Measurement of the longitudinal spin transfer to Λ and barΛ hyperons in polarised muon DIS

Abstract

The longitudinal polarisation transfer from muons to Λ and \bar\Λ hyperons, DLLΛ(barΛ),has been studied in deep-inelastic scattering off an unpolarised isoscalar target at the COMPASS experiment at CERN. The spin transfers to Λ and barΛ produced in the current fragmentation region exhibit different behaviours as a function of x and x F. The measured x and x F dependences of D LLΛ are compatible with zero, while D LLbarΛ tends to increase with x F, reaching values of 0.4-0.5. The resulting average values are D LLΛ = -0.012±0.047±0.024 and DLLbarΛ = 0.249±0.056±0.049. These results are discussed in the frame of recent model calculations. © 2009 Springer-Verlag / Società Italiana di Fisica.