We perform a case study of the behavior gluon radiation beyond soft approximation, using as an example Drell-Yan production cross section at NNLO. draw careful distinction between eikonal expansion, which is in powers energies, and expansion threshold variable $1 - z$, involves important hard-collinear effects. Focusing on contribution to NNLO K-factor arising from real-virtual interference, we use method regions classify all relevant contributions up next-to-leading power expansion. With...

Threshold logarithms become dominant in partonic cross sections when the selected final state forces gluon radiation to be soft or collinear. Such factorizes at level of scattering amplitudes, and this leads resummation threshold which appear leading power variable. In paper, we consider extension factorization include effects suppressed by a single Building upon Low-Burnett-Kroll-Del Duca (LBKD) theorem, propose decomposition radiative amplitudes into universal building blocks, contain all...

We resum the leading logarithms $\alpha_s^n \ln^{2 n-1}(1-z)$, $n=1,2,\ldots$ near kinematic threshold $z=Q^2/\hat{s}\to 1$ of Drell-Yan process at next-to-leading power in expansion $(1-z)$. The derivation this result employs soft-collinear effective theory position space and anomalous dimensions subleading-power soft functions, which are computed. Expansion resummed leads to fixed loop order, agreement with exact results NLO NNLO predictions from physical evolution kernel N$^3$LO N$^4$LO,...

A bstract We present a factorization theorem valid near the kinematic threshold $$ z={Q}^2/\hat{s}\to 1 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>z</mml:mi> <mml:mo>=</mml:mo> <mml:msup> <mml:mi>Q</mml:mi> <mml:mn>2</mml:mn> </mml:msup> <mml:mo>/</mml:mo> <mml:mover> <mml:mi>s</mml:mi> <mml:mo>̂</mml:mo> </mml:mover> <mml:mo>→</mml:mo> <mml:mn>1</mml:mn> </mml:math> of partonic Drell-Yan process q\overline{q}\to {\gamma}^{\ast }+X <mml:mi>q</mml:mi> <mml:mo>¯</mml:mo>...

We sum the leading logarithms $\alpha_s^n \ln^{2 n-1}(1-z)$, n=1,2,... near kinematic threshold $z=m_H^2/\hat{s}\to 1$ at next-to-leading power in expansion (1-z) for Higgs production gluon fusion. highlight new contributions compared to Drell-Yan quark-antiquark annihilation and show that final result can be obtained all orders by substitution of colour factor $C_F\to C_A$, confirming previous fixed-order results conjectures. also provide a numerical analysis logarithms, which indicates...

Considering $2\to 2$ gauge-theory scattering with general colour in the high-energy limit, we compute Regge-cut contribution to three loops through next-to-next-to-leading logarithms (NNLL) signature-odd sector. Our formalism is based on using non-linear Balitsky-JIMWLK rapidity evolution equation derive an effective Hamiltonian acting states a fixed number of Reggeized gluons. A new effect occurring first at NNLL mixing between $k$ and $k+2$ gluons due non-diagonal terms this Hamiltonian....

We study the phenomenology of simplified ${Z}^{\ensuremath{'}}$ models with a global $U(2{)}^{3}$ flavor symmetry in quark sector, broken solely by Standard Model Yukawa couplings. This symmetry, known as less-minimal violation, protects $\mathrm{\ensuremath{\Delta}}F=2$ processes from dangerously large new physics (NP) effects and at same time provides free complex phase $b\ensuremath{\rightarrow}s$ transitions, allowing for an explanation hints additional direct $CP$ violation kaon decays...

The lack of convergence the convolution integrals appearing in next-to-leading-power (NLP) factorization theorems prevents applications existing methods to resum power-suppressed large logarithmic corrections collider physics. We consider thrust distribution two-jet region for flavour-nonsinglet off-diagonal contribution, where a gluon-initiated jet recoils against quark-antiquark pair, which is power-suppressed. With help operatorial endpoint conditions, we obtain formula, individual terms...

Soft and collinear radiation is responsible for large corrections to many hadronic cross sections, near thresholds the production of heavy final states. There much interest in extending our understanding this next-to-leading power (NLP) threshold expansion. In paper, we generalise a previously proposed all-order NLP factorisation formula include non-abelian corrections. We define nonabelian radiative jet function, organising enhancements at NLP, compute it quark jets one loop. discuss detail...

Perturbative cross-sections in QCD are beset by logarithms of kinematic invariants, whose arguments vanish when heavy particles produced near threshold. Contributions this type often need to be summed all orders the coupling, order improve behaviour perturbative expansion, and it has long been known how do at leading power threshold variable, using a variety approaches. Recently, problem extending resummation suppressed single variable received considerable attention. In paper, we show that...

Recent progress in our understanding of infrared singularities multi-parton amplitudes has shown that the simplest form Regge factorization for high-energy gauge-theory fails starting at next-to-next-to-leading logarithmic accuracy. We provide a framework to organize calculation parton leading power t/s, terms factorizing and non-factorizing contributions. This allows us give explicit expressions Reggeization-breaking two-loop three-loop quark gluon QCD. In particular, using only...

There are strong similarities between charge-parity ($CP$) violating observables in hadronic $B$ decays (in particular $\mathrm{\ensuremath{\Delta}}{A}_{CP}^{\ensuremath{-}}$ $B\ensuremath{\rightarrow}K\ensuremath{\pi}$) and direct $CP$ violation kaon (${\ensuremath{\epsilon}}^{\ensuremath{'}}$): All these very sensitive to new physics (NP) which is at the same time isospin (i.e., NP with complex couplings different for up quarks down quarks). Intriguingly, both measurements of...

A bstract The off-diagonal parton-scattering channels g + γ * and q ϕ in deep-inelastic scattering are power-suppressed near threshold x → 1. We address the next-to-leading power (NLP) resummation of large double logarithms 1 − to all orders strong coupling, which present even DGLAP splitting kernels. appearance divergent convolutions prevents application factorization methods known from leading resummation. Employing d -dimensional consistency relations requiring /ϵ pole cancellations...

A bstract Using rapidity evolution equations we study two-to-two gauge-theory scattering amplitudes in the Regge limit. We carry out explicit computations at next-to-next-to-leading logarithmic accuracy through four loops and present new results for both infrared-singular finite contributions to amplitude. New techniques are devised order derive colour structure stemming from three-Reggeon exchange diagrams terms of commutators channel operators, obtaining that valid any gauge group, apply...

The high-energy limit of gauge-theory amplitudes features both a Regge pole and cuts. We show how to disentangle these, hence determine the trajectory beyond two loops. While nonplanar part multiple Reggeon t-channel exchange forms cut, planar contributes along with single Reggeon. With this, we find that infrared singularities are given by cusp anomalous dimension. By matching recent QCD results, quark gluon impact factors loops three

A bstract We perform an analysis of the one- and two-loop massive quark form factor in QED a region expansion, up to next-to-leading power mass. This yields extensive set regional integrals, categorized into three topologies, against which factorization theorems at could be tested. Our reveals number subtle aspects involving rapidity regulators, as well additional regions that manifest themselves only beyond one loop, level single diagrams, but cancel factor.

A bstract We consider the production of an arbitrary number colour-singlet particles near partonic threshold, and show that next-to-leading order cross sections for this class processes have a simple universal form at power (NLP) in energy emitted gluon radiation. Our analysis relies on recently derived factorisation formula NLP threshold effects amplitude level, therefore applies both if leading-order process is tree-level it loop-induced. It holds differential distributions as well. The...

We provide a complete and detailed study of the high-energy limit four-parton scattering amplitudes in QCD, giving explicit results at two loops higher orders, going beyond next-to-leading logarithmic (NLL) accuracy. Building upon recent results, we use techniques infrared factorization to investigate failure simplest form Regge factorization, starting next-to-next-to-leading accuracy (NNLL) ln(s/|t|). accounts expressions for terms responsible this breaking case two-loop three-loop quark...

We generalize the factorization of Abelian gauge theory amplitudes to next-to-leading power (NLP) in a soft scale expansion, following recent generalization for Yukawa theory. From an all-order counting analysis leading and regions, we infer factorized structure both parametrically small zero fermion mass. This requires introduction new universal jet functions, nonradiative single-radiative QED amplitudes, which compute at one-loop order. show that our formula reproduces relevant regions...

We study next-to-leading-power (NLP) threshold corrections in colour-singlet production processes, with particular emphasis on Drell-Yan (DY) and single-Higgs production. assess the quality of partonic hadronic expansions for each process up to NNLO. determine numerically NLP leading-logarithmic (LL) resummed contribution addition leading-power next-to-next-to-leading logarithmic (LP NNLL) DY Higgs cross sections, matched find that inclusion logarithms is more relevant than increasing...

A bstract We present a factorization theorem of the partonic Drell-Yan off-diagonal processes $$ g\overline{q}(qg)\to {\gamma}^{\ast }+X <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mi>g</mml:mi> <mml:mover> <mml:mi>q</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> <mml:mfenced> <mml:mi>qg</mml:mi> </mml:mfenced> <mml:mo>→</mml:mo> <mml:msup> <mml:mi>γ</mml:mi> <mml:mo>∗</mml:mo> </mml:msup> <mml:mo>+</mml:mo> <mml:mi>X</mml:mi> </mml:math> in kinematic threshold regime...

A bstract Scattering amplitudes of partons in QCD contain infrared divergences which can be resummed to all orders terms an anomalous dimension. Independently, the limit high-energy forward scattering, large logarithms energy using Balitsky-Fadin-Kuraev-Lipatov theory. We use latter analyse infraredsingular part perturbation theory and next-to-leading-logarithm accuracy limit, resumming two-Reggeon contribution. Remarkably, we find a closed form for infrared-singular part, predicting Regge...