FIAS June 25-27, 2008

Collaboration: Phys.Rev. C 74 (2006) Phys.Rev. C 77 (2008)

- 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) 99 Oller, Meissner, PL B500 (2001) 263 Lutz, Kolomeitsev, NP A700 (2002) 193 Garcia-Recio et al., PR D67 (2003) Lutz, Kolomeitsev, NP A700 (2002) 193 Borasoy, Nissler, Weise, PRL 94 (2005) ; EPJ A25 (2005) 79 Oller, Prades, Verbeni, PRL 95 (2005) J. A.Oller, EPJ A28 (2006) 63 Borasoy, Meissner, Nissler, PR C74 (2006) 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 obtained Ramos, Oset, NP A671 (2000) 481 Tolós, Ramos, Oset, PR C74 (2006) 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) Ramos,Magas,Oset,Toki,Nucl.Phys.A804 (08) 219

The KEK proton missing mass experiment: T. Suzuki et al., Phys. Lett. B597, 263 (2004) S 0 is a tribaryon with S = -1 and T = 1 If interpreted as a [K - pnn] bound system…  B K = 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, (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, (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 by the FINUDA collaboration of a peak in the proton missing mass spectrum at ~ 500 MeV/c (from K - absorbed in 6 Li) A study of the angular correlations (p and  - are emitted back-to-back) allow them to conclude that the reaction: in 6 Li is the most favorable one to explain their signal 6 Li 4 He

FINUDA experiment M. Agnello et al. Phys. Rev. Lett. 94, (2005) But here both emitted particles are detected!  the invariant mass of the  p pair is measured, M  p 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, (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 process The 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   ~2  N /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   ~2  N /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 for the 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 FSI M. 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 p p p n n n K  n p

p p p n n n K  n p 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 process Fermi 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   ~2  N /3

Transition to the g.s. of daughter nucleus How much strength should we expect? Formation probability (FP) x Survival probability (P S ) In light nuclei: FP ~ | | 2 = 0.1–0.5, P S ~ 0.6 (Li), 0.4 (C)  In heavier nuclei: FP increases, but P S decreases: ~0.26 (Al), 0.18 (V)  also below 30% First (narrow) peak: Our estimate: 7 Li (pp) -1  5 H

Can the peak be due to other processes? followed by This peaks around 2170 MeV (where there is indeed a small third peak 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