Measurement of the branching fractions of the <i>B</i><SUP>+</SUP> → η<i>l<SUP>+</SUP>ν<sub>l</sub></i> and <i>B</i><SUP>+</SUP> → η′<i>l<SUP>+</SUP>ν<sub>l</sub></i> decays with signal-side only reconstruction in the full <i>q</i><SUP>2</SUP> range

Abstract

The branching fractions of the decays B+ -> eta l(+)nu(l) and B+ -> eta'l(+)nu(l) are measured, where l is either an electron or a muon, using a data sample of 711 fb(-1) containing 772 x 10(6)B (B) over bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. To reduce the dependence of the result on the form factor model, the measurement is performed over the entire q(2) range. The resulting branching fractions are B(B+ -> eta l(+)nu(l)) = (2.83 +/- 0.55((stat.)) +/- 0.34((syst.))) x 10(-5) and B(B+ -> eta'l(+)nu(l)) = (2.79 +/- 1.29((stat.)) +/- 0.30((syst.))) x 10(-5).