Institute for Theoretical Particle Physics (TTP)

TTP07-03 Spin asymmetries and correlations in Lambda-pair production through the radiative return method

TTP07-03 Spin asymmetries and correlations in Lambda-pair production through the radiative return method

TTP07-03 Spin asymmetries and correlations in Lambda-pair production through the radiative return method

Exclusive baryon pair production through the radiative return

is a unique tool to determine the electric and the magnetic form factors
in the timelike region over a wide range of energies. The decay of 
$\Lambda$-baryons into $p +\pi^-$ can be used to measure
their spin and to analyze
spin-spin correlations in the  $\bar\Lambda\Lambda$ system.
We evaluate the spin dependent hadronic tensor, which describes this reaction,
calculate the corresponding cross section for 
$e^+e^- \to \Lambda\bar\Lambda$ and $e^+e^- \to \Lambda\bar\Lambda\gamma$
with subsequent decays of  $\Lambda$ and $\bar\Lambda$ and present a compact
formula for the correlated distribution. We demonstrate that the relative
phase between the electric and the magnetic form factor can be determined
in this analysis by considering single spin asymmetries and correlated
decay distributions. The reaction is implemented in the event generator
 PHOKHARA. It is demonstrated that the relative phase can be measured 

with the event sample presently accumulated at $B$- factories.

H. Czyz, A. Grzelinska and J.H. Kuhn
Phys.Rev. D75 074026 2007
PDF PostScript arXiv
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