We derive first next-to-next-to-leading logarithmic resummations for jet-veto efficiencies in Higgs and Z-boson production at hadron colliders. Matching with next-to-next-to-leading order results allows us to provide a range of phenomenological predictions for the LHC, including cross-section results, detailed uncertainty estimates and comparisons to current widely-used tools.In searches for new physics at hadron colliders such as the Tevatron and CERN's Large Hadron Collider (LHC), in order to select signal events and reduce backgrounds, events are often classified according to the number of hadronic jets -collimated bunches of energetic hadrons -in the final state. A classic example is the search for Higgs production via gluon fusion with a subsequent decay to. A severe background comes from tt production, whose decay products also include a W + W − pair. However, this background can be separated from the signal because its W + W − pair usually comes together with hard jets, since in each top decay the W is accompanied by an energetic (b) quark.Relative to classifications based on objects such as leptons (used e.g. to identify the W decays), one of the difficulties of hadronic jets is that they may originate not just from the decay of a heavy particle, but also as Quantum Chromodynamic (QCD) radiation. This is the case in our example, where the incoming gluons that fuse to produce the Higgs quite often radiate additional partons. Consequently, while vetoing the presence of jets eliminates much of the tt background, it also removes some fraction of signal events. To fully interpret the search results, including measuring Higgs couplings, it is crucial to be able to predict the fraction of the signal that survives the jet veto, which depends for example on the transverse momentum threshold p t,veto used to identify vetoed jets.One way to evaluate jet-veto efficiencies is to use a fixed-order perturbative expansion in the strong coupling α s , notably to next-next-to-leading order (NNLO), as in the Higgs-boson production calculations of [3][4][5]. Such calculations however become unreliable for p t,veto ≪ M , with M the boson mass, since large terms α n s L 2n appear (L = ln(M/p t,veto )) in the cross-section to all orders in the coupling constant. These enhanced classes of terms can, however, be resummed to all orders in the coupling, often involving a functional form .).There exist next-to-next-to-leading logarithmic (NNLL) resummations, involving the g n (α s L) functions up to and including g 3 , for a number of quantities that are more inclusive than a jet veto: e.g. a Higgs or vector-boson transverse momentum [6][7][8][9], the beam thrust [10], and related observables [11,12]. To obtain estimates for jet vetoes, some of these calculations have been compared to or used to reweight [10,[13][14][15][16] parton-shower predictions [17,18] matched to NLO results [19,20]. However, with reweighting, neither the NNLO nor NNLL accuracy of the original calculation carry through to the jet veto prediction.Recently ther...

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We present an approach to the momentum-space resummation of global, recursively infrared and collinear safe observables that can vanish away from the Sudakov region. We focus on the hadro-production of a generic colour singlet, and we consider the class of observables that depend only upon the total transverse momentum of the radiation, prime examples being the transverse momentum of the singlet, and φ * in Drell-Yan pair production. We derive a resummation formula valid up to next-to-next-to-next-to-leading-logarithmic accuracy for the considered class of observables. We use this result to compute state-of-the-art predictions for the Higgs-boson transverse-momentum spectrum at the LHC at next-to-next-to-next-to-leading-logarithmic accuracy matched to fixed next-to-next-to-leading order. Our resummation formula reduces exactly to the customary resummation performed in impact-parameter space in the known cases, and it also predicts the correct power-behaved scaling of the cross section in the limit of small value of the observable. We show how this formalism is efficiently implemented by means of Monte Carlo techniques in a fully exclusive generator that allows one to apply arbitrary cuts on the Born variables for any colour singlet, as well as to automatically match the resummed results to fixed-order calculations. arXiv:1705.09127v3 [hep-ph] 15 May 2018 2 Derivation of the master formulaWe consider the resummation of a continuously global, recursive infrared and collinear (rIRC) safe [41] observable V in the reaction pp → B, B being a generic colourless system with high invariant mass M . It is instructive to work out in detail the case of NLL resummation first. This will be done in Section 2.1, where we assume that the parton densities are independent of the scale. We then discuss the inclusion of higher-order corrections in Section 2.3, and the correct treatment of the parton luminosity will be dealt with in Section 2.3.2. Finally, in Section 2.4, we discuss the connection to the impact-parameter space formulation for transverse-momentum resummation.

We present a novel method to combine QCD calculations at next-to-next-toleading order (NNLO) with parton shower (PS) simulations, that can be applied to the production of heavy systems in hadronic collisions, such as colour singlets or a tt pair. The NNLO corrections are included by connecting the MiNLO method with transversemomentum resummation, and they are calculated at generation time without any additional reweighting, making the algorithm considerably efficient. Moreover, the combination of different jet multiplicities does not require any unphysical merging scale, and the matching preserves the structure of the leading logarithmic corrections of the Monte Carlo simulation for parton showers ordered in transverse momentum. We present proof-of-concept applications to hadronic Higgs production and the Drell-Yan process at the LHC.

Parton showers are among the most widely used tools in collider physics. Despite their key importance, none so far have been able to demonstrate accuracy beyond a basic level known as leading logarithmic order, with ensuing limitations across a broad spectrum of physics applications. In this Letter, we propose criteria for showers to be considered next-to-leading logarithmic accurate. We then introduce new classes of shower, for final-state radiation, that satisfy the main elements of these criteria in the widely used large-N C limit. As a proof of concept, we demonstrate these showers' agreement with all-order analytical next-to-leading logarithmic calculations for a range of observables, something never so far achieved for any parton shower.