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Resolving combinatorial ambiguities in dilepton t¯t event topologies with constrained M2 variables
Debnath, Dipsikha Kim, Doojin Kim, Jeong Han Kong, Kyoungchul Matchev, Konstantin T.
Debnath, Dipsikha
Kim, Doojin
Kim, Jeong Han
Kong, Kyoungchul
Matchev, Konstantin T.
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Abstract
We advocate the use of on-shell constrained M2 variables in order to mitigate the combinatorial problem in supersymmetry-like events with two invisible particles at the LHC. We show that in comparison to other approaches in the literature, the constrained M2 variables provide superior ansätze for the unmeasured invisible momenta and therefore can be usefully applied to discriminate combinatorial ambiguities. We illustrate our procedure with the example of dilepton t¯t events. We critically review the existing methods based on the Cambridge MT2 variable and MAOS reconstruction of invisible momenta, and show that their algorithm can be simplified without loss of sensitivity, due to a perfect correlation between events with complex solutions for the invisible momenta and events exhibiting a kinematic endpoint violation. Then we demonstrate that the efficiency for selecting the correct partition is further improved by utilizing the M2 variables instead. Finally, we also consider the general case when the underlying mass spectrum is unknown, and no kinematic endpoint information is available.
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2017-10-09
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American Physical Society
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Debnath_2017.pdf
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Debnath, D., (2017) Resolving combinatorial ambiguities in dilepton t¯t event topologies with constrained M2 variables. Physical Review. 96:7, https://doi.org/10.1103/PhysRevD.96.076005