Lineshape Measurement of the L1405 via gpSpK Reactions

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Lineshape Measurement of the L(1405)via gp?SpK
Reactions

• Jung Keun Ahn
• (Pusan National University)

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Motivation
Motivation
Is the L(1405) a KN Bound State or a q3 System or
anything else? Bgtaq3gtbq3qqgtgq3ggt
Event Selection

• Jp1/2- L(1405) 4-star Resonance
• - It must be mass-degenerate with Jp3/2-
  L(1520)
• - Jp1/2- N(1535) is heavier than L(1405)
• KN Bound State
• - Low-energy I0 KN interactions are strongly
  attractive
• - There must exist a new, as yet undetected,
  Jp1/2-L(1520)
• Hybrid
• - udsg? mL(1405) m L(1116) 290 MeV only

Lineshape
Outlook
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Coupled-channel c-dynamics
Motivation
Event Selection
Lineshape
Outlook
Nacher,Oset,Toki,Ramos PLB 455 (1999) 55
Lutz,Kolomeitsev NPA 700 (2002)193
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Two-pole structure of the L(1405)
Motivation
Event Selection
Lineshape
Outlook
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Experimental Data I
Motivation
p-p interactions at 1.6 GeV/c
Event Selection
Lineshape
ABBHHM Collaboration (1969) HBC Data
Outlook

• Thomas et al, Nucl.Phys.B 56 (1973) 15

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Experimental Data II
Motivation
p-
K-
p
p- p K0
Event Selection
p
S S- n
S(1660)
L(1405)
PDG refers to this data only
Lineshape
K-p? p0p0S0
CB collaboration
Outlook
Hemingways Data NPB253(1984)742
S. Prakhov et al., PRC 70(2004) 034605
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Acceptance for /- Particles
Motivation
Event Selection
f(1019)

• Equal Acceptance for ve and ve particles thank
  to good performance of the LEPS dipole
  spectrometer
• f(1019) reconstruction from p(g,K-p)K and
  p(g,Kp)K-

Lineshape
Outlook
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p(g,Kp)X Reaction
Motivation

• 50mm LH2 target run
• (Dec 2000 Jun 2001)
• 2x106 g/s flux
• 2x1012g in 1.5-2.4 GeV
• 3x105 (g,K) events

Event Selection
Lineshape
Outlook
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p(g,Kp) Reactions
Motivation
Event Selecion
Lineshape
Outlook
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Vertex Distributions
Motivation
g p? L(1405) K ? S 0p 0K
g p? L(1405) K ? S p -K
g p? S(1385) K ? Lp 0K
g p? L(1405) K ? S -p K
Event Selection
(S 0?Lg, L?pp -)
g
Scintillator
LH2
Lineshape
Outlook
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Closest Distance
Motivation
K
Event Selection
lt 1mm
p
lt 2mm
lt 3mm
Lineshape
lt 5mm
lt 10mm
K
Outlook
lt 20mm
p
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Missing Mass for p(g,Kp)X
Motivation
D m lt 20 MeV
Event Selection
Lineshape
Outlook
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Lineshape of the L(1405)
Motivation
Event Selection
Results
Outlook
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I0, I1 Amplitudes
Motivation
Event Selection
Without negligible I2 contribution, the
difference of the two charged channels shed some
light on the I1 amplitude contribution.
Lineshape
The sum of cross-sections for the two channels
provides information on the I0 dominant
lineshape.
Outlook
15
L(1405) in Nuclear Medium
Motivation
Lutz, Kolomeitsev NPA 700 (2002)193
Event Selection
Disappears at mK300MeV
V. Koch, Nucl. Lett. B337 7 (1994) KN bound
state 65 MeV/c2 of mass shift in the nuclear
matter
Lineshape
Nacher,Oset,Toki,Ramos PLB 455 (1999) 55
Aiming at Detecting Any possible change in Mass
and/or Width of the L(1405)
Outlook
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L(1405) and K(890)
Motivation
Williams et al, PRC 43 (1991)452
Hyodo et al, This Workshop
ds/dW is sensitive to the strong coupling
constant gKNL(1405)
Event Selection
Lineshape
gKNL3
Outlook
gKNL1.5
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Summary
Motivation

• No doubt on different line-shape of the L(1405)
  according to charge combination of pS
• Comparative analysis of L(1405) production in
  K-p and g p /p p reactions will test the
  existence of the two L(1405) states.
• LEPS/TPC experiment will soon give a hint on the
  hadronic structure of the L(1405)

Event Selection
Lineshape
Outlook