Measurement of W-boson helicity fractions in top-quark decays using <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mi mathvariant="normal">cos</mml:mi><mml:msup><mml:mi>θ</mml:mi><mml:mo>∗</mml:mo></mml:msup></mml:math>
Physics letters. B