In a quark-model calculation, X17 contributions to D*, B*, and J/psi Dalitz decays are too small to explain the BESIII D*0 e+e- excess unless quark couplings are far outside ATOMKI-favored ranges.
Analyzing lepton flavor universality in the decays $\Lambda_b\to\Lambda_c^{(\ast)}(\frac12^\pm,\frac32^-) + \ell\,\bar\nu_\ell$
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abstract
Lepton flavor universality can be tested in the semileptonic decays $\Lambda_b\to \Lambda_c^{(\ast)}$ where $\Lambda_c^{(\ast)}$ denotes either the ground state $\Lambda_c(2286)$ (with $J^P=1/2^+$) or its orbital excitations $\Lambda_c(2595)$ (with $J^P=1/2^-$) and $\Lambda_c(2625)$ (with $J^P=3/2^-$). We calculate the differential decay rates as well as the branching fractions of these decays for both tauonic and muonic modes with form factors obtained from a covariant confined quark model previously developed by us. We present results for the rate ratios of the tauonic and muonic modes which provide important tests of lepton flavor universality in forthcoming experiments.
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hep-ph 1years
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Probing the ATOMKI X17 vector boson using Dalitz decays $V\to Pe^+e^-$
In a quark-model calculation, X17 contributions to D*, B*, and J/psi Dalitz decays are too small to explain the BESIII D*0 e+e- excess unless quark couplings are far outside ATOMKI-favored ranges.