Spin Transfer in InclusiveΛ0Production by Transversely Polarized Protons at200GeV/c

Surprisingly large polarizations in hyperon production by unpolarized protons have been known for a long time. The spin dynamics of the production process can be further investigated with polarized beams. Recently, a negative asymmetry ${A}_{N}$ was found in inclusive ${\ensuremath{\Lambda}}^{0}$ production with a $200\mathrm{GeV}/c$ transversely polarized proton beam. The depolarization ${D}_{\mathrm{NN}}$ in $p\ensuremath{\uparrow}+p\ensuremath{\rightarrow}{\ensuremath{\Lambda}}^{0}+X$ has been measured with the same beam over a wide ${x}_{F}$ range and at moderate ${p}_{T}$. ${D}_{\mathrm{NN}}$ reaches positive values of about 30% at high ${x}_{F}$ and ${p}_{T}\ensuremath{\sim}1.0\mathrm{GeV}/c$. This result shows a sizable spin transfer from the incident polarized proton to the outgoing ${\ensuremath{\Lambda}}^{0}$.