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Register a new userEstimates of the Cross Section of the Production of Z Boson and J/{psi} at the LHC
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We calculate the leading order cross section for the associated production of Z and J/{psi}. Processes that include associated production of electroweak bosons and heavy quarlonium can give valuable insight to the production mechanism of quarkonia. We conclude that this process is accessible by the LHC statistics.
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The associated production of J/psi + gamma at the LHC is studied within the NRQCD framework. The signal we focus on is the production of a J/psi and an isolated photon produced back-to-back, with their transverse momenta balanced. It is shown that even for very large values of transverse momentum (pT of the order of 50 GeV) the dominant contribution to this process is not fragmentation. This is because of the fact that fragmentation-type contributions to the cross-section come from only a q q(bar) initial state, which is suppressed at the LHC. We identify gg-initiated diagrams higher-order in alpha(s) which do have fragmentation-type vertices. We find, however, that the contribution of these diagrams is negligibly small.
Charged lepton pairs are produced copiously in high-energy hadron collisions via electroweak gauge boson exchange, and are one of the most precisely measured final states in proton-proton collisions at the Large Hadron Collider (LHC). We propose that measurements of lepton angular distributions can be used to improve the accuracy of theoretical predictions for Higgs boson production cross sections at the LHC. To this end, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. By a detailed numerical analysis using the open-source platform xFitter, we find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run III and high-luminosity HL-LHC improve the PDF systematic uncertainties of the Higgs boson cross section predictions by 50% over a broad range of Higgs boson rapidities.
We present a complete evaluation for the prompt $eta_c$ production at the LHC at next-to-leading order in $alpha_s$ in nonrelativistic QCD. By assuming heavy quark spin symmetry, the recently observed $eta_c$ production data by LHCb results in a very strong constraint on the upper bound of the color-octet long distance matrix element $1S0$ of $J/psi$. We find this upper bound is consistent with our previous study of the $J/psi$ yield and polarization and can give good descriptions for the measurements, but inconsistent with some other theoretical estimates. This may provide important information for understanding the nonrelativistic QCD factorization formulism.
Improving previous calculations, we compute the $D + bar{D} to J/psi + pi $ cross section using the most complete effective lagrangians available. The new crucial ingredients are the form factors on the charm meson vertices, which are determined from QCD sum rules calculations. Some of them became available only very recently and the last one, needed for our present purpose, is calculated in this work.
The production of charmonium associated with Higgs boson via gluon fusion has been investigated in Ref.[Phys.Rev.D66,114002(2002)], in which they considered the contribution of final Higgs boson radiation off the charm quark at tree level and found that this process is to be far too rare to be observable in any of the considered experiments. In this paper, the production of prompt $J/psi$ associated with Higgs boson via gluon fusion at the 14 TeV LHC within the factorization formalism of NRQCD is revisited. After considering the contribution from the final Higgs boson radiation off the top quark in the loop, which is {more than} three orders of magnitudes over the charm quark at tree level, the production of prompt $J/psi$ associated with Higgs boson has great potential to be detected. The prompt $J/psi$ production includes the direct production and indirect production via radiative or hadronic decays of high excited charmonium states. For the direct $J/psi + H$ production via gluon fusion loop-induced, the ${}^{3}S^{(8)}_1$ Fock state gives dominant contribution to the cross section, which is about 95% to the total direct production. The indirect contribution via loop-induced is appreciable, since the summation of which from $psi(2S) + H$, $chi_{c1} + H$ and $chi_{c2} + H$ is about $34%$ to the total cross section of prompt $J/psi + H$. While the indirect contribution from $chi_{c0} + H$ is tiny, which can be neglected. With the great potential to be detected, prompt $J/psi$ production in associated with Higgs boson can help us to further understand the mechanism of colour-octet, as well as can be useful to further investigate the coupling of the Higgs boson and fermion.
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