Logo

Merging Multi-leg NLO Matrix Elements with Parton Showers

MCNET-12-17
LU-TP-12-43
arXiv:1211.7278
JHEP 1303 (2013) 166

by: Lönnblad, Leif (Lund U.) et al.

Abstract:
We discuss extensions of multi-jet matrix element and parton shower merging approaches, to also include next-to-leading order accuracy. Specifically, we generalise the so-called CKKW-L prescription and the recently developed unitarised matrix element + parton shower (UMEPS) scheme. Endowing tree-level merging methods with NLO corrections greatly enhances the perturbative accuracy of parton shower Monte Carlo programs.

Unitarising Matrix Element + Parton Shower merging

LU-TP-12-42
MCNET-12-14
arXiv:1211.4827
JHEP 1302 (2013) 094

by: Lonnblad, Leif (Lund U., Dept. Theor. Phys.) et al.

Abstract:
We revisit the CKKW-L method for merging tree-level matrix elements with parton showers, and amend it with an add/subtract scheme to minimise dependencies on the merging scale. The scheme is constructed to, as far as possible, recover the unitary nature of the underlying parton shower, so that the inclusive cross section is retained for each jet multiplicity separately.

Investigation of Monte Carlo Uncertainties on Higgs Boson searches using Jet Substructure

IPPP-12-46
DCPT-12-92
MCNET-12-08
arXiv:1207.0380
Eur.Phys.J. C72 (2012) 2178

by: Richardson, Peter (Durham U., IPPP) et al.

Abstract:
We present an investigation of the dependence of searches for boosted Higgs bosons using jet substructure on the perturbative and non-perturbative parameters of the Herwig++ Monte Carlo event generator. Values are presented for a new tune of the parameters of the event generator, together with the an estimate of the uncertainties based on varying the parameters around the best-fit values.

NLO corrections merged with parton showers for Z+2 jets production using the POWHEG method

IPPP-12-13
DCPT-12-26
MCNET-12-03
arXiv:1204.5433
JHEP 1210 (2012) 031

by: Re, Emanuele (Durham U., IPPP)

Abstract:
We present results for the QCD production of Z/{\gamma} + 2 jets matched with parton showers using the POWHEG method. Some technicalities relevant for the merging of NLO corrections for this process with parton showers are discussed, and results for typical distributions are shown, in presence of different sets of cuts. A comparison with ATLAS data is also presented, and good agreement is found.

W+ $n$-Jet predictions at the Large Hadron Collider at next-to-leading order matched with a parton shower

arXiv:1201.5882
SLAC-PUB-14859
IPPP-12-03
DCPT-12-06
LPN12-026
MCNET-12-01
FR-PHENO-2012-001
Phys.Rev.Lett. 110 (2013) 052001

by: Höche, Stefan (SLAC) et al.

Abstract:
For the first time, differential cross sections for the production of W-bosons in conjunction with up to three jets, computed at next-to leading order in QCD and including parton shower corrections, are presented and compared to recent experimental data from the Large Hadron Collider.