Logarithmic accuracy of parton showers: a fixed-order study

Journal of High Energy Physics, Sep 2018

Abstract We formulate some first fundamental elements of an approach for assessing the logarithmic accuracy of parton-shower algorithms based on two broad criteria: their ability to reproduce the singularity structure of multi-parton matrix elements, and their ability to reproduce logarithmic resummation results. We illustrate our approach by considering properties of two transverse-momentum ordered final-state showers, examining features up to second order in the strong coupling. In particular we identify regions where they fail to reproduce the known singular limits of matrix elements. The characteristics of the shower that are responsible for this also affect the logarithmic resummation accuracies of the shower, both in terms of leading (double) logarithms at subleading NC and next-to-leading (single) logarithms at leading NC.

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Logarithmic accuracy of parton showers: a fixed-order study

Journal of High Energy Physics September 2018, 2018:33 | Cite as Logarithmic accuracy of parton showers: a fixed-order study AuthorsAuthors and affiliations Mrinal DasguptaFrédéric A. DreyerKeith HamiltonPier Francesco MonniGavin P. Salam Open Access Regular Article - Theoretical Physics First Online: 07 September 2018 Received: 05 June 2018 Revised: 14 August 2018 Accepted: 26 August 2018 Abstract We formulate some first fundamental elements of an approach for assessing the logarithmic accuracy of parton-shower algorithms based on two broad criteria: their ability to reproduce the singularity structure of multi-parton matrix elements, and their ability to reproduce logarithmic resummation results. We illustrate our approach by considering properties of two transverse-momentum ordered final-state showers, examining features up to second order in the strong coupling. In particular we identify regions where they fail to reproduce the known singular limits of matrix elements. The characteristics of the shower that are responsible for this also affect the logarithmic resummation accuracies of the shower, both in terms of leading (double) logarithms at subleading NC and next-to-leading (single) logarithms at leading NC. Keywords NLO Computations QCD Phenomenology  ArXiv ePrint: 1805.09327 On leave from CNRS, UMR 7589, LPTHE, F-75005, Paris, France and from Rudolf Peierls Centre for Theoretical Physics, 1 Keble Road, Oxford OX1 3NP, U.K. . (Gavin P. Salam) Download to read the full article text Notes Open Access This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited. References [1] A. Buckley et al., General-purpose event generators for LHC physics, Phys. Rept. 504 (2011) 145 [arXiv:1101.2599] [INSPIRE]. [2] M.L. Mangano, M. Moretti and R. Pittau, Multijet matrix elements and shower evolution in hadronic collisions: \( Wb\overline{b} + n \) jets as a case study, Nucl. Phys. B 632 (2002) 343 [hep-ph/0108069] [INSPIRE]. [3] S. Catani, F. Krauss, R. Kuhn and B.R. Webber, QCD matrix elements + parton showers, JHEP 11 (2001) 063 [hep-ph/0109231] [INSPIRE]. [4] L. Lönnblad, Correcting the color dipole cascade model with fixed order matrix elements, JHEP 05 (2002) 046 [hep-ph/0112284] [INSPIRE]. [5] S. Frixione and B.R. Webber, Matching NLO QCD computations and parton shower simulations, JHEP 06 (2002) 029 [hep-ph/0204244] [INSPIRE]. [6] J. Alwall et al., The automated computation of tree-level and next-to-leading order differential cross sections and their matching to parton shower simulations, JHEP 07 (2014) 079 [arXiv:1405.0301] [INSPIRE].ADSCrossRefGoogle Scholar [7] P. Nason, A New method for combining NLO QCD with shower Monte Carlo algorithms, JHEP 11 (2004) 040 [hep-ph/0409146] [INSPIRE]. [8] S. Frixione, P. Nason and C. Oleari, Matching NLO QCD computations with Parton Shower simulations: the POWHEG method, JHEP 11 (2007) 070 [arXiv:0709.2092] [INSPIRE].ADSCrossRefGoogle Scholar [9] S. Alioli, P. Nason, C. Oleari and E. Re, A general framework for implementing NLO calculations in shower Monte Carlo programs: the POWHEG BOX, JHEP 06 (2010) 043 [arXiv:1002.2581] [INSPIRE].ADSCrossRefzbMATHGoogle Scholar [10] S. Jadach, W. Placzek, S. Sapeta, A. Siódmok and M. Skrzypek, Matching NLO QCD with parton shower in Monte Carlo scheme — the KrkNLO method, JHEP 10 (2015) 052 [arXiv:1503.06849] [INSPIRE].ADSCrossRefzbMATHGoogle Scholar [11] S. Hoeche, F. Krauss, M. Schonherr and F. Siegert, QCD matrix elements + parton showers: The NLO case, JHEP 04 (2013) 027 [arXiv:1207.5030] [INSPIRE].ADSCrossRefGoogle Scholar [12] K. Hamilton, P. Nason and G. Zanderighi, MINLO: Multi-Scale Improved NLO, JHEP 10 (2012) 155 [arXiv:1206.3572] [INSPIRE].ADSCrossRefGoogle Scholar [13] R. Frederix and S. Frixione, Merging meets matching in MC@NLO, JHEP 12 (2012) 061 [arXiv:1209.6215] [INSPIRE].ADSCrossRefGoogle Scholar [14] K. Hamilton, P. Nason, E. Re and G. Zanderighi, NNLOPS simulation of Higgs boson production, JHEP 10 (2013) 222 [arXiv:1309.0017] [INSPIRE].ADSCrossRefGoogle Scholar [15] S. Höche, Y. Li and S. Prestel, Drell-Yan lepton pair production at NNLO QCD with parton showers, Phys. Rev. D 91 (2015) 074015 [arXiv:1405.3607] [INSPIRE]. [16] S. Alioli, C.W. Bauer, C. Berggren, F.J. Tackmann, J.R. Walsh and S. Zuberi, Matching Fully Differential NNLO Calculations and Parton Showers, JHEP 06 (2014) 089 [arXiv:1311.0286] [INSPIRE].ADSCrossRefGoogle Scholar [17] T. Sjöstrand and M. van Zijl, A Multiple Interaction Model for the Event Structure in Hadron Collisions, Phys. Rev. D 36 (1987) 2019 [INSPIRE]. [18] J.M. Butterworth, J.R. Forshaw and M.H. Seymour, Multiparton interactions in photoproduction at HERA, Z. Phys. C 72 (1996) 637 [hep-ph/9601371] [INSPIRE]. [19] I. Borozan and M.H. Seymour, (...truncated)


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Mrinal Dasgupta, Frédéric A. Dreyer, Keith Hamilton, Pier Francesco Monni, Gavin P. Salam. Logarithmic accuracy of parton showers: a fixed-order study, Journal of High Energy Physics, 2018, pp. 33, Volume 2018, Issue 9, DOI: 10.1007/JHEP09(2018)033