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Pentaquark Baryon Production in Nuclear Reactions

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1. Pentaquark Baryon Production in Nuclear Reactions. Che-Ming Ko. Teaxs A&M University ... (Davidson and Workman, PRC 63, 058201 (2001)) with. Form factors. 7 ... – PowerPoint PPT presentation

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Title: Pentaquark Baryon Production in Nuclear Reactions


1
Pentaquark Baryon Production in Nuclear Reactions
Che-Ming Ko Teaxs AM University
  • Introduction
  • Photon-nucleon reactions
  • Proton-proton reactions
  • Meson-nucleon reactions
  • Relativistic heavy ion collisions
  • Summary

Collaborators Wei Liu, L.W. Chen, V. Greco, S.H.
Lee
2
Pentaquark baryons
chiral soliton model, diquark model
naïve quark model, lattice QCD
How is Theta produced in nuclear reactions? And
is the cross section sensitive to its spin and
parity?
3

LEPS at Sping-8 Nakano et al., PRL 91, 012002
(2003) CLAS at JLab Stepanyan et al.,
hep-exp/0307018
4
Coupling constants
5
Scattering amplitudes
6
Form factors
Cross section
Form factors
(Davidson and Workman, PRC 63, 058201 (2001))
with
is introduced to recover gauge invariance
Fitting charm production at 6 GeV
7
Charmed meson production in photoproton reactions
Liu, Lee, and Ko, NPA 724, 375 (2003)
Data (Abe et al., PRD 30, 1 (84)) s 20
nb at s1/2 6 GeV
8
Total and differential cross sections
Dominated by t-channel kaon and vector kaon
exchanges, which also lead to differential cross
sections that peak at forward angles.
9
Negative parity Theta
10
Cross section for negative parity Theta
First pointed out by Oh, Kim, and Lee, PRD 69,
014009 (2004)
Nam, Hosaka, and Kim, PLB 579, 43 (2004)
11
Other Theta photoproduction reactions
SAPHIR experiment at ELSA Barth et al., PLB
572, 127 (2003)
CLAS at JLab, Kubarovsky et al., PRL 92,032001
(2004).
12
(No Transcript)
13
Cross sections for Theta photoproduction
reactions
14
Angular distributions of Theta in photoproducton
15
Pentaquark cascade production in
Liu Ko, PRC 69, 045204 (2004)
16
Pentaquark cascade production in
17
(No Transcript)
18
Theta production in proton-proton reactions
Liu and Ko, PRC 68, 045203 (2003)
Comparable to 0.4 µb from COSY
19
Theta production from pion-nucleon reactions
20
Theta production from kaon-nucleon reactions
21
Theta production in heavy ion collisions
Chen, Greco, Ko, Lee and Liu, nucl-th/0308006
Quark coalescence model
with quark distribution function and Theta
Wigner function
22
Thermal partons
Light quarks
Strange quarks
Gluons
Take T170 MeV,
as in experimental data
23
Parton transverse momentum distributions
  • Thermal QGP
  • Power-law minijets
  • Choose

Consistent with data (PHENIX)
24
Theta absorption cross sections and thermal width
25
Time evolution of fireball after QGP
AuAu _at_ 200 AGeV
  • Dynamics governed by
  • entropy conservation
  • Normal hadrons are taken
  • to be in equilibrium

26
Kinetic model for Theta production
27
Time evolution of Theta abundance
  • Initial Theta number is
  • increased to 0.46 if its
  • size increases by 30.
  • Final Theta number
  • is sensitive to initial
  • number if Theta width
  • is small.
  • Compare to
  • 0.9 (Randrup, PRC 68)
  • 0.4 (Letessier et al,
  • PRC 68)
  • from statistical model

28
Summary
  • Predicted cross sections in other reactions (for
    )
  • and they are sensitive to Theta couplings and
    form factors.
  • Differential cross sections are forward peaked.
  • Cross sections for negative parity Theta are
    order of magnitude
  • smaller than those for positive parity Theta.
  • At
  • AT RHIC, about 0.19 Theta is produced during
    hadronization, but final
  • number depends on the width of Theta.
  • Anti-Theta and exotic cascades are slightly less.

0.2 GeV above threshold
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