Journal Article

Search for a new heavy scalar particle decaying into a Higgs boson and a new scalar singlet in final states with one or two light leptons and a pair of τ-leptons with the ATLAS detector

Walkowiak, W., Raine, J. A., Cuhadar Donszelmann, T., Garcia Alonso, A., Lucotte, A., Rendel, M. B., Watson, H., Introzzi, G., Zanzi, D., Pan, J., Gao, Y., Strom, D. M., Albouy, G. L., Meyer, J-P., Yang, Z., Ezhilov, A., Fabbri, L., Falke, P. J., Carminati, L., Cantero, J., Hsu, S.-C., Pedro, R., Carlotto, J. I., Meyer, C., Guerrieri, G., Luise, I., Mellado Garcia, B. R., Zhang, P., Diaz, M. A., Dudarev, A., Shi, X., Booth, C. D., Atmani, H., Borissov, G., Kajomovitz, E., Brüers, B., Yang, Y., Lyons, H., Algren, M., Catmore, J. R., Calafiura, P., Garg, R. B., Gonzalez-Sevilla, S., Korn, A., Shaheen, R., Sauerburger, F., Bhopatkar, V. S., Simpson, E. L., Hessey, N. P., Tnourji, A., Zhang, S., Zhukov, K., Golubkov, D., Kang, N. J., Krüger, H., Kupfer, T., Principe Martin, M. A., Heidorn, W. D., Berthold, A., Pintucci, L., Gazis, E. N., Batley, J. R., Vokac, P., Hawkings, R. J., Busch, E. L., Melo, A. H., Yang, X., Kim, Y. K., Levin, D., Tu, Y., Schwarz, T. A., Ward, R. J., Calace, N., Zoccoli, A., Raskina, V., Jia, J., Viehhauser, G. H. A., Pettee, M., Cameron, D., Tariq, K., Huang, S., Junkermann, T., Veloso, F., Zhang, R., Tikhomirov, V., Dervan, P., Nel

2023

Overview

A bstract A search for a new heavy scalar particle X decaying into a Standard Model (SM) Higgs boson and a new singlet scalar particle S is presented. The search uses a proton-proton ( pp ) collision data sample with an integrated luminosity of 140 fb − 1 recorded at a centre-of-mass energy of s = 13 TeV with the ATLAS detector at the Large Hadron Collider. The most sensitive mass parameter space is explored in X mass ranging from 500 to 1500 GeV, with the corresponding S mass in the range 200–500 GeV. The search selects events with two hadronically decaying τ -lepton candidates from H → τ + τ − decays and one or two light leptons ( ℓ = e , μ ) from S → VV ( V = W , Z ) decays while the remaining V boson decays hadronically or to neutrinos. A multivariate discriminant based on event kinematics is used to separate the signal from the background. No excess is observed beyond the expected SM background and 95% confidence level upper limits between 72 fb and 542 fb are derived on the cross-section σ ( pp → X → SH ) assuming the same SM-Higgs boson-like decay branching ratios for the S → VV decay. Upper limits on the visible cross-sections σ ( pp → X → SH → WWττ ) and σ ( pp → X → SH → ZZττ ) are also set in the ranges 3–26 fb and 6–33 fb, respectively.

• Publisher: Springer Berlin Heidelberg,Springer Nature B.V,Springer Nature
• Subject: Classical and Quantum Gravitation / Confidence intervals / Cross-sections / Elementary Particles / Hadron-Hadron Scattering / Higgs bosons / High energy physics / Kinematics / Large Hadron Collider / Leptons / Luminosity / Neutrinos / Parameter sensitivity / Particle decay / Physics / Physics and Astronomy / Protons / Quantum Field Theories / Quantum Field Theory / Quantum Physics / Quarks / Regular Article - Experimental Physics / Relativity Theory / Searching / Standard model (particle physics) / String Theory