volodymyr magas
DESCRIPTION
HADRON@FAIR FIAS June 25 -2 7 , 200 8. Volodymyr Magas. Two and three nucleon absorption of. the antikaon in nuclei. Collaboration:. V. Magas, Angels Ramos. University of Barcelona, Spain. Eulogio Oset. Hiroshi Toki. University of Valencia, Spain. RCNP, Osaka University, Japan. - PowerPoint PPT PresentationTRANSCRIPT
HADRON@FAIRFIAS
June 25-27, 2008
Collaboration:
Phys.Rev. C 74 (2006) 025206Phys.Rev. C 77 (2008) 065210
- 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
Goals
K N interaction
Since the pioneering work of Kaiser, Siegel and Weise [NP A594 (1995) 325] many other chiral coupled channel models have been developed:
Oset, Ramos, NP A635 (1998) 99Oller, Meissner, PL B500 (2001) 263Lutz, Kolomeitsev, NP A700 (2002) 193Garcia-Recio et al., PR D67 (2003) 076009
Lutz, Kolomeitsev, NP A700 (2002) 193Borasoy, Nissler, Weise, PRL 94 (2005) 213401; EPJ A25 (2005) 79 Oller, Prades, Verbeni, PRL 95 (2005) 172502J. A.Oller, EPJ A28 (2006) 63Borasoy, Meissner, Nissler, PR C74 (2006) 055201
more channels,next-to-leading order,Born terms beyond WT (s-channel, u-channel),fits including new data
A moderate attraction of about -40 MeV at 0 is obtainedRamos, 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
If true -- New era in nuclear physics
Critical review can be found in Oset, Toki, Phys.Rev.C74 (06) 015207Ramos,Magas,Oset,Toki,Nucl.Phys.A804 (08) 219
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
A conventional explanation
K- absorption by two nucleons leaving the other nucleons as spectators
Oset, Toki, Phys. Rev. C74, 015207 (2006)
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
Oset-Toki’s prediction:
Oset, Toki, Phys. Rev. C74, 015207 (2006)
Such a peak should be seen in other light or medium nuclei, and
it should be narrower and weaker as the nuclear size increases
The FINUDA proton missing mass experiment:
M. Agnello et al, Nucl. Phys. A775 (2006) 35
This view is consistent with the observation bythe 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 - are emitted back-to-back) allow them to conclude that the reaction:
in 6Li is the most favorable one to explain their signal
6Li4He
FINUDA experiment
M. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005)
But here both emitted particles are detected!
the invariant mass of the p pair is measured, Mp
The same elementary reaction as in KEK: K- p p p
(select p > 300 MeV/c to eliminate K- N
Nuclei:
Interpreted by the FINUDA experiment
as a (K-pp) bound state
FINUDA results
Transition to the g.s. of daughter nucleus
Conventional explanation
K- absorption by two nucleons leaving the other nucleons as spectators
A conventional explanation: Final State Interactions (FSI) of the primary and p (produced after K- absorption) as they cross the daughter nucleus!
Discarded by FINUDA on the basis of back-to-back correlations
Conventional explanation
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
S. Hirenzaki, Y. Okumura, H. Toki, E. Oset and A. Ramos,
Phys. Rev. C61, 055205 (2000)
K- wave function
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
Primary and N are emitted accordingly to PS:
The K- is absorbed by two nucleons with momenta randomly chosen within the local Fermi sea:
Nuclear density profile and overlap
K-pN N processThe K− absorption width from pN pairs in a nucleus is given in first approximation by
is the in-medium decay width for the process
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
Primary and N are emitted according to PS:
The K- is absorbed by two nucleons with momenta randomly chosen within the local Fermi sea:
Further collisions of and N as they cross the nucleus according to
a probability per unit length with ~2N/3
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
Primary and N are emitted according to PS:
The K- is absorbed by two nucleons with momenta randomly chosen within the local Fermi sea:
Further collisions of and N as they cross the nucleus according to
a probability per unit length with ~2N/3
Finally, the invariant p mass is reconstructed from the final events, experimental cuts are applied
Transition to the g.s. of daughter nucleus
for the light nuclei
First (narrow) peak:
Our model is not really suitable to reproduce this peak
Nucleons move in mean field Thomas-Fermi potenti al:
- ,
such that the maximum ΛN invariant mass allowed by our model
=
only forthe holes
=15-16 MeV (Li), 9.6 MeV (V)
we made a rough estimate of 10% of all events
Quasi-elastic peak (QEP) after K- absorption
A peak is generated in our Monte Carlo simulations: the primary 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’), (’),…(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!
Second (wider) peak:
Allowing up to three collisions
Results:
Compare to FINUDA
data
Back-to-back
Angular correlations
Results:
Our Estimate:
10 %
Mixture of the light targets
What have we learned?
Results:
What have we learned?
We can study the FSI for different nuclei
FINUDA experiment
M. Agnello et al. Phys. Lett. B654 (2007) 80-86
FINUDA results
No peak – because it is smeared out by the FSIM. Agnello et al. Phys. Lett. B654 (2007) 80-86
Interpreted by the FINUDA experiment
as a (K-pp) bound state
Evolution of the FINUDA ideas
Transition to the g.s. of daughter nucleus
Evolution of the FINUDA ideas
Now they learned that FSI is important for large nuclei
We suggest a conventional explanation:
K- absorption by three nucleons leaving the other nucleons as spectators
We suggest a conventional explanation:
K- absorption by three nucleons leaving the other nucleons as spectators
pp
p
n
n
nK
np
pp
p
n
n
nK
np
Our model
Results:
Good agreement with the data!
Results:
What have we learned?
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
K in a nuclear medium:The presence of the (1405) resonance makes the in-medium KN interaction to be very sensitive to the particular details of the many-body treatment. we’d better do a good job! (SELF-CONSISTENCY)
Pauli blocking
free(repulsive)
medium(attractive)
Self-consistent kaon dressing
pion and kaon dressing
K
K
K
K
K
K
Weise, Koch
Ramos,Oset
Lutz
We give a conventional explanation: Final State Interactions (FSI) of the primary and p (produced after K- absorption) as they cross the daughter nucleus!
FINUDA results
C(p,p’) H(p,p’)12 2
K-pN N processFermi sea
const,
And finally
where
p
p
p
FSI of the primary N
where kernel describes further propagation of and N as they cross the nucleus according to a probability per unit length with ~2N/3
Transition to the g.s. of daughter nucleus
How much strength should we expect?
Formation probability (FP) x Survival probability (PS)
In light nuclei: FP ~ | 0.3 - 0.7 |2 = 0.1–0.5, PS ~ 0.6 (Li), 0.4 (C) 0.1-0.3In heavier nuclei: FP increases, but PS decreases: ~0.26 (Al), 0.18 (V)
also below 30%
First (narrow) peak:
Our estimate:
7Li (pp)-1 5H
Can the peak be due to other processes?
followed by
This peaks around 2170 MeV (where there is indeed a small thirdpeak in the experiment) and has a smaller strength than
A)
B)
followed by
located in the region of the QEP and all events back-to-back,but strength is small, ~ 10-30% of events