factorization studies with SIDIS A1p

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factorization studies with SIDIS A1p
H.Avakian, P. Bosted, L. Elouadrhiri
SIDIS (gp-gtpX) x-section at leading twist
Structure functions FUU,FLL factorize into TMD
distributions (hep-ph 0405085)
Ji et al.
P- has contributions from distribution,
fragmentation and soft gluon radiation
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Kinematic dependences of structure functions
S-Sudakov suppression factor, mL-scale
The A1p PT-dependence will be the same for
different Q2 at fixed x and z
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Data analysis using histo-data files
Contain counts per bin, occupy small disk space
and are efficient for data analysis
N(i,j,k,l,m,n,h) array in a data file per run
used
i1,7 Q2-bins 0.453, 0.645, 0.919, 1.31, 1.87,
2.66, 3.79, 5.40
j1,6 x-bins 0.12-0.48
n 1-p, 2-p-, 3-p0
k1,8 z-bins 0.1-0.9
h1 helicity h2 helicity-
l1,6 PT-bins 0.0-1.2
m1,12 f-bins 0.0-360.0
Exactly the same structure created using the
PEPSI-MC with CLAS acceptance and smearing
included
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double spin asymmetry A1p
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NH3 dilution
Dilution function extracted from PEPSI-MC is
consistent with data
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Data vs MC
ep ? e p X ( Ee 5.7 GeV, MX gt 1.1)
eg2000
MC reasonably decribes the resolution of the MX
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Data vs MC A1p
DIS cuts for ep-gt e p X Ee 5.7 GeV, Q2gt1.3,
W2gt2, MX gt 1.1, ylt0.85, 0.4ltzlt0.7
(filled circles sum over all x)
Cut on z used for all x,pT dependent plots
0.4ltzlt0.7
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z-dependence data vs mc
A1p for Egt5GeV runs.
Good agreement of Data with MC (no significant pT
dependence)
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Data vs MC A1p
ep ? e p X ( Ee 5.7 GeV, MX gt 1.1)
Data consistent with MC, showing no z-dependence
at zgt0.4
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Data vs MC A1p
ep ? e p X ( Ee 5.7 GeV, MX gt 1.1)
Data consistent with MC, showing no x/z dependence
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Data vs MC A1p
ep ? e p X ( Ee 5.7 GeV, MX gt 1.1)
Data consistent with MC, and inclusive fit
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PT-dependence
A1p for Egt5GeV runs.
No significant pT dependence (filled circles sum
over all z)
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Data vs MC A1p
ep ? e p X ( Ee 5.7 GeV, MX gt 1.1)
May have a bit (10-15) different slope in PT
dependence
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PT-dependence
A1p for Egt5GeV runs.
ltxgt
inbending
outbending
Some pT dependence due to a different ltxgt for
different bins
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PT-dependence different x-bins
A1p for Egt5GeV runs.
While no significant pT dependence for average
(filled circles sum over all x), some dependence
is possible for different x-bins.
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Single-spin asymmetry AUL
Deformed sinf may have a contribution from cosf
terms in the x-section
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AUL as a function of x for p
Filled symbols AULp1sinfp2sin2f
Open symbols AUL(p1sinfp2sin2f)(1p3cosf)
Collins effect from Efremov et. al

• The sinf SSA is not sensitive to the fitting
  procedure and indicate, that
• only the Collins effect will not explain the
  large SSA.
• The magnitude of sin2f SSA shows some sensitivity
  to the fit procedure

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AUL as a function of PT for p

• The sinf and sin2f SSA consistent with increase
  with pT

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AUL as a function of z for p
Different from HERMES at large z

• The sinf and sin2f SSA consistent with increase
  with z

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AUL as a function of MX for p
Phys.Lett.B53585-92,2002
HERMES
Sign flip of exclusive SSA with the lepton charge?
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summary

• A1p data from eg2000 is consistent with
  factorization
• A1p dependence on PT and z extracted for the
  first time
• x,pT,z-dependens of longitudinall SSA extracted

• Prepare an analysis note and a publication on A1p
• and SSA

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Beam SSA sinf moment (CLAS _at_4.3 GeV)
ssinfLU FLUHLT 1/Q (Twist-3)
Beam SSA shows no significant dependence on W,E