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Register a new userLeptonic decays of D-wave vector quarkonia
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We give a short and basic introduction to our covariant Dyson-Schwinger-Bethe-Salpeter-equation approach using a rainbow-ladder truncated model of QCD, in which we investigate the leptonic decay properties of heavy quarkonium states in the pseudoscalar and vector channels. Comparing the magnitudes of decay constants, we identify radial 1-- excitations in our calculation with experimental excitations of J/Psi and Upsilon. Particular attention is paid to those states regarded as D-wave states in the quark model. We predict e+e- decay width of the Upsilon(1^3D_1) and Upsilon(2^3D_1) states of the order of ca. 15 eV or more. We also provide a set of predictions for decay constants of pseudoscalar radial excitations in heavy quarkonia.
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Inspired by the potential prospects of LHCb, Belle-II, STCF, CEPC and FCC-ee experiments, we discussed the probabilities of experimental investigation on the purely leptonic decays of the ground charged vector mesons including ${rho}^{pm}$, $K^{{ast}{pm}}$, $D_{d,s}^{{ast}{pm}}$ and $B_{u,c}^{{ast}{pm}}$.
We revisit earlier calculations of leptonic decay constants of vector charmonia and present and illustrate our decomposition of the corresponding covariant Bethe-Salpeter amplitudes in terms of orbital angular momentum as interpreted in the mesons rest frame. Our results confirm our previous conclusions drawn from the magnitudes of vector-meson leptonic decay constants, identifying the Psi(3770) and Psi(4160) as D-wave states in our setup.
The recent experimental developments require a more precise theoretical study of weak decays of heavy baryon $Lambda_b^0$. In this work, we provide an updated and systematic analysis of both the semi-leptonic and nonleptonic decays of $Lambda^0_b$ into baryons $Lambda^+_c$, $Lambda$, $p$, and $n$. The diquark approximation is adopted so that the methods developed in the $B$ meson system can be extended into the baryon system. The baryon-to-baryon transition form factors are calculated in the framework of a covariant light-front quark model. The form factors $f_3, ~g_3$ can be extracted and are found to be non-negligible. The semi-leptonic processes of $Lambda^0_bto Lambda^+_c(p)l^-bar u_l$ are calculated and the results are consistent with the experiment. We study the non-leptonic processes within the QCD factorization approach. The decay amplitudes are calculated at the next-to-leading order in strong coupling constant $alpha_s$. We calculate the non-leptonic decays of $Lambda^0_b$ into a baryon and a s-wave meson (pseudoscalar or vector) including 44 processes in total. The branching ratios and direct CP asymmetries are predicted. The numerical results are compared to the experimental data and those in the other theoretical approaches. Our results show validity of the diquark approximation and application of QCD factorization approach into the heavy baryon system.
The weak decays of the axial-vector tetraquark $T_{bb;bar{u} bar{d}}^{-}$ to the scalar state $Z_{bc;bar{u} bar{d}}^{0}$ are investigated using the QCD three-point sum rule approach. In order to explore the process $T_{bb; bar{u} bar{d}}^{-} to Z_{bc;bar{u} bar{d}}^{0}l bar{ u_l}$, we recalculate the spectroscopic parameters of the tetraquark $T_{bb;bar{u} bar{d}}^{-}$ and find the mass and coupling of the scalar four-quark system $Z_{bc;bar{u} bar{d}}^{0}$, which are important ingredients of calculations. The spectroscopic parameters of these tetraquarks are computed in the framework of the QCD two-point sum rule method by taking into account various condensates up to dimension ten. The mass of the $T_{bb;bar{u} bar{ d}}^{-}$ state is found to be $m=(10035~pm 260)~mathrm{MeV}$, which demonstrates that it is stable against the strong and electromagnetic decays. The full width $Gamma$ and mean lifetime $tau$ of $T_{bb;bar{u} bar{d} }^{-}$ are evaluated using its semileptonic decay channels $T_{bb; bar{u} bar{d}}^{-} to Z_{bc;bar{u} bar{d}}^{0}l bar{ u_l}$, $l=e,mu$ and $tau$. The obtained results, $Gamma=(7.17pm 1.23)times 10^{-8 } mathrm{MeV}$ and $tau =9.18_{-1.34}^{+1.90}~mathrm{fs}$, can be useful for experimental investigations of the doubly-heavy tetraquarks.
The measured rate for D_s -> l nu decays, where l is a muon or tau, is larger than the standard model prediction, which relies on lattice QCD, at the 3.8 sigma level. We discuss how robust the theoretical prediction is, and we show that the discrepancy with experiment may be explained by a charged Higgs boson or a leptoquark.
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