SU(3) corrections to B → Dl form factors at O()

Abstract

We compute the O( 1 M , m s ) heavy quark and SU(3) corrections to B s → D s eν form factors. In the limit of vanishing light quark mass, B s → D s eν form factors are given in terms of the the B → Deν form factors, the leading order chiral parameter g, and two O( 1 M ) chiral parameters g 1 and g 2 . All the chiral parameters can be extracted, in principle, from other heavy meson decays. Analytic counterterms proportional to the strange quark mass are presented for completeness, but no predictive power remains when they are included. Anomalously large loop corrections warn of poor convergence of the heavy quark chiral symmetry expansion for these processes. This suggests that naive extrapolations of B → D form factors relying on heavy quark and chiral symmetries, as often used in monte carlo simulations of lattice QCD, may incur large errors.

A puzzle in $$\varvec{\bar{B}_{(s)}^0 \rightarrow D_{(s)}^{(*)+} \lbrace \pi ^-, K^-\rbrace }$$ decays and extraction of the $$\varvec{f_s/f_d}$$ fragmentation fraction

“…We emphasize that the SU (3) F breaking of the amplitudes is numerically driven by the decay constants of the light-meson. The deviation from the symmetry limit in heavy-to-heavy form factors is additionally suppressed by the heavy-quark masses and therefore expected to be very small [7][8][9]. A recent analysis of the symmetry breaking in heavy-to-heavy form factors yields results that are compatible with this expectation [3].…”

Lattice QCD calculation ofB¯→Dlν¯decay form factors at zero recoil

“…A small, but non-analytic, dependence on m π is expected from chiral perturbation theory [28,29]. Such effects may be different in the quenched approximation.…”

Chiral corrections to the scalar form factor inBq→Dqtransitions

“…At LO in the chiral expansion no additional pseudo-Goldstone fields can be emitted from the weak current operator vertices. In the computation of the power suppressed PSfrag replacements chiral corrections to h + (w), one would need to consider contributions from the NLO HMχPT interaction Lagrangian [10]. These are however further suppressed when considering LO chiral corrections to the sub-leading form factor h − (w).…”

“…The leading order (LO) SU (3) chiral corrections at leading and next to leading order (NLO) in 1/m Q to the B q → D ( * ) q semileptonic form factors have previously been computed in [10]. However phenomenological discussion at the time was limited by the lack of experimental and lattice information available on the sub-leading form factor contributions.…”