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Electroproduction of φ Mesons in CLAS
Joe Santoro, Elton Smith Exclusive Reactions May 21, 2007
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φ photoproduction π, f2, P ω P p
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Kinematics
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Q2 (GeV2) W (GeV) Kinematic Coverage ep→epφ→epK+(K−)
e1a/e1b: E = 4.2 GeV, Q2~ 0.7 ─ 2.2 GeV2 e1-6a: E = 5.75 GeV Q2 ~ 1.7 ─ 3.8 GeV2 Q2 (GeV2) Q² W (GeV)
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e1-6 Experiment @ CLAS 5.75 GeV Beam Proton Target
21 mC integrated charge ep →epφ→K+(K-) Drift Chambers TOF Cherenkov Electromagnetic Calorimeter
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Electron Selection E/p vs P & EC energy Number of photoelectrons
in Cerenkov Counter Electron Fiducial cuts
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Hadron Identification
p and K+ selection K- from missing mass (2s selection cut) p TOF Mass (GeV) K+ p+ contamination Momentum (GeV) Mx(epK+X) (GeV)
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f yields ~4x number of φ’s as previous CLAS measurement in a
higher Q2 range K+ K- Invariant Mass (GeV)
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6-D Acceptance Correction
Variable Q2 W t cos(qH) y F Nbins 5 4 7 8 6 33,600 bins, 108 events Q2 y W -t cosqH F
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Radiative Corrections
COS(q)CM=0.345, Q2= 2.47 GeV2 EXCLURAD was used to obtain corrections in Q2,W,F, and COS(q)CM bins W ranges from 1.9 GeV to 3.0 GeV
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Total Cross Sections σ(Q2)
Laget Model NP A581: , 1995 Phys. Lett. B. 489: , 2000 Preliminary K+ K- Invariant Mass (GeV)
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Differential Cross Section in t
Nuc. Phys. A581: , 1995 Phys. Lett. B. 489: , 2000 Q2=1.6 GeV2 Q2=2.1 GeV2 Q2=2.6 GeV2 Q2=3.8 GeV2 Q2=5.0 GeV2 Preliminary K+ K- Invariant Mass (GeV)
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Differential Cross Section in t’
Preliminary K+ K- Invariant Mass (GeV) Lukashin, et. al.
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Differential Cross Section in Φ
c2const. = 1.9 SCHC Conserved Preliminary
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Angular Distributions
Preliminary Preliminary
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sL Extraction Preliminary
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Comparison to World Data
Filled previously unexplored region of phase space (low W, low-medium Q2) Preliminary
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production summary Kinematic Range
1.6 ≤ Q2 ≤ 3.8, 0.0 ≤ t’≤ -3.6, 2.0 ≤ W ≤ 3.0 (Q2) ~ 1/(Q2+M2) 3 ± 1 F angular distribution consistent with SCHC R=1.71 ± 0.30 , sL = 2.9 ± 0.8 nb integrated over Q2 t’ distribution slope bf=0.81 ± 0.18 GeV2 Interaction probes sizes ~ 1/3 fm. Theoretical input welcome.
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