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Register a new userThe Production of $X(3940)$ and $X(4160)$ in $B_c$ decays
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Considering $X(3940)$ and $X(4160)$ as $eta_c(3S)$ and $eta_c(4S)$, we study the productions of $X(3940)$ and $X(4160)$ in exclusive weak decays of $B_c$ meson by the improved Bethe-Salpeter(B-S) Method. Using the relativistic B-S equation and Mandelstam formalism, we calculate the corresponding decay form factors. The predictions of the corresponding branching ratios are: $Br(B_c^+to X(3940)e^+ u_e)$$=1.0times10^{-4}$ and $Br(B_c^+to X(4160)e^+ u_e)=2.4times10^{-5}$. That will provide us a new way to observe the $X(3940)$ and $X(4160)$ in the future, as well as to improve the knowledge of $B_c$ meson decay.
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The new mesons $X(3940)$ and $X(4160)$ have been found by Belle Collaboration in the processes $e^+e^-to J/psi D^{(*)}bar D^{(*)}$. Considering $X(3940)$ and $X(4160)$ as $eta_c(3S)$ and $eta_c(4S)$ states, the two-body open charm OZI-allowed strong decay of $eta_c(3S)$ and $eta_c(4S)$ are studied by the improved Bethe-Salpeter method combine with the $^3P_0$ model. The strong decay width of $eta_c(3S)$ is $Gamma_{eta_c(3S)}=(33.5^{+18.4}_{-15.3})$ MeV, which is closed to the result of $X(3940)$, therefore, $eta_c(3S)$ is a good candidate of $X(3940)$. The strong decay width of $eta_c(4S)$ is $Gamma_{eta_c(4S)}=(69.9^{+22.4}_{-21.1})$ MeV, considering the errors of the results, its closed to the lower limit of $X(4160)$. But the ratio of the decay width $frac{Gamma(Dbar D^*)}{Gamma (D^*bar D^*)}$ of $eta_c(4S)$ is larger than the experimental data of $X(4160)$. According to the above analysis, $eta_c(4S)$ is not the candidate of $X(4160)$, and more investigations of $X(4160)$ is needed.
Considering $Z(3930)$ and $X(4160)$ as $chi_{c2}(2P)$ and $chi_{c2}(3P)$ states, the semileptonic and nonleptonic of $B_c$ decays to $Z(3930)$ and $X(4160)$ are studied by the improved Bethe-Salpeter(B-S) Method. The form factors of decay are calculated through the overlap integrals of the meson wave functions in the whole accessible kinematical range. The influence of relativistic corrections are considered in the exclusive decays. Branching ratios of $B_c$ weak decays to $Z(3930)$ and $X(4160)$ are predicted. Some of the branching ratios are: $Br(B_c^+to Z(3930)e^+ u_e)$$=(3.03^{+0.09}_{-0.16})times 10^{-4}$ and $Br(B_c^+to X(4160)e^+ u_e)$$=(3.55^{+0.83}_{-0.35})times 10^{-6}$. These results may provide useful information to discover $Z(3930)$ and $X(4160)$ and the necessary information for the phenomenological study of $B_c$ physics.
We discuss the possibilities of producing the X(3872), which is assumed to be a D bar D^* bound state, in radiative decays of charmonia. We argue that the ideal energy regions to observe the X(3872) associated with a photon in e^+e^- annihilations are around the Y(4260) mass and around 4.45 GeV, due to the presence of the S-wave D bar D_1(2420) and D^* bar D_1(2420) threshold, respectively. Especially, if the Y(4260) is dominantly a D bar D_1 molecule and the X(3872) a D bar D^* molecule, the radiative transition strength will be quite large.
The lifetime of the $B_c^+$ meson is measured using semileptonic decays having a $J!/!psi$ meson and a muon in the final state. The data, corresponding to an integrated luminosity of $2mathrm{~fb^{-1}}$, are collected by the LHCb detector in $pp$ collisions at a centre-of-mass energy of $8,mathrm{TeV}$. The measured lifetime is $$tau = 509 pm 8 pm 12 mathrm{~fs},$$ where the first uncertainty is statistical and the second is systematic.
In this paper, we calculate the total decay widths for the $W^+$-boson decays, $W^+ to B_c+b+bar{s}+X$ and $W^+ to B^*_c+b+bar{s}+X$, up to next-to-leading order (NLO) accuracy within the framework of the nonrelativistic QCD theory. Both the fixed-order and the fragmentation approaches are adopted to do the calculation. Differential decay widths $dGamma/dz$ and $dGamma/ds_1$ are also given. We find that the NLO corrections are significant in those two $W^+$ decay channels. Our numerical results show that at the LHC, there are about $7.03times 10^4$ $B_c$-meson events and $5.10times 10^4$ $B^*_c$-meson events to be produced via the $W^+$-boson decays per operation year.
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