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Register a new userOrder $v^4$ corrections to Higgs boson decay into $J/psi + gamma$
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The process $H to J/psi + gamma$, where $H$ is the Higgs particle, provides a way to probe the size and the sign of the Higgs-charm coupling. In order to improve the theoretical control of the decay rate, we compute order $v^4$ corrections to the decay rate based on the nonrelativistic QCD factorization formalism. The perturbative calculation is carried out by using automated computer codes. We also resum logarithms of the ratio of the masses of the Higgs boson and the $J/psi$ to all orders in the strong coupling constant $alpha_s$ to next-to-leading logarithmic accuracy. In our numerical result for the decay rate, we improve the theoretical uncertainty, while our central value is in agreement with previous studies within errors. We also present numerical results for $H to Upsilon(nS) + gamma$ for $n=1,2$, and 3, which turn out to be extremely sensitive to the Higgs bottom coupling.
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Theoretical predictions for the decay width of Standard Model Higgs boson into bottom quarks and tau-leptons, in the case when M_H< 2M_W, are briefly reviewed. The effects of higher order perturbative QCD (up to alpha_s^4-level) and QED corrections are considered. The uncertainties of the decay width of Higgs boson into bb and tau+tau- are discussed.
Based on the framework of nonrelativistic Quantum Chromodynamics (NRQCD), we carry out next-to-leading order (NLO) QCD corrections to the decay of $Z$ boson into $chi_c$ and $chi_b$, respectively. The branching ratio of $Z to chi_{c}(chi_b)+X$ is about $10^{-5}(10^{-6})$. It is found that, for $Z to chi_c(chi_b)+X$, the single gluon fragmentation diagrams of $^3S_1^{[8]}$, which first appear at the NLO level, can provide significant contributions, leading to a great enhancement on the leading-order results. Consequently the contributions from the color octet (CO) channels will account for a large proportion of the total decay widths. Moreover, the introduction of the CO processes will thoroughly change the color singlet (CS) predictions on the ratios of $Gamma_{chi_{c1}}/Gamma_{chi_{c0}}$, $Gamma_{chi_{c2}}/Gamma_{chi_{c0}}$, $Gamma_{chi_{b1}}/Gamma_{chi_{b0}}$ and $Gamma_{chi_{b2}}/Gamma_{chi_{b0}}$, which can be regarded as an outstanding probe to distinguish the CO and CS mechanism. With regard to the CS ($^3P_J^{[1]}$) channels, the heavy quark pair associated processes serve as the leading role, however, in the case of $chi_b$, $Z to bbar{b}[^3P_J^{[1]}]+g+g$ can also contribute significantly. Summing over all the feeddown contributions from $chi_{cJ}$ and $chi_{bJ}$, respectively, we find $Gamma(Z to J/psi+X)|_{chi_c-textrm{feeddown}}=(0.28 - 2.4) times 10^{-5}$ and $Gamma(Z to Upsilon(1S)+X)|_{chi_b-textrm{feeddown}}=(0.15 - 0.49) times 10^{-6}$.
The exclusive decay of the Higgs boson to a vector meson ($ J/psi $ or $ Upsilon(1S) $) and $ Z $ boson is studied in this work. The decay amplitudes are separated into two parts in a gauge invariant manner. The first part comes from the direct coupling of the Higgs boson to the charm (bottom) quark and the other from the $ HZZ^{*} $ or the loop-induced $ HZgamma^{*} $ vertexes in the standard model. While the branching ratios from the direct channel are much smaller than those of the indirect channel, their interference terms give nontrivial contributions. We further calculate the QCD radiative corrections to both channels, which reduce the total branching ratios by around 20% for both $ J/psi $ and $ Upsilon(1S) $ production. These results may help to check the SM predictions of the $ H cbar{c}(H bbar{b}) $ coupling and to seek for hints of new physics at the High Luminosity LHC or future hadron colliders.
In supersymmetric theories, the decays of the neutral CP-even and CP-odd as well as the charged Higgs bosons into scalar quarks, in particular into top and bottom squarks, can be dominant if they are kinematically allowed. We calculate the QCD corrections to these decay modes in the minimal supersymmetric extension of the Standard Model, including all quark mass terms and squark mixing. These corrections turn out to be rather large, altering the decay widths by an amount which can be larger than 50%. The corrections can be either positive or negative, and depend strongly on the mass of the gluino. We also discuss the QCD corrections to the decays of heavy scalar quarks into light scalar quarks and Higgs bosons.
The cross section for e^+e^- to eta J/psi between sqrt{s}=3.8 GeV/c^2 and 5.3 GeV/c^2 is measured via initial state radiation using 980 fb^{-1} of data on and around the Upsilon(nS)(n=1,2,3,4,5) resonances collected with the Belle detector at KEKB. Two resonant structures at the psi(4040) and psi(4160) are observed in the eta J/psi invariant mass distribution. Fitting the mass spectrum with the coherent sum of two Breit-Wigner functions, one obtains BR(psi(4040)toeta J/psi)cdotGamma_{ee}^{psi(4040)} = (4.8pm0.9pm1.4) eV and BR(psi(4160)toeta J/psi)cdotGamma_{ee}^{psi(4160)} = (4.0pm0.8pm1.4) eV for one solution and BR(psi(4040)toeta J/psi)cdotGamma_{ee}^{psi(4040)} = (11.2pm1.3pm1.9) eV and BR(psi(4160)toeta J/psi)cdotGamma_{ee}^{psi(4160)} = (13.8pm1.3pm2.0) eV for the other solution, where the first errors are statistical and the second are systematic. This is the first measurement of this hadronic transition mode of these two states, and the partial widths to eta J/psi are found to be about 1 MeV. There is no evidence for the Y(4260), Y(4360), psi(4415), or Y(4660) in the eta J/psi final state, and upper limits of their production rates in e^+e^- annihilation are determined.
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