Measurement of V⁰ production ratios in pp collisions at and 7 TeV

The \( {{{\bar{\it{\Lambda} }}} \left/ {\it{\Lambda} } \right.} \) and \( {{{\bar{\it{\Lambda} }}} \left/ {{K_S^0}} \right.} \) production ratios are measured by the LHCb detector from 0.3 nb−1 of pp collisions delivered by the LHC at \( \sqrt {s} = 0.9 \) TeV and 1.8 nb−1 at \( \sqrt {s} = 7 \) TeV. Both ratios are presented as a function of transverse momentum, p T, and rapidity, y, in the ranges 0.15 < p T < 2.50 GeV/c and 2.0 < y < 4.5. Results at the two energies are in good agreement as a function of rapidity loss, ∆y = y beam − y, and are consistent with previous measurements. The ratio \( {{{\bar{\it{\Lambda} }}} \left/ {\it{\Lambda}} \right.} \), 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 \( {{{\bar{\it{\Lambda}}}} \left/ {{K_S^0}} \right.} \), measuring the baryon-to-meson suppression in strange quark hadronisation, is significantly larger than expected.