Modélisation mésoscopique des réseaux polymères à grande déformation

Polymeric networks, i.e. cross-linked elastomers, have been studiedfor a long time for their elastic properties combined with a remarkable mechanicalresistance. These materials can be found in different forms, from the well known familyof "rubber", to gels for exemple. All these materials have different characteristics atdifferent spatial and temporal scales. Moreover, innovation in polymer science relieson a complete understanding of their microstructure and the resulting macroscopicproperties. Experimental and simulation studies are therefore more than ever comple-mentary in this field. In simulation, these materials are well defined and are widelystudied at the molecular and macroscopic scales. However, it is still difficult to linkthese two scales when setting up a multi-scale modeling strategy. The objective ofthis thesis is to develop a model and tools to link the microscopic and macroscopicscales in a multi-scale modeling strategy of elastomers which are constituents of tirerubber. In order to bridge the scales and simulation times gap between the micro andmacroscopic, we have developed a mesoscopic elastic network model. We simulate onlythe dynamics of the cross-links and entanglements of the material, thus allowing tostudy large systems over long times with a reasonable computational cost. We haveshown that the choice to describe the material in this way allows us to understandthe effects of spatial and topological heterogeneities on the macroscopic mechanicalbehavior of the elastomer. The model is as efficient as analytical reference models,with respect to the reproduction of experimental results to produce constitutive laws,with the added possibility of localizing the stress in the system and adding a predictivepower. This work opens a possible way for the study of elastomers networks withentanglements, at a mesoscopic scale.Les réseaux polymères, c’est à dire des polymères réticulés, sont depuis longtemps étudiés pour leurs propriétés élastiques combiné à une résistante mécanique remarquables. On retrouve ces matériaux sous différentes formes, allant de la famille la plus connue des « caoutchoucs », aux gels. Tout ces matériaux présentent des caractéristiques différentes à des échelles spatiales et temporelles distinctes. L’innovation dans la science des polymères repose sur une compréhension complète de leur micro-structure et des propriétés macroscopiques qui en découlent. Les études expérimentales et par simulations sont donc plus que jamais complémentaires dans ce domaine. En simulation, ces matériaux sont bien définis et sont largement étudiés à l’échelle moléculaire et macroscopique. Il est cependant encore difficile de relier ces deux échelles de simulation lors de la mise en place d’une stratégie de simulation multi-échelles. Cette thèse a pour objectif de développer un modèle et des outils permettant de relier l’échelle microscopique à l’échelle macroscopique, dans une stratégie de simulation multi-échelle. Afin de combler les échelles et temps de simulation entre le micro et macroscopique, nous avons développé un modèle de réseau élastique à l’échelle mésoscopique. Nous simulons seulement la dynamique des points de réticulations et d’enchevêtrements du matériau, permettant ainsi d’étudier des grands systèmes sur des temps long avec un coût de calcul raisonnable. Nous montrons que le choix de décrire le matériau de cette manière permet de comprendre les effets d’hétérogénéités spatiales et topologiques sur le comportement mécanique macroscopique du réseau polymère. Le modèle est aussi performant que des modèles analytiques de références, vis-à-vis de la reproduction de résultats expérimentaux pour produire des lois de comportements, avec en plus la possibilité de comprendre comment la contrainte est distribuer de manière locale dans le système et en ajoutant un pouvoir prédictif vis-à-vis de nouvelles structures et topologies de réseaux. Ce travail ouvre une voie possible pour l’étude des réseaux polymères enchevêtrés à une échelle mésoscopique intermédiaire

Heterogeneity Effects in Highly Cross-Linked Polymer Networks

International audienceDespite their level of refinement, micro-mechanical, stretch-based and invariant-based models, still fail to capture and describe all aspects of the mechanical properties of polymer networks for which they were developed. This is for an important part caused by the way the microscopic inhomogeneities are treated. The Elastic Network Model (ENM) approach of reintroducing the spatial resolution by considering the network at the level of its topological constraints, is able to predict the macroscopic properties of polymer networks up to the point of failure. We here demonstrate the ability of ENM to highlight the effects of topology and structure on the mechanical properties of polymer networks for which the heterogeneity is characterised by spatial and topological order parameters. We quantify the macro- and microscopic effects on forces and stress caused by introducing and increasing the heterogeneity of the network. We find that significant differences in the mechanical responses arise between networks with a similar topology but different spatial structure at the time of the reticulation, whereas the dispersion of the cross-link valency has a negligible impact

Predicting Mechanical Constitutive Laws of Elastomers with Mesoscale Simulations

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Search for CPCP violation in D0^0→\to KS0^0_\mathrm{S}KS0^0_\mathrm{S} decays in proton-proton collisions at s\sqrt{s} = 13 TeV

International audienceA search is reported for charge-parity D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ violation in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ decays, using data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb$^{-1}$, which consists of about 10 billion events containing a pair of ẖadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays D$^{*+}$$\to$ D$^0\pi^+$ and D$^{*-}$$\to$ D$^0\pi^-$. The D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ asymmetry in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ is measured to be $A_{CP}$( K$^0_\mathrm{S}$K$^0_\mathrm{S}$) = (6.2 $\pm$ 3.0 $\pm$ 0.2 $\pm$ 0.8)%, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry in the D$^0$ $\to$ K$^0_\mathrm{S}\pi^+\pi^-$ decay. This is the first D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state

Measurement of inclusive and differential cross sections for W+^{+}W−^{-} production in proton-proton collisions at s= \sqrt{s} = 13.6 TeV

Measurements at $\sqrt{s}=$ 13.6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8 fb$^{-1}$. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavour and charge of the leptons, the number of jets, and number of jets originating from b quarks. An inclusive W$^{+}$W$^{-}$ production cross section of 125.7 $\pm$ 5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For first time in proton-proton collisions, WW events with at least two reconstructed jets are studied and compared with recent theoretical predictions.Measurements at $\sqrt{s}$ = 13.6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8 fb$^{-1}$. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavour and charge of the leptons, the number of jets, and number of jets originating from b quarks. An inclusive W$^+$W$^-$ production cross section of 125.7 $\pm$ 5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For first time in proton-proton collisions, WW events with at least two reconstructed jets are studied and compared with recent theoretical predictions

Search for a resonance decaying to a W boson and a photon in proton-proton collisions at s= \sqrt{s} = 13 TeV using leptonic W boson decays

A search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. Particle X has electric charge $\pm$1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%).A search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. Particle X has electric charge $\pm$1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%)

Search for CP violation in D0→KS0KS0 \mathrm{D^0}\to\mathrm{K^0_S}\mathrm{K^0_S} decays in proton-proton collisions at s= \sqrt{s} = 13 TeV

A search is reported for charge-parity CP violation in $\mathrm{D^0}\to\mathrm{K^0_S}\mathrm{K^0_S}$ decays, using data collected in proton-proton collisions at $\sqrt{s} =$ 13 TeV recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb$^{-1}$, which consists of about 10 billion events containing a pair of b hadrons, nearly all of which decay to charm hadrons. The flavor of the neutral $\mathrm{D}$ meson is determined by the pion charge in the reconstructed decays $\mathrm{D}^{*+}\to\mathrm{D^0}\pi^{+}$ and $\mathrm{D}^{*-}\to\overline{\mathrm{D}}^{0}\pi^{-}$. The CP asymmetry in $\mathrm{D^0}\to\mathrm{K^0_S}\mathrm{K^0_S}$ is measured to be $A_{CP}(\mathrm{K^0_S}\mathrm{K^0_S}) =$ (6.2 $\pm$ 3.0 $\pm$ 0.2 $\pm$ 0.8)%, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the CP asymmetry in the $\mathrm{D^0}\to\mathrm{K^0_S}\pi^{+}\pi^{-}$ decay. This is the first CP asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state.A search is reported for charge-parity D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ violation in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ decays, using data collected in proton-proton collisions at $\sqrt{s}$ = 13 TeV recorded by the CMS experiment in 2018. The analysis uses a dedicated data set that corresponds to an integrated luminosity of 41.6 fb$^{-1}$, which consists of about 10 billion events containing a pair of ẖadrons, nearly all of which decay to charm hadrons. The flavor of the neutral D meson is determined by the pion charge in the reconstructed decays D$^{*+}$$\to$ D$^0\pi^+$ and D$^{*-}$$\to$ D$^0\pi^-$. The D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$$CP$ asymmetry in D$^0$$\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ is measured to be $A_{CP}$( K$^0_\mathrm{S}$K$^0_\mathrm{S}$) = (6.2 $\pm$ 3.0 $\pm$ 0.2 $\pm$ 0.8)%, where the three uncertainties represent the statistical uncertainty, the systematic uncertainty, and the uncertainty in the measurement of the D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry in the D$^0$ $\to$ K$^0_\mathrm{S}\pi^+\pi^-$ decay. This is the first D$^0$ $\to$ K$^0_\mathrm{S}$K$^0_\mathrm{S}$ $CP$ asymmetry measurement by CMS in the charm sector as well as the first to utilize a fully hadronic final state

Search for a resonance decaying to a W boson and a photon in proton-proton collisions at s\sqrt{s} = 13 TeV using leptonic W boson decays

International audienceA search for a new charged particle X with mass between 0.3 and 2.0 TeV decaying to a W boson and a photon is presented, using proton-proton collision data at a center-of-mass energy of 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb$^{-1}$. Particle X has electric charge $\pm$1 and is assumed to have spin 0. The search is performed using the electron and muon decays of the W boson. No significant excess above the predicted background is observed. The upper limit at 95% confidence level on the product of the production cross section of the X and its branching fraction to a W boson and a photon is found to be 94 (137) fb for a 0.3 TeV resonance and 0.75 (0.81) fb for a 2.0 TeV resonance, for an X width-to-mass ratio of 0.01% (5%). This search presents the most stringent constraints to date on the existence of such resonances across the probed mass range. A statistical combination with an earlier study based on the hadronic decay mode of the W boson is also performed, and the upper limit at 95% confidence level for a 2.0 TeV resonance is reduced to 0.50 (0.63) fb for an X width-to-mass ratio of 0.01% (5%)

Measurement of inclusive and differential cross sections for W+^+W−^- production in proton-proton collisions at s\sqrt{s} = 13.6 TeV

International audienceMeasurements at $\sqrt{s}$ = 13.6 TeV of the opposite-sign W boson pair production cross section in proton-proton collisions are presented. The data used in this study were collected with the CMS detector at the CERN LHC in 2022, and correspond to an integrated luminosity of 34.8 fb$^{-1}$. Events are selected by requiring one electron and one muon of opposite charge. A maximum likelihood fit is performed on signal- and background-enriched data categories defined by the flavour and charge of the leptons, the number of jets, and number of jets originating from b quarks. An inclusive W$^+$W$^-$ production cross section of 125.7 $\pm$ 5.6 pb is measured, in agreement with standard model predictions. Cross sections are also reported in a fiducial region close to that of the detector acceptance, both inclusively and differentially, as a function of the jet multiplicity in the event. For first time in proton-proton collisions, WW events with at least two reconstructed jets are studied and compared with recent theoretical predictions