Measurement of V-0 production ratios in pp collisions at root s=0.9 and 7 TeV

The (Lambda) over bar/Lambda and (Lambda) over bar /K-S(0) production ratios are measured by the LHCb detector from 0.3 nb(-1) of pp collisions delivered by the LHC at root s = 0.9TeV and 1.8 nb-1 at root s = 7TeV. Both ratios are presented as a function of transverse momentum, p(T), and rapidity, y, in the ranges 0.15 < p(T) < 2.50GeV/c and 2.0 < y < 4.5. Results at the two energies are in good agreement as a function of rapidity loss, Delta y = y(beam) - y, and are consistent with previous measurements. The ratio (Lambda) over bar/Lambda, measuring the transport of baryon number from the collision into the detector, is smaller in data than predicted in simulation, particularly at high rapidity. The ratio (Lambda) over bar /K-S(0), measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.