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Register a new userInclusive semi-leptonic decays from lattice QCD
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We develop a method to compute inclusive semi-leptonic decay rate of hadrons fully non-perturbatively using lattice QCD simulations. The sum over all possible final states is achieved by a calculation of the forward-scattering matrix elements on the lattice, and the phase-space integral is evaluated using their dependence on the time separation between two inserted currents. We perform a pilot lattice computation for the B_s -> X_c l nu decay with an unphysical bottom quark mass and compare the results with the corresponding OPE calculation. The method to treat the inclusive processes on the lattice can be applied to other processes, such as the lepton-nucleon inelastic scattering.
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We propose a method to non-perturbatively calculate the forward-scattering matrix elements relevant to inclusive semi-leptonic B meson decays. Corresponding hadronic structure functions at unphysical kinematics are accessible through lattice QCD calculation of four-point correlation functions. The unphysical kinematical point may be reached by analytic continuation from the physical differential decay rate. A numerical test is performed for the B_s -> X_c l nu mode in the zero-recoil limit. We use lattice ensembles generated with 2+1 dynamical quark flavors. The valence charm quark mass is tuned to its physical value, while the bottom quark mass is varied in the range (1.56-2.44)m_c. From the numerical results we can identify the contributions of the ground state D_s^(*) meson as well as those of excited states or continuum states.
This talk reviews recent lattice QCD simulations of the K->pi semi-leptonic form factor.
Adding a hard photon to the final state of a leptonic pseudoscalar-meson decay lifts the helicity suppression and can provide sensitivity to a larger set of operators in the weak effective Hamiltonian. Furthermore, radiative leptonic $B$ decays at high photon energy are well suited to constrain the first inverse moment of the $B$-meson light-cone distribution amplitude, an important parameter in the theory of nonleptonic $B$ decays. We demonstrate that the calculation of radiative leptonic decays is possible using Euclidean lattice QCD, and present preliminary numerical results for $D_s^+ to ell^+ ugamma$ and $K^- to ell^-bar{ u}gamma$.
We propose a method for a QCD based calculation of one-particle inclusive decays of the form B to bar D X or B to bar D^* X. It is based on the heavy mass limit and a short distance expansion of the amplitudes, which yield a power series in the parameter 1/M^2_X for the spectra and in Lambda_QCD m_b/(m_b - m_c)^2 for the rates. We study the leading term of this expansion for the case of the semi--leptonic decays B to bar D X l^+ u.
We report on a two-flavour lattice QCD study of the D_s and D_s^* leptonic decays parameterized by the decay constants f_{D_s} and f_{D_s^*}. As the phenomenology in the D_s sector seems very promising in the next years with the experiments LHCb and Belle II, it is worth putting a big effort in lattice computations regarding its non-perturbative QCD contributions. Before examining more challenging processes such as hadron-hadron transitions, a natural first step is to address some basic aspects in the context of leptonic decays, where systematic uncertainties from excited state contaminations and cut-off effects in the computation of charmed meson decay matrix elements can be investigated in a more straightforward setting.
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