in collaboration with : V.K. Magas , E. Oset , R. Molina, L . Tolós ,

1. Strange mesons in nuclei S=-1 mesons: - K (Jp=0-) - K* (Jp=1-) A. Ramos University of Barcelona (JPS+SPHERE meeting, Vila Lanna, Prague 4-6 September, 2010) in collaboration with : V.K. Magas, E. Oset, R. Molina, L. Tolós, J. Yamagata-Sekihara, S. Hirenzaki

2. PseudoscalarK mesons in nuclei • Understanding the properties of Kbar mesons has been one of the major goals in strange nuclear physics. • How attractive is the Kbar-nucleus optical potential? • May kaon condensation occur in neutron star interiors? • Phenomenological fits to kaonic atom data preferred UK(r0) ~ -200 MeV OK • Self-consistent theoretical calculationsthat use realisticKbar N interactions • (KN data reproduced, chiral dynamics) obtain UK(r0) ~ -50 to -70 MeV X • Evidences of deeply bound K- nuclear states (BK ~ 100 MeV) from slow kaon reactions on nuclei has been claimed

3. The observed peaks in nuclear reactions using slowkaons: • (K-stop, p) (bump) • (K-stop, Lp) • (K-stop, Ld) • can be explained in terms of conventional input that combines: • an absorption mechanism • K-NN  LN (in 1. and 2.) • K-NNN  Ld (in 3.) • nuclear medium effects: • Fermi motion/recoil • (direct reaction peaks broaden) • FSI of the emitted particles (if daughter nucleus is big enough) • ( secondary peaks/structures may appear) M. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005) T. Suzuki et al., Mod. Phys. Lett. A23, 2520 (2008) M. Agnello et al. Phys. Lett. B654, 80 (2007) T. Suzuki al. Phys. Rev .C76, 068202 (2007) E. Oset, H. Toki, Phys. Rev. C74, 015207 (2006) V.K. Magas, E. Oset and A. Ramos, Phys. Rev C77, 065210 (2008) V.K. Magas, E. Oset, A. Ramos and H. Toki, Nucl.Phys. A804, 219 (2008) V.K. Magas, E. Oset, A. Ramos and H. Toki, Phys. Rev. 74 (2006) 025206

4. Another “evidence” for a very deeply attractive K- nucleus potential: The (K-,p) reaction on 12C at KEK T. Kishimoto et al., Prog. Theor. Phys. 118 (2007) 181 pK = 1 GeV/c • in-flight kaons • forward nucleons qp < 4.1o (the most energetic) plus “coincidence requirement”: (at least one charged particle in decay counters surrounding the target) claimed not to affect the spectrum shape

5. J. Yamagata, H. Nagahiro and S. Hirenzaki, Phys.Rev. C74, 014604 (2006) deep shallow

6. Analysis of T. Kishimoto et al., Prog. Theor. Phys. 118 (2007) 181 • Process: quasielastic scattering K- p  K- p in nuclei • Green’s function method • Normalization: fitted to experiment • Background: fitted to experiment Re UK=−60 MeVIm UK=−60 MeV Re UK=−190 MeVIm UK=−40 MeV Re UK=−160 MeVIm UK=−50 MeV

7. The only mechanism for fast proton emission in the Green’s function method is the quasielastic process K- p  K- p where the low-energy kaonin the final statefeels a nuclear optical potential and can occupy stable orbits (no width) , unstable orbits, or be in the continuum (quasifree process) However, there are other mechanisms that can contribute: • Multistep processes: • K- and/or N undergo secondary collisions as they leave the nucleus • One-nucleon absorption: • K- N  p L and K- N  p S • followed by decay of L or S into pp • Two-body absorption: • K- N N S N and K- N N L N • followed by hyperon decays Taken from J. Yamagata and S. Hirenzaki, Eur. Phys. J. A 31, 255{262 (2007) We implement these processes in a Monte Carlo simulation of K- absorption in nuclei

8. Monte Carlo simulation (details in next talk by V. Magas) • Thenucleusisdescribedby a nuclear densityprofiler(r) • Theincoming K- willexperience a certainprocess (quasielastic, • one-nucleonortwo-nucleonabsorption) at a pointrwith a probability • givenbysqerdl, s1Nrdl ors2Nrdlwheredlis a typicalstepsize. • Once a process has beendecided, we determine the local momenta • of theemittedparticlesaccordingtophasespace • Furthercollisions of theemittedparticles as theycrossthenucleus. • Wefollow: theK-untilitleavesthenucleusorgets absorbed • allenergeticp and n(untiltheyleavethenucleus) • allenergeticL and S(untiltheyleavethenucleusand decayintopN) • Finally, werepresentthespectra of theemergingprotons

9. Proton spectrum V.K. Magas, J. Yamagata-Sekihara, S. Hirenzaki, E. Oset and A. Ramos, Phys. Rev. C81, 024609 (2010). No coincidence - 1N-absorption, rescattering 2N absorption, rescattering

10. Comparison with KEK data:

11.  Oursimulationshouldconsider the coincidence requirement of KEK-PS E548 “The experiment measures the proton PLUS at least one charged particle in the decay counters surrounding the target” The simulation of such coincidence requirement is tremendously difficult, because it would imply keeping track of all charged particles coming out from all possible scatterings and decays. The best we can do is to eliminateprocesses that, for sure, cannot have a coincidence: quasi-elastic K- p  K- p events where neither the p nor the K-suffer secondary collisions. (In this type of processes the fast p moves forward and the K- escapes undetected through the back).  minimal coincidence requirement

12. Comparison with KEK data: The coincidence requirement removes a substantial fraction of events and changes the shape of the spectrum drastically

13. Comparison with KEK data: Supp. ~ 1.0 Supp. ~0.7 Low energy p – multiparticle final states  should be less supressed!

14. The results of the in-flight 12C(K-,N) reaction at KEK (PS-E548) can probably be • explained with a conventional kaonoptical potential(UK(r0) ~ -60 MeV) • We have seen that the coincidence requirement introduces a non-negligible • distortion in the spectrum • This distortion is comparable in size (even bigger) than that produced by using a • different kaon optical potential.

15. Vector K* mesons in nuclei  From (K-,K*-) reaction in nuclei (see V. Magas’ talk) The study of vector meson properties in the nuclear medium has received a lot of attention, since they are tied to fundamental aspects of QCD ρ meson: KEK325, CLAS-g7, CERES, NA60 ω meson: NA60, CBELSA/TAPS ϕ meson: KEK325, LEPS, COSY-ANKE Less attention has been paid to the K* meson! (probably because it does not decay into dileptons).

16. = + K* N interaction in free space: (coupled-channels model) E. Oset, A. Ramos, Eur.Phys.J. A44 (2010) 431 channels: K*N ωΛ, ωΣ ρΛ, ρΣ ϕΛ, ϕΣ K*Ξ Tij = Vij + Vil GlTlj transition potential  From local hidden gauge formalism Bando et al. Phys. Rev. Lett. 54, 1215 (85); Phys. Rep. 164, 217 (88) • Deals simultaneously with vector and pseudoscalarmesons • Implements chiral symmetry naturally • Leads to the same lowest order Lagrangian for pseudoscalarmesons • Reproduces all the empirically successful low-energy relations of the rmeson (KSFR) relation, vector meson dominance,…)

17. transition potential VB->VB VVVvertex Bando et al, PRL 112 (1985) and Phys. Rep. 164 (1988) 217  KSFR relation BBV vertex Klingl, Kaiser, Weise, NPA 624 (1997) 527 (same s-wave amplitude as in P B  P B S-wave scattering) Loop function G incorporates mass distribution (width) of vector meson

18. L* S* 1783, Γ=9 PDG: Λ(1690) 3/2- Λ(1800) 1/2- 1830, Γ=42 PDG: Σ(1750) 1/2- Our resonances are narrower than known PDG states because coupling to pseudoscalar-baryon channels is not included

19. K* self-energy in the medium a) K*  K p and medium modifications free decay : G = -ImP/MK*= 50 MeV medium corrections (absorption) N N, D vertex corrections The K* width increases substantially (factor 2) due to pion self-energy in nuclear matter MK*

20. = + Tij = Vij + Vil GlTlj = + Tij(r) = Vij + VilGl(r)Tlj(r) b) K* N interaction in the medium: q.e. process K*N  K*N , and also new absorption processes: K*N  pKN, K*NN  KNN Free space meson dressing Medium Pauli blocking and baryon dressing = + + DressedK* meson:

21. L. Tolos, R. Molina, E. Oset, and A. Ramos, arXiv:1006.3454 [nucl-th]. K* self-energy in the medium K* width at normal nuclear matter density (r0) is 5-6 times larger than in free space!! Can it be checked by some reaction in nuclei?? (V. Magas, next talk ) free Λ(1784)N-1 Σ(1830)N-1 MK*

22. Thank you for your attention