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Peter Schichtel

Publications and source records attributed to Peter Schichtel.

At least 19 recordsLinked to original sources

Quantifying Quality of Class-Conditional Generative Models in Time-Series Domain

Generative models are designed to address the data scarcity problem. Even with the exploding amount of data, due to computational advancements, some applications (e.g., health care, weather forecast, fault detection) still suffer from data insufficiency, especially in the time-series domain. Thus generative models are essential and powerful tools, but they still lack a consensual approach for quality assessment. Such deficiency hinders the confident application of modern implicit generative models on time-series data. Inspired by assessment methods on the image domain, we introduce the InceptionTime Score (ITS) and the Frechet InceptionTime Distance (FITD) to gauge the qualitative performance of class conditional generative models on the time-series domain. We conduct extensive experiments on 80 different datasets to study the discriminative capabilities of proposed metrics alongside two existing evaluation metrics: Train on Synthetic Test on Real (TSTR) and Train on Real Test on Synthetic (TRTS). Extensive evaluation reveals that the proposed assessment method, i.e., ITS and FITD in combination with TSTR, can accurately assess class-conditional generative model performance.

cs.LG

Random Noise vs State-of-the-Art Probabilistic Forecasting Methods : A Case Study on CRPS-Sum Discrimination Ability

The recent developments in the machine learning domain have enabled the development of complex multivariate probabilistic forecasting models. Therefore, it is pivotal to have a precise evaluation method to gauge the performance and predictability power of these complex methods. To do so, several evaluation metrics have been proposed in the past (such as Energy Score, Dawid-Sebastiani score, variogram score), however, they cannot reliably measure the performance of a probabilistic forecaster. Recently, CRPS-sum has gained a lot of prominence as a reliable metric for multivariate probabilistic forecasting. This paper presents a systematic evaluation of CRPS-sum to understand its discrimination ability. We show that the statistical properties of target data affect the discrimination ability of CRPS-Sum. Furthermore, we highlight that CRPS-Sum calculation overlooks the performance of the model on each dimension. These flaws can lead us to an incorrect assessment of model performance. Finally, with experiments on the real-world dataset, we demonstrate that the shortcomings of CRPS-Sum provide a misleading indication of the probabilistic forecasting performance method. We show that it is easily possible to have a better CRPS-Sum for a dummy model, which looks like random noise, in comparison to the state-of-the-art method.

cs.LG

Constraining strongly coupled new physics from cosmic rays with machine learning techniques

Cosmic rays interacting with the atmosphere allow for the probing of fundamental interactions at ultra-high energies. We thus obtain limits on strongly coupled new physics models via their imprints on cosmic-ray air showers. Using the Monte Carlo event generators Herwig and HERBVI, and the air shower simulator CORSIKA, to simulate such processes, we apply machine learning algorithms to the simulated observables to discriminate the events arising via new physics from the QCD background. We then use the signal and background discrimination performance to set potential limits on the cross sections of the new physics models.

hep-ph

Probabilistic Forecasting of Sensory Data with Generative Adversarial Networks - ForGAN

Time series forecasting is one of the challenging problems for humankind. Traditional forecasting methods using mean regression models have severe shortcomings in reflecting real-world fluctuations. While new probabilistic methods rush to rescue, they fight with technical difficulties like quantile crossing or selecting a prior distribution. To meld the different strengths of these fields while avoiding their weaknesses as well as to push the boundary of the state-of-the-art, we introduce ForGAN - one step ahead probabilistic forecasting with generative adversarial networks. ForGAN utilizes the power of the conditional generative adversarial network to learn the data generating distribution and compute probabilistic forecasts from it. We argue how to evaluate ForGAN in opposition to regression methods. To investigate probabilistic forecasting of ForGAN, we create a new dataset and demonstrate our method abilities on it. This dataset will be made publicly available for comparison. Furthermore, we test ForGAN on two publicly available datasets, namely Mackey-Glass dataset and Internet traffic dataset (A5M) where the impressive performance of ForGAN demonstrate its high capability in forecasting future values.

cs.LG

Stress-testing the VBF approximation in multijet final states

We consider electro-weak Higgs plus three jets production at NLO QCD beyond strict VBF acceptance cuts. We investigate, for the first time, how accurate the VBF approximation is in these regions and within perturbative uncertainties, by a detailed comparison of full and approximate calculations. We find that a rapidity gap between the tagging jets guarantees a good approximation, while an invariant mass cut alone is not sufficient, which needs to be confronted with experimental choices. We also find that a significant part of the QCD corrections can be attributed to Higgs-Strahlungs-type topologies.

hep-ph

Mad-Maximized Higgs Pair Analyses

We study Higgs pair production with a subsequent decay to a pair of photons and a pair of bottoms at the LHC. We use the log-likelihood ratio to identify the kinematic regions which either allow us to separate the di-Higgs signal from backgrounds or to determine the Higgs self-coupling. We find that both regions are separate enough to ensure that details of the background modelling will not affect the determination of the self-coupling. Assuming dominant statistical uncertainties we determine the best precision with which the Higgs self- coupling can be probed in this channel. We finally comment on the same questions at a future 100 TeV collider.

hep-ph

Herwig 7.1 Release Note

A new release of the Monte Carlo event generator Herwig (version 7.1) is now available. This version introduces a number of improvements, notably: multi-jet merging with the dipole shower at LO and NLO QCD; a new model for soft interactions and diffraction; improvements to mass effects and top decays in the dipole shower, as well as a new tune of the hadronisation parameters.

hep-ph

Same-sign W pair production in composite Higgs models

Non-minimal composite Higgs scenarios can contain exotic Higgs states which, if getting observed at the Large Hadron Collider, will help to constrain the underlying UV structure of the strong dynamics. Doubly charged Higgs bosons are well-motivated scalar degrees of freedom in this context. Their phenomenology in typical composite scenarios can differ from well-established Higgs triplet extensions of the SM. Related search strategies are not necessarily adapted to such a scenario as a consequence. In this paper we discuss the sensitivity reach to doubly charged Higgs bosons with decays into pairs of same-sign $W$ bosons. While production cross sections are small, we show that significant constraints on $H^{\pm\pm}\to W^{\pm}W^{\pm}$ can be obtained, providing a new opportunity to constrain the potential composite structure of the TeV scale up to $m_{H^{\pm\pm}}\simeq 800$~GeV.

hep-ph

Parton Shower Uncertainties with Herwig 7: Benchmarks at Leading Order

We perform a detailed study of the sources of perturbative uncertainty in parton shower predictions within the Herwig 7 event generator. We benchmark two rather different parton shower algorithms, based on angular-ordered and dipole-type evolution, against each other. We deliberately choose leading order plus parton shower as the benchmark setting to identify a controllable set of uncertainties. This will enable us to reliably assess improvements by higher-order contributions in a follow-up work.

hep-ph

Cosmic ray air showers from sphalerons

The discovery of the Higgs boson marks a key ingredient to establish the electroweak structure of the Standard Model. Its non-abelian gauge structure gives rise to, yet unobserved, non-perturbative baryon and lepton number violating processes. We propose to use cosmic ray air showers, as measured at the Pierre Auger Observatory, to set a limit on the hadronic production cross section of sphalerons. We identify several observables to discriminate between sphaleron and QCD induced air showers.

hep-ph

NLO efforts in Herwig++

With the advent and recent extension of the BLHA standard to interface Monte Carlo event generators and one-loop matrix element providers, the Herwig++ event generator has expanded its range of applicability to a multitude of underlying hard processes at NLO QCD. The new NLO development is centered around the Matchbox framework, which turns fixed NLO QCD calculations into parton shower matched calculations - to be matched to the two parton shower variants of Herwig++. Matchbox provides thereby for the automated setup of the underlying fixed NLO QCD calculations and the interface to the one-loop matrix element providers, as well as for an efficient and automated multi-channel phase space sampling, and forms the basis for the NLO capabilities of the new release of Herwig++. Along with several other new features and developments, the new release marks the end of distinguishing Herwig++ and (Fortran) HERWIG, and constitutes the first major release of version 7 of the Herwig event generator.

hep-ph

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 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.

hep-ph

Jet properties at high-multiplicity

We investigate the behaviour of jets at high-multiplicity using analytic techniques. We consider in detail the rates, areas and the intermediate splitting scales as a function of the number of jets. In each case, we are able to characterise a general scaling behaviour characteristic for QCD processes, which we compare with results from the parton shower. The study of these observables potentially offers a very general handle in the difficult to describe regime of high-jet multiplicity.

hep-ph

Spying an invisible Higgs

We investigate the potential of multivariate techniques to improve the LHC search for invisible Higgs decays in weak boson fusion. We find that in the coming runs the LHC will be able to probe an invisible Higgs width of 28% within a year and 3.5% during a high luminosity run. A significant improvement over these estimates requires an analysis of QCD radiation patterns down to 10 GeV. Such an analysis can improve the reach at the high luminosity run to 2%. Throughout our analysis we employ a conservative, data driven background determination.

hep-ph

Improving Higgs plus Jets analyses through Fox--Wolfram Moments

It is well known that understanding the structure of jet radiation can significantly improve Higgs analyses. Using Fox--Wolfram moments we systematically study the geometric patterns of additional jets in weak boson fusion Higgs production with a decay to photons. First, we find a significant improvement with respect to the standard analysis based on an analysis of the tagging jet correlations. In addition, we show that replacing a jet veto by a Fox-Wolfram moment analysis of the extra jet radiation almost doubles the signal-to-background ratio. Finally, we show that this improvement can also be achieved based on a modified definition of the Fox--Wolfram moments which avoids introducing a new physical scale below the factorization scale. This modification can reduce the impact of theory uncertainties on the Higgs rate and couplings measurements.

hep-ph

MadMax, or Where Boosted Significances Come From

In an era of increasingly advanced experimental analysis techniques it is crucial to understand which phase space regions contribute a signal extraction from backgrounds. Based on the Neyman-Pearson lemma we compute the maximum significance for a signal extraction as an integral over phase space regions. We then study to what degree boosted Higgs strategies benefit ZH and ttH searches and which transverse momenta of the Higgs are most promising. We find that Higgs and top taggers are the appropriate tools, but would profit from a targeted optimization towards smaller transverse momenta. MadMax is available as an add-on to Madgraph5.

hep-ph

Scaling Patterns for QCD Jets

Jet emission at hadron colliders follows simple scaling patterns. Based on perturbative QCD we derive Poisson and staircase scaling for final state as well as initial state radiation. Parton density effects enhance staircase scaling at low multiplicities. We propose experimental tests of our theoretical findings in Z+jets and QCD gap jets production based on minor additions to current LHC analyses.

hep-ph

From Jet Counting to Jet Vetoes

The properties of multi-jet events impact many LHC analysis. The exclusive number of jets at hadron colliders can be described in terms of two simple patterns: staircase scaling and Poisson scaling. In photon plus jets production we can interpolate between the two patterns using simple kinematic cuts. The associated theoretical errors are well under control. Understanding such exclusive jet multiplicities significantly impacts Higgs searches and searches for supersymmetry at the LHC.

hep-ph