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Register a new userNext-to-leading order QCD corrections to the decay of Higgs to vector meson and Z boson
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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.
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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 $Gamma(Z to Upsilon(1S)+X)|_{chi_b-textrm{feeddown}}=(0.15 - 0.49) times 10^{-6}$.
We present the NLO QCD corrections for light Higgs pair production via vector boson fusion at the LHC within the CP conserving type II two higgs doublet model in the form of a fully flexible parton--level Monte Carlo program. Scale dependences on integrated cross sections and distributions are reduced with QCD K-factors of order unity.
We present the calculation of the dominant next to leading order QCD corrections to Higgs boson production in association with three jets via vector boson fusion in the form of a NLO parton-level Monte Carlo program. QCD corrections to integrated cross sections are modest, while the shapes of some kinematical distributions change appreciably at NLO. Scale uncertainties are shown to be reduced at NLO for the total cross section and for distributions. We consider a central jet veto at the LHC and analyze the veto probability for typical vector boson fusion cuts. Scale uncertainties of the veto probability are sufficiently small at NLO for precise Higgs coupling measurements at the LHC.
We calculate the complete ${cal O}(alpha_s)$ corrections to the quark decay $bto ccs$ taking full account of the quark masses, but neglecting penguin contributions. For a c to the b quark mass ratio $m_c/m_b= 0.3$ and a strange quark mass of $0.2,$GeV, we find that the next-to-leading order (NLO) corrections increase $Gamma(bto ccs)$ by $(32pm 15)%$ with respect to the leading order expression, where the uncertainty is mostly due to scale- and scheme-dependences. Combining this result with the known NLO and non-perturbative corrections to other B meson decay channels we obtain an updated value for the semileptonic branching ratio of B mesons, $B_{SL}$, of $(12.0pm 1.4)% $ using pole quark masses and $(11.2pm 1.7)% $ using running $overline{mbox{MS}}$ masses.
Cross sections and differential distributions for ZA production in association with two jets via vector boson fusion are presented at next-to-leading order in QCD. The leptonic decays of the Z boson with full off-shell effects and spin correlations are taken into account. The uncertainties due to different scale choices and pdf sets are studied. Furthermore, we analyze the effect of including anomalous quartic gauge couplings at NLO QCD.
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