector and physics acceptance (current/target fragmentation)

Replace 2 sectors of LTCC with a proximity RICH detector to identify Kaons approved by JLab PAC34

JLab, Jan 201027

Hall-A: Experimental Setup and parameters

Beam: 50 A, E=8.8 and 11 GeV (80% long. Pol.)Target: 65% polarized 3He GEn(2)/PR-09-016 Luminosity: 1.4×1037 cm-2s-1 , 0.05 sr

BB: e-arm at 30o

= 45 msrGEM TrackerGas CherenkovShower GMn/PR-09-019

SBS:h-arm at 14o

= 50 msrGEM trackerexcellent PID / RICHHadron CALO

e+3He→e’+(K)+X

Event rate: ~104×HERMES60 days of production expected stat. accuracy:

1/10 of proton HERMES

JLab/HallAG. Cates, E. Cisbani, G.B. Franklin, B. Wojtsekhowski

JLab, Jan 201028

Objectives: Extract charge symmetry violating valence PDFs (δd – δu) as function of x

for different Q2 bins.

Where and

RMeasD (x,z)

4RY (x,z) 1

1 RY (x,z)

Experiment: Measure Charged pion electroproduction in semi inclusive DIS off deuterium

E09-002: Executive Summary

RY (x,z) Y D

(x,z)

Y D

(x,z)Conditions: 11 GeV electron beam 10 cm long Liquid deuterium target Hall C SHMS for electron detection Hall C HMS for charged pion detection 17 days of beam time

d d p un

u up dn

28

SHMS

HMS

Hafidi,Gaskell,Dutta

JLab, Jan 201029

Flavor decomposition using CLAS12

10% systematics on asymmetries

E12-09-007 K.Hafidi et al

JLab, Jan 201030

Transverse Momentum Dependence of Semi-Inclusive Pion Production PR12-09-017

(Mkrtchyan,Bosted,Ent)

PR12-09-017: Map the pT dependence (pT ~ < 0.5 GeV) of + and - production off proton and deuteron targets to measure the kT dependence of up and down quarks

Significant net orbital angular momentum of valence quarks implies significant transverse momentum of quarks

Can only be done using spectrometer setup capable of %-

type measurements (an essential ingredient of the global SIDIS program!)

Beam time request: 32 days of beam time in Hall CBeam time request: 32 days of beam time in Hall CSpin-off: Radiative correction modeling for (e,e’)

Single-spin asymmetries at low pT (< 0.2 GeV)

Low-energy (x,z) factorization for kaons

2.9 < Mx2 < 7.8 GeV2

JLab, Jan 20103131

A1 PT-dependence in SIDIS E12-07-107

M.Anselmino et al hep-ph/0608048

•ALL ) sensitive to difference in kT distributions for f1 and g1 •Wide range in PT allows studies of transition from TMD to perturbative approach

02=0.25GeV2

D2=0.2GeV2

Perturbative limit calculations available for :

J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238

JLab, Jan 201032

Boer-Mulders Asymmetry with CLAS12 & EIC

CLAS12 and EIC studies of transition from non-perturbative to perturbative regime will provide complementary info on spin-orbit correlations and test unified theory (Ji et al)

Nonperturbative TMDPerturbative region

Transversely polarized quarks in the unpolarized nucleon

-

CLAS12

EIC

e p5-GeV 50 GeV

sin(C) =cos(2h)

Perturbative limit calculations available for :

J.Zhou, F.Yuan, Z Liang: arXiv:0909.2238

E12-06-112

JLab, Jan 201033

sinLU(UL) ~FLU(UL)~ 1/Q (Twist-3)

1/Q behavior expected (fixed x bin)

Study for Q2 dependence of beam SSA allows to check the higher twist nature and access quark-gluon correlations.

Q2-dependence of beam SSA

Hall-C: E12-06-104R.Ent & H.MkrtchyanStudy R and FL

CLAS: E12-06-112

JLab, Jan 201034

Nonperturbative TMD Perturbative region

sinLU(UL) ~FLU(UL)~ 1/Q (Twist-3)

In the perturbative limit 1/PT behavior expected

Study for SSA transition from non-perturbative to perturbative regime.

EIC will significantly increase the PT range.

PT-dependence of beam SSA E12-06-112

4x60 100 days, L=1033cm-2s-1

JLab, Jan 201035

Study the reaction mechanism in SIDIS

•Check the NLO predictions in the collinear approximation•Provide input to the analysis of other SIDIS experiments in JLab

CLAS12 PR10-010 Puckett et al x=0.4,z=0.5

JLab, Jan 201036

Summary

Measurements of azimuthal dependences of multiplicities as well as 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.

JLab 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.

Large kinematical acceptance of CLAS12@ 11 GeV with L=1035cm-2sec-1 combined with high luminosity L=1037cm-2sec-1 precision measurements at Hall-A/C would allow JLab12 to study in details the 3D structure of the nucleon in the valence region.

JLab, Jan 201037

Support slides….

JLab, Jan 201038

Transverse momentum dependence of SIDISGeneral formalism for (e,e’h) coincidence reaction w. polarized beam:

( = azimuthal angle of e’ around the electron beam axis w.r.t. an arbitrary fixed direction)

[A. Bacchetta et al., JHEP 0702 (2007) 093]

LUUTUU

thh

FFx

y

xyQdPdzddxdyd

d,,

22

2

2

2,

{2

1)1(2

}sin)2cos(cos sin)1(2)2cos(cos)1(2 hhhLUheUUhUUh FFF

JLab, Jan 201039

CLAS12: Kinematical coverage

Large Q2 accessible with CLAS12 are important for separation of HT contributions

Q2>1GeV2

W2>4 GeV2(10)y<0.85MX>2GeV

SIDIS kinematics

eX

x=0.3 → Q2=~2 GeV2 (CLAS), ~5 GeV2 (HERMES) ~15 GeV2 (COMPASS)

JLab, Jan 201040

Trento, Nov 1240

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!

JLab, Jan 201041

SSA with long. polarized target

quark polarization

JLab, Jan 201042

SSA with long. polarized target

quark polarization

JLab, Jan 201043

SSA with unpolarized target

quark polarization

JLab, Jan 201044

SSA with unpolarized target

quark polarization

JLab, Jan 201045

JLab, Nov 2545

Azimuthal moments with unpolarized target

quark polarization

JLab, Jan 201046

JLab, Nov 2546

Azimuthal moments with unpolarized target

quark polarization

JLab, Jan 201047

JLab, Nov 2547

SSA with unpolarized target

quark polarization

JLab, Jan 201048

JLab, Nov 2548

SSA with unpolarized target

quark polarization

JLab, Jan 201049

More lattice studies

d-quark opposite to ud-quark has wider kT-distribution

JLab, Jan 201050

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

JLab, Jan 201051

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

-

JLab, Jan 20105252

What we know about What we know about ??Boffi EINN2009