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Volodymyr Magas

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.

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Volodymyr Magas

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  1. HADRON@FAIR FIAS June25-27, 2008 Volodymyr Magas Two and three nucleon absorption of the antikaon in nuclei

  2. Collaboration: V. Magas, Angels Ramos University of Barcelona, Spain Eulogio Oset Hiroshi Toki University of Valencia, Spain RCNP, Osaka University, Japan Phys.Rev.C74 (2006) 025206 Phys.Rev.C77 (2008) 065210

  3. Goals • Critical review of some claims of observed deeply • bound antikaonstates 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

  4. 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: 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

  5. 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

  6. 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

  7. Experimental search for the deeply bound antikaon states

  8. 1st hope

  9. 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

  10. 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

  11. Oset-Toki’s 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)

  12. 6Li 4He 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

  13. 2st hope

  14. 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 > 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

  15. FINUDA results Interpreted by the FINUDA experiment as a (K-pp) bound state Transition to the g.s. of daughter nucleus

  16. Conventional explanation Magas, Oset, Ramos, Toki, PRC 74 (06) 025206 – a conventionalexplanation: + Final StateInteractions (FSI) of theprimaryL and p (producedafter K- absorption) as theycrossthedaughternucleus! K- absorption by two nucleons leaving the other nucleons as spectators

  17. 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

  18. 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

  19. K- wave function S. Hirenzaki, Y. Okumura, H. Toki, E. Oset and A. Ramos, Phys. Rev. C61, 055205 (2000)

  20. The K- is absorbed by two nucleons with momenta randomly chosen • within the local Fermi sea: • Primary L and N are emitted accordingly to PS: 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

  21. K-pN  N process Nuclear density profile and overlap 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

  22. The K- is absorbed by two nucleons with momenta randomly chosen • within the local Fermi sea: • Primary L and N are emitted according to PS: 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 sL~2sN/3

  23. The K- is absorbed by two nucleons with momenta randomly chosen • within the local Fermi sea: • Primary L and N are emitted according to PS: 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 sL~2sN/3 • Finally, the invariant Lp mass is reconstructed from the final events, experimental cuts are applied

  24. 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 ΛN invariant mass allowed by our model = =15-16 MeV (Li), 9.6 MeV (V)

  25. 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!

  26. Results: Back-to-back Allowing up to three collisions Compare to FINUDA data

  27. Results: Angular correlations Our Estimate: 10 %

  28. Mixture of the light targets

  29. What have we learned?

  30. Results:

  31. What have we learned? We can study the FSI for different nuclei

  32. 3rd hope

  33. FINUDA experiment M. Agnello et al. Phys. Lett. B654 (2007) 80-86

  34. FINUDA results No peak – because it is smeared out by the FSI M. Agnello et al. Phys. Lett. B654 (2007) 80-86

  35. Evolution of the FINUDA ideas Interpreted by the FINUDA experiment as a (K-pp) bound state Transition to the g.s. of daughter nucleus

  36. Evolution of the FINUDA ideas Now they learned that FSI is important for large nuclei

  37. Magas, Oset, Ramos, Toki, PRC 77 (08) 065210 We suggest a conventional explanation: K- absorption by three nucleonsleaving the other nucleons as spectators

  38. Magas, Oset, Ramos, Toki, PRC 77 (08) 065210 We suggest a conventional explanation: K- absorption by three nucleonsleaving the other nucleons as spectators n p n K n p p L p n

  39. Our model n p n K n p p L p n

  40. Results: Good agreement with the data!

  41. Results:

  42. What have we learned?

  43. 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

  44. K in a nuclear medium: The presence of the L(1405) resonance makes the in-medium KN interaction to be very sensitive to the particular details of the many-body treatment. free (repulsive)  we’d 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

  45. 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’) 2 12

  46. K-pN  N process Fermi sea  const, And finally where

  47. FSI of the primaryN where kernel describes further propagation ofLand N as they cross the nucleus according to a probability per unit lengthsrwithsL~2sN/3 p L L p p L

  48. First (narrow) peak: Transition to the g.s. of daughter nucleus How much strength should we expect? Our estimate: Formation probability(FP)xSurvival probability (PS) 7Li (pp)-1  5H In light nuclei: FP ~ | 0.3 - 0.7 |2 = 0.1–0.5, 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%

  49. 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

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