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Convergence d'un système de Zakharov stochastique vers l'équation de NLS multiplicative
No full textInternational audienceWe study the convergence of a Zakharov system driven by a time white noise, colored in space, to a multiplicative stochastic nonlinear Schrödinger equation, as the ion-sound speed tends to infinity. In the absence of noise, the conservation of energy gives bounds on the solutions, but this evolution becomes singular in the presence of the noise. To overcome this difficulty, we show that the problem may be recasted in the diffusion-approximation framework, and make use of the perturbed test-function method. We also obtain convergence in probability. The result is limited to dimension one, to avoid too much technicalities. As a prerequisite, we prove the existence and uniqueness of regular solutions of the stochastic Zakharov system.Nous étudions la convergence d'un système de Zakharov forcé par un bruit blanc temporel, coloré en espace, vers une équation de Schrödinger non linéaire stochastique multiplicative. En l'absence de bruit, la conservation de l'énergie donne des bornes uniformes sur les solutions, mais cette évolution devient singulière en présence du bruit. Pour surmonter cette difficulté, nous montrons que le problème peut être replacé dans le cadre de l'approximation-diffusion, et nous utilisons la méthode de la fonction-test perturbée. Nous obtenons également une convergence en probabilité. Le résultat est limité à la dimension un, pour éviter trop de technicité. En préambule, nous prouvons l'existence et l'unicité de solutions régulières du système de Zakharov stochastique
Search for dark matter produced in association with a pair of bottom quarks in proton-proton collisions at = 13 TeV
No full textInternational audienceA search for dark matter (DM) particles produced in association with bottom quarks is presented. The analysis uses proton-proton collision data at a center-of-mass energy of = 13 TeV, corresponding to an integrated luminosity of 138 fb. The search is performed in the final state with large missing transverse momentum and a pair of jets originating from bottom quarks. No significant excess of data is observed with respect to the standard model expectation. Results are interpreted in the context of a type-II two-Higgs-doublet model with an additional light pseudoscalar (2HDM+a). An upper limit is set on the mass of the lighter pseudoscalar, excluding masses up to 260 GeV at 95% confidence level. This is the first search at the LHC to probe DM produced in association with two nonresonant bottom quarks in the 2HDM+a model. Sensitivity to the parameter space with the ratio of the vacuum expectation values of the two Higgs doublets, , greater than 15 is achieved, capitalizing on the enhancement of couplings between pseudoscalars and bottom quarks with high
Measurement of the Drell--Yan forward-backward asymmetry and of the effective leptonic weak mixing angle in proton-proton collisions at = 13 TeV
No full textInternational audienceThe forward-backward asymmetry in Drell-Yan production and the effective leptonic electroweak mixing angle are measured in proton-proton collisions at = 13 TeV, collected by the CMS experiment and corresponding to an integrated luminosity of 138 fb. The measurement uses both dimuon and dielectron events, and is performed as a function of the dilepton mass and rapidity. The unfolded angular coefficient is also extracted, as a function of the dilepton mass and rapidity. Using the CT18Z set of parton distribution functions, we obtain = 0.23157 0.00031, where the uncertainty includes the experimental and theoretical contributions. The measured value agrees with the standard model fit result to global experimental data. This is the most precise measurement at a hadron collider, with a precision comparable to the results obtained at LEP and SLD
Lighting up the Photon Wigner Distribution via Dilepton Productions
No full textInternational audienceWe present a systematic investigation of lepton pair production through photon-photon fusion processes in heavy-ion collisions. It is demonstrated that the dilepton production at a given impact parameter () with a fixed transverse momentum imbalance () can be factorized into a unified formula in terms of the Wigner photon distribution of heavy nuclei. We show that this framework provides a comprehensive description of all the relevant data from RHIC to the LHC, with a strong evidence that the quasi-real photon can be radiated not only from the nucleus as a whole, standing for the coherent contribution, but also from the sub-structures inside the nucleus, representing the incoherent contribution. Further predictions are made for the anisotropies in the correlations between , , and the dilepton transverse momentum (). This will help us to constrain the photon Wigner distribution which plays a crucial role to study the gluonic matter of nucleus at small- through the diffractive photoproduction processes in heavy ion collision
Search for a standard model-like Higgs boson in the mass range between 70 and 110 GeV in the diphoton final state in proton-proton collisions at = 13 TeV
No full textInternational audienceThe results of a search for a standard model-like Higgs boson decaying into two photons in the mass range between 70 and 110 GeV are presented. The analysis uses the data set collected by the CMS experiment in proton-proton collisions at = 13 TeV corresponding to integrated luminosities of 36.3 fb, 41.5 fb and 54.4 fb during the 2016, 2017, and 2018 LHC running periods, respectively. No significant excess over the background expectation is observed and 95% confidence level upper limits are set on the product of the cross section and branching fraction for decays of an additional Higgs boson into two photons. The maximum deviation with respect to the background is seen for a mass hypothesis of 95.4 GeV with a local (global) significance of 2.9 (1.3) standard deviations. The observed upper limit ranges from 15 to 73 fb
Exploring orbital angular momentum and spin-orbit correlation for gluons at the Electron-Ion Collider
No full textInternational audienceIn our previous work [Phys. Rev. Lett. 128, 182002 (2022)], we introduced a pioneering observable aimed at experimentally detecting the orbital angular momentum (OAM) of gluons. Our focus was on the longitudinal double spin asymmetry observed in exclusive dijet production during electron-proton scattering. We demonstrated the sensitivity of the angular correlation between the scattered electron and proton as a probe for gluon OAM at small- and its intricate interplay with gluon helicity. This current work provides a comprehensive exposition, diving further into the aforementioned calculation with added elaboration and in-depth analysis. We reveal that, in addition to the gluon OAM, one also gains access to the spin-orbit correlation of gluons. We supplement our work with a detailed numerical analysis of our observables for the kinematics of the Electron-Ion Collider. In addition to dijet production, we also consider the recently proposed semi-inclusive diffractive deep inelastic scattering process which potentially offers experimental advantages over dijet measurements. Finally, we investigate quark-channel contributions to these processes and find an unexpected breakdown of collinear factorization
A logarithm law for nonautonomous systems fastly converging to equilibrium and mean field coupled systems
No full textInternational audienceWe prove that if a nonautonomous system has in a certain sense a fast convergence to equilibrium (faster than any power law behavior) then the time τ_r(x,y) needed for a typical point x to enter for the first time in a ball B(y,r) centered in y, with small radius r scales as the local dimension of the equilibrium measure μ at y, i.e.lim(r→0) log [τ_r(x,y)]/ [-log(r)]We then apply the general result to concrete systems of different kind, showing such a logarithm law for asymptotically authonomous solenoidal maps and mean field coupled expanding maps
Volume growth of Funk geometry and the flags of polytopes
No full text36 pages, 3 figuresInternational audienceWe consider the Holmes-Thompson volume of balls in the Funk geometry on the interior of a convex domain. We conjecture that for a fixed radius, this volume is minimized when the domain is a simplex and the ball is centered at the barycenter, or in the centrally-symmetric case, when the domain is a Hanner polytope. This interpolates between Mahler's conjecture and Kalai's flag conjecture. We verify this conjecture for unconditional domains.For polytopal Funk geometries, we study the asymptotics of the volume of balls of large radius, and compute the two highest-order terms. The highest depends only on the combinatorics, namely on the number of flags. The second highest depends also on the geometry, and thus serves as a geometric analogue of the centro-affine area for polytopes.We then show that for any polytope, the second highest coefficient is minimized by a unique choice of center point, extending the notion of Santaló point. Finally, we show that, in dimension two, this coefficient, with respect to the minimal center point, is uniquely maximized by affine images of the regular polygon
Constraining Glueball Couplings
No full textInternational audienceWe set up a numerical S-matrix bootstrap problem to rigorously constrain bound state couplings given by the residues of poles in elastic amplitudes. We extract upper bounds on these couplings that follow purely from unitarity, crossing symmetry, and the Roy equations within their proven domain of validity. First we consider amplitudes with a single spin 0 or spin 2 bound state, both with or without a self-coupling. Subsequently we investigate amplitudes with the spectrum of bound states corresponding to the estimated glueball masses of pure SU(3) Yang-Mills. In the latter case the 'glue-hedron', the space of allowed couplings, provides a first-principles constraint for future lattice estimates
Search for charged-lepton flavor violation in the production and decay of top quarks using trilepton final states in proton-proton collisions at = 13 TeV
No full textInternational audienceA search is performed for charged-lepton flavor violating processes in top quark (t) production and decay. The data were collected by the CMS experiment from proton-proton collisions at a center-of-mass energy of 13 TeV and correspond to an integrated luminosity of 138 fb. The selected events are required to contain one opposite-sign electron-muon pair, a third charged lepton (electron or muon), and at least one jet of which no more than one is associated with a bottom quark. Boosted decision trees are used to distinguish signal from background, exploiting differences in the kinematics of the final states particles. The data are consistent with the standard model expectation. Upper limits at 95% confidence level are placed in the context of effective field theory on the Wilson coefficients, which range between 0.024-0.424 TeV depending on the flavor of the associated light quark and the Lorentz structure of the interaction. These limits are converted to upper limits on branching fractions involving up (charm) quarks, teu (tec), of 0.032 (0.498)10, 0.022 (0.369)10, and 0.012 (0.216)10 for tensor-like, vector-like, and scalar-like interactions, respectively