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Mass dependence of inclusive nuclear f photoproduction

Mass dependence of inclusive nuclear f photoproduction. D. Cabrera 1 , L. Roca 1 , E. Oset 1 , H. Toki 2 and M.J. Vicente Vacas 1. 1 University of Valencia and IFIC 2 Research Center for Nuclear Physics, Osaka University.

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Mass dependence of inclusive nuclear f photoproduction

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  1. Mass dependence of inclusive nuclear f photoproduction D. Cabrera 1, L. Roca 1, E. Oset 1, H. Toki 2 and M.J. Vicente Vacas 1 1 University of Valencia and IFIC 2 Research Center for Nuclear Physics, Osaka University International Workshop on “Chiral Restoration in Nuclear Medium” (Chiral 05) RIKEN, 15-17 Feb 2005

  2. The f meson is an appropriate probe for in-medium modification of mesons and the possibility of a partial restoration of Chiral Symmetry in hadronic matter. • Isolated in the mass spectrum • Changes of properties comparatively larger than other mesons • f properties in nuclear medium strongly related to the renormalization of kaon properties • Kaon selfenergy • Kaon condensation astrophysical implications Experimental observation in principle easier Variety of models, predict different kaon potentials Good reproduction of data (K-atoms, HIC) Motivation Experimental information from f decay valuable info on kaon selfenergy

  3. Lines of work Theoretical calculations of f properties f mass Effective Lagrangian approach Weise et al.; Kuwabara and Hatsuda; Song; Bhatttachayya et al. QCD sum rules Asakawa and Ko; Kampfer et al. f decay width Dropping of meson masses Bhattacharyya et al.; Ko et al.; Shuryak et al.; Panda et al. Collisional broadening by f-baryon and f-meson interactions Smith and Haglin; Alzarez-Ruso and Koch Modification of f decay channels (f selfenergy approach, kaon selfenergies) Weise et al.; Ramos et al. Sizable renormalization of f width and small mass shift in nuclear medium

  4. Lines of work Proposed reactions to test f properties in nuclear medium AA, pA collisions p-pfn in nuclei gN fN in nuclei Experiments KEK-PS J LEPS J Near future... HADES CLAS

  5. Purpose of this work • Calculate the f meson selfenergy in nuclear medium from which Mf and Gf can be obtained. • Apply the results to study recent experimental proposal to study f properties in nuclear medium by means of nuclear inclusive f photoproduction (g,f) D. Cabrera and M.J. Vicente Vacas, Phys. Rev C 67, 045203 (2003) D. Cabrera, L. Roca, E. Oset, H. Toki and M.J. Vicente Vacas, Nucl. Phys. A 733 (2004) 130

  6. Model for f coupling to KK and f selfenergy. Nuclear medium effects. Outline Results: f mass and decay width in the nuclear medium. Comparison with Experiment: study of nuclear inclusive f photoproduction.

  7. f meson selfenergy in vacuum • Interested in the f to KK couplingmain f decay channel in vacuum, BR 85% (ignore other contributions). f KK Lagrangian in a gauge vector representation • Gives rise to a f selfenergy built from: • KK loop diagram • Kaon tadpole diagram

  8. Nuclear medium effects We modify the kaon propagators with selfenergy accounting for interactions with the nuclear medium

  9. pand K selfenergies Selfconsistent calculation of the S-wave selfenergy Kaon selfenergy: S-wave Kaon and anti-kaon interactions with nucleons are rather different we treat them separately • KN: smooth at low energies, since there are not S=1 resonances We use t aproximation • KN: strongly dominated by the excitation of sub-thresholdL(1405). Chiral unitary model in coupled channels for S-wave KN scattering N. Kaiser, P.B. Siegel and W. Weise, Nucl. Phys. A 594 (1995) 325 E. Oset and A. Ramos, Nucl. Phys. A 635 (1998) 99 Pauli blocking Mean-field potentials A. Ramos and E. Oset, Nucl.Phys. A 671 (2000) 481

  10. Kaon selfenergy: P-wave S*=S* (1385) Built from Lh,ShandS*h excitations, found to be an important source of f renormalization in a nuclear medium. KNY interaction from lowest order chiral Lagrangian coupling pseudoscalar meson and 1/2+ baryon octets. Klingl, Waas and Weise 98; Oset and Ramos 01

  11. f meson selfenergy in the medium • f decay channels which open in the medium due to K : • S-wave: • P-wave: Use of spectral (Lehmann) representation for kaon, anti-akon propagator, guarantees crossing Kaon propagator:

  12. Vertex corrections and gauge invariance Herrmann, Friman and Noremberg 93; Chanfray and Schuck 93 P- and S-wave kaon selfenergy insertions and realted vertex corrections: • (a) included by using the renormalized kaon & antikaon propagators • (b-d) generated by vertex corrections • Contact vertices: can be obtained by imposing W.I.

  13. Vertex corrections and gauge invariance (II) Detailed analysis of necessary diagrams to satisfy gauge invariance in a non-realtivistic approximation of vertices involving baryons and baryon propagators ( f at rest in n.m.)

  14. Results: fmass and decay width in the nuclear medium • f width grows considerably with the density: Gf30 MeV, r=r0 • Sizeable energy dependence due to the f  K S*h channel (thres. 940 MeV) • KS-wave: mildly attractive contribution, compensates partly K repulsion • KP-wave:small contribution from S, sizeable from L and S* excitations • Vertex corrections: further enhancement of the total width F. Klingl, T. Waas and W. Weise, Phys. Lett. B 431 (1998) 254; E. Oset and A. Ramos, Nucl. Phys. A 679 (2001) 616

  15. Results: f mass and decay width in the nuclear medium (II) • Real part of f selfenergy: very small, attractive up to 1.1 GeV • f mass change: (-8) MeV at r=r0

  16. Experimental information on f properties in the nuclear medium • Several experimental proposals to observe changes in the f properties in a nuclear medium: • HIC’s (p-A, A-A collisions) • p-p  fN • gN  fN • Results from p-A reaction: KEK-PS E325, K. Ozawa et al., Nucl. Phys. A 698 (2002) 535c

  17. Problems: • Long f lifetime:f decays outside the nuclear medium • f is produced with high Pf • Kinematical cuts to isolate small-Pf events poor statistics • Distortion in K+K- distribution (Coulomb interaction may bind K-in nucleus) Experimental information on f properties in the nuclear medium • Results from p-A reaction: KEK-PS E325, K. Ozawa et al., Nucl. Phys. A 698 (2002) 535c • HIC’s 28Si + 196Au: BNL-AGS E802, Y. Akiba et al., Phys. Rev. Lett. 96 (1996) 2021 • gAK+K-X: LEPS, T. Ishikawa et al., nucl-ex/0411016 Medium effects on the mass or decay width of the f meson are not observed P. Muhlich, T. Falter, C. Greiner, J. Lehr, M. Post and U. Mosel, Phys. Rev. C 67 (2003) 024605

  18. Study of inclusive nuclear f photoproduction Proposal: observation of loss of f flux due to nuclear effects and its A dependence • No need to cut f phase space better statistics • A dependence of f flux can be related to the f decay width in the nuclear medium But: Most of the produced f’s carry a high momentum Experiment: Spring8/Osaka (g, f) with Eg [1.5-2.4] GeV Pf 1.8 GeV LEPS Extension of our model for finite Pf

  19. Absorption factor Study of inclusive nuclear f photoproduction f flux and f decay width: Nuclear cross section for inclusive nuclear f photoproduction: f survival probability:

  20. Inclusive nuclear f photoproduction: results (II) A dependence Pf dependence 12C Pf = 2 GeV 64Cu Pf = 1.4 GeV • Clear loss of f flux: enhanced effect for small Pf and heavy nuclei • Eg = 1.6 GeV Pf 1000 MeV in fwd direction Pout  0.65 for 64Cu, and smaller for heavier nuclei

  21. Inclusive nuclear f photoproduction: results Other nuclear effects: Pauli blocking and Fermi motion 64Cu qfL = 5 º Pf = 2 GeV qfL = 0 º • Pauli blocking of the final nucleon is important for high Pf (small momentum transfer) • f photoproduction is forward peaked, thus actual effect is to be found somewhere in qfL < a few degrees

  22. Inclusive nuclear f photoproduction: experimental results LEPS Collaboration T. Ishikawa et al., nucl-ex/0411016

  23. Inclusive nuclear f photoproduction: experimental results LEPS Collaboration, T. Ishikawa et al., nucl-ex/0411016 • Separation of the coherent f photoproduction is important, particularly for light nuclei • Stronger effect than theoretically predicted, as seen in model independent results normalized to Li • Other possible sources of fN interactions. Ex: f 3p, pion selfenergy!

  24. Conclusions f meson mass and decay width in a nuclear medium • f decay width increases considerably in nuclear matter (6-8 Gffree at r0) • Very small change in the f mass • Experimental results from K+K- and dilepton spectra do not need in-medium f mass change to fit the data Inclusive nuclear f photoproduction: A dependence • A dependence of loss of f flux can be related to the in-medium f decay width • Clear deviation from unity in the calculated f survival probability indicates a loss of f flux due to nuclear medium effects • Experimental results from the LEPSCollaboration find a reduction in the survival probability, stronger effect than calculated

  25. r spectral function in nuclear matter D. Cabrera, E. Oset and M.J. Vicente Vacas, Nucl Phys. A705 (2002) 90 • M(3p) = 420 MeV • M(rp) = 910 MeV • M(N* hp)  600 MeV

  26. Antikaon spectral function for several nuclear densities A. Ramos and E. Oset, Nucl.Phys. A 671 (2000) 481

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