Eur. Phys. J. C (2009) 64: 171-179
https://doi.org/10.1140/epjc/s10052-009-1143-7

Letter

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

¹ Fakultät für Physik, Universität Bielefeld, 33501, Bielefeld, Germany
² Institut für Experimentalphysik, Universität Bochum, 44780, Bochum, Germany
³ Helmholtz-Institut für Strahlen- und Kernphysik, Universität Bonn, 53115, Bonn, Germany
⁴ Physikalisches Institut, Universität Bonn, 53115, Bonn, Germany
⁵ AS CR, Institute of Scientific Instruments, 61264, Brno, Czech Republic
⁶ Burdwan University, Burdwan, 713104, India
⁷ Matrivani Institute of Experimental Research & Education, Calcutta, 700 030, India
⁸ Joint Institute for Nuclear Research, 141980, Dubna, Moscow Region, Russia
⁹ Physikalisches Institut, Universität Erlangen–Nürnberg, 91054, Erlangen, Germany
¹⁰ Physikalisches Institut, Universität Freiburg, 79104, Freiburg, Germany
¹¹ CERN, 1211, Geneva 23, Switzerland
¹² Technical University in Liberec, 46117, Liberec, Czech Republic
¹³ LIP, 1000-149, Lisbon, Portugal
¹⁴ Institut für Kernphysik, Universität Mainz, 55099, Mainz, Germany
¹⁵ University of Miyazaki, Miyazaki, 889-2192, Japan
¹⁶ Lebedev Physical Institute, 119991, Moscow, Russia
¹⁷ Department für Physik, Ludwig-Maximilians-Universität München, 80799, Munich, Germany
¹⁸ Physik Department, Technische Universität München, 85748, Garching, Germany
¹⁹ Nagoya University, 464, Nagoya, Japan
²⁰ Faculty of Mathematics and Physics, Charles University, 18000, Prague, Czech Republic
²¹ Czech Technical University in Prague, 16636, Prague, Czech Republic
²² Institute for High Energy Physics, State Research Center of the Russian Federation, 142281, Protvino, Russia
²³ CEA DAPNIA/SPhN Saclay, 91191, Gif-sur-Yvette, France
²⁴ School of Physics and Astronomy, Tel Aviv University, 69978, Tel Aviv, Israel
²⁵ Trieste Section of INFN, 34127, Trieste, Italy
²⁶ Department of Physics and Trieste Section of INFN, University of Trieste, 34127, Trieste, Italy
²⁷ Abdus Salam ICTP and Trieste Section of INFN, 34127, Trieste, Italy
²⁸ Department of Physics and Torino Section of INFN, University of Turin, 10125, Turin, Italy
²⁹ Torino Section of INFN, 10125, Turin, Italy
³⁰ 1500 Alessandria, and Torino Section of INFN, University of Eastern Piedmont, 10125, Turin, Italy
³¹ Sołtan Institute for Nuclear Studies and University of Warsaw, 00-681, Warsaw, Poland
³² Institute of Radioelectronics, Warsaw University of Technology, 00-665, Warsaw, Poland
³³ Yamagata University, Yamagata, 992-8510, Japan

^* e-mail: Gerhard.Mallot@cern.ch

Received: 3 July 2009
Published online: 7 October 2009

Abstract

The longitudinal polarisation transfer from muons to Λ and  hyperons, , has been studied in deep-inelastic scattering off an unpolarised isoscalar target at the COMPASS experiment at CERN. The spin transfers to Λ and  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 _LL ^Λ are compatible with zero, while tends to increase with x _F , reaching values of 0.4–0.5. The resulting average values are D _LL ^Λ = −0.012±0.047±0.024 and = 0.249±0.056±0.049. These results are discussed in the frame of recent model calculations.