Study of the production of Λ_b^0 band ~0 hadrons in pp collisions and first measurement of the Λ_b^0→J/ψpK^- branching fraction

The product of the ∧0/b （-B/0） differential production cross-section and the branching fraction of the decay ∧0/b→ J/ψ pK-（-B/0→ J/ψ-K＊（892）0）is measured as a function of the beauty hadron transverse momentum, PT, and rapidity, y. The kinematic region of the measurements is pT〈20 GeV/c and 2.0 〈g〈4.5.The measurements use a data sample corresponding to an integrated luminosity of 3fb-1 collected by the LHCb detector in pp collisions at centre-of-mass energies √s=7 TeV in 2011 and √s=8 TeV in 2012. Based on previous LHCb results of the fragmentation fraction ratio,f∧0/b/fd,the branching fraction of the decay ∧0/b→ J/ψ pK-is measured to be B（∧0/b→ J/ψ pK-）=（3.17±0.04±0.07±0.34＋0.45/-0.28）×10-4,where the first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the branching fraction of the decay -B/0 →J/ψ-K＊（892）0,and the fourth is due to the knowledge of f∧0/b/fd.The sum of the asymmetries in the production and decay between ∧0/b and ∧0/bis also measured as a function of PT and y.The previously published branching fraction of ∧0/b→ J/ψ pπ-,relative to that of ∧0/b→ J/ψ pK-,is updated. The branching fractions of ∧0/b→P＋c（→ J/ψp）K-are determined.

Climatic and Edaphic Controls on Soil pH in Alpine Grasslands on the Tibetan Plateau,China:A Quantitative Analysis

Soil acidity is an important parameter that can regulate ecosystem structure and function.However,a quantitative understanding of the relationships between soil pH and environmental factors remains unavailable.In this study,relationships of soil pH with both climatic and edaphic factors in alpine grasslands on the Tibetan Plateau,China were quantified using data obtained from a regional soil survey during 2001-2004.Our results showed that soil pH decreased along the gradient of both mean annual temperature and precipitation.Likewise,soil pH exhibited consistent negative correlations with soil moisture and silt content.However,soil organic and inorganic carbon contents played opposite roles in shaping patterns of soil pH:the accumulation of soil organic matter led to higher soil acidity,while the existence of soil inorganic matter was favorable for maintaining higher soil alkalinity.The variation partitioning analysis indicated that the combination of climatic and edaphic variables explained 74.3%of the variation in soil acidity.These results suggest that soil pH could be predicted from routinely-measured variables,allowing a robust pedotransfer function to be developed.The pedotransfer function may facilitate land surface models to generate more reliable predictions on ecosystem structure and function around the world.