Soft QCD Effects in VBS/VBF Topologies

We consider the impact of multi-parton interactions, colour reconnection and hadronization on the modeling of vector boson fusion and vector boson scattering (VBS) final states at the Large Hadron Collider (LHC). We investigate how the variation of the model parameters, compatible with a reasonable spread of predictions around typical tuning observables, extrapolates into the VBS phase space. We study the implications of this variation on the total uncertainty budget attached to realistic simulation of the final states in current event generator predictions. We find that the variations have a non-trivial phase space dependence and become comparable in size to the perturbative uncertainties once next-to-leading order predictions are combined with parton shower evolution.Comment: 9 pages, 5 figures. Additional figures can be found at: https://cern.ch/apapaefs/VBSQCD

Voltage-Gated Ion Channel Dysfunction Precedes Cardiomyopathy Development in the Dystrophic Heart

Duchenne muscular dystrophy (DMD), caused by mutations in the dystrophin gene, is associated with severe cardiac complications including cardiomyopathy and cardiac arrhythmias. Recent research suggests that impaired voltage-gated ion channels in dystrophic cardiomyocytes accompany cardiac pathology. It is, however, unknown if the ion channel defects are primary effects of dystrophic gene mutations, or secondary effects of the developing cardiac pathology.To address this question, we first investigated sodium channel impairments in cardiomyocytes derived from dystrophic neonatal mice prior to cardiomyopahty development, by using the whole cell patch clamp technique. Besides the most common model for DMD, the dystrophin-deficient mdx mouse, we also used mice additionally carrying an utrophin mutation. In neonatal cardiomyocytes, dystrophin-deficiency generated a 25% reduction in sodium current density. In addition, extra utrophin-deficiency significantly altered sodium channel gating parameters. Moreover, also calcium channel inactivation was considerably reduced in dystrophic neonatal cardiomyocytes, suggesting that ion channel abnormalities are universal primary effects of dystrophic gene mutations. To assess developmental changes, we also studied sodium channel impairments in cardiomyocytes derived from dystrophic adult mice, and compared them with the respective abnormalities in dystrophic neonatal cells. Here, we found a much stronger sodium current reduction in adult cardiomyocytes. The described sodium channel impairments slowed the upstroke of the action potential in adult cardiomyocytes, and only in dystrophic adult mice, the QRS interval of the electrocardiogram was prolonged.Ion channel impairments precede pathology development in the dystrophic heart, and may thus be considered potential cardiomyopathy triggers

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

The W±W±W^{\pm}W^{\pm} Scattering Process −- Theoretical Studies, Observation, Cross-section Measurement, and EFT Reinterpretation at s=13\sqrt{s}=13 TeV with the ATLAS Detector

Vector Boson Scattering (VBS) processes involving massive, electroweak gauge bosons include the fundamental interactions of the triple and quartic electroweak self-couplings, and the exchange of the Higgs boson. Hence, the interplay of the gauge structure and the Electroweak Symmetry Breaking mechanism of the Standard Model (SM) shape this class of processes. Containing VBS contributions, the \ew production of two like-charge $W^\pm$ bosons in association with two jets ($W^\pm W^\pm jj$-EW6), can be employed to simultaneously probe these two fundamental components in the SM and beyond. This thesis presents comprehensive investigations of the electroweak $W^\pm W^\pm$ scattering process in the fully leptonic final state in proton-proton collisions at a centre-of-mass energy of $13$ TeV. An amount of $36.1$ fb$^{-1}$ of data, taken with the ATLAS detector, is utilised. The theoretical predictions of the $W^\pm W^\pm jj$ and, in particular, the $W^\pm W^\pm jj$-EW6 process are studied. Three different Monte-Carlo (MC) event generation programmes are employed: the PowhegBox programme at NLO QCD accuracy with the VBS approximation, the Sherpa programme in a LO multi-jet merged setup with up to three jets in the matrix-element, and the MadGraph5_aMC@NLO programme at LO accuracy. The predictions of the three nominal setups in the fiducial region are found to disagree beyond their uncertainty envelopes. Subsequently, their individual settings, such as the nominal renormalisation and factorisation scales in the matrix-element calculations and the parton shower configurations, are investigated. The first observation of the $W^\pm W^\pm jj$-EW6 process with data from the ATLAS experiment is established and published in Ref. [1] by rejecting the background-only hypothesis with a significance in experimental data of $6.5\sigma$. The expected significance, employing the prediction from Sherpa for the $W^\pm W^\pm jj$-EW6 process, is $4.4\sigma$. The fiducial cross-section of the $W^\pm W^\pm jj$-EW6 process as predicted by the SM is measured as $\left(2.89^{+0.59}_{-0.56}\right)$ fb, which, per construction of the analysis, includes the contribution of the interference with $W^\pm W^\pm jj$-EW4 process. This measurement is dominated by the statistical uncertainty of the data sample. All three studied theoretical predictions agree with the measured fiducial cross-section within the total uncertainty envelopes. The components of the analysis of the SM $W^\pm W^\pm jj$-EW6 process are reutilised for a reinterpretation of the experimental data in terms of an Effective Field Theory (EFT) model describing beyond SM extensions which generate anomalous quartic gauge couplings in the electroweak sector through operators of mass dimension eight [2,3]. For the first time, one-dimensional exclusion bounds on the coefficients of these operators are determined in the fully leptonic $W^\pm W^\pm jj$ final state with data from the ATLAS experiment, at the same time presenting the first overall dimension-eight EFT parameter exclusion bounds derived with $\sqrt{s}=13$ TeV data from the ATLAS experiment. Comparisons with existing results of all final states show that the obtained results are less stringent. The thesis' focus for this part lies in the investigation of the fundamental ingredients for the analysis of dimension-eight EFT models. The novel technique of amplitude decomposition is employed for the MC generation of the EFT signal contributions. It considerably improves the signal predictions and accuracy, as well as the simulation efficiency in the sensitive regions of the EFT contribution at high invariant masses. Moreover, along the profound validation of this new approach, it is found that the conventional simulation technique is insufficient in terms of phase space integration accuracy in the MC event generation. The application of the clipping unitarisation on the EFT signal contributions is thoroughly investigated, and exclusion limits obtained with this approach are derived, alongside the ununitarised exclusion bounds. For the first time in the $W^\pm W^\pm jj$ final state, exclusion bounds scanning multiple values of the clipping energy are shown in this thesis. Comparisons with unitarity bounds calculated from Ref. [4] shown that the obtained results do not yet reach physically reasonable regions in terms of unitarity. Moreover, exclusion bounds are studied, including the impact of dimension-six EFT operators on the \wz-EW4 background process. The results of this study constitute the first of their kind across final states and experiments. The inclusion of effects of dimension-six EFT operators with coefficients at their current best limit values yields no sizable effect on the exclusion bounds of the dimension-eight coefficients in the tested configuration

Unfolding W + jets Event Distributions at 7 TeV with the ATLAS Detector

This report presents a study on the unfolding of the exclusive jet multiplicity distribution in W + jets events generated by Alpgen and Sherpa Monte Carlo event generators. After implementing the particle level event selection on Monte Carlo, two dierent unfolding procedures are tested, the bin-by-bin method and the iterative Bayesian approach by D'Agostini. For the bin-by-bin method the correction factor for both Alpgen and Sherpa is computed. With the iterative Bayesian method a closure test in Alpgen was performed in order to validate the procedure and gaining an estimate of the systematic eects of unfolding. The migration matrix and the result of this closure test are presented

Study of Vector Boson Scattering Processes with WW and WZ final states at the ATLAS detector

A summary of recent ATLAS results using $36.1 fb^{-1}$ of data collected in Run 2 of the LHC (2015+2016) at $\sqrt{s} = 13 TeV$ in fully leptonic Vector Boson Scattering final states of $W^{\pm}W^{\pm}jj$ and $W^{\pm}Zjj$ is presented

Investigation of mass reconstruction techniques for resonances in the scattering of W±W±→W±W±W^{\pm}W^{\pm} \to W^{\pm}W^{\pm} at the LHC

Physics scenarios of electroweak symmetry breaking beyond the Standard Model introduce new resonances in the scattering of massive, weak gauge bosons. Due to the best signal to background ratio, the like-sign "W^{\pm}W^{\pm}"jj channel is the most favourable final state for a first glance at resonances in vector boson scattering (VBS) at a hadron collider such as the LHC. Resonances in this scattering process can be modelled with the approach of an effective field theory and the K-matrix unitarisation method. This thesis presents a study of mass reconstruction of resonances in the fully leptonic decay channel of like-sign "W^{\pm}W^{\pm}" scattering. Special emphasis lies on the technique of constrained minimisation leading to mass bound variables. For different resonance types, variables providing the best discovery potential in proton-proton collisions at a centre-of-mass energy of "\unit[8]{TeV}" and an integrated luminosity of "\unit[20]{fb^{-1}}" are determined and characterised

Precision WZ cross sections and polarisation at 13 TeV

Measurements of W±Z production in pp collisions at a center-of-mass energy of 13 TeV are presented. The data were collected in 2015 and 2016 by the ATLAS experiment at the Large Hadron Collider, and correspond to an integrated luminosity of 36.1 fb−1. The W±Z candidate events are reconstructed using leptonic decay modes into electrons and muons of the gauge bosons. The measured inclusive cross section in the detector fiducial region for leptonic decay modes is σfid.W±Z→ℓ′νℓℓ=63.7± 1.0 (stat.)± 2.3 (sys.)± 0.3 (mod.)± 1.5 (lumi.) fb, in agreement with the next-to-next-to-leading-order Standard Model prediction of 61.5+1.4−1.3 fb. Cross sections for W+Z and W−Z production and their ratio are presented as well as differential cross sections for several kinematic observables. An analysis of angular distributions of lepton decays of W and Z bosons is performed and integrated helicity fractions in the detector fiducial region are measured for each of the W and Z bosons. The longitudinal helicity state of pair-produced vector bosons is measured in hadronic collisions

Cell size induced bias of current density in hypertrophic cardiomyocytes

Alterations in ion channel expression and function known as “electrical remodeling” contribute to the development of hypertrophy and to the emergence of arrhythmias and sudden cardiac death. However, comparing current density values – an electrophysiological parameter commonly utilized to assess ion channel function – between normal and hypertrophied cells may be flawed when current amplitude does not scale with cell size. Even more, common routines to study equally sized cells or to discard measurements when large currents do not allow proper voltage-clamp control may introduce a selection bias and thereby confound direct comparison. To test a possible dependence of current density on cell size and shape, we employed whole-cell patch-clamp recording of voltage-gated sodium and calcium currents in Langendorff-isolated ventricular cardiomyocytes and Purkinje myocytes, as well as in cardiomyocytes derived from trans-aortic constriction operated mice. Here, we describe a distinct inverse relationship between voltage-gated sodium and calcium current densities and cell capacitance both in normal and hypertrophied cells. This inverse relationship was well fit by an exponential function and may be due to physiological adaptations that do not scale proportionally with cell size or may be explained by a selection bias. Our study emphasizes the need to consider cell size bias when comparing current densities in cardiomyocytes of different sizes, particularly in hypertrophic cells. Conventional comparisons based solely on mean current density may be inadequate for groups with unequal cell size or non-proportional current amplitude and cell size scaling