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Measurement of the Higgs boson total decay width using the H WW e decay channel in proton-proton collisions at = 13 TeV
No full textInternational audienceThe Higgs boson (H) decay width is determined from the ratio of off- and on-shell production of H WW e using proton-proton collision data corresponding to an integrated luminosity of 138 fb collected at = 13 TeV by the CMS experiment at the LHC. The off-shell signal strength is measured as = 1.2. The Higgs boson total decay width is = 3.9 MeV, in agreement with the standard model prediction. The uncertainty in this result represents a factor of three improvement over the previous CMS result in this decay channel
Online robust covariance matrix estimation and outlier detection
No full textRobust estimation of the covariance matrix and detection of outliers remain major challenges in statistical data analysis, particularly when the proportion of contaminated observations increases with the size of the dataset. Outliers can severely bias parameter estimates and induce a masking effect, whereby some outliers conceal the presence of other outliers, further complicating their detection. Although many approaches have been proposed for covariance estimation and outlier detection, to our knowledge, none of these methods have been implemented in an online setting. In this paper, we focus on online covariance matrix estimation and outlier detection. Specifically, we propose a new method for simultaneously and online estimating the geometric median and variance, which allows us to calculate the Mahalanobis distance for each incoming data point before deciding whether it should be considered an outlier. To mitigate the masking effect, robust estimation techniques for the mean and variance are required. Our approach uses the geometric median for robust estimation of the location and the median covariance matrix for robust estimation of the dispersion parameters. The new online methods proposed for parameter estimation and outlier detection allow real-time identification of outliers as data are observed sequentially. The performance of our methods is demonstrated on simulated datasets
Cognitive ageing: sex and life course social class differences in England
No full textInternational audienc
Accessing baryon-antibaryon generalized distribution amplitudes in
No full textInternational audienceγ∗γ→BB¯ is the golden process to access chiral-even di-baryon generalized distribution amplitudes (GDAs) as deeply virtual Compton scattering has proven to be for the generalized parton distributions. In the framework of colinear QCD factorization where the leading twist amplitude is the convolution of GDAs and a perturbatively calculable coefficient function, we study the scattering amplitude for the baryonic channels where B is a spin 1/2 baryon such as the nucleon or hyperon Λ,Σ. Taking into account the interfering QED amplitude, we calculate the cross section of the e±γ→e±BB¯ process that can be experimentally studied in e−e+ as well as in electron-ion facilities. We explore both the final state polarization summed case and the polarization dependent effects. Numerical estimates are presented for e−γ→e−pp¯, using motivated models for GDAs. Our results show that a first extraction of baryon-antibaryon GDAs from experimental measurements is feasible at Belle II.12 pages, 7 figure
Unitary perturbation theory on the light cone
No full textInternational audienceLight-cone perturbation theory is a powerful tool for calculating high-energy scattering amplitudes, particularly for quantum particles such as electrons, photons, or protons scattering off heavy nuclei, a process analogous to potential scattering. Central to these computations are the light-cone wave functions of incoming and outgoing particles, representing the projection of dressed initial and final states onto partonic Fock states. The dressed states are obtained by applying an evolution operator in the Dirac picture to bare partonic states, which may be interpreted physically as a time evolution from preparation to interaction. In standard approaches, a non-unitary operator is used, and proper normalization is imposed a posteriori. Here, we systematically develop perturbation theory from a perturbatively unitary evolution operator, using adiabatic switching to regularize the infinite-time limits. This provides a theoretically coherent framework for organizing calculations, reproducing known results entirely diagrammatically without enforcing unitarity by hand. We illustrate the method with a simple quantum mechanical model, enabling calculations to arbitrary perturbative orders, and then evaluate wave functions in field theories quantized on the light cone, focusing on a massive scalar theory with cubic interaction at one-loop accuracy
Search for resonances decaying to an anomalous jet and a Higgs boson in proton-proton collisions at = 13 TeV
No full textInternational audienceThis paper presents a search for new physics through the process where a new massive particle, X, decays into a Higgs boson and a second particle, Y. The Higgs boson subsequently decays into a bottom quark-antiquark pair, reconstructed as a single large-radius jet. The decay products of Y are also assumed to produce a single large-radius jet. The identification of the Y particle is enhanced by computing the anomaly score of its candidate jet using an autoencoder, which measures deviations from typical QCD multijet jets. This allows a simultaneous search for multiple Y decay scenarios within a single analysis. In the main benchmark process, Y is a scalar particle that decays into WW. Two other benchmark processes are also considered, where Y is a scalar particle decaying into a light quark-antiquark pair, or into a top quark-antiquark pair. The last benchmark considers Y as a hadronically decaying top quark, arising from the decay of a vector-like quark into a top quark and a Higgs boson. Data recorded by the CMS experiment at a center-of-mass energy of 13 TeV in 20162018, and corresponding to an integrated luminosity of 138 fb, are analyzed. No significant excess is observed, and upper limits on the benchmark signal cross section for various masses of X and Y, at 95% confidence level, are placed
Measurement of the branching fraction of the decay and isospin asymmetry of decays
No full textInternational audienceThis paper describes a measurement of the \LbJpsiLambda branching fraction using data collected with the LHCb experiment in proton-proton collisions from 2016 to 2018. The dataset corresponds to an integrated luminosity of 5.4\invfb. The branching fraction is determined relative to that of decays, yielding , where the first uncertainty is statistical, the second systematic, the third due to external inputs on branching fractions and the fourth due to the ratio of baryon and meson hadronisation fractions. In addition, the isospin asymmetry between the rates of and decays is measured to be , where the first uncertainty is statistical and the second systematic
Riemannian Stochastic Interpolants for Amorphous Particle Systems
No full textModern generative models hold great promise for accelerating diverse tasks involving the simulation of physical systems, but they must be adapted to the specific constraints of each domain. Significant progress has been made for biomolecules and crystalline materials. Here, we address amorphous materials (glasses), which are disordered particle systems lacking atomic periodicity. Sampling equilibrium configurations of glass-forming materials is a notoriously slow and difficult task. This obstacle could be overcome by developing a generative framework capable of producing equilibrium configurations with well-defined likelihoods. In this work, we address this challenge by leveraging an equivariant Riemannian stochastic interpolation framework which combines Riemannian stochastic interpolant and equivariant flow matching. Our method rigorously incorporates periodic boundary conditions and the symmetries of multi-component particle systems, adapting an equivariant graph neural network to operate directly on the torus. Our numerical experiments on model amorphous systems demonstrate that enforcing geometric and symmetry constraints significantly improves generative performance
Prospects for the production and detection of Breit-Wheeler tunneling positrons in Experiment 320 at the FACET-II accelerator
No full textInternational audienceThe SLAC Experiment 320 collides 10 TW-class laser pulses with the high-quality, 10 GeV electron beam from the FACET-II RF LINAC. This setup is expected to produce a sizable number of pairs via nonlinear Breit-Wheeler mechanism in the strong-field tunneling regime, with an estimated yield of ~0.01-0.1 pairs per collision. This small signal rate typically comes along with large backgrounds originating, e.g., from dumping the high-charge primary beam, secondaries induced by the beam halo, as well as photons and low-energy electrons produced in the electron-laser collision itself. These backgrounds may reach densities of O(100) charged particles per cm^2 (and even more neutral particles) at the surface of the sensing elements, making it a tremendous challenge for an unambiguous detection of single particles. In this work, we demonstrate how detectors and methods adapted from high-energy physics experiments, can enable this measurement. The solution presented is based on a highly granular, multi-layer, radiation-hard pixel detector paired with powerful particle-tracking algorithms. Using a detailed simulation of the existing experimental setup, we show how the false-positive rate due to background processes can be reduced by more than an order of magnitude relative to the expected signal after full reconstruction. Furthermore, we show that the high spatial tracking resolution achievable (<10 microns) allows for positron momentum measurements with a resolution of <2%, enabling spectral characterization of the nonlinear Breit-Wheeler process. Based on our extensive simulation, with a conservatively large background assumption, we show that it is possible to measure single Breit-Wheeler positrons in the coming data taking campaign of E320. That would be the first statistically significant observation and characterization of this elusive process in the (deep) tunneling regime
Guia para a apresentação de dados de redes sociais e redes pessoais: o caso da revista REDES
No full textInternational audienceThe objective of this work was to describe the guidelines used in the articles published in the journal REDES to report relational data. For this purpose, 363 articles published in the journal between 2002 and 2023 were analyzed. First, a working group was created that carried out a descriptive analysis systematizing the information on the keywords, thematic contents and the network measures used. Second, the working group was based on a list of 18 previous recommendations to assess their degree of application in the journal's publications as well as develop specific recommendations. The results showed the diversity of network measures, and the heterogeneity of the reporting format used. We reflect on the relevance of standardizing network reports in each thematic area analyzed.El objetivo de este trabajo fue describir cuáles son las pautas utilizadas en los artículos publicados en la revista REDES para informar de los datos relacionales. Se analizaron 363 artículos publicados en la revista entre 2002 y 2023. Para ello se creó un grupo de trabajo que, en primer lugar, realizó un análisis descriptivo sistematizando la información sobre las palabras clave, los contenidos temáticos y las medidas de redes utilizadas. En segundo lugar, el grupo de trabajo se basó en una lista de 18 recomendaciones previas para valorar su grado de aplicación en las publicaciones de la revista y elaborar recomendaciones específicas. Los resultados mostraron la diversidad de indicadores de redes y la heterogeneidad del formato de informe utilizados. Se reflexiona sobre la pertinencia de estandarizar los informes de redes en cada área temática analizada.L'objectif de ce travail était de décrire les lignes directrices utilisées dans les articles publiés dans la revue REDES pour présenter les données relationnelles. À cette fin, 363 articles publiés dans la revue entre 2002 et 2023 ont été analysés. Tout d'abord, un groupe de travail a été constitué pour réaliser une analyse descriptive systématisant les informations sur les mots-clés, les contenus thématiques et les mesures de réseau utilisées. Ensuite, ce groupe de travail s'est appuyé sur une liste de 18 recommandations antérieures pour évaluer leur degré d'application dans les publications de la revue, ainsi que pour élaborer des recommandations spécifiques. Les résultats ont montré la diversité des mesures de réseau et l'hétérogénéité du format de présentation utilisé. Nous réfléchissons à la pertinence de standardiser les rapports de réseau dans chaque domaine thématique analysé.O objetivo deste trabalho foi descrever as diretrizes utilizadas nos artigos publicados na revista REDES para apresentar dados relacionais. Para isso, foram analisados 363 artigos publicados na revista entre 2002 e 2023. Primeiramente, foi criado um grupo de trabalho que realizou uma análise descritiva, sistematizando as informações sobre as palavras-chave, os conteúdos temáticos e as medidas de rede utilizadas. Em seguida, o grupo de trabalho baseou-se em uma lista de 18 recomendações prévias para avaliar seu grau de aplicação nas publicações da revista, bem como desenvolver recomendações específicas. Os resultados mostraram a diversidade de medidas de rede e a heterogeneidade do formato de apresentação utilizado. Refletimos sobre a relevância de padronizar os relatórios de rede em cada área temática analisada