Polarization of Lambda and anti-Lambda in 920-GeV fixed-target proton-nucleus collisions.

HERA-B COLLABORATION , H. WAHLBERG

PHYSICS LETTERS B

Año: 2006 vol. 638 p. 415 - 421

0370-2693

A measurement of the polarization of Lambda and Anti-Lambda baryons produced in pC and pW collisions at sqrt(s)=41.6 GeV has been performed with the HERA-B spectrometer. The measurements cover the kinematic range of 0.6 GeV/c < p_T<1.2 GeV/c in transverse momentum and -0.15<x_F<0.01 in Feynman-x. The polarization results from the two different targets agree within the statistical error. In the combined data set, the largest deviation from zero, +0.054 +- 0.029, is measured for x_F < -0.07. Zero polarization is expected at x_F=0 in the absence of nuclear effects. The polarization results for the Lambda agree with a parametrization of previous measurements which were performed at positive x_F values, where the Lambda polarization is negative. Results of Anti-Lambda polarization measurements are consistent with zero.