Vector boson production in joint resummation

We study the transverse momentum ($Q_T$) distribution of an electro-weak vector boson produced via the Drell-Yan mechanism, in the context of joint resummation. This formalism allows for the simultaneous resummation of logarithmic contributions that are enhanced at small $Q_T$ and at partonic threshold. We extend joint resummation to next-to-next-to leading logarithmic accuracy and we present resummed and matched results for three different phenomenological setups. In particular, we study the production of a $Z$ boson at the Tevatron and at the Large Hadron Collider (LHC), as well as the production of a heavier $Z^\prime$ at the LHC. We compare our findings to standard $Q_T$ resummation, as well as to fixed-order perturbation theory. We find that joint resummation provides a moderate (but not flat) correction with respect to $Q_T$ resummation and it leads to a reduction of the scale dependence of the results. However, our study also shows some limitations of this formalism. While the use of joint resummation for $Z$ production at the Tevatron and $Z^\prime$ production at the LHC appears to be justified, our implementation suffers from a stronger dependence on power corrections for processes which are further away from threshold, such as $Z$ production at the LHC, for which we cannot claim an improvement over standard $Q_T$ resummation.Comment: 28 pages, 10 figures, published versio

Soft gluon resummation for associated ttˉHt \bar{t} H production at the LHC

We perform resummation of soft gluon corrections to the total cross section for the process $pp \to t\bar{t}H$. The resummation is carried out at next-to-leading-logarithmic (NLL) accuracy using the Mellin space technique, extending its application to the class of $2 \to 3$ processes. We present an analytical result for the soft anomalous dimension for a hadronic production of two coloured massive particles in association with a colour singlet. We discuss the impact of resummation on the numerical prediction for the associated Higgs boson production with top quarks at the LHC.Comment: 11 pages, 4 figure

Improving predictions for associated ttˉHt\bar{t} H production at the LHC : soft gluon resummation through NNLL accuracy

In the following we present our recent results on the resummation of soft gluon corrections to the $pp\rightarrow t\bar{t}H$ cross section at the LHC. The resummation was carried out at next-to-next-to-leading-logarithmic (NNLL) accuracy using the Mellin space technique. Obtained results were matched to the NLO cross section. We show that the resummation leads to reduction of scale-variation uncertainty of the total $pp\rightarrow t\bar{t}H$ cross section.Comment: 6 pages, 1 figure, 1 table, proceedings prepared for the European Physical Society Conference on High Energy Physics (EPS-HEP 2017), 5-12 July 2017, Venice, Ital

Associated ttˉHt \bar{t} H production at the LHC: theoretical predictions at NLO+NNLL accuracy

We perform threshold resummation of soft gluon corrections to the total cross section and the invariant mass distribution for the process $pp \to t\bar{t}H$. The resummation is carried out at next-to-next-to-leading-logarithmic (NNLL) accuracy using the direct QCD Mellin space technique in the three-particle invariant mass kinematics. After presenting analytical expressions we discuss the impact of resummation on the numerical predictions for the associated Higgs boson production with top quarks at the LHC. We find that NLO+NNLL resummation leads to predictions for which the central values are remarkably stable with respect to scale variation and for which theoretical uncertainties are reduced in comparison to NLO predictions.Comment: 21 pages, 9 figures; NNLL results accounting now for color decomposition of the one-loop hard function, discussion of the literature added, typos correcte

Soft gluon resummation for gluon-induced Higgs Strahlung

We study the effect of soft gluon emission on the total cross section predictions for the $gg\to HZ$ associated Higgs production process at the LHC. To this end, we perform resummation of threshold corrections at the NLL accuracy in the absolute threshold production limit and in the threshold limit for production of a $ZH$ system with a given invariant mass. Analytical results and numerical predictions for various possible LHC collision energies are presented. The perturbative stability of the results is verified by including universal NNLL effects. We find that resummation significantly reduces the scale uncertainty of the $gg\to HZ$ contribution, which is the dominant source of perturbative uncertainty to $ZH$ production. We use our results to evaluate updated numbers for the total inclusive cross section of associated $pp \to ZH$ production at the LHC. The reduced scale uncertainty of the $gg\to HZ$ component translates into a decrease of the overall scale error by about a factor of two.Comment: 22 pages, 4 figures, 2 table

Soft gluon resummation for the associated production of a top quark pair with a W boson at the LHC

We present our results on soft gluon resummation in the invariant mass threshold applied to the associated production of a top quark pair with a W boson at the LHC in the Mellin space formalism.Comment: 6 pages, 4 figures, 1 table, proceedings prepared for the European Physical Society Conference on High Energy Physics (EPS-HEP 2017), 5-12 July 2017, Venice, Ital

Associated top-pair production with a heavy boson production through NLO+NNLL accuracy at the LHC

In this talk we present results of our recent calculations of cross sections and distributions for the associate production of top-antitop quark pairs with a heavy boson (Higgs, W, Z) at the LHC, obtained using threshold resummation in direct QCD, i.e. in the Mellin-space approach.Comment: 4 pages, 6 figures, contribution to the 2019 QCD session of the 54th Rencontres de Morion

Associated top quark pair production with a heavy boson: differential cross sections at NLO+NNLL accuracy

We present theoretical predictions for selected differential cross sections for the process $pp \to t \bar{t} B$ at the LHC, where $B$ can be a Higgs ($H$), a $Z$ or a $W$ boson. The predictions are calculated in the direct QCD framework up to the next-to-next-leading logarithmic (NNLL) accuracy and matched to the complete NLO results including QCD and electroweak effects. Additionally, results for the total cross sections are provided. The calculations deliver a significant improvement of the theoretical predictions, especially for the $t \bar{t} H$ and the $t \bar{t} Z$ production. In these cases, predictions for both the total and differential cross sections are remarkably stable with respect to the central scale choice and carry a substantially reduced scale uncertainty in comparison with the complete NLO predictions.Comment: 28 pages, 23 figures; Published versio

Top Precision for Associated Top-Pair Production Processes at the LHC

The studies of the associated production processes of a top-quark pair with a colour-singlet boson, e.g. Higgs, W or Z, are among the highest priorities of the LHC programme. Correspondingly, improvements in precision of theoretical predictions for these processes are of central importance. In this talk, we review our latest results on resummation of soft gluon corrections. The resummation is carried out using the direct QCD Mellin space technique in three-particle invariant mass kinematics. We discuss the impact of the soft gluon corrections on predictions for total cross sections and differential distributions.Comment: 12 pages, 9 figures, proceedings of the XXVI Cracow Epiphany Conference on LHC Physics: Standard Model and Beyond, to be published in Acta Physica Polonica