▁good ▁agreement ▁with ▁these ▁predictions ▁of ▁the ▁Standard ▁Model . ▁ ▁Mu on ▁decay ▁ ▁Consider ▁the ▁decay ▁of ▁the ▁positive ▁mu on : ▁ ▁In ▁the ▁mu on ▁rest ▁frame , ▁energy ▁and ▁angular ▁distributions ▁of ▁the ▁posit rons ▁em itted ▁in ▁the ▁decay ▁of ▁a ▁polar ised ▁mu on ▁expressed ▁in ▁terms ▁of ▁Michel ▁parameters ▁are ▁the ▁following , ▁neglect ing ▁electron ▁and ▁neut r ino ▁masses ▁and ▁the ▁radi ative ▁corre ctions : ▁ ▁where ▁ ▁is ▁mu on ▁polar isation , ▁, ▁and ▁ ▁is ▁the ▁angle ▁between ▁mu on ▁spin ▁direction ▁and ▁posit ron ▁momentum ▁direction . ▁For ▁the ▁decay ▁of ▁the ▁negative ▁mu on , ▁the ▁sign ▁of ▁the ▁term ▁containing ▁ ▁should ▁be ▁invert ed . ▁ ▁For ▁the ▁decay ▁of ▁the ▁positive ▁mu on , ▁the ▁expected ▁decay ▁distribution ▁for ▁the ▁Standard ▁Model ▁values ▁of ▁Michel ▁parameters ▁is ▁ ▁Integr ation ▁of ▁this ▁expression ▁over ▁electron ▁energy ▁gives ▁the ▁angular ▁distribution ▁of ▁the ▁daughter ▁posit rons : ▁ ▁The ▁posit ron ▁energy ▁distribution ▁integrated ▁over ▁the ▁polar ▁angle ▁is ▁ ▁References ▁▁ ▁L ect ure ▁on ▁Le pton ▁Univers ality ▁by ▁Michel ▁Dav ier ▁at ▁the ▁ 1 9 9 7 ▁SL AC ▁Summer ▁Institute . ▁ ▁Elect ro weak ▁Cou pl ings , ▁Le pton ▁Univers ality , ▁and ▁the ▁Origin ▁of ▁Mass : ▁An ▁Ex perimental ▁Pers pective , ▁article ▁by ▁John ▁Sw ain , ▁from ▁the ▁Pro ceed ings ▁of ▁the ▁Third ▁Latin ▁American ▁Sym pos ium ▁on ▁High ▁Energy ▁Physics .