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STRANGENESS NUCLEAR PHYSICS

STRANGENESS NUCLEAR PHYSICS. Àngels Ramos Recent Progress in Many-Body Theories 14 Barcelona, July 16-20, 2007. Strangeness nuclear physics is a field that emerged after the discover of the strange particles ( L,S ,K - ,K + ) in 1947. (in lates 50’s  emulsions, from 70’s  colliders).

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STRANGENESS NUCLEAR PHYSICS

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  1. STRANGENESS NUCLEAR PHYSICS Àngels Ramos Recent Progress in Many-Body Theories 14 Barcelona, July 16-20, 2007

  2. Strangeness nuclear physics is a field that emerged after the discover of the strange particles (L,S,K-,K+) in 1947. (in lates 50’s emulsions, from 70’s  colliders) It has experienced an steady progress in major laboratories across the world CERN (Europe) Brookhaven (USA) KEK (Japan) Past (1970-2005) Jlab (USA) FiNUDA@DAPHNE (Italy) MAMIc@Mainz (Germany) Present J-PARC (Japan) HypHI@FAIR PANDA@FAIR 2008 Future 2012?

  3. This field studies nuclear phenomena involving one or morestrangeparticles (containing thesquark or antiquark) This talk will focuss on: HYPERNUCLEI KAON PHYSICS NEUTRON STARS (briefly)

  4. HYPERNUCLEI The hypernuclear chart as of 1989 And almost 20 years later: basically the same hypernuclei … but measured with better statistics and energy resolution  excited hypernuclear states are now available!

  5. (K-,p-) (p+,K+) (g,K+) g A LA PRODUCTION OF HYPERNUCLEI (collider era) Strangeness exchange: CERN, BNL, KEK, DAPHNE Associated production: BNL, KEK JLab Electroproduction:

  6. p+ K+ L n H. Hotchi et al., PRC64 (2001) 044302 Fixing the indicent beam energy and the detection angle, the energy of the emitted meson (K+) is directly related to the L binding energy

  7. RN ULc See e.g. D.J. Millener, C.B. Dover and A. Gal, Phys. Rev. C38 (1988) 2700

  8. Spin-orbit potential ~6 MeV 6 MeV  neutron spin orbit: 6 MeV • neutron PLUS L hyperon spin orbit: • ~ 6 MeV Spin-orbit potential for the L hyperon is very weak! W. Brückner et at, Phys. Lett. 55B(1975)107

  9. YN interaction (bare) Isospin L= 0 Isospin p= 1 Juelich A,B B. Hozelkamp, K. Holinde, J. Speth, NPA500 (1989) 485 J. Haidenbauer, U.G. Meissner, PRC72 (2005) 044005 Juelich (EFT) H. Polinder, J. Haidenbauer, U.G. Meissner, NPA779 (2006) 244 Nijmegen NSC89 M.M. Nagels, Th.A. Rijken, J.J. de Swart, PRC40 (1989) 2226 Nijmegen NSC97 Th. A. Rijken, Y. Yamamoto, V.G.J. Stoks, PRC59 (1999) 21 Nijmegen ESC04 Th. A. Rijken, Y. Yamamoto, V.G.J. Stoks, PRC73 (2006) 044008 4300 data on NN scattering Fitted to: + SU(3) 35 data on YN scattering

  10. Total cross sections for YN scattering

  11. B3 B4 B3 B3 B4 B4 V G B5 B6 B1 B1 B2 B2 B2 B1 = + Bi Bj Bi Effective YN interaction (G-matrix: microscopical approach) • Medium effects: • Pauli blocking • Baryon dressing Coupled channel problem! S=-1:LN,SN S=-2:LL,XN,SS I. Vidaña, A. Polls, A. Ramos and M. Hjorth-Jensen, Nucl. Phys. A644 (1998) 201 I. Vidaña, A. Polls, A. Ramos and H.-J. Schulze, Phys. Rev. C64 (2001) 044301 • YN models explain the depth of the L nucleus potential • the spin-dependence varies considerably in the different YN models  apreciable differences in the spectra of hypernuclei!

  12. New info from precise g-ray (coincidence) experiments ! BNL E930, Tamura speakperson H. Akikawa et al, PRL88 (2002) 082501 Nijmegen NSC97f  spin-orbit splitting in 9LBe: 150-200 keV E.Hiyama et al., PRL85 (2000) 270 Nijmegen ESC03  spin-orbit splittings in 9LBe: ~ 80 keV The new generation of experiments performed in the last 5 years have disclosed many interesting aspects of hypernuclear structure  crucial information for constraining the YN interaction!

  13. Sigma-hypernuclei Not confirmed with better statistics! R. Bertini et al, Phys.Lett 83B (1979) 306 Narrow S states in spite of SNLN conversion? S. Bart et al, Phys. Rev. Lett 83 (1999) 5238

  14. (K-,p-) (p+,K+) (g,K+) g A LA WEAK HYPERNUCLEAR DECAY Hypernuclear structure Weak decay of hypernuclei allows to obtain new and complementary information on the properties of hypernuclei and the weak YN interaction

  15. p N L N N N N N ~~~ N L L N N WEAK HYPERNUCLEAR DECAY MESONIC Gp- : L p-p kN~100 MeV/c < kF Gp0 : L p0n Pauli blocked! NON-MESONIC Gn: Lnn n kN~400 MeV/c Gp: Lpn p G2: L N N  n N N kN~340 MeV/c GT= GM+ GNM = Gp-+Gp0 + Gn+Gp+G2

  16. Observed decay rates free L : GLfree= 3.8 109 s -1 Gp-free : L g p-p Gp0free : L g p0n Gp-free/Gp0free=1.78 ~ 2  DI=1/2 ! Hypernuclear width:GT ~ GLfree BNL, 91 KEK, 95, 98 Jülich, 93, 97, 98

  17. NON-MESONIC DECAY: L N  N N Q ~ mL - mN ~ 175 MeV The emerging nucleons are very energetic and this process is not sensitive to nuclear structure details • Ideal process to characterize the baryon-baryon weak interaction! In particular, for processes havingDS=1 (LNNN), the PC amplitude is not masked by the strong interaction like in the caseDS=0 (NNNN) DS=1 DS=0 Both PC and PV weak amplitudes can be studied from hypernuclear weak decay Only the PV amplitudes are accessible W.M. Alberico and G. Garbarino, Phys. Reports 369 (2002) 1 E. Oset and A. Ramos, Prog. Part. Nucl. Phys. 41 (1998) 191

  18. Gn:Ln  n n weak interacction: • meson exchange: p,h,K,r,w,K* • quark models  Decay width G1=Gn+Gp well reproduced by all models but…  not the ratio Gn/Gp ! OPE mechanism dominated by tensor transitions p 3S1 3D1 LN  NN Antisymmetry requires isospin I=0 nn pairs are in isospin I=1  Gn: Ln  nn supressed in OPE! Non-mesonic processes: Gp:Lp  n p strong interaction between initialLNand finalNNpair

  19. 0 0.5 1 1.5 2 A. Parreño, A. Ramos and C. Bennhold, PRC 56 (1997) 339 K. Sasaki, T. Inoue and M. Oka, NPA 669 (2000) 331 Theoretical models D. Jido, E. Oset and J. E. Palomar, NPA 694 (2001) 525 K. Itonaga, T. Ueda and T. Motoba, PRC65 (2002) 034617 . . . Gn/Gp BNL, 91 KEK, 95 KEK, 02 BNL, 91 A challenge in hypernuclear weak decay for many years!

  20. n n p p L n n n p n L L n p Theoretical improvements A realistic analysis ofGn/Gp must consider: 1. The influence of the 2-nucleon induced decay (G2) A. Ramos, E. Oset and L.L. Salcedo, PRC50 (1994) 2314 Nn = Gp + 2 Gn + 2 G2 Np = Gp + G2 2. The final state interaction (FSI) of the primary nucleons The primary nucleons produced in the weak decay continuously change energy, direction, charge and new secondary nucleons are emitted. A. Ramos, M.J. Vicente-Vacas and E. Oset, PRC55 (1997) 735-743; Erratum: ibid. C66 (2002) 039903

  21. Energy correlations: T1+T2 Angular correlations q12 T2 T1 Experimental improvement: NN coincidences Measuring distributions of NN pairs in coincidence permits a better determination of the ratio Gn/Gp . The more exclusive measurement of final states: • Reduces contamination from the process G2: LNN  NNN • Eliminatessome FSI effects

  22. Single proton spectra

  23. Neutron spectrum

  24. Angular correlation between n and p pairs

  25. Kinetic energy correlations between np pairs

  26. B.H. Kang et al., Phys. Rev. lett. 96 (2006) 062301

  27. Ln  n n Without FSI and ignoring G2: Lp  n p With FSI: Nnn, Nnp:number of nucleon-nucleon per weak decay (after FSI) G. Garbarino, A. Parreño and A. Ramos, PRL 91, 112501 (2003) The Gn/Gp problem has been solved!

  28. New challenge in hypernuclear decay: Asymmetry E278 0.5 E462 aL 0 -0.5 E508 -1 y: polarization axis p+ n  K+L p K+ p+ 12C L n K. Sasaki, T. Inoue, M.Oka, Nucl. Phys. A707 (2002) 477 A. Parreño and A. Ramos, Phys. Rev. C65 (2002) 015204 W. Alberico, G. Garbarino, A. Parreño and A. Ramos, Phys. Rev. Lett. 94 (2005) 082501 (FSI)

  29. Recent improvements: An EFT study has revealed the dominance of an scalar (J=0) and isoscalar (I=0) contact term which is crucial to reproduce the small value of the asymmetry parameter aL A. Parreño, C. Bennhold and B.R. Holstein, Phys. Rev. C70 (2004) 051601(R) This term can be interpreted as coming from the exchange of the broads meson (J=0,I=0). Ms ~ 450 MeV From a fundamental point of view, the s meson is dynamically generated from correlated two-pion exchange D. Jido, E. Oset, J.E. Palomar, Nucl. Pys. A694 (2001) 525

  30. OME OME+2p C. Chumillas, G. Garbarino, A. Parreño, A. Ramos,, e-Print: arXiv:0705.0231 [nucl-th]

  31. (MeV) 400 mK 200 me r/r0 1 2 3 (ANTI)KAONS IN THE MEDIUM The K- feels attraction in the medium • Kaon condensation in neutron stars? • D.B. Kaplan and A.E. Nelson, Phys. Lett. B175 (1986) 57 G. E. Brown and H. A. Bethe, Astrophys. Jour. 423 (1994) 659 Kaons are bosons  a condensate of (anti)kaons would appear

  32. Phenomenology: Best fits to kaonic atoms seem to prefer UK~ - 200 MeV at r0 K- A E. Friedman, A. Gal, and C.J. Batty, NPA 579 (1994) 518

  33. Microscopic theory: Mi Mj Vij = Bj Bi KN = + 1) Take an elementary KN interaction (e.g. from Chiral Lagrangian) Implement Unitarity  Coupled-channel Bethe-Salpeter equation 2) Tij = Vij + VilGlTlj In the S=-1 strangeness sector L(1405) resonance 27 MeV below K-p thresold pL pS hL hS KX 1255 1331 1435 (MeV) 1663 1741 1814

  34. Since the pioneering work of Kaiser, Siegel and Weise [Nucl. Phys. A594 (1995) 325] many other chiral coupled channel models have been developed. E. Oset and A. Ramos, Nucl. Phys. A635 (1998) 99 J.A. Oller and U.G. Meissner, Phys. Lett. B500 (2001) 263 M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193 C.Garcia-Recio et al., Phys. Rev. D (2003) 07009 M.F.M. Lutz, E.E. Kolomeitsev, Nucl. Phys. A700 (2002) 193 B.Borasoy, R. Nissler, and W. Weise, Phys. Rev. Lett. 94, 213401 (2005); Eur. Phys. J. A25, 79 (2005) J.A. Oller, J. Prades, and M. Verbeni, Phys. Rev. Lett. 95, 172502 (2005) J. A.Oller, Eur.Phys.J.A28, 63 (2006) B. Borasoy, U. G. Meissner and R. Nissler, Phys.Rev.C74, 055201,2006. more channels, next-to-leading order, Born terms beyond WT (s-channel, u-channel), Fits including new data …

  35. 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

  36. Microscopic models moderate attraction for the K-nucleus potential! A. Ramos and E. Oset, NPA 671 (2000) 481 and kaonic atom data are also well described! S. Hirenzaki et al., PRC61 (2000) 055205 A. Baca, C. García-Recio, J. Nieves, NPA 673 (2000) 335 Kaonic atom data are not sensitive to the K-nucleus potential at r0  only the nuclear surface (up to r~r0/4) is explored!

  37. Deeply bound kaonic nuclear states? In spite of te relatively shallow potentials (UK = -70 to -50 MeV) predicted by various self-consistent many-body approaches: A. Ramos, E. Oset, Nucl. Phys. A671, 481 (2000) L. Tolós, A. Ramos, E. Oset, Phys. Rev. C (2006) • J. Schaffner-Bielich, V.Koch, M. Effenberber, Nucl. Phys. A669, 153 (2000) • A.Cieply, E.Friedman, A.Gal, J.Mares, Nucl. Phys. A696, 173 (2001) there has been high expectations about the existence of deeply bound kaonic states triggered by the work of Akaishi and Yamazaki Y.Akaishi, T.Yamazaki, Phys.Rev.C65,044005 (2002) Simplelocal KN-pS potential: +simplifiedmany-body treatment (self-consistency ignored) Subsequent few body calculations (variational): Y.Akaishi, A. Dote, T.Yamazaki,Phys.Lett.B613, 140 (2005)  nucleus shrinked enourmously(r(0)~10r0!) and BK = 169 MeV in ppn-K- (T=0) • BK = 194 MeV in pnn-K- (T=1)

  38. 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 pnn-K- bound system…  BK =197 MeV formation rate: 1% per absorbed K- But withdrawn in a recent reanalysis of data (Iwasaki, HYP06) arXiv:0706.0297[nucl-ex]

  39. Conventional view: E. Oset, H. 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 some Fermi motion broadening is possible,  it would explain the ~60 MeV/c peak spreading

  40. 6Li 4He The FINUDA proton missing mass experiment: M. Agnello et al, Nucl. Phys. A775, 35 (2006) 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

  41. Another FINUDA experiment: measuring the (Lp) invariant mass M. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005) Nuclei: • The same elementary reaction takes place: K- p p  L p (select pL > 300 MeV/c to eliminate K- N  L p) • But here both emitted particles are detected! (not just the proton)  the invariant mass of the Lp pair is measured, MLp • A peak for the transition to the g.s. of the daugther nucleus should be observed at:

  42. Interpreted by the FINUDA experiment as a (K-pp) bound state Another view (conventional): Final State Interactions (FSI) of the primary L and p (produced after K- absorption) in their way out of the daughter nucleus! Transition to the g.s. of daughter nucleus M. Agnello et al. Phys. Rev. Lett. 94, 212303 (2005)

  43. The K- is absorbed by two nucleons with momenta randomly chosen within the local Fermi sea: • Primary L and N emitted according to phase space: Monte Carlo simulation of K- absorption by pp and pn pairs in nuclei V.K. Magas, E. Oset, A. Ramos, H. Toki, Phys.Rev. C74, 025206 (2006) • The L or N scatter within the nucleus, loosing energy and producing new (slow) nucleons • Finally, the invariant Lp mass is reconstructed from the final events

  44. A peak is generated when the primary L and p, undergo quasi-elastic collisions with the nucleus, exciting it to the continuum. • (it is the analogue of thequasi-elastic peakobserved innuclearinclusive reactionsusing a variety of different probes: (e,e’), (p,p’), (p,p’),…)

  45. All the experimental claims for the existence of very deeply bound kaonic nuclear states can be explained in terms of conventional nuclear physics processes. This is further substantiated by NEW theoretical developments:  realistic few body calculations of the K-pp system: N.V. Shevchenko, A. Gal, J. Mares, Phys.Rev.Lett.98,08230 1(2007)(Fadeev) A. Doté, W. Weise, nucl-th/071050 (Variational) G ~ 100 MeV BK ~ 50-70 MeV Crucial ingredient: realistic NN SRC (which prevent from reaching densities r~10ro!)

  46. u ds STRANGENESS IN NEUTRON STARS Mass ~ 1.4 to 2.2 Msun Radius ~ 10 km Central density ~ rc = (4 – 8) r0 (r0 = 0.17 fm-3 = 2.8 1014 g/cm3) hyperons: S-, L confined form kaons: K- Strangeness deconfined form strange quark matter

  47. HYPERONS IN NEUTRON STARS  HYPERONIC MATTER First proposed in 1960:V.A. Ambartsumyan, G.S. Saakyan, Sov. Astron. AJ. 4 (1960) 187 The core of a neutron star is a fluid of neutron rich matter in equilibrium with respect to the weak interactions (b-stable nuclear matter) Why is it likely to have hyperons? • The central density of a neutron star is high • rc = (4 – 8) r0(r0 = 0.17 fm-3 = 2.8 1014 g/cm3) • The nucleon chemical potential increases very rapidly with density  Above a threshold density, rT = (2– 3) r0 , hyperons are created in the stellar interior!

  48. b-stable hadronic matter • Equilibrium with respect to weak interaction processes: • Charge neutrality:

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