Köln 2004 – scientific programme
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HK: Physik der Hadronen und Kerne
HK 13: Poster Session: Theory
HK 13.15: Poster
Tuesday, March 9, 2004, 13:30–15:30, Foyer
Microscopic Investigation of Gauge-Restoration Procedures for Strangeness Photoproduction — •Olaf Scholten1 and Alexander Korchin2 — 1KVI, 9747 AA Groningen, The Netherlands — 2NSC KIPT, 61108 Kharkov, Ukraine
We have calculated[1] loop corrections to the strong K+pΛ vertex as well as the additional 4-point amplitude in an effective Lagrangian model for photo-induced K+ Λ production off the proton. The main focus in our gauge-invariant approach has been on the scalar amplitude A2(s,t). The results were compared with two commonly used phenomenological procedures, namely Ohta’s minimal-substitution method[2] and Davidson - Workman’s recipe[3].
The calculation shows that there is a strong cancellation between 3-point loop corrections, often parameterized via form factors, and 4-point loop corrections, often written as contact terms restoring gauge invariance. In addition it is shown that the form factors usually taken in phenomenological approaches, may not be realistic. In a microscopic model the form factors are necessarily complex, with cusp structures in the real part. Non-trivial structures of the form factors extracted from a microscopic calculation were also observed in[4].
[1] A.Yu. Korchin and O. Scholten, Phys. Rev. C68, 045206 (2003)
[2] K. Ohta, Phys. Rev. C40, 1335 (1989); S. Kondratyuk and O. Scholten, Nucl. Phys. A677, 396 (2000)
[3] R.M. Davidson and R. Workman, Phys. Rev. C63, 025210 (2001); and Phys. Rev. C63, 058201 (2001)
[4] S. Kondratyuk and O. Scholten, Phys. Rev. C64, 024005 (2001)