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Hypernuclear Production in proton- and pion- nucleus

Hypernuclear Production in proton- and pion- nucleus Collisions: A Fully Relativistic Description. Radhey Shyam. Saha Institute of Nuclear Physics, Kolkata, India Z.Zt. Institut f. Theo. Physik, Uni Giessen, Germany. PLAN OF THE PRESENTATION.

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Hypernuclear Production in proton- and pion- nucleus

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  1. Hypernuclear Production in proton- and pion- nucleus Collisions: A Fully Relativistic Description Radhey Shyam Saha Institute of Nuclear Physics, Kolkata, India Z.Zt. Institut f. Theo. Physik, Uni Giessen, Germany PLAN OF THE PRESENTATION • Introduction - Production of Hypernuclei • Kinematics and Elementary processes of the proton induced Hypernuclear production. • 3. Brief sketch of the theoretical model • 4. Results, cross sections, spectroscopy • 5. Conclusions

  2. Production of  Hypernuclei • (K‾, ‾) reaction on Nuclei K- stopped + AZ AZ + - Low momentum transfer  only substitutional states are populated. Momentum transfer larger than the Fermi momentum  (n-hole, -particle) configuration in a series of orbits (even deepest one) (+, K+) reaction on Nuclei Streched states with maximum spin are preferentially excited.

  3. With proton beams p + A(N, Z)  B(N-1, Z) + n + K+, p + A(N, Z)  B(N, Z-1) + p + K+, p + A(N, Z)  B(N, Z) + K+, (Exclusive Reaction, two-body FS) Elementary process p + p  p +  + K+

  4. Kinematics, elementary processes, theoretical formulation Thresholds for the A(p,K+)B reaction depends on the target mass. 0.739 GeV for 12C and 0.602 GeV for 208Pb. pp  pK+ reaction: 1.582 GeV. Effective Lagrangian Model describes the pp  pK+ reaction well. R. Shyam, Phys. Rev. C 60 (1999) 055213, C73 (2006) 035211 Excitation of N * (1650), N*(1710), N*(1720) baryonic resonances.

  5. Some characteristics of the A(p,K+)B reaction Larger momentum transfer (1.0 GeV/c) as compared to (0.33 GeV/c) in (, K+) reaction Samples bound state wave functions in a region where they are very small. pCM = pi – pK Unlikely with other reactions

  6. Mechanism of the A(p,K+)B Reaction ONM  one active nucleon to carry entire momentum transfer to the nucleus. One-nucleon model Two-nucleon model TNM  three active baryons to share the large momntum transfer

  7. A Covarient TNP model for A(p,K+)B reaction Effective Lagrangians Target emission In medium meson propagators MESON SELF ENERGIES: For pion, p-h and -h excitations produced by the propagating pion. Short range repulsion by Landau-Migdal parameter g’. . Bound state nucleon and hyperon spinors Distorted waves for initial and final states. R. Shyam, H. Lenske and U. Mosel, Nucl. Phys. 764 (2006) 313 Projectile emission

  8. Bound Hypernuclear wave function Pure single particle configuration with core remaining inert In the region of the momentum transfer of interest, the lower component of the spinor is not negligible.

  9. Contributions of two TNM Diag. Role of the parameter.g’ TE PE pion in-medium propagator D(q) = /[q02 – q2 - m2 - (q)] (q) is renormalized by including the short range repulsion effects through the Landau-Migdal parameter g’ TE: q0 = B1 -B2 PE: q0 Ep TE  (q) is real and attractive PE  (q) is complex

  10. Contributions of Various Meson Exchange Processes       • exchange dominates,  and  exchange more important at back angles due to large momentum transfers.

  11. Relative Contribution of Various Resonances N*(1710) dominates But inteference effects are visible. Similar to what is found is the pp  pK+ reaction

  12. Differetial cross sections on 12C and 40Ca targets B (C) 13  0p1/2 0.708 MeV 0p3/2 0.860 MeV 0s1/2 11.690 MeV B (Ca) 41  0d3/2 0.753 MeV 0d5/2 1.544 MeV 0p1/2 9.140 MeV 0s1/2 17.882 MeV Maxima are not at 0 deg. effect of using Dirac spinors Strong binding energy selectivity, peak cross sections ~ 1 nb.

  13. Results for 4He target For momentum transfers of interest, the Dirac spinors are smoothly varying, and are devoid of structures.

  14. Beam Energy Dependence of the Total Production Cross Section Threshold Energy 0.739 GeV Threshold Energy 0.603 GeV Threshold opens at lower Beam energy

  15. Application to the (+, K+) reaction on Nuclei State with stretched angular momentum configuration has the largest cross section N*(1710) dominates in his case too.

  16. SUMMARY AND OUTLOOK Hypernuclei can be produced by means of the A(p,K+)B reaction, which is analternative way of studying such systems. A fully covariant description of this reaction is essential. Hypernuclear states with low binding energies are preferentially excited. Cross sections are maximum for the hypernuclear states with largest orbital angular momentum, typical of large momentum trasfer reaction. Differences in the angular distributions of the reaction on very light and heavier targets. The covariant theory has also be used to describe the (+, K+) reaction. Work is in progress to include distortions in the entrance and outgoing Channels so also is the study of (, K+) reaction on nuclei. Coll: H. Lenske, U. Mosel, S. Bender, Uni. Giessen

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