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A modified version of the CKKW matrix element merging algorithm is presented, suitable for use in an angular-ordered parton shower, using truncated showers and forced splittings. The algorithm is implemented in the Herwig++ Monte Carlo…

High Energy Physics - Phenomenology · Physics 2009-11-13 Keith Hamilton , Peter Richardson , Jon Tully

We investigate the effects of combining next-to-leading order QCD results with parton-shower effects in $W^+W^-jj$ production via vector-boson fusion including leptonic decays. Using the Herwig 7 framework interfaced to VBFNLO 3, we compare…

High Energy Physics - Phenomenology · Physics 2016-07-04 Michael Rauch , Simon Plätzer

In this work we present the implementation of generators for W and Z bosons in association with two jets interfaced to parton showers using the POWHEG BOX. We incorporate matrix elements from the parton-level Monte Carlo program MCFM in the…

High Energy Physics - Phenomenology · Physics 2015-06-15 John M. Campbell , R. Keith Ellis , Paolo Nason , Giulia Zanderighi

In conventional parton showers (including ones based on dipoles/antennae), a given $(\mathrm{Born}+m)$-parton configuration can typically be reached via ${\mathcal O}(m!)$ different "shower histories". In the context of…

High Energy Physics - Phenomenology · Physics 2020-08-26 Helen Brooks , Christian T Preuss , Peter Skands

A parton shower method for the photonic radiative correction is applied to the single W-boson production processes. The energy scale for the evolution of the parton shower is determined so that the correct soft-photon emission is…

High Energy Physics - Phenomenology · Physics 2009-01-07 Y. Kurihara , J. Fujimoto , T. Ishikawa , Y. Shimizu , K. Kato , K. Tobimatsu , T. Munehisa

We compare different procedures for combining fixed-order tree-level matrix element generators with parton showers. We use the case of W-production at the Tevatron and the LHC to compare different implementations of the so-called CKKW…

High Energy Physics - Phenomenology · Physics 2007-05-23 Stefan Hoeche , Frank Krauss , Nils Lavesson , Leif Lonnblad , Michelangelo Mangano , Andreas Schaelicke , Steffen Schumann

In a previous paper, hereafter referred to as I, we have analyzed the 7 TeV LHC data on W + jets events from the standpoint of IR-improved DGLAP parton shower effects, using the IR-improved Herwiri1.031 parton shower MC in comparison with…

High Energy Physics - Phenomenology · Physics 2020-11-18 B. Shakerin , B. F. L. Ward

We present the first combination of NLO QCD matrix elements for di-Higgs production, retaining the full top quark mass dependence, with a parton shower. Results are provided within both the POWHEG-BOX and MadGraph5_aMC@NLO Monte Carlo…

High Energy Physics - Phenomenology · Physics 2017-12-05 G. Heinrich , S. P. Jones , M. Kerner , G. Luisoni , E. Vryonidou

The merging of matrix elements and parton showers is an established calculational tool for the description of multi-jet final states at hadron colliders. These methods have recently been promoted to next-to-leading order accuracy in the…

High Energy Physics - Phenomenology · Physics 2013-11-15 Marek Schonherr , Stefan Hoeche , Frank Krauss , Frank Siegert

We study the structure of generalized parton distributions in impact parameter space with the aim of determining the size and role of small transverse separations components in the quarks wave function. We analyze the relation between…

High Energy Physics - Phenomenology · Physics 2009-11-10 S. Liuti , S. K. Taneja

We describe the use of doubly-unintegrated parton distributions in hadron-hadron collisions, using the (z,k_t)-factorisation prescription where the transverse momentum of the incoming parton is generated in the last evolution step. We apply…

High Energy Physics - Phenomenology · Physics 2014-11-17 G. Watt , A. D. Martin , M. G. Ryskin

We study in this paper the production, in hadronic collisions, of final states with W gauge bosons, heavy quark pairs and n extra jets (with n up to 4). The complete partonic tree-level QCD matrix elements are evaluated using the ALPHA…

High Energy Physics - Phenomenology · Physics 2008-11-26 Michelangelo L. Mangano , Mauro Moretti , Roberto Pittau

We present results for renormalized matrix elements related to the unpolarized quasi-distribution function of the $\Delta^+$ baryon making use of the large momentum effective theory. Two ensembles of $N_f=2+1+1$ twisted mass fermions with a…

We propose a method for combining QCD matrix elements and parton showers in Monte Carlo simulations of hadronic final states in $e^+e^-$ annihilation. The matrix element and parton shower domains are separated at some value $y_{ini}$ of the…

High Energy Physics - Phenomenology · Physics 2010-02-03 S. Catani , F. Krauss , R. Kuhn , B. R. Webber

We provide a theoretical study of a novel variable introduced in Ref. \cite{WV} to study the transverse momentum of the Z boson at hadron colliders. The variable we consider has experimental advantages over the standard $p_T$ distribution…

High Energy Physics - Phenomenology · Physics 2009-06-24 Andrea Banfi , Mrinal Dasgupta , Rosa Maria Duran Delgado

The event generator based on the higher-twist energy loss formalism -- Modular All Twist Transverse-scattering Elastic-drag and Radiation (MATTER) -- is further developed and coupled to a hydrodynamic model for studying jet modification in…

Nuclear Theory · Physics 2020-02-07 Shanshan Cao , Abhijit Majumder

We give a report of medium modification of Z+jet correlations in Pb+Pb collisions at the Large Hadron Collider using Sherpa to generate initial Z+jet at next-leading-order matrix element matched parton shower, and the Linear Boltzmann…

Nuclear Theory · Physics 2018-12-10 Shan-Liang Zhang , Tan Luo , Xin-Nian Wang , Ben-Wei Zhang

I discuss the recent implementation of medium-modified splitting functions within the HERWIG angular-ordered parton shower algorithm and present a few results on transverse momentum, energy and angular distributions.

High Energy Physics - Phenomenology · Physics 2010-11-19 Gennaro Corcella

This article gives an introduction to transverse momentum dependent (TMD) parton distribution functions and their use in shower Monte Carlo event generators for high-energy hadron collisions, and describes recent progress in the treatment…

High Energy Physics - Phenomenology · Physics 2012-05-30 F. Hautmann , M. Hentschinski , H. Jung

We discuss two ways in which parton shower algorithms can be supplemented by matrix-element corrections to ensure the correct hard limit: by using complementary phase-space regions, or by modifying the shower itself. In the former case,…

High Energy Physics - Phenomenology · Physics 2010-04-06 Michael H. Seymour