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Register a new userPerturbative QCD Forbidden Charmonium Decays and Gluonia
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We address the problem of observed charmonium decays which should be forbidden in perturbative QCD. We examine the model in which these decays proceed through a gluonic component of the $J/Psi$ and the $eta_c$, arising from a mixing of $(cbar c)$ and glueball states. We give some bounds on the values of the mixing angles and propose the study of the $p bar{p} to phi phi$ reaction, at $sqrt{s} simeq 3$ GeV, as an independent test of the model.
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We extend the formalism based on perturbative QCD that was developed in our previous work, and compute the hyperfine splittings of the bottomonium spectrum as well as the fine and hyperfine splittings of the charmonium spectrum. All the corrections up to O(alpha_s^5 m) are included in the computations. We find agreement (with respect to theoretical uncertainties) with the experimental values whenever available and give predictions for not yet observed splittings.
We calculate the next-to-leading order (NLO) quantum chromodynamics (QCD) corrections to inclusive processes $W^+to J/psi(eta_c)+c+bar{s}+X$ and $W^+to B_c(B_c^{*})+b+bar{s}+X$ in the framework of nonrelativistic QCD (NRQCD) factorization formalism. Result indicates that the NLO corrections are significant, and the uncertainties in theoretical predictions with NLO corrections are greatly reduced. The charmonium and $B_c$ meson yielding rates at the Large Hadron Collider (LHC) are given.
Although the spectra of heavy quarkonium systems has been successfully explained by certain QCD motivated potential models, their strong decays are difficult to deal with. We perform a microscopic calculation of charmonium strong decays using the same constituent quark model which successfully describes the $cbar{c}$ meson spectrum. We compare the numerical results with the $^{3}P_{0}$ and the experimental data. Comparison with other predictions from similar models are included.
The Bc --> J/psi pi, etac pi decays are studied with the perturbative QCD approach. It is found that form factors and branching ratios are sensitive to the parameters w, v, f_J/psi and f_etac, where w and v are the parameters of the charmonium wave functions for Coulomb potential and harmonic oscillator potential, respectively, f_J/psi and f_etac are the decay constants of the J/psi and etac mesons, respectively. The large branching ratios and the clear signals of the final states make the Bc --> J/psi pi, etac pi decays to be the prospective channels for measurements at the hadron colliders
In this work, we provide estimates of the branching ratios, direct $CP$ asymmetries and triple product asymmetries in $B_{(s)} to (pipi)(Kpi)$ decays in the perturbative QCD approach, where the $pipi$ and $Kpi$ invariant mass spectra are dominated by the vector resonances $rho(770)$ and $K^*(892)$, respectively. Some scalar backgrounds, such as $f_0(500,980) to pipi$ and $K^*_0(1430) to Kpi$ are also accounted for. The $rho(700)$ is parametrized by the Gounaris-Sakurai function. The relativistic Breit-Wigner formula for the $f_0(500)$ and Flatte model for the $f_0(980)$ are adopted to parameterize the time-like scalar form factors $F_S(omega^2)$. We also use the D.V. Bugg model to parameterize the $f_0(500)$ and compare the relevant theoretical predictions from different models. While in the region of $Kpi$ invariant mass, the $K^*_0(1430)$ is described with the LASS lineshape and the $K^*(892)$ is modeled by the Breit-Wigner function. We find that the decay rates for the considered decay modes agree with currently available data within errors. As a by-product, we extract the branching ratios of two-body decays $B_{(s)} to rho(770)K^*(892)$ from the corresponding four-body decay modes and calculate the relevant polarization fractions. Our prediction of longitudinal polarization fraction for $B^0to rho(770)^0 K^*(892)^0$ decay deviates a lot from the recent LHCb measurement, which should be resolved. It is shown that the direct $CP$ asymmetries are large due to the sizable interference between the tree and penguin contributions, but they are small for the tree-dominant or penguin-dominant processes. The PQCD predictions for the triple product asymmetries are small which are expected in the standard model, and consistent with the current data reported by the LHCb Collaboration.Our results can be tested by the future precise data from the LHCb and Belle II experiments.
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