Diapositiva 1

1
HADRON_at_FAIR FIAS June 25-27, 2008
Volodymyr Magas
Two and three nucleon absorption of
the antikaon in nuclei
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Collaboration
V. Magas, Angels Ramos
University of Barcelona, Spain
Eulogio Oset
Hiroshi Toki
University of Valencia, Spain
RCNP, Osaka University, Japan
Phys.Rev. C 74 (2006) 025206
Phys.Rev. C 77 (2008) 065210
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Goals

• Critical review of some claims of observed
  deeply
• bound antikaon states in nuclei
• - Present a conventional explanation of the data
• Attempt to extract new physics from the data,
• even if experiment has been done for reasons
  which
• are not supported a posteriori

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Since the pioneering work of Kaiser, Siegel and
Weise NP A594 (1995) 325 many other chiral
coupled channel models have been developed
more channels, next-to-leading order, Born terms
beyond WT (s-channel, u-channel), fits including
new data
Oset, Ramos, NP A635 (1998) 99 Oller, Meissner,
PL B500 (2001) 263 Lutz, Kolomeitsev, NP A700
(2002) 193 Garcia-Recio et al., PR D67 (2003)
076009 Lutz,
Kolomeitsev, NP A700 (2002) 193
Borasoy, Nissler, Weise, PRL 94 (2005) 213401
EPJ A25 (2005) 79 Oller, Prades, Verbeni, PRL 95
(2005) 172502 J. A.Oller, EPJ A28 (2006)
63 Borasoy, Meissner, Nissler, PR C74 (2006)
055201
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A moderate attraction of about -40 MeV at r0 is
obtained
Ramos, Oset, NP A671 (2000) 481 Tolós, Ramos,
Oset, PR C74 (2006) 015203
Similar results for optical potentials
Schaffner-Bielich, Koch, Effenberber, NP A669
(00) 153 Cieply, Friedman, Gal, Mares, NP A696
(2001) 173
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If true -- New era in nuclear physics
Critical review can be found in Oset, Toki,
Phys.Rev.C74 (06) 015207Ramos,Magas,Oset,Toki,Nuc
l.Phys.A804 (08) 219
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Experimental search for the deeply bound antikaon
states
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1st hope
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The KEK proton missing mass experiment
T. Suzuki et al., Phys. Lett. B597, 263 (2004)
S0 is a tribaryon with S -1 and T 1 If
interpreted as a K- pnn bound system ? BK
197 MeV
New experiment with a more precise
measurement only a broad bump remains Sato et
al., PL B659 (2008) 107
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A conventional explanation
Oset, Toki, Phys. Rev. C74, 015207 (2006)
K- absorption by two nucleons leaving the other
nucleons as spectators
do not absorbe energy nor momentum from the probe
Fermi motion mometum conservation explain the
peak width
Ramos, Magas, Oset, Toki, Nucl. Phys. A804 (08)
219
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Oset-Tokis prediction
Such a peak should be seen in other light or
medium nuclei, and it should be narrower and
weaker as the nuclear size increases
Oset, Toki, Phys. Rev. C74, 015207 (2006)
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The FINUDA proton missing mass experiment
M. Agnello et al, Nucl. Phys. A775 (2006) 35
This view is consistent with the observation
by the FINUDA collaboration of a peak in the
proton missing mass spectrum at 500
MeV/c (from K- absorbed in 6Li)
A study of the angular correlations (p and S-
are emitted back-to-back) allow them to conclude
that the reaction in 6Li is the most favorable
one to explain their signal
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2st hope
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FINUDA experiment
M. Agnello et al. Phys. Rev. Lett. 94, 212303
(2005)
Nuclei

• The same elementary reaction as in KEK K- p
  p ? L p
• (select pL gt 300 MeV/c to eliminate K- N ? L
  p)

• But here both emitted particles are detected!
• ? the invariant mass of the Lp pair is
  measured, MLp

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FINUDA results
Transition to the g.s. of daughter nucleus
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Conventional explanation
Magas, Oset, Ramos, Toki, PRC 74 (06) 025206
a conventional explanation Final State
Interactions (FSI) of the primary L and p
(produced after K- absorption) as they cross the
daughter nucleus!
K- absorption by two nucleons leaving the other
nucleons as spectators
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Conventional explanation
A conventional explanation Final State
Interactions (FSI) of the primary L and p
(produced after K- absorption) as they cross the
daughter nucleus!
Discarded by FINUDA on the basis of back-to-back
correlations
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Our calculations
Monte Carlo simulation of K- absorption by pp
and pn pairs in nuclei

• The K- is absorbed mainly from the lowest atomic
  orbit for which the energy shift has been measured

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K- wave function
S. Hirenzaki, Y. Okumura, H. Toki, E. Oset and
A. Ramos, Phys. Rev. C61, 055205 (2000)
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Our calculations
Monte Carlo simulation of K- absorption by pp
and pn pairs in nuclei

• The K- is absorbed mainly from the lowest atomic
  orbit for which the energy shift has been measured

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K-pN ? ?N process
The K- absorption width from pN pairs in a
nucleus is given in first approximation by
PRC 50, 2314
is the in-medium decay width for the
process
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Our calculations
Monte Carlo simulation of K- absorption by pp
and pn pairs in nuclei

• The K- is absorbed mainly from the lowest atomic
  orbit for which the energy shift has been measured

• Further collisions of L and N as they cross the
  nucleus according to
• a probability per unit length sr with sL2sN/3

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Our calculations
Monte Carlo simulation of K- absorption by pp
and pn pairs in nuclei

• The K- is absorbed mainly from the lowest atomic
  orbit for which the energy shift has been measured

• Further collisions of L and N as they cross the
  nucleus according to
• a probability per unit length sr with sL2sN/3

• Finally, the invariant Lp mass is reconstructed
  from the final events, experimental cuts are
  applied

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First (narrow) peak
Transition to the g.s. of daughter nucleus
for the light nuclei
Our model is not really suitable to reproduce
this peak
we made a rough estimate of 10 of all events
Nucleons move in mean field Thomas-Fermi potenti
al
only for the holes
- ?,
such that the maximum ?N invariant mass allowed
by our model

?15-16 MeV (Li), 9.6 MeV (V)
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Second (wider) peak
Quasi-elastic peak (QEP) after K- absorption
A peak is generated in our Monte Carlo
simulations the primary L and p (produced after
K- absorption) undergo quasi-elastic collisions
with the nucleus exciting it to the continuum
This is the analogue of the quasi-elastic peaks
observed in nuclear inclusive reactions using a
variety of different probes (e,e), (p,p),
(p,p), (The QEP comes mostly from one collision
of the particles exciting the nucleus to the
continuum)

• The QEP accounts for the second peak of
• 
  the FINUDA experiment!

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Results
Back-to-back
Allowing up to three collisions
Compare to FINUDA data
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Results
Angular correlations
Our Estimate 10
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Mixture of the light targets
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What have we learned?
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Results
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What have we learned?
We can study the FSI for different nuclei
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(No Transcript)
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3rd hope
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FINUDA experiment
M. Agnello et al. Phys. Lett. B654 (2007) 80-86
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FINUDA results
No peak because it is smeared out by the FSI
M. Agnello et al. Phys. Lett. B654 (2007) 80-86
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Evolution of the FINUDA ideas
Transition to the g.s. of daughter nucleus
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Evolution of the FINUDA ideas
Now they learned that FSI is important
for
large nuclei
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Magas, Oset, Ramos, Toki, PRC 77 (08) 065210
We suggest a conventional explanation
K- absorption by three nucleons leaving the
other nucleons as spectators
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Magas, Oset, Ramos, Toki, PRC 77 (08) 065210
We suggest a conventional explanation
K- absorption by three nucleons leaving the
other nucleons as spectators
n
p
n
K
n
p
p
L
p
n
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Our model
n
p
n
K
n
p
p
L
p
n
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Results
Good agreement with the data!
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Results
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What have we learned?
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Conclusion
We have shown that there are (so far?) no
experimental evidences of deeply bound K- state
in nuclei
All signals of deeply bound state can be
explained in conventional scheme
K- absorption by two or three nucleons leaving
the others as spectators
Final State Interaction for heavy nuclei
However, the FINUDA data allows to study in
details the two and three nucleon K- absorption
mechanisms
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? wed better do a good job! (SELF-CONSISTENCY)
medium (attractive)
K
K
p
Pauli blocking
Weise, Koch
K
K
p
Self-consistent kaon dressing
Lutz
K
K
p
pion and kaon dressing
Ramos,Oset
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FINUDA results
We give a conventional explanation Final State
Interactions (FSI) of the primary L and p
(produced after K- absorption) as they cross the
daughter nucleus!
C(p,p) H(p,p)
12
2
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K-pN ? ?N process
Fermi sea
? const,
And finally
where
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FSI of the primary ?N
where kernel describes further
propagation of L and N as they cross the nucleus
according to a probability per unit length sr
with sL2sN/3
p
L
L
p
p
L
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First (narrow) peak
Transition to the g.s. of daughter nucleus
How much strength should we expect?
Our estimate
Formation probability (FP) x
Survival probability (PS)
7Li (pp)-1 ? 5H
In light nuclei FP 0.3 - 0.7 2 0.10.5,
PS 0.6 (Li), 0.4 (C) ? 0.1-0.3
In heavier nuclei FP increases, but PS
decreases 0.26 (Al), 0.18 (V) ? also below 30
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Can the peak be due to other processes?
A)
followed by
This peaks around 2170 MeV (where there is indeed
a small third peak in the experiment) and has a
smaller strength than
B)
followed by
? located in the region of the QEP and all events
back-to-back, but strength is small, 10-30 of
events