The form factors of the semileptonic $B_c\to S(AV)\ellν$ $(\ell=τ, μ, e)$ transitions, where S and AV denote the scalar $X_{c0}$ and axial vector $(X_{c1}, h_{c})$ mesons, are calculated within the framework of the three-point QCD sum rules. The heavy quark effective theory limit of the form factors are also obtained and compared with the values of the original transition form factors. The results of form factors are used to estimate the total decay widths and branching ratios of these transitions. A comparison of our results on branching ratios with the predictions of other approaches is also presented.
B_c mesons are laboratories for probing heavy quark physics. Furthermore, they decay into charmonia and hence their decays can be used to analyze possible exotic charmonium. In this work, the semileptonic decays of B_c mesons into P wave charmonia are analysed using light cone QCD sum rules (LCSR). The distributions amplitudes for the charmonia are taken from a quark model computation. The obtained decay rates for the ground state and excited charmonia are compared with the results found in the literature.
Decays $J/ψ\to B\bar B$ into octet baryon-antibaryons pairs are studied within the QCD factorisation framework. The next-to-leading power correction to the leading-order decay amplitude is calculated for the first time. The phenomenological analysis also includes the interference with the electromagnetic decay $J/ψ\to γ^*\to B\bar B$. The branching fractions and the angular coefficients $α_B$ are described with an accuracy of about $20\%$. The obtained results allow us to conclude that the calculated amplitudes provide a dominant contribution and therefore QCD factorisation provides a suitable…
We investigate the mass-shift of $P$-wave charmonium (${χ_c}_0$, ${χ_c}_1$) and $S$ and $P$-wave bottomonium ($η_b$, $Υ$, ${χ_b}_0$ and ${χ_b}_1$) states in magnetized hot asymmetric nuclear matter using the unification of QCD sum rules (QCDSR) and chiral $SU(3)$ model. Within QCDSR, we use two approaches, $i.e.$, moment sum rule and Borel sum rule. The magnetic field induced scalar gluon condensate $\left\langle \frac{α_{s}}π G^a_{μν} {G^a}^{μν} \right\rangle$ and the twist-2 gluon operator $\left\langle \frac{α_{s}}π G^a_{μσ} {{G^a}_ν}^σ \right\rangle $ calculated in chiral $SU(3$) model are…
The phenomenology of leptonic decays of quarkonia holds many interesting features: for instance, it can establish constraints on scenarios beyond the Standard Model with the Higgs sector enriched by a light CP-odd state. In the following paper, we report on a two-flavor lattice QCD study of the $η_c$ and $J/ψ$ decay constants, $f_{η_c}$ and $f_{Jψ}$. We also examine some properties of the first radial excitation $η_c(2S)$ and $ψ(2S)$.
The hadronic form factors of $B_c$ semileptonic decays to the $P-$wave charmonium 4-plet can be expressed near the zero-recoil point in terms of universal functions, performing a systematic expansion in QCD in the relative velocity of the heavy quarks and in $1/m_Q$. Such functions are independent of the member of the multiplet involved in the transitions. We present the results of an NLO calculation up to $O(1/m_Q^2)$ classifying the universal functions at this order. We work out a set of relations among the form factors of the same mode and of different modes, which should be reproduced by e…
The precision of lattice QCD calculations has been steadily improving for some time and is now approaching, or has surpassed, the 1% level for multiple quantities. At this level QED effects, i.e. the fact that quarks carry electric as well as color charge, come into play. In this report we will summarise results from the first lattice QCD+QED computations of the properties of ground-state charmonium and bottomonium mesons by the HPQCD Collaboration.
We analyze the semileptonic $ B_{s} \rightarrow D_{s2}^{*}(2573)\ell\bar{ν}_{\ell}$ transition, where $\ell=τ,~μ$ or $e$, within the standard model. We apply the QCD sum rule approach to calculate the transition form factors entering the low energy Hamiltonian defining this channel. The fit functions of the form factors are used to estimate the total decay widths and branching fractions in all lepton channels. The orders of branching ratios indicate that this transition is accessible at LHCb in near future.
Motivated by the experimental findings of some new exotic states decaying into channels like $J/ψϕ$, we investigate the formation of resonances/bound states in the $D^*_s\bar D^*_s$ system using QCD sum rules. To do this we start with a current of the type vector times vector and use spin projectors to separate the spin 0, 1 and 2 contributions to the correlation function. We find three states with isospin 0, nearly spin degenerate, with a mass around 4.1 GeV. We have also investigated the decay of these states to $J/ψϕ$ and provide the corresponding partial widths. Such information should be …
Light-cone QCD sum rules for the semileptonic decay Lambda_b --> p lepton anti-neutrino
在全QCD和HQET中，用光锥求和规则研究了唯一的半轻子重子衰变Λ_bPDMATHABMM p l \bar ν.计算描述衰减的形状因子，并用于预测衰减宽度和微分分布。由全QCD得到的总衰变宽度与以前的理论预测一致，而HQET结果通常要小一个数量级。这两个结果都与实验上限相一致，并可以与未来改进的实验数据进行比较。
The spectrum of charmonium resonances contains a number of unanticipated states along with several conventional quark-model excitations. The hadrons of different quantum numbers $J^P$ appear in a fairly narrow energy band, where $J^P$ refers to the spin-parity of a hadron at rest. This poses a challenge for Lattice QCD studies of (coupled-channel) meson-meson scattering aimed at the determination of scattering amplitudes and resonance pole positions. A wealth of information for this purpose can be obtained from the lattice spectra in frames with nonzero total momentum. These are particularly d…
