Measurement of Prompt Hadron Production Ratios in pp Collisions at √s = 0.9 and 7 TeV

The charged-particle production ratios anti-p/p, K−/K+, π−/π+, (p + anti-p)/(π+ + π−), (K+ + K−)/(π+ + π−) and (p + anti-p)/(K+ + K−) are measured with the LHCb detector using 0.3 nb^−1 of pp collisions delivered by the LHC at √s = 0.9 TeV and 1.8 nb^−1 at √s = 7 TeV. The measurements are performed as a function of transverse momentum pT and pseudorapidity η. The production ratios are compared to the predictions of several Monte Carlo generator settings, none of which are able to describe adequately all observables. The ratio anti-p/p is also considered as a function of rapidity loss, Δy ≡ y_beam − y, and is used to constrain models of baryon transport.