In search of K K- molecule

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In search of KK- molecule
Michal Silarski Jagiellonian University
Frascati Spring School May 12 16, 2008
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• Physical motivation
• Kaon pairs production in nucleon nucleon
  collisions
• Measurements of the pp?ppKK- reaction with
  COSY-11
• Study of the KK- final state interaction
• Generalizations of the Dalitz Plot Chodrow and
  Goldhaber approach
• Present status of analysis

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Physical motivation

• a0 and f0 mesons as a KK- molecules
• Nature of ?(1405) K-p bound state (?)
• Physics of heavy ion collisions
• Physics of neutron stars
• kaon condensates

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Kaon pair production in nucleons collisions

• Production of a non-strange meson which decays
  into KK-
• 
  ( DISTO, ANKE )
• Associated production

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Kaon pair production in nucleons collisions

• Proton-proton collisions close to KK-
  threshold ( COSY-11, ANKE )

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Cooler Synchrotron COSY
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COSY-11 apparatus

• positively charged particles detection
• Drift chambers momentum reconstruction
• scintilators S1 and S3 velocity determination
• K- detection
• - Silicon pad detector position of negatively
  charged particle (background reduction )

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Measurements of pp ? ppKK- reaction at threshold
COSY-11 C. Quentmeier et al., Phys.Lett. B 515
(2001) 276-282 COSY-11 P. Winter et al., Phys.
Lett. B 635 (2006) 23-29 COSY-11 M. Wolke, PhD
thesis DISTO F. Balestra et al.., Phys. Rev. C
63, 024004 (2001) ANKE Y.Maeda et al. Phys.,
Rev. C 77, 01524 (2008)
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Measurements of pp ? ppKK- reaction at threshold

• Significant discrepancy between experimental
  data and pure phase space calculations
• Inclusion of the pp fsi does not fully account
  for the difference
• Introduction of the fsi in the K-p system still
  underestimates data very close to threshold
• Possible influence of KK- final state interaction

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Study of the KK- final state interaction

• General idea analysis of the differential
  cross-sections for the reaction pp ? ppKK-
• In the investigation we will use data obtained
  from two measurements at COSY
• Q 10 MeV ( 27 events )
• Q 28 MeV ( 30 events )
• The experimental data are compared to the
  results of Monte Carlo simulations generated with
  various parameters of the KK- interaction

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Dalitz plot - convenient method of analysis for
three particles in final state

• Homogeneous event density on entire plot
• Area of the plot proportional to phase space
  volume
• Boundary of the physically allowed region well
  defined smooth closed curve
• Interaction effects show up as a modification of
  event density on Dalitz plot

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Generalization of the Dalitz Plot
There are several extensions of Dalitz plot for
four particles Two very convenient
? Chodrow plot ? Goldhaber plot
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Generalization of the Dalitz Plot
Probability of reaction yielding a state with the
i-th particle in momentum range dpi

• Chodrow approach ( Nuvo Cim. 50 (1967) 647 )
• Assuming that f depends only on energies, when
  particles 1 and 2 are identical and E2 gtE1 one
  gets

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Chodrow plot

• Resonances may be directly read off event
  distribution in FE2-plane

• Event density on Chodrow plot is not
  homogeneous( but well defined)

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Goldhaber plot

• Goldhaber approach (Goldhaber et al. Phys. Rev.
  Lettes 9 (1962 ) 330)
• Assumption f depends only on invariant masses of
  the particles

Projection of the physical region on (M12 ,M34
)plane gives heterogenous event distribution
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Goldhaber plot

• Lorentz - invariant distribution
• The physical region interior of the right
  isosceles triangle bounded by

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Present status of analysis
Q10 MeV Q28 MeV
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Present status of analysis
Q10 MeV Q28 MeV
Experiment Monte Carlo (pp-FSI only)
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In the near future

• Quantitative comparsion with Monte Carlo results
• Conclusions,

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Thank you for attention