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Abstract: Once new particles are discovered at the LHC and their masses are measured,it will be of crucial importance to determine their spin, in order to identifythe underlying new physics model. We investigate the method first suggested byBarr and later extended by others to distinguish between Supersymmetry andalternative models, e.g. Universal Extra Dimensions, in a certain cascadedecay. This method uses invariant mass distributions of the outgoing StandardModel particles to measure the spin of intermediate particles, by exploitingthe quark-anti-quark asymmetry of the LHC as a pp collider, which is limitedfor first generation quarks. In this work, we suggest instead to measure thecharge of the outgoing quark, in case it is a third generation quark. Theresulting asymmetry for a bottom quark is similar to the previous method, whileit is independent of hadronic uncertainties. Furthermore, for a top quark, theasymmetry allows better distinction between the models, as demonstrated by aquantitative analysis of model discrimination. We also show that the top-sdecay products can be used instead of the top itself, when the reconstructionof the top momentum is difficult to accomplish, and still provide informationabout the spin.

Autor: Oram Gedalia, Seung J. Lee, Gilad Perez

Fuente: https://arxiv.org/

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