We determine, by means of lattice QCD calculations, the local form factors describing the Bs→μ+μ-γ decay, in the so-called electroquenched approximation. For this analysis we make use of the gauge configurations produced by the ETM Collaboration with Nf=2 +1 +1 flavor of Wilson-Clover twisted-mass fermions at maximal twist. To obtain the Bs meson form factors, we perform simulations for several heavy-strange meson masses mHsin the range mH s∈[mDs,2mD s], and extrapolate to the physical Bs meson point mB s≃5.367 GeV making use of the HQET scaling laws. We cover the region of large dimuon invariant masses √{q2}>4.16 GeV , and use our results to determine the branching fraction for Bs→μ+μ-γ , which has been recently measured by LHCb in the region √{q2}>4.9 GeV . The largest contribution to the uncertainty in the partial branching fractions at values of √{q2}<4.8 GeV is now due to resonance and other long-distance effects, including those from "charming penguins," which we estimate by summing over the contributions from the JP=1- charmonium resonances.
Frezzotti, R., Tantalo, N., Gagliardi, G., Sanfilippo, F., Simula, S., Lubicz, V., et al. (2024). The $B_{s}\to \mu^+\mu^-\gamma$ decay rate at large $q^2$ from lattice QCD. PHYSICAL REVIEW D, 109(11) [10.1103/physrevd.109.114506].
The $B_{s}\to \mu^+\mu^-\gamma$ decay rate at large $q^2$ from lattice QCD
Gagliardi, G.;Lubicz, V.;
2024-01-01
Abstract
We determine, by means of lattice QCD calculations, the local form factors describing the Bs→μ+μ-γ decay, in the so-called electroquenched approximation. For this analysis we make use of the gauge configurations produced by the ETM Collaboration with Nf=2 +1 +1 flavor of Wilson-Clover twisted-mass fermions at maximal twist. To obtain the Bs meson form factors, we perform simulations for several heavy-strange meson masses mHsin the range mH s∈[mDs,2mD s], and extrapolate to the physical Bs meson point mB s≃5.367 GeV making use of the HQET scaling laws. We cover the region of large dimuon invariant masses √{q2}>4.16 GeV , and use our results to determine the branching fraction for Bs→μ+μ-γ , which has been recently measured by LHCb in the region √{q2}>4.9 GeV . The largest contribution to the uncertainty in the partial branching fractions at values of √{q2}<4.8 GeV is now due to resonance and other long-distance effects, including those from "charming penguins," which we estimate by summing over the contributions from the JP=1- charmonium resonances.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
