179 research outputs found

    Topography Estimation Using Particle Swarm Optimization

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    The Earth‚Äôs Vertical Gravity Gradient (VGG) can be used to map seafloor topography but presents a challenging inverse problem. A promising approach is forward modeling, in which one searches over a set of candidate topographies and selects the one whose predicted VGG best fits the observed one. The main bottleneck here is solving the associated high-dimensional and non-linear optimization problem. Yang et al (2018) demonstrated a method in which the topography is parametrized by heights of mass elements on a rectangular grid and the ‚Čą 104 dimensional optimization problem is tackled with simulated annealing (SA). We propose a computationally much cheaper method, using a stochastic optimization method known as Particle Swarm Optimization (PSO) and representing the topography as a linear combination of Radial Basis Functions (RBFs). First results, obtained without any tuning, show that the MATLAB code achieves an RMS error of 650 m with 500 RBFs (1500 parameters) and a 30 min run time. This is comparable to the error of 300 m from the much more expensive SA method that takes hours on a super-computer. Improvements to our method are likely to result in state of the art performance levels

    Measurements of inclusive and differential cross sections for the Higgs boson production and decay to four-leptons in proton-proton collisions at s\sqrt{s} = 13 TeV

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    Measurements of the inclusive and differential fiducial cross sections for the Higgs boson production in the H ‚Üí\to ZZ ‚Üí\to 4‚Ąď\ell (‚Ąď\ell = e,őľ\mu) decay channel are presented. The results are obtained from the analysis of proton-proton collision data recorded by the CMS experiment at the CERN LHC at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of 138 fb‚ąí1^{-1}. The measured inclusive fiducial cross section is 2.73¬Ī\pm0.26 fb, in agreement with the standard model expectation of 2.86¬Ī\pm0.1 fb. Differential cross sections are measured as a function of several kinematic observables sensitive to the Higgs boson production and decay to four leptons. A set of double-differential measurements is also performed, yielding a comprehensive characterization of the four leptons final state. Constraints on the Higgs boson trilinear coupling and on the bottom and charm quark coupling modifiers are derived from its transverse momentum distribution. All results are consistent with theoretical predictions from the standard model

    Search for scalar leptoquarks produced in lepton-quark collisions and coupled to ŌĄ\tau leptons