Article
Physics, Particles & Fields
Stefano Frixione, Bryan R. Webber
Summary: This article discusses how color flows can simplify the computation of matrix elements and enable parton shower Monte Carlos to achieve accuracy beyond leading color. By systematically employing these color flows, tree-level matrix elements and their soft limits can be given in a closed form that does not require any color algebra. Additionally, the study examines how color loops and dipole graphs can help extend the accuracy of Monte Carlos by including subleading-color effects.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Daniel de Florian, Ignacio Fabre, Gudrun Heinrich, Javier Mazzitelli, Ludovic Scyboz
Summary: This study combines NLO predictions with full top-quark mass dependence with approximate NNLO predictions for Higgs-boson pair production in gluon fusion. It examines the impact of anomalous couplings on various observables and provides numerical coefficients for the approximate NNLO cross section as a function of the anomalous couplings at root s = 14TeV.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Dhimiter D. Canko, Costas G. Papadopoulos, Nikolaos Syrrakos
Summary: Analytic expressions for three families of planar two-loop five-point Master Integrals with one off-shell leg are presented in terms of polylogarithmic functions, using the Simplified Differential Equations approach. The results are relevant for studying various 2 -> 3 scattering processes at the LHC, particularly for leading-color W + 2 jets production.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Bakul Agarwal, Stephen P. Jones, Andreas von Manteuffel
Summary: This study calculates the two-loop QCD corrections to gg -> ZZ involving a closed top-quark loop using a new method, with the amplitude expressed in terms of finite integrals derived by employing syzygies. Numerical integration results show agreement with previous expansions in asymptotic limits and provide ab initio results for intermediate partonic energies and non-central scattering at higher energies.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Luca Buonocore, Paolo Nason, Francesco Tramontano, Giulia Zanderighi
Summary: This study examines several basic photon and lepton-initiated processes at the LHC, utilizing recently developed photon and lepton parton densities for computation. The comparison of different calculation methods and their application in searching for exotic particles and observing Standard-Model processes are discussed.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Matthias Heller, Andreas von Manteuffel, Robert M. Schabinger, Hubert Spiesberger
Summary: The study focuses on the qq-initiated two-loop electroweak-QCD Drell-Yan scattering amplitude with vanishing light quark and lepton masses using dimensional regularization schemes. It is found that the infrared pole terms of the mixed two-loop amplitude are controlled by a known generalization of the dipole formula, and that exactly the same two-loop polarized hard scattering functions are obtained in both the standard 't Hooft-Veltman-Breitenlohner-Maison gamma(5) scheme and Kreimer's anticommuting gamma(5) scheme.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Fabrizio Caola, Silvia Ferrario Ravasio, Giovanni Limatola, Kirill Melnikov, Paolo Nason
Summary: In this study, we investigate the impact of linear power corrections related to QCD on certain collider observables. By presenting arguments, we conclude that such corrections do not appear in inclusive observables with respect to QCD radiation. Although our study is conducted in a simplified framework, the results can be applied, to some extent, to processes in both lepton and hadron colliders.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Simone Alioli, Alessandro Broggio, Matthew A. Lim
Summary: We study the resummation of the 0-jettiness resolution variable tau(0) for the top-quark pair production process in hadronic collisions. Starting from an effective theory framework, we derive a factorisation formula for this observable and calculate its corrections. By matching with fixed order calculations, we obtain the most accurate prediction for the process.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Jeffrey R. Forshaw, Jack Holguin
Summary: In QCD, coherence violation is an interesting and counter-intuitive phenomenon, almost all observables sensitive to soft radiation at hadron colliders will violate coherence to some degree.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Anatoly Radyushkin, Shuai Zhao
Summary: This study presents one-loop corrections for the newly introduced gluon condensate PDF F(x) and provides the expression for the gg-part of its evolution kernel. By strictly adhering to gauge invariance requirements and utilizing on-shell states, it was discovered that there were terms such as q^2δ(x) found for the ξ = 0 GPD F(x, q^2) at nonzero momentum transfer q. The results did not align with the original attempt of one-loop calculations for gluon states, indicating caution for calculations using matrix elements with virtual external gluons.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Daniele Lombardi, Marius Wiesemann, Giulia Zanderighi
Summary: This study computes the NNLO+PS predictions for W+W- production in hadronic collisions, matching them consistently with parton showers using the MINNLOPS method. By including spin correlations, interferences, and off-shell effects, the evaluation time of the two-loop contribution has been significantly reduced. The results show good agreement with experimental measurements from ATLAS and CMS, highlighting the importance of NNLO corrections and matching to parton showers for an accurate simulation of W+W- events.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Martin Beneke, Philipp Boer, Jan-Niklas Toelstede, K. Keri Vos
Summary: This paper discusses the generalization of the leading-twist light-cone distribution amplitude for light mesons including QED effects and its renormalization group evolution at the strong-interaction scale Lambda(QCD). For charged mesons, there are qualitative differences in scale evolution between QCD and QED-generalized, especially regarding the endpoint behavior. The evolution equation is analytically solved to first order in the electromagnetic coupling alpha(em), which resums large logarithms in QCD while providing numerical estimates for QED corrections to Gegenbauer coefficients and inverse moments relevant to (QED-generalized) factorization theorems for hard exclusive processes.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
C. A. Flett, J. A. Gracey, S. P. Jones, T. Teubner
Summary: We calculate the exclusive electroproduction, gamma*p -> Vp, of heavy quarkonia V to NLO in the collinear factorisation scheme, which has been formally proven for this process, extending the photoproduction phase space of the exclusive heavy quarkonia observable to electroproduction kinematics with an off-shell virtuality Q(2) carried by the photon. This process is relevant for diffractive scattering at HERA and the upcoming EIC, as well as at the proposed LHeC and FCC.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Dhimiter D. Canko, Nikolaos Syrrakos
Summary: The article details two resummation methods derived from the Simplified Differential Equations approach applied to a canonical basis of master integrals. The first method facilitates determining boundary conditions by establishing relationships between basis elements, while the second method shows how solutions to a canonical basis with one mass less can be obtained through the x -> 1 limit. Both methods utilize residue matrices for the {0, 1} letters of the canonical differential equation, and are demonstrated through the application to a three-loop ladder-box canonical basis.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Piotr Bargiela, Fabrizio Caola, Andreas von Manteuffel, Lorenzo Tancredi
Summary: This study is of great importance for calculating the NNLO QCD corrections to diphoton production in gluon fusion. The researchers employed a new method to calculate scattering amplitudes, providing accurate and compact analytical results.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Multidisciplinary
Simon Badger, Heribertus Bayu Hartanto, Simone Zoia
Summary: An analytic computation of two-loop QCD corrections to u (d) over bar -> W(+)b (b) over bar for an on-shell W boson was presented using leading color and massless bottom quark approximations. Integration-by-parts reduction of the unpolarized squared matrix element was achieved through finite field reconstruction techniques, leading to the identification of an independent basis of special functions allowing for analytic subtraction of infrared and ultraviolet poles. This basis is applicable to all planar topologies for five-particle scattering with an off-shell leg.
PHYSICAL REVIEW LETTERS
(2021)
Article
Physics, Particles & Fields
Giuseppe Bevilacqua, Huan-Yu Bi, Heribertus Bayu Hartanto, Manfred Kraus, Michele Lupattelli, Malgorzata Worek
Summary: This study presents the calculation of next-to-leading order QCD corrections to the production of a tt pair in association with two heavy-flavour jets at the LHC. The results are analyzed extensively to investigate theoretical uncertainties and potential impacts of bottom-quark parton density contributions. The findings have important implications for measurements related to ttH(H -> bb) and the Higgs coupling to the top quark, as well as for precise measurements and modeling of top-quark decay at the LHC.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Physics, Particles & Fields
Simon Badger, Ekta Chaubey, Heribertus Bayu Hartanto, Robin Marzucca
Summary: The paper presents a complete set of analytic helicity amplitudes for top quark pair production via gluon fusion at two-loops in QCD, including corrections due to massive fermion loops and the missing master integrals needed to compute the amplitude. The results are obtained in terms of iterated integrals using rationalised kinematics and finite field sampling, with a study on the numerical evaluation of the iterated integrals.
JOURNAL OF HIGH ENERGY PHYSICS
(2021)
Article
Computer Science, Interdisciplinary Applications
S. Abreu, J. Dormans, F. Febres Cordero, H. Ita, M. Kraus, B. Page, E. Pascual, M. S. Ruf, V. Sotnikov
Summary: CARAVEL is the first public version of a C++17 framework designed for computing multi-loop scattering amplitudes in quantum field theory using the numerical unitarity method. The framework consists of modules for various computations related to multi-loop amplitudes, showcasing functionalities through provided programs. Dependencies include Python, meson, and optional libraries such as Doxygen, Eigen, GiNaC, GMP, and Lapack.
COMPUTER PHYSICS COMMUNICATIONS
(2021)
Editorial Material
Multidisciplinary Sciences
Zoltan Trocsanyi, Adam Kardos, Giuseppe Bevilacqua
Article
Physics, Particles & Fields
G. Bevilacqua, M. Garzelli, A. Kardos, L. Toth
Summary: This paper discusses the hadroproduction of a W boson in association with a charm quark at the Large Hadron Collider, presenting predictions matched with parton shower approach for comparison with experimental data.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Daniel Stremmer, Malgorzata Worek
Summary: This study reports on the calculation of next-to-leading order QCD corrections to Higgs boson production and decay associated with top quarks, considering hadronic processes resulting from top quark decays. Resonant and non-resonant Feynman diagrams, interferences, and off-shell effects are thoroughly investigated, along with the inclusion of Higgs boson decays in the narrow-width approximation. Different theoretical uncertainties and the impact of bottom-quark parton density contributions are also examined.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Physics, Particles & Fields
Giuseppe Bevilacqua, Heribertus Bayu Hartanto, Manfred Kraus, Jasmina Nasufi, Malgorzata Worek
Summary: Motivated by ongoing searches for new physics in the top-quark sector at the Large Hadron Collider, this study calculates the NLO QCD corrections to the Standard Model process pp -> t (t) over barZ + X in the tetra-lepton decay channel. The calculation includes all resonant and non-resonant Feynman diagrams, interferences, and off-shell effects of the top quark, W and Z gauge bosons, as well as photon-induced contributions.
JOURNAL OF HIGH ENERGY PHYSICS
(2022)
Article
Astronomy & Astrophysics
G. Bevilacqua, H. Y. Bi, H. B. Hartanto, M. Kraus, M. Lupattelli, M. Worek
Summary: We investigate the full off-shell effects in the production of tt over bar bb over bar in the dilepton channel at the LHC with a center-of-mass energy of 13 TeV. We calculate the next-to-leading-order (NLO) QCD corrections to the pp -e+νeμ-ν over barμbb over bar bb over bar + X process and provide a method to distinguish between prompt b jets and b jets from the decay of top quarks. Our findings show that full off-shell effects are subdominant compared to scale uncertainties for most observables, but significant for certain observables related to beyond the Standard Model searches. Additionally, our b-jet labeling prescription allows for successful disentanglement of prompt b jets and b jets from top-quark decays.
Article
Astronomy & Astrophysics
Tomas Jezo, Manfred Kraus
Summary: In this study, a new Monte Carlo event generator for the hadronic production of four top quarks is presented. It includes subleading electroweak production channels and investigates various sources of theoretical uncertainties.
Article
Astronomy & Astrophysics
G. Bevilacqua, H. Y. Bi, F. Febres Cordero, H. B. Hartanto, M. Kraus, J. Nasufi, L. Reina, M. Worek
Summary: In this study, the theoretical uncertainties for multilepton signatures are investigated in light of recent discrepancies between modeling and measurements. The comparison is performed between the full off-shell calculation and its narrow-width approximation, as well as the on-shell t(t) over barW(+/-) calculation with spin correlations. The predictions for multilepton signatures at the LHC are studied for both NLO perturbative orders, and a method to incorporate full off-shell effects in the NLO computation is proposed.
