Journal Article

Search for a scalar partner of the top quark in the all-hadronic tt¯ plus missing transverse momentum final state at s=13 TeV with the ATLAS detector

Walkowiak, W., Peiffer, T., Raine, J. A., Cuhadar Donszelmann, T., Lucotte, A., Rendel, M. B., Introzzi, G., Zanzi, D., Gao, Y., Strom, D. M., Fehr, A., Li, C.-Q., Yang, Z., Ezhilov, A., Fabbri, L., Falke, P. J., Emerman, A., Aguilar-Saavedra, J. A., Carminati, L., Cantero, J., Hubaut, F., Hsu, S.-C., Pedro, R., Gregersen, K., Meyer, C., Luise, I., Mellado Garcia, B. R., Diaz, M. A., Dudarev, A., Booth, C. D., Atmani, H., Borissov, G., Bruni, L. S., Kajomovitz, E., Brüers, B., Yang, Y., Beddall, A., Lyons, H., La Ruffa, F., Catmore, J. R., Asimakopoulou, E. M., Calafiura, P., Gonzalez-Sevilla, S., Korn, A., Pogrebnyak, I., Laplace, S., Sauerburger, F., AbouZeid, O. S., Bhopatkar, V. S., Hessey, N. P., Schaefer, D., Trofymov, A., Zhang, S., Zhukov, K., Golubkov, D., Kang, N. J., Krüger, H., Kupfer, T., Butti, P., Heidorn, W. D., Berthold, A., Hamdaoui, H., Gazis, E. N., Batley, J. R., Vokac, P., Hawkings, R. J., Yang, X., Kim, Y. K., Levin, D., Ronzani, M., Tu, Y., Schwarz, T. A., Lehmann, K., Calace, N., Rosin, G., Zoccoli, A., Jia, J., Viehhauser, G. H. A., Pettee, M., Cameron, D., Tariq, K., Ambroz, L., Looper, K. A., Veloso, F., Zhang, R., Nibigira,

2020

Overview

A search for direct pair production of scalar partners of the top quark (top squarks or scalar third-generation up-type leptoquarks) in the all-hadronic t t ¯ plus missing transverse momentum final state is presented. The analysis of 139  fb - 1 of s = 13  TeV proton–proton collision data collected using the ATLAS detector at the LHC yields no significant excess over the Standard Model background expectation. To interpret the results, a supersymmetric model is used where the top squark decays via t ~ → t ( ∗ ) χ ~ 1 0 , with t ( ∗ ) denoting an on-shell (off-shell) top quark and χ ~ 1 0 the lightest neutralino. Three specific event selections are optimised for the following scenarios. In the scenario where m t ~ > m t + m χ ~ 1 0 , top squark masses are excluded in the range 400–1250 GeV for χ ~ 1 0 masses below 200 GeV at 95% confidence level. In the situation where m t ~ ∼ m t + m χ ~ 1 0 , top squark masses in the range 300–630 GeV are excluded, while in the case where m t ~ < m W + m b + m χ ~ 1 0 (with m t ~ - m χ ~ 1 0 ≥ 5  GeV), considered for the first time in an ATLAS all-hadronic search, top squark masses in the range 300–660 GeV are excluded. Limits are also set for scalar third-generation up-type leptoquarks, excluding leptoquarks with masses below 1240 GeV when considering only leptoquark decays into a top quark and a neutrino.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V
• Subject: Astronomy / Astrophysics and Cosmology / Confidence intervals / Elementary Particles / Fysik / Hadrons / Heavy Ions / Large Hadron Collider / Measurement Science and Instrumentation / Natural Sciences / Naturvetenskap / Neutrinos / Nuclear Energy / Nuclear Physics / Pair production / Particle collisions / Physical Sciences / Physics / Physics and Astronomy / Protons / Quantum Field Theories / Quantum Field Theory / Quarks / Regular Article - Experimental Physics / Searching / String Theory / Subatomic Physics / Subatomär fysik / Transverse momentum