# Measurement of the $\Lambda$ polarization in $\nu_\mu$ charged current interactions in the NOMAD experiment

Abstract : The $\Lambda$ polarization in $\nu_\mu$ charged current interactions has been measured in the NOMAD experiment. The event sample (8087 reconstructed $\Lambda$'s) is more than an order of magnitude larger than that of previous bubble chamber experiments, while the quality of event reconstruction is comparable. We observe negative polarization along the $W$-boson direction which is enhanced in the target fragmentation region: $P_x (x_F 0) = -0.21 \pm 0.04 \mbox{(stat)} \pm 0.02 \mbox{(sys)}$. In the current fragmentation region we find $P_x (x_F 0) = -0.09 \pm 0.06 \mbox{(stat)} \pm 0.03 \mbox{(sys)}$. These results provide a test of different models describing the nucleon spin composition and the spin transfer mechanisms. A significant transverse polarization (in the direction orthogonal to the $\Lambda$ production plane) has been observed for the first time in a neutrino experiment: $P_y = -0.22 \pm 0.03 \mbox{(stat)} \pm 0.01 \mbox{(sys)}$. The dependence of the absolute value of $P_y$ on the $\Lambda$ transverse momentum with respect to the hadronic jet direction is in qualitative agreement with the results from unpolarized hadron-hadron experiments.
Mots-clés :
Document type :
Journal articles

Cited literature [6 references]

http://hal.in2p3.fr/in2p3-00006059
Contributor : Claudine BOMBAR Connect in order to contact the contributor
Submitted on : Monday, November 20, 2000 - 1:59:54 PM
Last modification on : Tuesday, November 17, 2020 - 3:12:13 PM

### Identifiers

• HAL Id : in2p3-00006059, version 1

### Citation

P. Astier, D. Autiero, A. Baldisseri, M. Baldo-Ceolin, M. Banner, et al.. Measurement of the $\Lambda$ polarization in $\nu_\mu$ charged current interactions in the NOMAD experiment. Nuclear Physics B, Elsevier, 2000, 588, pp.3-36. ⟨in2p3-00006059⟩

Record views