Observation of a first <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:msub><mml:mi>ν</mml:mi><mml:mi>τ</mml:mi></mml:msub></mml:math> candidate event in the OPERA experiment in the CNGS beam
Physics letters. B