Search

We analyze the low-energy dynamics of gap-between-jets cross sections at hadron colliders, for which phase factors in the hard amplitudes spoil collinear cancellations and lead to double (``super-leading'') logarithmic behavior. Based on a method-of-regions analysis, we identify three-loop contributions from perturbative active-active Glauber-gluon exchanges with the right structure to render the cross section consistent with PDF factorization below the gap veto scale. The Glauber contributions we identify are unambiguously defined without regulators beyond dimensional regularization., Comment: 7 pages, 3 figures

We discuss recent developments in descriptions of processes using power expansion around the lightcone within Soft-Collinear Effective Theory. First, we present an overview of the systematically improvable framework that enables factorization of high-energy scattering processes beyond leading power in the expansion in ratios of energy scales. As an illustration of the relevant concepts, we describe the recently derived factorization theorem for the off-diagonal channel of the Drell-Yan production process at threshold. This example exposes endpoint divergences appearing in convolution integrals in factorization formulas. Lastly, we discuss the solution to these complications developed in the context of ''gluon thrust'' in $e^+e^-$ collisions., Comment: Extended version of the contribution to Matter To The Deepest: Recent Developments In Physics Of Fundamental Interactions XLV International Conference of Theoretical Physics, 2023

We present a factorization theorem of the partonic Drell-Yan off-diagonal processes $g\bar{q}\,(qg) \to \gamma^* + X$ in the kinematic threshold regime $z=Q^2/\hat{s} \to 1$ at general subleading powers in the $(1-z)$ expansion. Focusing on the first order of the expansion (next-to-leading power accuracy with respect to the leading power $q \bar{q}$ channel), we validate the bare factorization formula up to $\mathcal{O}(\alpha^2_s)$. This is achieved by carrying out an explicit calculation of the generalized soft function in $d$-dimensions using the reduction to master integrals and the differential equations method. The collinear function is a universal object which we compute from an operator matching equation at one-loop level. Next, we integrate the soft and collinear functions over the convolution variables and remove the remaining initial state collinear singularities through PDF renormalization. The resulting expression agrees with the known cross section in the literature., Comment: 44 pages, 8 figures. Matches published version

We present a method of merging the exclusive LO-matched high energy resummation of High Energy Jets (HEJ) with the parton shower of Pythia which preserves the accuracy of the LO cross sections and the logarithmic accuracy of both resummation schemes across all of phase space. Predictions produced with this merging prescription are presented with comparisons to data from experimental studies and suggestions are made for further observables and experimental cuts which highlight the importance of both high energy and soft-collinear effects., Comment: Proceedings of 51st International Symposium on Multiparticle Dynamics (ISMD2022)

The wealth of experimental data collected at laboratory experiments suggests that there is some scale separation between the Standard Model (SM) and phenomena beyond the SM (BSM). New phenomena can manifest itself as small corrections to SM predictions, or as signals in processes where the SM predictions vanish or are exceedingly small. This makes precise calculations of the SM expectations essential, in order to maximize the sensitivity of current and forthcoming experiments to BSM physics. This topical group report highlights some past and forthcoming theory developments critical for maximizing the sensitivity of the experimental program to understanding Nature at the shortest distances., Comment: 36 pages, 2 figures. Report of the TF06 topical group for Snowmass 2021. V2: minor updates

Endpoint divergences in the convolution integrals appearing in next-to-leading-power factorization theorems prevent a straightforward application of standard methods to resum large logarithmic power-suppressed corrections in collider physics. We study the power-suppressed configuration of the thrust distribution in the two-jet region, where a gluon-initiated jet recoils against a quark-antiquark pair. With the aid of operatorial endpoint factorization conditions, we derive a factorization formula where the individual terms are free from endpoint divergences and can be written in terms of renormalized hard, (anti) collinear, and soft functions in four dimensions. This framework enables us to perform the first resummation of the endpoint-divergent SCET$_{\rm I}$ observables at the leading logarithmic accuracy using exclusively renormalization-group methods., Comment: Contribution to the Proceedings of "Loops and Legs in Quantum Field Theory - LL2022", 25-30 April, 2022, Ettal, Germany

Resummation techniques are essential for high-precision phenomenology at current and future high-energy collider experiments. Perturbative computations of cross sections often suffer from large logarithmic corrections, which must be resummed to all orders to restore the reliability of predictions from first principles. The precise understanding of the all-order structure of field theories allows for fundamental tests of the Standard Model and new physics searches. In this white paper, we review recent progress in modern resummation techniques and outline future directions. In particular, we focus on the resummation beyond leading power, the joint resummation of different classes of logarithms relevant for jets and their substructure, small-$x$ resummation in the high-energy regime and the QCD fragmentation process in the small-$z_h$ limit., Comment: Contribution to Snowmass 2021

We calculate the generalized soft functions at $\mathcal{O}(\alpha_s^2)$ at next-to-leading power accuracy for the Drell-Yan process at threshold. The operator definitions of these objects contain explicit insertions of soft gauge and matter fields, giving rise to a dependence on additional convolution variables with respect to the leading power result. These soft functions constitute the last missing ingredient for the validation of the bare factorization theorem to NNLO accuracy. We carry out the calculations by reducing the soft squared amplitudes into a set of canonical master integrals and we employ the method of differential equations to evaluate them. We retain the exact $d$-dimensional dependence of the convolution variables at the integration boundaries in order to regulate the fixed-order convolution integrals. After combining our soft functions with the relevant collinear functions, we perform checks of the results at the cross-section level against the literature and expansion-by-regions calculations, at NNLO and partly at N$^3$LO, finding agreement., Comment: 32 pages, 4 figures

The off-diagonal parton-scattering channels $g+\gamma^*$ and $q+\phi^*$ in deep-inelastic scattering are power-suppressed near threshold $x\to 1$. We address the next-to-leading power (NLP) resummation of large double logarithms of $1-x$ to all orders in the strong coupling, which are present even in the off-diagonal DGLAP splitting kernels. The appearance of divergent convolutions prevents the application of factorization methods known from leading power resummation. Employing $d$-dimensional consistency relations from requiring $1/\epsilon$ pole cancellations in dimensional regularization between momentum regions, we show that the resummation of the off-diagonal parton-scattering channels at the leading logarithmic order can be bootstrapped from the recently conjectured exponentiation of NLP soft-quark Sudakov logarithms. In particular, we derive a result for the DGLAP kernel in terms of the series of Bernoulli numbers found previously by Vogt directly from algebraic all-order expressions. We identify the off-diagonal DGLAP splitting functions and soft-quark Sudakov logarithms as inherent two-scale quantities in the large-$x$ limit. We use a refactorization of these scales and renormalization group methods inspired by soft-collinear effective theory to derive the conjectured soft-quark Sudakov exponentiation formula., Comment: 50 pages, LaTeX

We present the next-to-leading power (NLP) factorization formula for the $q\bar{q}\to \gamma^*+X$ channel of the Drell-Yan production near the kinematic threshold limit. The formalism used for the computation of next-to-leading power corrections within soft-collinear effective field theory is introduced, we discuss the emergence of new objects, the NLP collinear functions, and define them through an operator matching equation. We review the leading power factorization before extending it to subleading powers. We also present the one-loop result for the newly introduced collinear function, and demonstrate explicitly conceptual issues in performing next-to-leading logarithmic resummation at next-to-leading power., Comment: 12 pages, contribution to the proceedings of the 14th International Symposium on Radiative Corrections (RADCOR2019), 9-13 September 2019, Avignon, France. Based on arXiv: 1912.01585

We present a factorization theorem valid near the kinematic threshold $z=Q^2/\hat{s}\to 1$ of the partonic Drell-Yan process $q\bar q\to\gamma^*+X$ for general subleading powers in the $(1-z)$ expansion. We then consider the specific case of next-to-leading power. We discuss the emergence of collinear functions, which are a key ingredient to factorization starting at next-to-leading power. We calculate the relevant collinear functions at $\mathcal{O}(\alpha_s)$ by employing an operator matching equation and we compare our results to the expansion-by-regions computation up to the next-to-next-to-leading order, finding agreement. Factorization holds only before the dimensional regulator is removed, due to a divergent convolution when the collinear and soft functions are first expanded around $d=4$ before the convolution is performed. This demonstrates an issue for threshold resummation beyond the leading-logarithmic accuracy at next-to-leading power., Comment: Matches published version

We sum the leading logarithms $\alpha_s^n \ln^{2 n-1}(1-z)$, n=1,2,... near the kinematic threshold $z=m_H^2/\hat{s}\to 1$ at next-to-leading power in the expansion in (1-z) for Higgs production in gluon fusion. We highlight the new contributions compared to Drell-Yan production in quark-antiquark annihilation and show that the final result can be obtained to all orders by the substitution of the colour factor $C_F\to C_A$, confirming previous fixed-order results and conjectures. We also provide a numerical analysis of the next-to-leading power leading logarithms, which indicates that they are numerically relevant., Comment: 19 pages, 2 figures, and 2 tables

We resum the leading logarithms $\alpha_s^n \ln^{2 n-1}(1-z)$, $n=1,2,\ldots$ near the kinematic threshold $z=Q^2/\hat{s}\to 1$ of the Drell-Yan process at next-to-leading power in the expansion in $(1-z)$. The derivation of this result employs soft-collinear effective theory in position space and the anomalous dimensions of subleading-power soft functions, which are computed. Expansion of the resummed result leads to the leading logarithms at fixed loop order, in agreement with exact results at NLO and NNLO and predictions from the physical evolution kernel at N$^3$LO and N$^4$LO, and to new results at the five-loop order and beyond., Comment: 40 pages, 3 figures, v2: matching the published version in JHEP