Study Neutron Spin Structure with a Solenoid Jian-ping Chen, Jefferson Lab Hall A Collaboration Meeting June 22-23, 2006 Inclusive DIS: Valence quark spin structure: A 1 at high x g 2 , d 2 and higher-twist effects (twist-3) g 3 , f 2 (twist-4) Semi-inclusive DIS Example: transversity. •Acknowledgement: E. Chudakov (simulation), X. Zheng, W. Korsch, Z. Meziani, K. Kumar, P. Souder, …
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Study Neutron Spin Structure with a Solenoid Jian-ping Chen, Jefferson Lab Hall A Collaboration Meeting June 22-23, 2006 Inclusive DIS: Valence quark spin.
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Study Neutron Spin Structure with a Solenoid
Jian-ping Chen, Jefferson LabHall A Collaboration Meeting
June 22-23, 2006
Inclusive DIS:
Valence quark spin structure: A1 at high x
g2, d2 and higher-twist effects (twist-3)
g3, f2 (twist-4)
Semi-inclusive DIS
Example: transversity.•Acknowledgement: E. Chudakov (simulation), X. Zheng, W. Korsch,
Z. Meziani, K. Kumar, P. Souder, …
Introduction
• DIS provided rich information on quark-gluon structure of the nucleon and the strong interaction (QCD)
• High energy: asymptotic freedom
perturbative QCD calculation works, QCD well tested
parton distributions functions (PDFs) extracted from DIS data
• Projection with Solenoid, Statistical only, will be systematic limited? Improved Lattice Calculation (QCDSF, hep-lat/0506017)
g3: Parity Violating Spin Structure Functionf2: twist-4, color polarizabilities
Color “Polarizabilities”Color “Polarizabilities”
f2 and Color Polarizabilities Extraction
• JLab + world n data,
4 = (0.019+-0.024)M2
• Twist-4 term 4 = (a2+4d2+4f2)M2/9
• extracted from 4 term f2 = 0.034+-0.005+-0.043
• Color polarizabilities
= 0.033+-0.029
B = -0.001+-0.016
Z. Meziani et al. PLB 93 (2004) 212001
g3: Parity Violating Spin Structure Function
• f2 can be directly measured from:
1
0
23
22
21
222 )),(9),(12),(7(
2
1)( dxQxgQxgQxgxQf
g3 is a parity violating spin structure function.
• Never been measured so far
• g3: unpolarized beam and polarized target
ZZA
ZZV ggyxyggy
dxdy
d
dxdy
d 13
2
)2()1(~
g3 in Naïve Parton Model
• Naïve Parton Model:
•Provide a clean way to measure sea-quark spin•Asymmetry expected to be at the same level as the other DIS parity asymmetry (~10-5 Q2 – 10-4 Q2)•Need high luminosity and large acceptance
)()(23 qqgexgq
qAqZ
Measurement of g3n
• Rate estimation with the Solenoid detector: polarized 3He target in front the solenoid 1036 neutron/s luminosity, 50% target polarization 11 GeV beam, 10o - 22o, W > 2 GeV x: 0.1 - 0.65, Q2: 2 – 8 GeV2, <x> ~ 0.25, <Q2> ~ 4 GeV2
rate is 3.3 KHz 1000 hours beam, statistical precision for asymmetry will be 1.8x10-5. A significant first measurement (~ a few )
• Some characteristics of transversity:• δq(x) = Δq(x) for non-relativistic quarks• δq and gluons do not mix → Q2-evolution different• Chiral-odd → not accessible in inclusive DIS
• It takes two chiral-odd objects to measure transversity• Semi-inclusive DIS
Chiral-odd distributions function (transversity)
Chiral-odd fragmentation function (Collins function)
JLab 6 GeV Projections (n) and World Data (p, d)
π- π+The errors with approved beam time will be 33% higher.
COMPASS (d)
HERMES (p)
JLab 6 GeV (n)
Collins CollinsSivers Sivers
Collins and Sivers Asymmetries
• Projections with MADII (1200 hours)
• Solenoid option:
-- Acceptance for both e
and improved by
~ 1 order of magnitude
-- Total improvement
~ 2 orders of magnitude
• + case
Two halves different
baffles
• Simulations to be done
- +
Collins
Sivers
Summary
• A powerful tool for inclusive DIS study at high-x • Improvement of a factor of 10-30 in acceptance
• A1n at high-x
• Crucial input to fundamental understanding of valence quark picture
• d2n
• twist-3 matrix element: q-g correlations• direct comparison with Lattice QCD
• First g3n measurement
• Twist-4 (f2n), color polarizabilities, sea-quark spin
• Even better for semi-inclusive DIS• An example: transversity: 2 orders of magnitude improvement