https://doi.org/10.1051/epjconf/201919903009
Λ hyperon spin polarization and CP tests at BESIII
Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden
* e-mail: patrik.adlarson@physics.uu.se
Published online: 1 February 2019
In these proceedings two preliminary results from the BESIII collaboration on polarized Λ and 
are reported. Both results are first observations and concern the resonant and non-resonant processes 
and 
at 
, respectively. For 
the relative phase between the electric and magnetic form factors, ΔΦ, has for the first time been determined, 
. That 
allows for a simultaneous measurement also of the asymmetry decay parameters 
, 
and 
. The measured value of 
differs by 17(3)% from the PDG value. The simultaneous measurement for the asymmetry parameters allows for the most precise test of CP violation conducted for Λ decays, ACP = −0.006(12)stat(7)syst. The reaction 
at 
is the first complete measurement of the time-like electric (GE) and magnetic (GM) form factor of any baryon as also the ratio R = |(GE/(GM)| and ΔΦ have been determined: R = 0.96(14)(12) and 
. The obtained cross-section and effective form factor are σ = 119.0(53)stat(51)syst pb and |G| = 0.123(3)stat(3)syst, respectively.
© The Authors, published by EDP Sciences, 2019
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