arXiv subjects

Benjamin Fuks

Publications and source records attributed to Benjamin Fuks.

157 records · Page 9Linked to original sources

arXiv2012

UFO - The Universal FeynRules Output

We present a new model format for automatized matrix-element generators, the so- called Universal FeynRules Output (UFO). The format is universal in the sense that it features compatibility with more than one single generator and is designed to be flexible, modular and agnostic of any assumption such as the number of particles or the color and Lorentz structures appearing in the interaction vertices. Unlike other model formats where text files need to be parsed, the information on the model is encoded into a Python module that can easily be linked to other computer codes. We then describe an interface for the Mathematica package FeynRules that allows for an automatic output of models in the UFO format.

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arXiv2012

Exploring compactified HEIDI models at the LHC

Models with multi-scalar Higgs sectors inspired by a higher-dimensional setup are interesting alternatives to the Standard Model because, although they have a Higgs sector which gives mass to the W and Z gauge bosons as well as the SM fermions, this Higgs sector is potentially undiscoverable at the Large Hadron Collider or shows considerable deviations from the Standard Model Higgs sector. We investigate a compactified version of such models and study its phenomenology in the "golden" four-lepton channel at the LHC in areas of parameter space compatible with electroweak precision observables.

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arXiv2012

Introducing an interface between WHIZARD and FeynRules

While Monte Carlo event generators like WHIZARD have become indispensable tools in studying the impact of new physics on collider observables over the last decades, the implementation of new models in such packages has remained a rather awkward and error-prone process. Recently, the FeynRules package was introduced which greatly simplifies this process by providing a single unified model format from which model implementations for many different Monte Carlo codes can be derived automatically. In this note, we present an interface which extends FeynRules to provide this functionality also for the WHIZARD package, thus making WHIZARD's strengths and performance easily available to model builders.

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arXiv2012

Beyond the Minimal Supersymmetric Standard Model: from theory to phenomenology

Thanks to the latest development in the field of Monte Carlo event generators and satellite programs allowing for a straightforward implementation of any beyond the Standard Model theory in those tools, studying the property of any softly-broken supersymmetric theory is become an easy task. We illustrate this statement in the context of two non-minimal supersymmetric theories, namely the Minimal Supersymmetric Standard Model with R-parity violation and the Minimal R-symmetric Supersymmetric Standard Model and choose to probe interaction vertices involving a non-standard color structure and the sector of the top quark. We show how to efficiently implement these theories in the Mathematica package FeynRules and use its interfaces to Monte Carlo tools for phenomenological studies. For the latter, we employ the latest version of the MadGraph program.

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arXiv2011

Phenomenology of anomaly-mediated supersymmetry breaking scenarios with non-minimal flavour violation

In minimal anomaly-mediated supersymmetry breaking models, tachyonic sleptons are avoided by introducing a common scalar mass similar to the one introduced in minimal supergravity. This may lead to non-minimal flavour-violating interactions, e.g., in the squark sector. In this paper, we analyze the viable anomaly-mediated supersymmetry breaking parameter space in the light of the latest limits on low-energy observables and LHC searches, complete our analytical calculations of flavour-violating supersymmetric particle production at hadron colliders with those related to gluino production, and study the phenomenological consequences of non-minimal flavour violation in anomaly-mediated supersymmetry breaking scenarios at the LHC. Related cosmological aspects are also briefly discussed.

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arXiv2011

Monotops at the LHC

We explore scenarios where top quarks may be produced singly in association with missing energy, a very distinctive signature, which in analogy with monojets, we dub monotops. We find that monotops can be produced in a variety of modes, typically characterized by baryon number violating or flavor changing neutral interactions. We build a simplified model that encompasses all the possible (tree-level) production mechanisms and study the LHC sensitiveness to a few representative scenarios by considering fully hadronic top decays. We find that constraints on such exotic models can already be set with one inverse femtobarn of integrated luminosity collected at seven TeV.

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arXiv2011

A superspace module for the FeynRules package

We describe an additional module for the Mathematica package FeynRules that allows for an easy building of any N=1 supersymmetric quantum field theory, directly in superspace. After the superfield content of a specific model has been implemented, the user can study the properties of the model, such as the supersymmetric transformation laws of the associated Lagrangian, directly in Mathematica. While the model dependent parts of the latter, i.e., the soft supersymmetry-breaking Lagrangian and the superpotential, have to be provided by the user, the model independent pieces, such as the gauge interaction terms, are derived automatically. Using the strengths of the Feynrules program, it is then possible to derive all the Feynman rules associated to the model and implement them in all the Feynman diagram calculators interfaced to FeynRules in a straightforward way.

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arXiv2010

Transverse-momentum resummation for gaugino-pair production at hadron colliders

We present a first precision analysis of the transverse-momentum spectrum of gaugino pairs produced at the Tevatron and the LHC with center-of-mass energies of 1.96 and 10 or 14 TeV, respectively. Our calculation is based on a universal resummation formalism at next-to-leading logarithmic accuracy, which is consistently matched to the perturbative prediction at ${\cal O}(α_s)$. Numerical results are given for the "gold-plated" associated production of neutralinos and charginos decaying into three charged leptons with missing transverse energy as well as for the pair production of neutralinos and charginos at two typical benchmark points in the constrained Minimal Supersymmetric Standard Model. We show that the matched resummation results differ considerably from the Monte Carlo predictions employed traditionally in experimental analyses and discuss the impact on the determination of supersymmetric mass parameters from derived transverse-mass spectra. We also investigate in detail the theoretical uncertainties coming from scale and parton-density function variations and non-perturbative effects.

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arXiv2009

A comprehensive approach to new physics simulations

We describe a framework to develop, implement and validate any perturbative Lagrangian-based particle physics model for further theoretical, phenomenological and experimental studies. The starting point is FeynRules, a Mathematica package that allows to generate Feynman rules for any Lagrangian and then, through dedicated interfaces, automatically pass the corresponding relevant information to any supported Monte Carlo event generator. We prove the power, robustness and flexibility of this approach by presenting a few examples of new physics models (the Hidden Abelian Higgs Model, the general Two-Higgs-Doublet Model, the most general Minimal Supersymmetric Standard Model, the Minimal Higgsless Model, Universal and Large Extra Dimensions, and QCD-inspired effective Lagrangians) and their implementation/validation in FeynArts/FormCalc, CalcHep, MadGraph/MadEvent, and Sherpa.

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arXiv2008

Precision predictions for Z' production at the LHC

We present precision calculations of the transverse-momentum spectrum, the invariant-mass distribution and the total cross section for Z' production at hadron colliders. We implement joint resummation at the next-to-leading logarithmic accuracy and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant. We confront our numerical predictions with the Monte Carlo generator PYTHIA and with a new implementation of extra neutral gauge bosons in the Monte Carlo generator MC@NLO. The impact of scale dependence is also studied.

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arXiv2007

Transverse-momentum, threshold and joint resummations for slepton pair production at hadron colliders

We present precision calculations of the transverse-momentum spectrum and the invariant-mass distribution for slepton pair production at hadron colliders. We implement the transverse-momentum, threshold and joint resummation formalisms at the next-to-leading logarithmic accuracy and consistently match the obtained result with the pure perturbative result at the first order in the strong coupling constant, i.e. at order alpha_s. We give numerical predictions for selectron and stau pair production, and compare the various resummed cross sections with the perturbative result.

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arXiv2007

QCD-resummation and non-minimal flavour-violation for supersymmetric particle production at hadron colliders

Cross sections for supersymmetric particles production at hadron colliders have been extensively studied in the past at leading order and also at next-to-leading order of perturbative QCD. The radiative corrections include large logarithms which have to be resummed to all orders in the strong coupling constant in order to get reliable perturbative results. In this work, we perform a first and extensive study of the resummation effects for supersymmetric particle pair production at hadron colliders. We focus on Drell-Yan like slepton-pair and slepton-sneutrino associated production in minimal supergravity and gauge-mediated supersymmetry-breaking scenarios, and present accurate transverse-momentum and invariant-mass distributions, as well as total cross sections. In non-minimal supersymmetric models, novel effects of flavour violation may occur. In this case, the flavour structure in the squark sector cannot be directly deduced from the trilinear Yukawa couplings of the fermion and Higgs supermultiplets. We perform a precise numerical analysis of the experimentally allowed parameter space in the case of minimal supergravity scenarios with non-minimal flavour violation, looking for regions allowed by low-energy, electroweak precision, and cosmological data. Leading order cross sections for the production of squarks and gauginos at hadron colliders are implemented in a flexible computer program, allowing us to study in detail the dependence of these cross sections on flavour violation.

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arXiv2006

Slepton pair production at hadron colliders

In R-parity conserving supersymmetric models, sleptons are produced in pairs at hadron colliders. We show that measurements of the longitudinal single-spin asymmetry at possible polarization upgrades of existing colliders allow for a direct extraction of the slepton mixing angle. A calculation of the transverse-momentum spectrum shows the importance of resummed contributions at next-to-leading logarithmic accuracy in the small and intermediate transverse-momentum regions and little dependence on unphysical scales and non-perturbative contributions.

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