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Hoi, I rechecked my formulas, I think the only bug was that I had swapped the lifetimes. Ergo once more: # Lifetimes of B+ and B0 > tnu := 1.542: > tch := 1.674: # B(B->Xlnu) > bf := 0.1087: # Assume f+-/f00 = 1, i.e. sl BF is equally from B+ and B0 > f:= 0.5: # Assume further b+/b0 = tch/tnu (with equal s.l. widths) # and then solve b = f*b+ + (1-f)*b0 for either b+ or b0 > bfch := bf / (f + (1-f)*tnu/tch); bfch := .1131615672 > bfnu := bf / (f*tch/tnu + (1-f)); bfnu := .1042384329 # Calculate the visible BF on the BRECO sample > nch := 20583: > nnu := 11582: > bfeff := (nch*bfch + nnu*bfnu) / (nch + nnu); bfeff := .1099485176 # Calculate weighted lifetime > teff := (nch*tch + nnu*tnu) / (nch +nnu); teff := 1.626469330 # Calculate weighted lifetime > nuch := 91: > nunu := 76: > tefff:= (nuch*tch + nunu*tnu) / (nuch +nunu); tefff:= 1.613928144 Using these number for BF(B->Xu l nu) and |Vub| I find BF(Brecoil ->X l nu) tau BF(Brecoil -> Xu lnu) |Vub| ---------------------------------------------------------------------- 10.87 1.608 2.14 4.52 (original) 10.99 1.608 2.17 4.55 10.99 1.6265 2.17 4.52 10.99 1.6139 2.17 4.54 The formulas are BF(B -> u l nu) = BF(B -> X l nu) * BRBR Vub = 0.4 * sqrt( BF(B -> u l nu) / tau ) The BF changes by 1.1%, |Vub| correspondingly less (if you look at more digits than displayed up there). There is compensation: B+ have a higher BF(B->X l nu), thus raise BF(B ->u l nu). They have a longer lifetime and thus will lower |Vub|. Assigning a systematic error of 1% should cover all grounds. Again, an independent cross check might be good. Cheers, --U.