Gionata Luisoni

Antenna subtraction at NNLO with hadronic initial states: initial-final configurations

We extend the antenna subtraction method to include initial states containing one hadron at NNLO. We present results for all the necessary subtraction terms, antenna functions, for the master integrals required to integrate them over the relevant phase space and finally for the integrated antennae themselves. Where applicable, our results are cross-checked against the known NNLO coefficient functions for deep inelastic scattering processes.

Determination of the strong coupling constant using matched NNLO+NLLA predictions for hadronic event shapes in e+e− annihilations

We present a determination of the strong coupling constant from a fit of QCD predictions for six event-shape variables, calculated at next-to-next-to-leading order (NNLO) and matched to resummation in the next-to-leading-logarithmic approximation (NLLA). These event shapes have been measured in e+e? annihilations at LEP, where the data we use have been collected by the ALEPH detector at centre-of-mass energies between 91 and 206 GeV. Compared to purely fixed order NNLO fits, we observe that the central fit values are hardly affected, but the systematic uncertainty is larger because the NLLA part re-introduces relatively large uncertainties from scale variations. By combining the results for six event-shape variables and eight centre-of-mass energies, we find ?s(MZ) = 0.1224???0.0009?(stat)???0.0009?(exp)???0.0012?(had)???0.0035?(theo), which improves previously published measurements at NLO+NLLA. We also carry out a detailed investigation of hadronisation corrections, using a large set of Monte Carlo generator predictions.

Two-loop soft corrections and resummation of the thrust distribution in the dijet region

The thrust distribution in electron-positron annihilation is a classical precision QCD observable. Using renormalization group (RG) evolution in Laplace space, we perform the resummation of logarithmically enhanced corrections in the dijet limit, T → 1 to next-to-next-to-leading logarithmic (NNLL) accuracy. We independently derive the two-loop soft function for the thrust distribution and extract an analytical expression for the NNLL resummation coefficient g3. Our findings confirm earlier NNLL resummation results for the thrust distribution in soft-collinear effective theory. To combine the resummed expressions with the fixed-order results, we derive the log(R)-matching and R-matching of the NNLL approximation to the fixed-order NNLO distribution.

Multi-leg one-loop massive amplitudes from integrand reduction via Laurent expansion

A bstractWe present the application of a novel reduction technique for one-loop scattering amplitudes based on the combination of the integrand reduction and Laurent expansion. We describe the general features of its implementation in the computer code Ninja, and its interface to GoSam. We apply the new reduction to a series of selected processes involving massive particles, from six to eight legs.

Power corrections in the dispersive model for a determination of the strong coupling constant from the thrust distribution

In the context of the dispersive model for non-perturbative corrections, we extend the leading renormalon subtraction to NNLO for the thrust distribution in e+e− annihilation. Within this framework, using a NNLL+NNLO perturbative description and including bottom-quark mass effects to NLO, we analyse data in the centre-of-mass energy range

Matching NLLA + NNLO for event shape distributions

\sqrt{s}=14\mbox{--}206~\mbox{GeV}

GoSam: A program for automated one-loop calculations

in view of a simultaneous determination of the strong coupling constant and the non-perturbative parameter α0. The fits are performed by matching the resummed and fixed-order predictions both in the R and the log-R matching schemes. The final values in the R scheme are

Multi-loop Integrand Reduction via Multivariate Polynomial Division

\alpha_{s}(M_{Z}) = 0.1131^{+0.0028}_{-0.0022}

Determining alpha_s at NNLO from event-shape data

,

Finite mass effects in Higgs production in association with jets

\alpha_{0}(2~\mathrm{GeV}) = 0.538^{+0.102}_{-0.047}