Experimental Study of Duality in SIDIS at JLab

1
Experimental Study of Duality in SIDIS at JLab
P. Bosted (JLab), for the E00-108
Collaboration
DNP05, September 2005

• Semi-inclusive processes
• Factorization as a test of quark-hadron duality
• Factorization tests in unpolarized SIDIS

2
Semi-inclusive DIS
pion
Main focus of SIDIS studies
MX

• orbital angular momentum of quarks
• parton distributions at large x

X.Ji

• Where region I/II boundary?
• Can useful information
• come from Region II?

3
SIDIS kinematic plane and relevant variables
4
Missing mass of pions in ep-gtepX
p0
p-
p
n
D
D0
Duality question is MXgt1.4 GeV (approximately
zlt0.7 for Q2-2.5 GeV2, W2.5 GeV) needed for
SIDIS factorization to work?
5
EXPERIMENT E00-108 at JLAB

• Unpolarized electrons E6 GeV
• Scattered electrons E1.6 GeV, 30 deg.
• Detected positive and negative pions near 12
  degrees
• Proton and deuteron targets
• Made scans in x,z,pt
• Data analysis nearing completion

6
Z-Dependence of cross sections
Jlab E00-108, Preliminary
Pretty good agreement with prediction using
CTEQ5M PDFs and Binnewies fragmentation
functions, except for zgt0.7, or Mxgt1.4 GeV.
X0.3, Q22.5 GeV2, W2.5 GeV
7
Unpolarized SIDIS new test A
Simple picture in valence region sp(p)
4u(x)D(z) d(x)D-(z) sp(p-) 4u(x)D-(z)
d(x)D(z) sd(p) u(x)d(x) 4D(z)
D-(z) sd(p-) u(x)d(x) 4D-(z)
D(z) Rpd sp(p) sp(p-) / sd(p)
sd(p-) 4u(x) d(x) / 5u(x)d(x)
sp(x)/sd(x)
Rpd should be independent of z and pt
x-dependence of Rpd should be same as inclusive
sp(x)/sd(x)
8
Unpolarized SIDIS new test A
Rpd is independent of z for 0.4ltzlt0.7 for W2.5
GeV, Q22.5 GeV2, x0.3, low pt Good
agreement GRV LO (solid curve), NLO (dashed
curve, using Lund PEPSI MC) 15 level
deviations for zgt0.7 (Mxlt1.4 GeV) Influence of
Delta?
Open (closed) circles are without (with)
diffractive rho contribution
9
Unpolarized SIDIS new test A
Rpd is independent of pt for z0.55 W2.5 GeV,
Q22.5 GeV2, x0.3 Good agreement GRV98
10
Unpolarized SIDIS new test A
Rpd follows expected x-dependence for
z0.55 W2.5 GeV, Q22.5 GeV2, low pt Pretty
good agreement with GRV (using PEPSI MC, solid
histogram)
11
Unpolarized SIDIS new test B
Simple picture in valence region sp(p)
4u(x)D(z) d(x)D-(z) sp(p-) 4u(x)D-(z)
d(x)D(z) sd(p) u(x)d(x) 4D(z)
D-(z) sd(p-) u(x)d(x) 4D-(z)
D(z) Rpd sp(p) - sp(p-) / sd(p) -
sd(p-) 4uv(x) - dv(x) /
3uv(x)dv(x)
Rpd should be independent of z and pt
x-dependence of Rpd should follow PDF predictions
12
Unpolarized SIDIS new test B
Rpd is independent of z for 0.4ltzlt0.7 for W2.5
GeV, Q22.5 GeV2, x0.3, low pt Good
agreement GRV LO (solid curve), NLO (dashed
curve, using Lund PEPSI MC) 15 level
deviations for zgt0.7 (Mxlt1.4 GeV) Influence of
Delta?
13
Unpolarized SIDIS new test B
Rpd is independent of pt for z0.55 W2.5 GeV,
Q22.5 GeV2, x0.3 Good agreement GRV98
14
Unpolarized SIDIS new test B
Rpd follows expected x-dependence for
z0.55 W2.5 GeV, Q22.5 GeV2, low pt Pretty
good agreement with GRV (using PEPSI MC, solid
histogram)
15
Summary

• Factorization tests with both unpolarized SIDIS
  work surprisingly well for W2.5 GeV, Q2gt2 GeV2,
  0.3ltzlt0.7, ptlt0.5 GeV, even for Mxlt2 GeV, as long
  as Mxgt1.4 GeV (another evidence of quark-hadron
  duality)
• Breakdown of factorization at high z may be due
  to Delta(1232) excitation (diffraction vector
  meson production does not appear to be as
  important)
• Data may be used even with 6 GeV electrons to
  study PDFs, at least in limited kinematic region
• More data planned all final states at 6 GeV and
  with 11 GeV at Jlab. High statistical accuracy
  tests will better quantify the useful kinematic
  range of SIDIS