Measurement of the transverse polarization of Λ and [bar over Λ] hyperons produced in proton-proton collisions at √s = 7 TeV using the ATLAS detector

Abstract

The transverse polarization of Λ and [bar over Λ] hyperons produced in proton-proton collisions at a center-of-mass energy of 7 TeV is measured. The analysis uses 760 μb[superscript −1] of minimum bias data collected by the ATLAS detector at the LHC in the year 2010. The measured transverse polarization averaged over Feynman x[subscript F] from 5 × 10[superscript −5] to 0.01 and transverse momentum p[subscript T] from 0.8 to 15 GeV is −0.010 ± 0.005(stat) ± 0.004(syst) for Λ and 0.002 ± 0.006(stat) ± 0.004(syst) for [bar over Λ]. It is also measured as a function of x[subscript F] and p[subscript T], but no significant dependence on these variables is observed. Prior to this measurement, the polarization was measured at fixed-target experiments with center-of-mass energies up to about 40 GeV. The ATLAS results are compatible with the extrapolation of a fit from previous measurements to the x[subscript F] range covered by this measurement.