Investigation Few-Nucleon System Dynamics in Medium Energy Domain

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Investigation Few-Nucleon System Dynamics in
Medium Energy Domain
Hartmut Machner Fakultät für Physik Universität
Duisburg-Essen
The strong interaction is mediated in priciple by
gluons. However, between hadrons it shows up as a
residual interaction. Changing the quark content
inside the hadrons gives hopefully- insights
into the bare interaction.
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Baryon-Baryon Interactions
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Baryon-baryon interaction
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Example neutron-neutron scattering
neutron and proton coincidences different sides
of the beam
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neutron-neutron scattering
Bonn equipment at TUNL yielded
Obviously ist the geometry which makes the
difference. Three body effects? Better method a
meson in the final state
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Problem
Why meson assisted?
baryon-baryon interaction strong meson-baryon
interaction weak
factorisation
with
leads to
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resonances
Strategy choose beam momentum so that no
resonance is close to the fsi region.
Note different sign conventions in a. alt0 unbound
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The ppp0pp case
Elastic pp scattering, Coulomb force seems to be
well under controle app-7.83 fm However an
IUCF group
Claimed the data require app-1.5 fm. They
questioned the validity of the factorization. Expe
riment at GEM, differential and total cross
sections.
FIT Ss, Pp (Ps from polarisation experiments) no
D resonance with D resonance, usual fsi with D
but fsi with half the usual pp scattering length
No need to change the standard value!
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Saclay ppp(pn) 1000 MeV
triplet (from fit to all) singlet (from deuteron)
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Data from Uppsala and GEM
p1642.5 MeV/c
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Triplet FSI absolute
at and rt close to literature values
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Singlet FSI absolute
singlet fraction Ref.
0.400.05 Boudard et al.
lt 0.10 Betsch et al.
lt0.10 Uzikov Wilkin
lt 0.10 Abaev et al.
lt 0.003 GEM
No singlet state!
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More experiments
Fäldt-Wikin relation
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Full 3 body calculation
Relativistic phase space Reid soft core potential
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Lp elastic scattering
378224 events in a 82 cm bubble chamber
fit as rs at rt
A -2.0 5.0 -2.2 3.5
B 0 0 -2.3 3.0
F -8.0 1.5 -0.6 5.0
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ppLpK
Simultaneous fit
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S0 production
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Resonances
without/with resolution folding
Upper limits (99) solid G1 MeV dashed 0.5
MeV dotted 0.1 MeV
Aerts and Dover
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L deuteron?
FW-theorem 2000 nb Exp. 753 nb c2/dof 1.3
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peak
Peak below threshold S-deuteron
Peak at threshold cusp
Peak above threshold Resonance (dibaryon?)
Shaded HIRES only Lp dots TOF (submitted)
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Peak analysis
lower mass peak at Sn threshold higher mass peak
or shoulder ???
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Flatté analysis
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Elastic Lp scattering
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Potential models

• - bound state (deuteron like SN)
• 3D1 phase passes through 90
• Nijmegen NSC97f, Nijmegen NF, Jül89
• S1 phase passes through 90
• Nijmegen ESC04, TokerGalEisenberg
• inelastic virtual state peak direct at
  threshold genuine cusp, none of the relevant
  phases passes through 90
• Nijmegen NSC89, ND, ESC08, Jülich05, EFT

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All LL hypernuclei
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LL interaction
Clear FSI peak. Weakly attractive, No indication
of S-2 (H) dibaryon
C.-J. Yoon et al., PRC 77(2007) 022201
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Summary
Meson accompanied baryon-baryon interaction is a
powerful tool to study bb-potential. Low energy
interaction can be studied via fsi and resonances
as well as bound states. ppp0pp indicates the
factorization is valid. No different parameters
than in pppp elastic scattering. ppppn only
triplet scattering. Why? ppKLp mostly singlet
scattering. Why? The potential is to weak to form
a bound state. No dibaryon resonance! Strong
enough to form a resonance? ppKSN potential
strong enough to bind? But no fsi visible. LLLL
shows FSI. Weakly attractive. No S-2 dibaryon
Thank you to my collaborators esp. Johann
Haidenbauer, Frank Hinterberger, Jouni Niskanen,
Andrzej Magiera, Jim Ritman, Regina Siudak