Analysis of fragmentation functions of narrow band ν and <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" altimg="si1.gif" overflow="scroll"><mml:mrow><mml:mover accent="true"><mml:mi>v</mml:mi><mml:mo stretchy="true">¯</mml:mo></mml:mover></mml:mrow></mml:math> interactions on an isoscalar target