Fully Differential Higgs Boson Production to Third Order in QCD.

We present the first fully differential predictions for the production cross section of a Higgs boson via the gluon fusion mechanism at next-to-next-to-next-to-leading order (N^{3}LO) in QCD perturbation theory. Differential distributions are shown for the two-photon final state produced by the decay of the Higgs boson for a realistic set of fiducial cuts. The N^{3}LO corrections exhibit complex features and are in part larger than the inclusive N^{3}LO corrections to the production cross section. Overall, we observe that the inclusion of the N^{3}LO QCD corrections significantly reduces the perturbative uncertainties and leads to a stabilization of the perturbative expansion.

Predictions for Z-Boson Production in Association with a b-Jet at O(α_{s}

Precise predictions are provided for the production of a Z boson and a b-jet in hadron-hadron collisions within the framework of perturbative QCD, at O(α_{s}^{3}). To obtain these predictions, we perform the first calculation of a hadronic scattering process involving the direct production of a flavored jet at next-to-next-to-leading-order accuracy in massless QCD and extend techniques to also account for the impact of finite heavy-quark mass effects. The predictions are compared to CMS data obtained in pp collisions at a center-of-mass energy of 8 TeV, which are the most precise data from run I of the LHC for this process, where a good description of the data is achieved. To allow this comparison, we have performed an unfolding of the data, which overcomes the long-standing issue that the experimental and theoretical definitions of jet flavor are incompatible.

Triple Differential Dijet Cross Section at the LHC.

The measurement of the triple-differential dijet production cross section as a function of the average transverse momentum p_{T,avg}, half the rapidity separation y^{*}, and the boost y_{b} of the two leading jets in the event enables a kinematical scan of the underlying parton momentum distributions. We compute for the first time the second-order perturbative QCD corrections to this triple-differential dijet cross section, at leading color in all partonic channels, thereby enabling precision studies with LHC dijet data. A detailed comparison with experimental CMS 8 TeV data is performed, demonstrating how the shape of this differential cross section probes the parton densities in different kinematical ranges.

Next-to-Next-to-Leading-Order QCD Corrections to the Transverse Momentum Distribution of Weak Gauge Bosons.

The transverse momentum spectra of weak gauge bosons and their ratios probe the underlying dynamics and are crucial in testing our understanding of the standard model. They are an essential ingredient in precision measurements, such as the W boson mass extraction. To fully exploit the potential of the LHC data, we compute the second-order [next-to-next-to-leading-order (NNLO)] QCD corrections to the inclusive-p_{T}^{W} spectrum as well as to the ratios of spectra for W^{-}/W^{+} and Z/W. We find that the inclusion of NNLO QCD corrections considerably improves the theoretical description of the experimental CMS data and results in a substantial reduction of the residual scale uncertainties.

Next-to-Next-to Leading Order QCD Predictions for Single Jet Inclusive Production at the LHC.

We report the first calculation of fully differential jet production at leading color in all partonic channels at next-to-next-to leading order in perturbative QCD and compare to the available ATLAS 7 TeV data. We discuss the size and shape of the perturbative corrections along with their associated scale variation across a wide range in jet transverse momentum, p_{T}, and rapidity, y. We find significant effects, especially at low p_{T}, and discuss the possible implications for parton distribution function fits.

Precise Predictions for Dijet Production at the LHC.

We present the calculation of dijet production, doubly differential in dijet mass m_{jj} and rapidity difference |y^{*}|, at leading color in all partonic channels at next-to-next-to-leading order (NNLO) in perturbative QCD. We consider the long-standing problems associated with scale choice for dijet production at next-to-leading order (NLO) and investigate the impact of including the NNLO contribution. We find that the NNLO theory provides reliable predictions, even when using scale choices that display pathological behavior at NLO. We choose the dijet invariant mass as the theoretical scale on the grounds of perturbative convergence and residual scale variation and compare the predictions to the ATLAS 7 TeV 4.5 fb^{-1} data.

Precise QCD Predictions for the Production of a Z Boson in Association with a Hadronic Jet.

We compute the cross section and differential distributions for the production of a Z boson in association with a hadronic jet to next-to-next-to-leading order (NNLO) in perturbative QCD, including the leptonic decay of the Z boson. We present numerical results for the transverse momentum and rapidity distributions of both the Z boson and the associated jet at the LHC. We find that the NNLO corrections increase the NLO predictions by approximately 1% and significantly reduce the scale variation uncertainty.

Precise QCD predictions for W-boson production in association with a charm jet.

The production of a W-boson with a charm quark jet provides a highly sensitive probe of the strange quark distribution in the proton. Employing a novel flavour dressing procedure to define charm quark jets, we compute W+charm-jet production up to next-to-next-to-leading order (NNLO) in QCD. We study the perturbative stability of production cross sections with same-sign and opposite-sign charge combinations for the W boson and the charm jet. A detailed breakdown according to different partonic initial states allows us to identify particularly suitable observables for the study of the quark parton distributions of different flavours.

Second-order QCD corrections to jet production at hadron colliders: the all-gluon contribution.

We report the calculation of next-to-next-to-leading order QCD corrections in the purely gluonic channel to dijet production and related observables at hadron colliders. Our result represents the first next-to-next-to-leading order calculation of a massless jet observable at hadron colliders, and opens the path towards precision QCD phenomenology with the LHC.

NNLO QCD predictions for Z-boson production in association with a charm jet within the LHCb fiducial region.

We compute next-to-next-to-leading order (NNLO) QCD corrections to neutral vector boson production in association with a charm jet at the LHC. This process is studied in the forward kinematics at s = 13  TeV, which may provide valuable constraints on the intrinsic charm component of the proton. A comparison is performed between fixed order and NLO predictions matched to a parton shower showing mutual compatibility within the respective uncertainties. NNLO corrections typically lead to a reduction of theoretical uncertainties by a factor of two and the perturbative convergence is further improved through the introduction of a theory-inspired constraint on the transverse momentum of the vector boson plus jet system. A comparison between these predictions with data will require an alignment of a flavour-tagging procedure in theory and experiment that is infrared and collinear safe.

NNLO interpolation grids for jet production at the LHC.

Fast interpolation-grid frameworks facilitate an efficient and flexible evaluation of higher-order predictions for any choice of parton distribution functions or value of the strong coupling α s . They constitute an essential tool for the extraction of parton distribution functions and Standard Model parameters, as well as studies of the dependence of cross sections on the renormalisation and factorisation scales. The APPLfast project provides a generic interface between the parton-level Monte Carlo generator and both the APPLgrid and the fastNLO libraries for the grid interpolation. The extension of the project to include hadron-hadron collider processes at next-to-next-to-leading order in perturbative QCD is presented, together with an application for jet production at the LHC.

Precise determination of the strong coupling constant at NNLO in QCD from the three-jet rate in electron-positron annihilation at LEP.

We present the first determination of the strong coupling constant from the three-jet rate in e{+}e{-} annihilation at LEP, based on a next-to-next-to-leading-order (NNLO) perturbative QCD prediction. More precisely, we extract alpha{s}(M{Z}) by fitting perturbative QCD predictions at O(alpha{s}{3}) to data from the ALEPH experiment at LEP. Over a large range of the jet-resolution parameter y{cut}, this observable is characterized by small nonperturbative corrections and an excellent stability under renormalization scale variation. We find alpha{s}(M{Z})=0.1175+/-0.0020(expt)+/-0.0015(theor), which is more accurate than the values of alpha{s}(M{Z}) from e{+}e{-} event-shape data currently used in the world average.

Vector boson production in association with a jet at forward rapidities.

Final states with a vector boson and a hadronic jet allow one to infer the Born-level kinematics of the underlying hard scattering process, thereby probing the partonic structure of the colliding protons. At forward rapidities, the parton collisions are highly asymmetric and resolve the parton distributions at very large or very small momentum fractions, where they are less well constrained by other processes. Using theory predictions accurate to next-to-next-to-leading order (NNLO) in QCD for both W ± and Z production in association with a jet at large rapidities at the LHC, we perform a detailed phenomenological analysis of recent LHC measurements. The increased theory precision allows us to clearly identify specific kinematical regions where the description of the data is insufficient. By constructing ratios and asymmetries of these cross sections, we aim to identify possible origins of the deviations, and highlight the potential impact of the data on improved determinations of parton distributions.

Calculations for deep inelastic scattering using fast interpolation grid techniques at NNLO in QCD and the extraction of α s from HERA data.

The extension of interpolation-grid frameworks for perturbative QCD calculations at next-to-next-to-leading order (NNLO) is presented for deep inelastic scattering (DIS) processes. A fast and flexible evaluation of higher-order predictions for any a posteriori choice of parton distribution functions (PDFs) or value of the strong coupling constant is essential in iterative fitting procedures to extract PDFs and Standard Model parameters as well as for a detailed study of the scale dependence. The APPLfast project, described here, provides a generic interface between the parton-level Monte Carlo program NNLOjet and both the APPLgrid and fastNLO libraries for the production of interpolation grids at NNLO accuracy. Details of the interface for DIS processes are presented together with the required interpolation grids at NNLO, which are made available. They cover numerous inclusive jet measurements by the H1 and ZEUS experiments at HERA. An extraction of the strong coupling constant is performed as an application of the use of such grids and a best-fit value of α s ( M Z ) = 0.1170 ( 15 ) exp ( 25 ) th is obtained using the HERA inclusive jet cross section data.

Jet rates in electron-positron annihilation at O(alpha(s)3) in QCD.

We compute production rates for two, three, four, and five jets in electron-positron annihilation at the third order in the QCD coupling constant. At this order, three-jet production is described to next-to-next-to-leading order in perturbation theory while the two-jet rate is obtained at next-to-next-to-next-to-leading order. Our results yield an improved perturbative description of the dependence of jet multiplicity on the jet resolution parameter y{cut}, particularly at small values of y{cut}.

Second-order QCD corrections to the thrust distribution in electron-positron annihilation.

We compute the next-to-next-to-leading-order (NNLO) QCD corrections to the thrust distribution in electron-positron annihilation. The corrections turn out to be sizable, enhancing the previously known next-to-leading-order prediction by about 15%. Inclusion of the NNLO corrections significantly reduces the theoretical renormalization scale uncertainty on the prediction of the thrust distribution.