Measurement of neutron spin Measurement of neutron spin asymmetry Aasymmetry A11

nn in the valence quark in the valence quark region using the Solenoidregion using the Solenoid

Nilanga LiyanageNilanga Liyanage

University of VirginiaUniversity of Virginia

OutlineOutline•Physics:

Neutron spin structure at high x: • test fundamental predictions of nucleon structure.• flavor decomposition of polarized pdfs

One of the most exciting experiments awaiting 12 GeV beam

•Technology: • high energy beam• highest possible polarized luminosity • large acceptance spectrometers

Inclusive Electron ScatteringInclusive Electron Scattering

2222 sin'4 EEqQ

4-momentum transfer squared

W 2 M 2 2M Q2

Invariant mass squared

x Q2

2M

Bjorken variable

),( kEe

)','(' kEe

p (M,0 )

q (,q )

d2ddE '

Mott

1

F2(x,Q2)

2

MF1(x,Q2)tan2

2

Unpolarized case {

d2

ddE '

d2

ddE '

4 2E '

EQ2 E E 'cos g1(x,Q2) 2Mxg2(x,Q2) Polarized case {

Virtual Photon AsymmetryVirtual Photon Asymmetry

N

hN=+hq=+h=+

hq=+

1/2

N

hN=-hq=+h=+

hq=+

3/2

1

1

2/32/1

2/32/11 F

gA

Nucleon Nucleon ModelModel

FF22nn/F/F22

pp d/ud/u u/uu/u d/dd/d AA11nn AA11

pp

SU(6)SU(6) 2/32/3 1/21/2 2/32/3 -1/3-1/3 00 5/95/9

Valence Valence QuarkQuark

1/41/4 00 11 -1/3-1/3 11 11

pQCDpQCD 3/73/7 1/51/5 11 11 11 11

Neutron Wavefunction (Spin and Flavor Symmetric)

Nucleon Structure at large xNucleon Structure at large xBjBjNucleon Structure at large xNucleon Structure at large xBjBj

11

110

)(3

2)(

3

1

)(3

1)(

18

1)(

2

1

SS

SSS

dduddu

uddudduddn

Nucleon Nucleon ModelModel

FF22nn/F/F22

pp d/ud/u u/uu/u d/dd/d AA11nn AA11

pp

SU(6)SU(6) 2/32/3 1/21/2 2/32/3 -1/3-1/3 00 5/95/9

Valence Valence QuarkQuark

1/41/4 00 11 -1/3-1/3 11 11

pQCDpQCD 3/73/7 1/51/5 11 11 11 11

Neutron Wavefunction (Spin and Flavor Symmetric)

Nucleon Structure at large xNucleon Structure at large xBjBjNucleon Structure at large xNucleon Structure at large xBjBj

11

110

)(3

2)(

3

1

)(3

1)(

18

1)(

2

1

SS

SSS

dduddu

uddudduddn

Nucleon Nucleon ModelModel

FF22nn/F/F22

pp d/ud/u u/uu/u d/dd/d AA11nn AA11

pp

SU(6)SU(6) 2/32/3 1/21/2 2/32/3 -1/3-1/3 00 5/95/9

Valence Valence QuarkQuark

1/41/4 00 11 -1/3-1/3 11 11

pQCDpQCD 3/73/7 1/51/5 11 11 11 11

Neutron Wavefunction (Spin and Flavor Symmetric)

Nucleon Structure at large xNucleon Structure at large xBjBjNucleon Structure at large xNucleon Structure at large xBjBj

11

110

)(3

2)(

3

1

)(3

1)(

18

1)(

2

1

SS

SSS

dduddu

uddudduddn

Nucleon Nucleon ModelModel

FF22nn/F/F22

pp d/ud/u u/uu/u d/dd/d AA11nn AA11

pp

SU(6)SU(6) 2/32/3 1/21/2 2/32/3 -1/3-1/3 00 5/95/9

Valence Valence QuarkQuark

1/41/4 00 11 -1/3-1/3 11 11

pQCDpQCD 3/73/7 1/51/5 11 11 11 11

Neutron Wavefunction (Spin and Flavor Symmetric)

Nucleon Structure at large xNucleon Structure at large xBjBjNucleon Structure at large xNucleon Structure at large xBjBj

11

110

)(3

2)(

3

1

)(3

1)(

18

1)(

2

1

SS

SSS

dduddu

uddudduddn

Suppressed by an extra (1-x)2

•pQCD and SU(6) breaking quark models A1p, A1n 1 as x 1 and large Q2

•But the mechanisms are very different•CQM – hyperfine interaction between quarks: symmetric configurations suppressed.•pQCD – at high x quark carrying the much of the nucleon momentum has the same spin direction as the nucleon: HHC

From Close and Melnitchouk

•pQCD power counting with Lz=1 state included

A1n versus of Q2 and x in the valence region

•role of OAM in the nucleon

•extraction of higher twist

F2=

1

1

2/32/1

2/32/11 F

gA

Approved Approved ExperimentsExperimentsApproved Approved

ExperimentsExperiments

•6.6 GeV, 8.8 GeV polarized electron beams: 10 A, Pe = 0.8•Hall A polarized 3He target: 30 cm of useful length.•Bigbite Spectrometer @ 30o

•HRS-L @ 30o

Using Bigbite with 6.6 GeV and 8.8 GeV beam ~ 500 h

Using HMS+SHMS with 11 GeV beam, ~ 1200 h

Approved Approved ExperimentsExperimentsApproved Approved

ExperimentsExperiments

Projected data: DIS

MPS: 75 hoursMPS: 25 hours

MPS 600 hours@ 40o

DIS

Resonance

Kinematic CoverageKinematic CoverageKinematic CoverageKinematic Coverage

8.8 Gev beam @ 30 o

6.6 Gev beam @ 30 o

11 Gev beam @ 30 o

11 Gev beam @ 40 o

Projected data for the solenoidProjected data for the solenoidProjected data for the solenoidProjected data for the solenoid

Solenoid will allow high precision DIS data over a fine grid of Q2 and X:

But highest x is still limited to ~ 0.75 as in Bigbite of Super-Bigbite

Study Q2 dependence, higher-twist etc.

DIS

Resonance

Kinematic CoverageKinematic CoverageKinematic CoverageKinematic Coverage

8.8 Gev beam @ 30 o

6.6 Gev beam @ 30 o

11 Gev beam @ 30 o

11 Gev beam @ 40 o

Projected data for Bigbite in Resonance region: better coverage with solenoid.

Solenoid will allow high precision data in Resonance region over a fine grid of Q2 and X: If little or no Q2 dependence -> DIS behavior (duality): can use this resonance data to extract polarized PDFs at very high x

DIS

Resonance

<Q2> = 1 GeV2

<Q2> = 1.7 GeV2

<Q2> = 2.6 GeV2

<Q2> = 3.6 GeV2

New A1 results from Hall A experiment E01-012