In the proton-proton collisions at the LHC, the associate production of the Higgs boson with two top quarks has not been observed yet. This ttH channel allows directly probing the coupling of the Higgs boson to the top quark. The observation of this process could be a highlight of the ongoing Run 2 data taking.
Unlike to supervised methods (neural networks, decision trees, support vector machines, …), the Matrix Element Method (MEM) allows to classify events by computing the probability that a final state occurs thanks to the physic laws involved. This sophisticated method is however very CPU time consuming to explore all possible final states and requires huge powerful computing platform to perform the CMS analyses carried out at our laboratory in a reasonable time.
The Matrix Element method is based on the computation of high dimensional integrals. We will describe how we develop and deploy our MEM production code on GPU's platform. Especially, how we adapted the main components of these computations into OpenCL kernels: VEGAS, the MadGraph code generator to compute the Matrix Element terms and the parton distribution function calculations for LHAPDF part.
We will conclude by discussing about the gain obtained on GPU's platforms (> 20 GPUs) compared with classical CPU's platforms.