1 Perspectives on SSA with a transversely polarized 3 He target in JLab Hall-A • JLab Hall-A proposal E03-004 – Goals of the proposed measurements – Experimental approach and expected sensitivities • Feasibility of Sivers function measurements in SSA Drell-Yan • Feasibility of h ┴ 1 measurement in unpolarized Drell-Yan Jen-Chieh Peng Transversity Workshop, October 6-7, 2003, Athens, Greece University of Illinois
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1 Perspectives on SSA with a transversely polarized 3 He target in JLab Hall-A JLab Hall-A proposal E03-004 –Goals of the proposed measurements –Experimental.
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Perspectives on SSA with a transversely polarized 3He target in JLab Hall-A
• JLab Hall-A proposal E03-004– Goals of the proposed measurements– Experimental approach and expected
sensitivities• Feasibility of Sivers function measurements in
SSA Drell-Yan
• Feasibility of h┴1 measurement in unpolarized
Drell-Yan
Jen-Chieh Peng
Transversity Workshop, October 6-7, 2003, Athens, GreeceUniversity of Illinois
• Some characteristics of transversity:– δq(x) = Δq(x) for non-relativistic quarks– δq and gluons do not mix → Q2-evolution for δq and Δq are different– Chiral-odd → not accessible in inclusive DIS
• It takes two chiral-odd objects to measure transversity– Drell-Yan (Doubly transversely polarized p-p collision)– Semi-inclusive DIS
Chiral-odd distributions function (transversity)
Chiral-odd fragmentation function (Collins function)
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Observation of Single-Spin Azimuthal Asymmetry
Longitudinally polarized target
ep → e’πx HERMES
hep-ex/0104005
<ST> ~ 0.15• Suggests transversity, δq(x), is sizeable
• Suggests Collins T-odd fragmentation function is sizeable
• Other effects (Sivers effect, higher twist) could also contribute
• Requires a transversely polarized target
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Leading-Twist Quark Distributions
No K┴ dependence
K┴ - dependent, T-odd
K┴ - dependent, T-even
( A total of eight distributions)
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All Eight Quark Distributions Are Probed in Semi-Inclusive DIS
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26 4
Q
sxd
),()(])1(1{[ 211
,
22 h
qq
qqq PzDxfey
),()()sin()1(||
),()()2sin(4
)1(||
),()()2cos(4
)1(
2
,11
2
2
,1
)1(1
22
2
2
,1
)1(1
22
2
hqq
qqq
lS
lh
h
hT
hqq
qqLq
lh
hN
hL
hqq
qqq
lh
hN
h
PzHxhezM
PyS
PzHxheMMz
PyS
PzHxheMMz
Py
)},()()cos()2
11(||
),()()2
11(||
),()()3sin(6
)1(||
),()()sin()2
11(||
21
)1(1
,
2
21
,1
2
,
21
)2(1
223
3
21
)1(1
,
22
hqq
Tqq
qlS
lh
N
hTe
hq
qq
qqLe
qqh
qqTq
lS
lh
hN
hT
hqq
Tqq
qlS
lh
N
hT
PzDxgezM
PyyS
PzDxgeyyS
PzHxheMMz
PyS
PzDxfezM
PyyS
Unpolarized
Polarized target
Polarzied beam and
target
SL and ST: Target Polarizations; λe: Beam Polarization
Sivers
Transversity
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Azimuthal Asymmetry with longitudinnaly polarized targets
• HERMES data on longitudinally polarized deuterium and proton targets
• π+, π-, π0 and K+ are detected• Data well described by models of transversity• SSA data with transversely polarized targets
are collected at HERMES and COMPASS
HERMES, PL B562 (2003) 182
SSA measurements using transversely polarized 3He target is complementary to HERMES and COMPASS
Projected HERMES sensitivities
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JLab Hall-A E03-004 Experiment
• High luminosity– 15 μA electron beam on 10-atm 40-cm 3He target
• Measure neutron transversity– Sensitive to δd, complementary to HERMES
• Disentangle Collins/Sivers effects
• Probe other K┴-dependent distribution functions
Measurement of Single Target-Spin Asymmetry in Semi-Inclusive Pion Electroproduction on a
Transversely Polarized 3He Target
Argonne, CalState-LA, Duke, E. Kentucky, FIU, UIUC, JLab, Kentucky, Maryland, UMass, MIT, ODU, Rutgers, Temple, UVa, W&M, USTC-China, CIAE-China, Glasgow-UK, INFN-Italy, U. Ljubljana-Slovenia, St. Mary’s-
Canada, Tel Aviv-Israel, St. Petersburg-Russia
Spokespersons: J.-P. Chen (JLab), X. Jiang (Rutgers), J. C. Peng (UIUC)
In quark-diquark model, h1┴ is identical to Sivers function
No Cos2Ф depenence for unpolarized p-p Drell-Yan has been reported yet (The effect from h1
┴ is expected to be smaller)
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Unpolarized p-p and p-d dimuon production
Fermilab E866, √s = 38.8 GeV
J/Ψ
Ψ’
Υ
~ 2.5 x 105 Drell-Yan events
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Ф – coverage of the E866 dimuon data
J/Ψ events Drell-Yan events
Not corrected for acceptance yet
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Summary• JLab experiment E03-004 will measure SSA using
transversely polarized 3He target.• Information complementary to the HERMES SSA data
on transversely polarized proton could be obtained.• SSA Drell-Yan with transversely polarized proton
appears feasible at RHIC. • Azimuthal asymmetry with unpolarized Drell-Yan
could also be pursued at RHIC. Existing fixed-target p-p Drell-Yan data might provide useful information on the origin of the azimuthal asymmetry observed in pion-induced Drell-Yan data.