Triple Prompt J/ψ Hadroproduction as a Hard Probe of Multiple-Parton Scatterings.

We propose that the process of triple prompt J/ψ hadroproduction is a very clean hard probe of multiple-parton scatterings at high-energy hadron colliders, especially the least known triple-parton scattering. A first complete study is carried out by considering single-, double-, and triple-parton scatterings coherently. Our calculation shows that it is a golden channel to probe double- and triple-parton scatterings, as the single-parton scattering is strongly suppressed.

Precise predictions for same-sign W-boson scattering at the LHC.

Vector-boson scattering processes are of great importance for the current run-II and future runs of the Large Hadron Collider. The presence of triple and quartic gauge couplings in the process gives access to the gauge sector of the Standard Model (SM) and possible new-physics contributions there. To test any new-physics hypothesis, sound knowledge of the SM contributions is necessary, with a precision which at least matches the experimental uncertainties of existing and forthcoming measurements.

Gluon Shadowing in Heavy-Flavor Production at the LHC.

We study the relevance of experimental data on heavy-flavor [D^{0}, J/ψ, B→J/ψ and ϒ(1S) mesons] production in proton-lead collisions at the LHC to improve our knowledge of the gluon-momentum distribution inside heavy nuclei. We observe that the nuclear effects encoded in both most recent global fits of nuclear parton densities at next-to-leading order (nCTEQ15 and EPPS16) provide a good overall description of the LHC data. We interpret this as a hint that these are the dominant ones.

QCD next-to-leading-order predictions matched to parton showers for vector-like quark models.

Vector-like quarks are featured by a wealth of beyond the Standard Model theories and are consequently an important goal of many LHC searches for new physics. Those searches, as well as most related phenomenological studies, however, rely on predictions evaluated at the leading-order accuracy in QCD and consider well-defined simplified benchmark scenarios. Adopting an effective bottom-up approach, we compute next-to-leading-order predictions for vector-like-quark pair production and single production in association with jets, with a weak or with a Higgs boson in a general new physics setup.

Complete Study of Hadroproduction of a ϒ Meson Associated with a Prompt J/ψ.

We present the first complete study of ϒ and prompt J/ψ production from single-parton scattering, including the complete O(α_{S}^{6}) color-singlet contribution, the O(α_{S}^{2}α^{2}) electroweak contribution, and the complete nonrelativistic S-wave and P-wave color-octet contribution as well as the feeddown contribution. Our study was motivated by the recent evidence reported by the D0 Collaboration of prompt J/ψ and ϒ simultaneous production at the Tevatron. With our complete evaluation, we are able to refine the determination of the double-parton scattering contribution made by the D0 Collaboration.

η(c) production at LHC and implications for the understanding of J/ψ production.

We present a complete evaluation for the prompt η_{c} production at the LHC at next-to-leading order in α_{s} in nonrelativistic QCD. By assuming heavy-quark spin symmetry, the recently observed η_{c} production data by LHCb results in a very strong constraint on the upper bound of the color-octet long-distance matrix element ⟨O^{J/ψ}(^{1}S_{0}^{[8]})⟩ of J/ψ. We find this upper bound is consistent with our previous study of the J/ψ yield and polarization and can give good descriptions for the measurements, but the upper bound is inconsistent with some other theoretical estimates.

Polarizations of χc1 and χc2 in prompt production at the LHC.

Prompt χc production at hadron colliders may provide a unique test for the color-octet mechanism in nonrelativistic QCD. We present an analysis for the polarization observables of χc1 and χc2 at next-to-leading order in αS and propose to measure them at the LHC, which is expected to be important for testing the validity of nonrelativistic QCD.

Production of J / ψ + η(c) versus J / ψ + J / ψ at the LHC: importance of real α(s)(5) corrections.

We proceed for the first time to the evaluation of the Born cross section for J / ψ + η(c) production, namely, via g + g → J/ψ+ η(c) + g, and show that it has a harder P(T) spectrum than the J/ψ-pair yield at the Born level. If one stuck to a comparison at the Born level, one would conclude that J / ψ + η(c) production would surpass that of J / ψ + J / ψ at large P(T). This is nonetheless not the case since J / ψ-pair production, as for single J / ψ, receives leading-P(T) contributions at higher orders in α(s).

J/ψ polarization at hadron colliders in nonrelativistic QCD.

With nonrelativistic QCD factorization, we present a full next-to-leading order computation of the polarization observable for J/ψ production at hadron colliders including all important Fock states, i.e., 3S(1)([1,8]), 1S(0)([8]), and 3P(J)([8]).