One major challenge for the legacy measurements at the LHC is that the likelihood function is not tractable when the collected data is high-dimensional and the detector response has to be modeled. We ...review how different analysis strategies solve this issue, including the traditional histogram approach used in most particle physics analyses, the Matrix Element Method, Optimal Observables, and modern techniques based on neural density estimation. We then discuss powerful new inference methods that use a combination of matrix element information and machine learning to accurately estimate the likelihood function. The MadMiner package automates all necessary data-processing steps. In first studies we find that these new techniques have the potential to substantially improve the sensitivity of the LHC legacy measurements.
We present a new way to define and compute the maximum significance achievable for signal and background processes at the LHC, using all available phase space information. As an example, we show that ...a light Higgs boson produced in weak-boson fusion with a subsequent decay into muons can be extracted from the backgrounds. The method, aimed at phenomenological studies, can be incorporated in parton-level event generators and accommodate parametric descriptions of detector effects for selected observables.
Likelihood ratio tests are a key tool in many fields of science. In order to evaluate the likelihood ratio the likelihood function is needed. However, it is common in fields such as High Energy ...Physics to have complex simulations that describe the distribution while not having a description of the likelihood that can be directly evaluated. In this setting it is impossible or computationally expensive to evaluate the likelihood. It is, however, possible to construct an equivalent version of the likelihood ratio that can be evaluated by using discriminative classifiers. We show how this can be used to approximate the likelihood ratio when the underlying distribution is a weighted sum of probability distributions (e.g. signal plus background model). We demonstrate how the results can be considerably improved by decomposing the ratio and use a set of classifiers in a pairwise manner on the components of the mixture model and how this can be used to estimate the unknown coefficients of the model, such as the signal contribution.
Groundwater flow through aquifer soils or packed bed systems can fluctuate for various reasons, which could affect the concentration of natural colloids and per- and polyfluoroalkyl substances (PFAS) ...in the pore water. In such cases, PFAS concentration could either decrease due to matrix diffusion of PFAS or increase by the detachment of colloids carrying PFAS. Yet, the effect of flow fluctuation on PFAS transport or release in porous media has not been examined. To examine the relative importance of either process, we interrupted the flow during an injection of groundwater spiked with perfluorobutanoic acid (PFBA), perfluorooctanoic acid (PFOA), and bromide as conservative tracer through clay-rich soil, so that diffusive transport would be prominent during flow interruption. After flow interruption, the PFAS concentration did not decrease indicating an insignificant contribution of matrix diffusion. The concentration increased, potentially due to enhanced release of colloid-associated PFAS. Analysis of samples before and after flow interruption by particle size analysis and SEM confirmed an increase in soil colloid concentration after the flow interruption. XRD analysis of soil and the colloids proved that PFAS were associated with specific sites of the colloids. Due to a higher affinity of PFOA to soil colloids, the total PFOA concentration in the effluent samples increased more than PFBA after the flow interruption process. The results indicate that colloids may have a disproportionally higher role in the transport of PFAS in conditions that release colloids from porous media. Thus, fluctuations in groundwater flow can increase this colloid facilitated mobility of PFAS.
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•Flow interruption increases pore water PFAS concentrations in saturated soil.•Soil colloids released during flow interruption increase PFAS concentration.•Colloid-facilitated transport of PFAS is chain-length dependent.•Removal of colloids from water samples can underestimate PFAS concentration.
Kernel estimation provides an unbinned and non-parametric estimate of the probability density function from which a set of data is drawn. In the first section, after a brief discussion on parametric ...and non-parametric methods, the theory of kernel estimation is developed for univariate and multivariate settings. The second section discusses some of the applications of kernel estimation to high-energy physics. The third section provides an overview of the available univariate and multivariate packages. This paper concludes with a discussion of the inherent advantages of kernel estimation techniques and systematic errors associated with the estimation of parent distributions.
AbstractThe potential for the discovery of a Standard Model Higgs boson in the mass range mH < 2 mZ in the vector boson fusion mode has been studied for the ATLAS experiment at the LHC. The ...characteristic signatures of additional jets in the forward regions of the detector and of low jet activity in the central region allow for an efficient background rejection. Analyses for the H → WW(*) and H → ττ decay modes have been performed using a realistic simulation of the expected detector performance. The results obtained demonstrate the large discovery potential in the H → WW(*) decay channel and the sensitivity to Higgs boson decays into τ-pairs in the low-mass region around 120 GeV/c2.
Complementary to parallel open access and analysis preservation initiatives, ATLAS is taking steps to ensure that the data taken by the experiment during Run-1 remain accessible and available for ...future analysis by the collaboration. An evaluation of what is required to achieve this is underway, examining the ATLAS data production chain to establish the effort required and potential problems. Several alternatives are explored, but the favoured solution is to bring the Run 1 data and software in line with the equivalent to that which will be used for Run 2. This will result in a coherent ATLAS dataset for the data already taken and that to come in the future.
We present a set of recommendations for the presentation of LHC results on searches for new physics, which are aimed at providing a more efficient flow of scientific information between the ...experimental collaborations and the rest of the high energy physics community, and at facilitating the interpretation of the results in a wide class of models. Implementing these recommendations would aid the full exploitation of the physics potential of the LHC.
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•Dry-wet and freeze-thaw cycles mobilized PFOA in subsurface soil.•Weathering increased the release of colloids carrying PFOA.•Up to 36 % of total PFOA leached were associated with ...soil colloids.•Colloid removal before analysis underestimates water PFAS concentrations.•Conceptual site models for subsurface leaching should account for weathering.
Subsurface soil naturally experiences dry-wet and freeze-thaw cycles, which could affect the leaching of previously adsorbed pollutants. A slow release of poly- and perfluoroalkyl substances (PFAS) from impacted subsurface soil may serve as a long-term diffuse source of PFAS to groundwater. Yet, the extent to which these weathering conditions may affect the subsurface release of PFAS is unknown. We subjected columns packed with soil pre-adsorbed with perfluorooctanoic acid (PFOA) to dry-wet and freeze-thaw cycles and observed a spike in PFOA concentration in leachate following each weathering treatment compared to no weathering treatment. Weathering conditions released a high concentration of soil colloids, which were confirmed by particle-size distribution analysis, SEM-EDS, and XRD. Fractionation of PFOA in the water sample reveals that up to 36 % of leached PFOA was associated with soil colloids. Thus, previous studies that did not account for colloids might have underestimated the leaching of PFAS from the soil. Overall, the results indicate that natural weathering conditions can enhance subsurface leaching of colloids and colloid-associated PFOA. Therefore, current conceptual site models to quantify the leaching of PFAS from source zones should account for weathering and the contribution of colloids.
Abstract Atrazine (ATRA) is metabolized by cytochrome P450s to the chlorinated metabolites, 2-chloro-4-ethylamino-6-amino-1,3,5-triazine (ETHYL), 2-chloro-4-amino-6-isopropylamino-1, 3, 5-triazine ...(ISO), and diaminochlorotriazine (DACT). Here, we develop a set of physiologically based pharmacokinetic (PBPK) models that describe the influence of oral absorption and oxidative metabolism on the blood time course curves of individual chlorotriazines (Cl-TRIs) in rat after oral dosing of ATRA. These models first incorporated in vitro metabolic parameters to describe time course plasma concentrations of DACT, ETHYL, and ISO after dosing with each compound. Parameters from each individual model were linked together into a final composite model in order to describe the time course of all 4 Cl-TRIs after ATRA dosing. Oral administration of ISO, ETHYL and ATRA produced double peaks of the compounds in plasma time courses that were described by multiple absorption phases from gut. An adequate description of the uptake and bioavailability of absorbed ATRA also required inclusion of additional oxidative metabolic clearance of ATRA to the mono-dealkylated metabolites occurring in GI a tract compartment. These complex processes regulating tissue dosimetry of atrazine and its chlorinated metabolites likely reflect limited compound solubility in the gut from dosing with an emulsion, and sequential absorption and metabolism along the GI tract at these high oral doses.
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