Andreas Papaefstathiou

Herwig 7.0/Herwig++ 3.0 release note

A major new release of the Monte Carlo event generator Herwig++ (version 3.0) is now available. This release marks the end of distinguishing Herwig++ and HERWIG development and therefore constitutes the first major release of version 7 of the Herwig event generator family. The new version features a number of significant improvements to the event simulation, including: built-in NLO hard process calculation for virtually all Standard Model processes, with matching to both angular-ordered and dipole shower modules via both subtractive (MC@NLO-type) and multiplicative (Powheg-type) algorithms; QED radiation and spin correlations in the angular-ordered shower; a consistent treatment of perturbative uncertainties within the hard process and parton showering. Several of the new features will be covered in detail in accompanying publications, and an update of the manual will follow in due course.

Higgs boson pair production in the D=6 extension of the SM

A bstractWe derive the constraints that can be imposed on the dimension-6 effective theory extension of the Standard Model, using gluon fusion-initiated Higgs boson pair production at the LHC. We use a realistic analysis focussing on the hh→bb¯τ+τ−

Triple Higgs boson production at a 100 TeV proton-proton collider

hhto left(boverline{b}right)left({tau}^{+}{tau}^{-}right)

Phenomenological aspects of new physics at high energy hadron colliders

final state, including initial-state radiation and non-perturbative effects. We include the statistical uncertainties on the signal rates as well as conservative estimates of the theoretical uncertainties. We first consider a theory containing only modifications of the trilinear coupling, through a c6λ H6/v2 Lagrangian term, and then examine the full parameter space of the effective theory, incorporating current bounds obtained through single Higgs boson measurements. We also consider an alternative scenario, where we vary a smaller sub-set of parameters. Allowing, finally, the values of the other coefficients to vary within projected experimental ranges, we find that the currently unbounded parameter, c6, could be constrained to lie within |c6| ≲ 0.6 at 1σ confidence, at the end of the high-luminosity run of the LHC (14 TeV) in the full model, and to −0.6 ≲ c6 ≲ 0.5 in the alternative model. This study constitutes a first step towards the inclusion of multi-Higgs boson production in a full fit to the dimension-6 effective field theory framework.

NLO efforts in Herwig

We consider the process of Higgs boson pair production at a future proton collider with a center-of-mass energy of 100 TeV, focusing on rare final states that include a bottom-antibottom quark pair and multiple isolated leptons:

Standard Model processes

hhensuremath{rightarrow}(boverline{b})+nensuremath{ell}+X

Higgs and EW symmetry breaking studies

,

Herwig 7.1 Release Note : arXiv

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