Work

Resolving combinatorial ambiguities in dilepton tt¯ event topologies with constrained M2 variables

Year: 2017

Type: article

Abstract: We advocate the use of on-shell constrained ${M}_{2}$ 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 ${M}_{2}$ variables provide superior ans\"atze for the unmeasured invisible momenta and therefore can be usefully applied to discriminate combinatorial ambiguities. We illustrate our procedure with the example of dilepton $t\overline{t}$ events. We critically review the existing methods based on the Cambridge ${M}_{T2}$ 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 ${M}_{2}$ variables instead. Finally, we also consider the general case when the underlying mass spectrum is unknown, and no kinematic endpoint information is available.

Source: Physical review. D/Physical review. D.

DOI: 10.1103/physrevd.96.076005

Authors: Dipsikha Debnath, Doojin Kim, Jeong Han Kim, Kyoungchul Kong, Konstantin T. Matchev

Institutions: University of Florida, European Organization for Nuclear Research, University of Kansas, University of Pittsburgh

Language: Latvian

Topic: Particle physics theoretical and experimental studies

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: hybrid