Prompt <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msubsup><mml:mi>K</mml:mi><mml:mi mathvariant="normal">S</mml:mi><mml:mn>0</mml:mn></mml:msubsup></mml:math> production in pp collisions at <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si2.gif" overflow="scroll"><mml:msqrt><mml:mi>s</mml:mi></mml:msqrt><mml:mo>=</mml:mo><mml:mn>0.9</mml:mn><mml:mtext> TeV</mml:mtext></mml:math>

The production of K 0 S mesons in pp collisions at a centre-of-mass energy of 0.9 TeV is studied with the LHCb detector at the Large Hadron Collider. The luminosity of the analysed sample is determined using a novel technique, involving measurements of the beam currents, sizes and positions, and is found to be 6.8 1.0 b -1 . The differential prompt K 0 S production cross-section is measured as a function of the K 0 S transverse momentum and rapidity in the region 0 < p T < 1.6 GeV/c and 2.5 < y < 4.0. The data are found to be in reasonable agreement with previous measurements and generator expectations.