paper

B->eta(') Form Factors in QCD

arXiv:0706.3628 · doi:10.1088/1126-6708/2007/08/025

Abstract

We calculate the semileptonic form factors and from QCD sum rules on the light-cone (LCSRs), to NLO in QCD, and for small to moderate q^2, . We include in particular the so-called singlet contribution, i.e.\ weak annihilation of the B meson with the emission of two gluons which, thanks to the U(1) anomaly, couple directly to $\etap$. This effect is included to leading-twist accuracy. This contribution has been neglected in previous calculations of the form factors from LCSRs. We find that the singlet contribution to can be up to 20%, while that to is, as expected, much smaller and below 3%. We also suggest to measure the ratio to better constrain the size of the singlet contribution.

21 pages; version to appear in JHEP

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